[Closed] Steel frames, climbing and psychology

Gearing? Is it the same on both? Are you in the same gear on the same climb on both

Tyres? Different Tyres? Pressures? Or the same as before?

Position? Is your position on the bikes Much different from each other? Sometimes a small change e.g.. seatpost height can have a comparatively large effect on your efficiency.

Is your position the same on both bikes. And is it right/any good on either bike?

Seat post angle should make no difference at all. Just gives you a different possible range of positions.

Reach is far more important.

You were younger when you had the steel frame.

Age gets to us all innit.

These are all seated climbs (I very rarely stand). Despite the steeper seat angle on the Dude the effective top tube is the 12mm longer.

I've run exactly the same tyres (and wheels) on both and pressure is the same (measured using the same digital gauge).

Originally I did just put it down to being a year older, but I'm not convinced.

There is one 20 minute climb where I've set a faster time on the Dude. I overtook somebody at the start and although I try not to be silly about these things it's hard not to give it the beans when you know there is somebody behind. On that climb my fastest time on the Dude is 16% faster than my fastest on the ICT, which does tend to suggest that I can be faster on the Dude I just don't tend to try as hard for some reason.

Stiffer frame losing traction?

Fitness / fatness an issue?

I know I'm slower than I was last year after a miserable three or four months of constant illness.

These are all seated climbs (I very rarely stand). Despite the steeper seat angle on the Dude the effective top tube is the 12mm longer.

Ignore effective top tube. Whats the change in your position over the bottom bracket?

If thats changed that could explain a lot of the differences.

CBA?
Tired?

Unless you're really smashing it and finding a difference, probably just those. I find my speed at a "comfy" pace varies greatly.

Obviously my flat out speed varies a bit too, considerably more than 5-10%. And the weather/ground conditions make a difference even more than that.

How long did you have the last bike for? Are you comparing your fastest ride on the old bike to whatever you happen to do on a given day on the new one?

Whats the change in your position over the bottom bracket?

This.  I spent ages fiddling around on my other bike because I realised that some fairly small changes had a significant impact on my pedaling efficiency.  Seat fore/aft even by small amounts made a helluva difference.

I suspect if you spend some time getting the position sorted on the new bike you'll feel a difference, and see a difference on your segments.

But yeah, also fatter/older/less fit? 🙂

You can’t cheat physics, so either more of my power is getting to the back wheel on the steel frame, which seems unlikely, or I’m putting out more power for some reason. I’m tending towards the latter, but it’s still a mystery. There is more “spring” to the steel frame, so I wonder if that just eggs me on to try harder for some reason?

Maybe .. Google "Jan Haine planing".

I doubt it's all as one or the other as he suggests but I do think the stiffer BB = faster climbing bike think is b0llocks. A stiff bike simply responds to your input differently and feels more 'responsive'. That will egg on riders of a certain nature who buy stiff light bikes. But over a longer climb or ride all that matters in that respect is how you and the bike work together, so I can see where Jan is coming from re 'bikes that plane'. If I go from one of my road bikes to another, one difference in feel is BB stiffness. The softer bike isn't slower in any way, it just has a different response. I like it on open roads yet I don't like frames that get too whippy overall.

5lbs won't make a huge difference on a climb either. Some, but not at a level that's easy to measure.

Just lost a reply, gg STW forum...

Worn tyres when on Dude?

More weight over rear wheel on ICT?

Worse fitness/fatigue/form when on Dude?

Wind direction?

I've climbed Old Winchester Hill on both my ~9Kg road bike and my ~13Kg Wazoo (29x2.35" G-one front and 4" Jumbo Jim rear), yet despite the ~4Kg difference, their best times are 9mins40secs vs 10min37secs. Similar crosswind, both mid summer, within a week of each other. Does not compute! 😆

https://www.strava.com/activities/1068540608/analysis/1318/1536

https://www.strava.com/activities/1059909803/analysis/4857/5494

If you don't think frame flex is an issue, try this: Grab your frame and pull hard on the bb, see it flex.  Now do this once a second for five minutes, reckon you'll get tired?  You'll have used up a noticeable amount of energy, and gone nowhere.

Now, not saying one way or the other definitively, but it's worth some thought.

OP, this article  on frame stiffness by Jan Heine of Compass Bicycles might interest you (edit - I think this is what jameso is referring to).

I don't know if it's relevant in your particular case, but I do suspect that (for road frames especially) aluminium, titanium and carbon have supplanted steel as the mainstream before all the advantages and disadvantages of steel's properties were fully understood and recognised (and I'm not sure that they are even now).

In other words, although it's possible to change the performance characteristics of carbon frames by changing the lay up etc., which should result in bikes that perform as well or better than steel and be much lighter/stronger as well, you need to know precisely what those performance characteristics are that you want your carbon frame to possess.

I think a lot of the desirable properties of steel frames were/are inherent to the material, the smaller diameter tubesets historically used for steel, and some of the construction limitations (e.g. lugged and brazed with horizontal top tubes). Because there was no alternative to those steel frames and design/construction methods, there was never any incentive for those properties to be thoroughly researched and understood. When aluminium and carbon came along, their obvious advantage of lighter weight was so compelling and they were so quickly successful in replacing steel (especially in road racing), that there was no commercial incentive for the industry to seek to replicate some of the less obvious/less well understood desirable properties of steel in its aluminium or carbon frames.

I'd just take the bike out of the equation. 10% slower is you putting out 10% less power (or howether that works) for whatever reason. The Dude being lighter and stiffer will be faster. If it bothers you try to find out why your powers down.

Did you suddenly put the pie shop on speed dial ?

Do you get passed more in races?

Is there someone that used to be slower ,that is now beating you up your fav climbs?

Can you even remember what gears you were using on the other frame?

These ^^are all Friday questions,so feel free to ignore all of them ;-p

Fatter.

If you don’t think frame flex is an issue, try this: Grab your frame and pull hard on the bb, see it flex.  Now do this once a second for five minutes, reckon you’ll get tired?  You’ll have used up a noticeable amount of energy, and gone nowhere.

Do the same thing on your super stiff frame and you'll still get tired, it's all about how much energy you put in 😉

Go push as hard as you can against a brick wall, then let go, what happens? you get tired and go nowhere. Repeat procedure on a vertical trampoline, what happens?

The assumption you've made is that none of the energy is returned. It is. If you put 200N into the BB of the flexy frame it'll deflect Xmm, if you put that same 200N into the BB of the stiff frame it might deflect Ymm (where Y<X), but they both spring back. You still put 200N in both cases, so the question actually becomes how much of your input force would get transmitted to the back wheel?

At some point the reaction force from the frame will be such that your input wont deflect it any further, and so the 'excess'* input then has to go somewhere, hopefully to the back wheel. On the face of it the common sense answer is 'more' will be transferred on the stiffer frame, and in general that's true but it's not quite as simple as you think, the interesting bit is that at some point the frame will spring back and, the biomechanics of pedalling means that how your output is delivered, and for how long over the pedal cycle is not straightforward, that springing back can work with your pedal stroke as much as it can against it.

Frames are springy** yes and not ALL of the energy you put into deflecting them is returned, but a very very large percentage is. The interesting questions start when you ask if the way in which it is returned, and the timing WRT to pedalling, has any impact on how your leg power actually gets transmitted, and whether or not that impact is greater than the tiny amount of work actually 'lost' in deflecting the frame.

Too stiff can be just as bad as too flexy, there's a sweet spot, well a sweet range anyway, in the middle, but it's dependant on the rider, their power output and way in which it's delivered too. It's also relevant whether you're talking about an immediate response like in a sprint or short burst of power, versus a longer output and getting into a rhythm, it can be very fatiguing pushing against a very stiff thing over and over, and in some cases less so than pushing against something with a little give if it works better with your particular output.

I'm not saying that's what's going on here OP, if could just as easily be position change, or pure dumb luck, but the whole stiffer=faster thing doesn't always hold water in the real world.

* TBC 'excess' not because you can't deflect any further if you pushed in that direction, but because the component of your input force acting in that direction is the limit, which illustrates even more why it's related to the pedal stroke.

** regardless of material, its the amount of flex that's important.

The Ice Cream Truck is the better bike.....there, I said it. Somebody had to! I have a Truck and a significantly lighter, soon to be returned sadly,  cannondale fat caad. I love the Cannondale but the Truck wins every time when I am going out for a ride. I think the added weight means I just go at a steady pace and feel no need to sprint like a dafty. Oh and it definitely climbs better too. My suspicion is that it has just that bit more traction and is less easily deflected on rocky climbs than the fat caad.

If you don’t think frame flex is an issue, try this: Grab your frame and pull hard on the bb, see it flex. Now do this once a second for five minutes, reckon you’ll get tired? You’ll have used up a noticeable amount of energy, and gone nowhere.

Now, not saying one way or the other definitively, but it’s worth some thought.

Same here, I don't think it's either-or. But if I put the same amount of muscle force into an immoveable bar I'll be equally tired (edit, as said above - slow typing here). The flex is irrelevant in that example. In a bike drivetrain the frame flex is linked to pedalling motion, both are cyclic and linked. I can't add it all up or model it but I can see and feel how it works and I don't see it as a loss of power overall, only a change in delivery that I can work with.

Assuming the chain stays tight, the BB sway is working with my pedal motion and if the frame isn't getting hot there's nothing being lost in that flex. We don't put out power in a square wave manner so we don't need absolute stiffness either. Some just prefer how it feels. Oval rings change how power is delivered in a different way and they have fans and detractors.

I'd say it's simply easier for a brand to sell you Lighter and Stiffer and it's easier to manufacture as much stiffness as possible, compared to getting frame flex levels right for frame size, rider weight and pedal style. But when all those flex and power aspects balance up I can believe that it works as well and perhaps better than a very stiff frame, for some riders.

It isn't something as simple as a dragging disc or hub is it...?

If not, I am going with steel being narrower tubing, so lest wind resistance...

Do the same thing on your super stiff frame and you’ll still get tired

But then build it into a bike and see what happens.  When you pedal you are adding force which is resisted by two things - the frame, and the wheel.  The stiffness of the frame provides a reaction to your pedalling force.

Imagine a frame made of rubber.  What would happen when you tried to pedal?  The frame would boing and you'd go nowhere.

f the frame isn’t getting hot there’s nothing being lost in that flex

It is getting warmer, just not enough to feel cos it's being lost to the environment.  Your energy is going into potential energy stored in the springy metal, but it's not being returned to the drive train.  It's the energy spent wiggling the BB from side to side which doesn't make you go anywhere.

Steel is magic?

Xmas/N Year  kills fitness for at least 2 months following?

ymmv

Imagine a frame made of rubber. What would happen when you tried to pedal? The frame would boing and you’d go nowhere.

That doesn't mean that a steel frame that flexes a little side to side is losing power though. Steel (carbon, Al, Ti also) flexes and returns with very little loss. Loss would be generating heat - there isn't anything significant happening there.

The BB springs back around the dead spot of the pedal cycle and your natural pedal motion has a side to side element to it, it's all linked. And the BB doesn't move side to side only, it moves up and down / rotates as the ST flexes in a sway type of motion and that's where the 'past the dead spot' return flex balances out. The power phase of a pedal stroke is only about 90 degrees or so of the 180 from top to bottom anyway. A bit of wind-up then spring-back there is more sympathetic to early and end stages of repeated muscle action than something 100% fixed. It's why we don't run with solid soled trainers, the sudden spike is less efficient to the body than a more gradual loading. Not too gradual though - so not too flexy a frame.

A track or TdF sprinter's bike might justify that stiffness while a bike for long distances doesn't, it'd detract overall.  The rest are somewhere in between and it's more about reaction to input type or load timing than measureable losses.

Imagine a frame made of rubber.  What would happen when you tried to pedal?  The frame would boing and you’d go nowhere.

I believe this particular bit of reductio ad absurdum was covered by:

"Too stiff can be just as bad as too flexy, there’s a sweet spot, well a sweet range anyway, in the middle"

And the rest of the post...matching flex to rider power and style is the important bit, not simply stifferer = betterer.

The actual % of energy lost in warming up the frame, making noise etc. is tiny. It really really is. The potential energy (most of anyway) stored in the frame is returned, not directly into the drivetrain no, but how and when it is returned as the frame springs back can have a significant impact on you physiologically, and when matched appropriately to the rider/power source it can be dwarf the impact of the tiny losses.

Again, if you read my post in it's entirety you'll see I was also saying it's important whether you're talking about a single short bust attack style power delivery, vs a 20-30minute steady output at rhythm, the former scenario can favour a stiffer frame, the latter can favour something with an appropriate amount of give, the way that give works with your power delivery isn't a trivial matter. (as it seems Jameso is also highlighting while I was typing this post)

My point isn't that flexier is always better, it's that stiffer isn't always better.

Appropriate amount of flex, matched to the rider and situation/use is important.

I believe this particular bit of reductio ad absurdum was covered by:

It's not reductio ad absurdum - that's for debating, this is science.  One can discover the nature of a problem in a thought experiment by extrapolation of variables.

The actual % of energy lost in warming up the frame, making noise etc. is tiny. It really really is.

Can you show your working?

I've not done any calculations so I cannot offer a specific solution, I'm only mulling it over for the purposes of group discussion.

Appropriate amount of flex, matched to the rider and situation/use is important.

Of course, there are loads of variables overall. I'm more interested in considering the specifics of bb flex vs efficiency at this point.

A track or TdF sprinter’s bike might justify that stiffness

You make a good point arguing why bb stiffness doens't matter, and then you say that it might after all..

Thanks folks. Some great ideas and interesting further reading in there. Just to try and deal with a few of them:

You are just putting out more power on the ICT? Yes, that's my conclusion too. Although I'm still open to it being down to differences in the bike I suspect it's really me. The question then is why I'd regularly put out more power on one bike than another?

Just less fit? Yes unless I can prove otherwise that has to be the logical answer. It doesn't feel right to me i.e. I don't feel any less fit, I did as many miles (slightly more) last year as the year before, don't weigh any more etc. But since I don't race I don't have an external measure of fitness that I can use. However, I did take the Truck out for a ride on Thursday night (cold and dark). There is only one climb of note on that loop but despite a dusting of snow on the lower section I set the fastest time in my last 15 attempts (most of which were on the Dude). I have to go back to May (in the sunshine) to find a faster time, which doesn't suggest that I've lost fitness. I wasn't targeting that climb or anything. It's just in the middle of a loop and I wasn't thinking about it.

Just having a good day? If it were one ride I'd dismiss it as that, but I'm comparing my best time (from multiple attempts) on both bikes. Again, if it were just one climb I'd dismiss it, but it seems to hold true for pretty much every climb of longer than 10 minutes or so.

Body position? They are never going to be exactly the same, but I've set them up to be pretty similar. The Dude has the steeper seat angle and conventional wisdom says that should make it climb better, but it doesn't.

ICT/Steel is magic? I'm refusing to contemplate that until I've ruled out more logical explanations, but it does make me wonder.

Steel is betterer

So why are you selling the ICT then? Faster uphill, eggs you on, faster downhill, got that "thing"...

what gives, roverpig?

I'd love to take it off your hands, but I Don't Need Another Bike.

I Don't Need Another Bike,
I Don't Need Another Bike,
I Don't Need Another Bike,
I Don't Need Another Bike,
I Don't Need Another Bike...

You make a good point arguing why bb stiffness doens’t matter, and then you say that it might after all..

I didn't say it doesn't matter, I said it's not the ultimate aim that most bike brands present in marketing stuff or the ideal for all riders. Well, actually I started by saying 'stiffer BB = faster climbing bike is bollocks" : )

Then I'm just saying why I believe one or the other may be better for you. Or Roverpig.

The Dude has the steeper seat angle and conventional wisdom says that should make it climb better, but it doesn’t.

Similar thing there - steeper is only better if it's steeper than a bike that was too slack : )

So why are you selling the ICT then? Faster uphill, eggs you on, faster downhill, got that “thing”…

what gives, roverpig?

Don't ask me 🙂

Because I'm a logical sort of person I guess and logic tells me that the Dude is the better bike. It's lighter, stiffer and has a steeper seat angle. It's just annoying that the actual evidence points in the opposite direction 🙁 Actually that's not fair. I do prefer the longer reach on the Dude when descending, although it's not a big improvement and it still annoys me that it doesn't destroy the ICT on the climbs when everything I've read suggests that it should. Well, everything I'd read until this thread anyway 🙂

Actually, I've just agreed to sell the wheels from the ICT on their own, so I'll be stripping it down over the weekend. Hopefully somebody will snap up the fame. Otherwise I fear I may be tempted into more experiments which will no doubt just lead to more confusion.

Did you have fun on the ICT?

If yes, then why are you selling it?

Riding bikes should be FUN!

I can't believe no-one's sad this already, but you need to back to back the two frames in identical conditions, same climb,  with same fitness level before obsessing about BB flex or seatpost angles.

You make a good point arguing why bb stiffness doens’t matter

Stop being so binary! neither of us have said it doesn't matter, we've said that it's a complex system with a window of acceptable values, and that within that window the impact overall isn't that great, and that in some circumstances a bit of flex can work with the rider in a way that overshadows any small losses.

It's also worth noting that cadence also has a part to play, flex charateristics at low cadence/high force are different to high cadence/low force, and that's why rider and use/matching is relevant too.

One can discover the nature of a problem in a thought experiment by extrapolation of variables.

No one can't, it's a false assumption that extrapolation of a limited data set will lead to a complete expression of a solution. You can make a hypothesis and attempt to test it empirically, but this isn't simple maths of force in/out and static vectors. The way in which a human being applies force, the magnitude of that force, direction of it from one moment to the next and how interacts with the dynamic system of bike and rest of rider is very complex and extremely hard to model, at lest in terms of what you can post in a thread like this.

I'm curious what you make of Jan Heines writings on the subject of frame flex? He's far from the only one to have written, but is one of the easiest to find online. Have you read about the results from his double blind studies? There is actually an awful lot of dicussion about this very topic already out there on the internet fromt he last 20 years or more, and it makes for very interesting reading. Some of it is pure anecdote, some of it is demonstrably false, and some of it is well backed up by both theoretical and experimental science, none of it is conclusive though, because it's complex 😉

Have you done any experiments of your own testing things back to back while trying to keep other factors the same?

I've tried, far from rigorous for sure, but I have spent a fair amount of time experimenting as well as reading and thinking.

Body position? They are never going to be exactly the same, but I’ve set them up to be pretty similar. The Dude has the steeper seat angle and conventional wisdom says that should make it climb better, but it doesn’t.

Ah, 'conventional wisdom' don't get me started on that 😉

The steeper SA might make a person climb better on a bike, but it depends on you more than anything, if the steeper SA has put you in a position that is sub-optimal for your body then you might be putting out less power.

For example, if I sit more upright I can't pedal as hard or put out as much power, there's an optimal hip angle for my body, and it works in tandem with reaction forces of my arms on bars, the result being that simply changing SA by itself, unless paired with a corresponding change in bar height or reach might have a negative effect if it moves your body into a less than optimal position. Even if the bars are adjusted to maintain the actual same relationship between contact points it might now put me in a sub-optimal position in terms of weight distribution/traction etc. which means again I might not be able to best make use of my output. And this can depend on terrain as well, so body even body position alone isn't it, as always, it's complex 😉

You are expecting one bike to be faster than the other, if you didn't you wouldn't have posted this. It doesn't matter how much you try to put that belief out of your mind when riding you can't know how that's affecting the result.

You are psychologically driven to put more power out on the steel bike and less on the carbon, the issue is that your inner belief in the difference in power required is wrong and you aren't putting out enough power on the carbon bike. I'm not suggesting that is the only reason but I'm sure it's a contributory factor.

Have you done any experiments of your own testing things back to back while trying to keep other factors the same?

No, because I evaluate my bikes based on feel 🙂  I have discovered that I really enjoy bigger tyres with a very stiff frame - but I have no idea if it's faster than the alternative. I spent quite a few years riding a bike that was so flexy that if I stood up and pedalled hard it would shift the front chainring!  I didn't feel it held me back though except for the fact it stopped me standing up and pedalling hard.

I think my Patriot needs a steeper seat angle - it's old fashioned and hence slack - but because I want the rear wheel moved back without extending the reach too much.

>Maybe .. Google “Jan Haine planing”.

I just did, it's fascinating!! 🙂

https://janheine.wordpress.com/2014/11/23/what-is-planing/

No, because I evaluate my bikes based on feel

As we all should, it would stop a lot of arguments! 😉

I do find the occasional experiment interesting though, and even when not trying to prove one thing or another it can be very rewarding to actually try stuff out and it provides a way to quantify things in terms of both numbers and feel.

Still curious to hear your thoughts on Jan Heine's ideas* on frame flex? FWIW I don't necessarily agree with everything he says... but it's always interesting to hear other peoples thoughts and you seem genuinely interested in the topic so would love to discuss.

* as I said earlier, they're not really 'his ideas' as there's been similar discussions and thoughts in various circles for over a century, but his writings on that topic, and his 'discovery' of those ideas if you know what I mean...

The time of year perhaps? I built up a new bike last November (although the difference in build is fair greater than yours) and I'm struggling to tell which is/was faster.

I've yet to have a ride on the new bike that wasn't affected by rain, cold or wind (often all 3). I can't wait for better weather.

Because I’m a logical sort of person I guess and logic tells me that the Dude is the better bike. It’s lighter, stiffer and has a steeper seat angle. It’s just annoying that the actual evidence points in the opposite direction

Logic - or marketing and assumed wisdom? Plus, as said above, the evidence might be flawed anyway. Hard to do good science for bike comparisons outside simple measurements, such a complex system once it's all considered. I know I tried to detach my thinking on bike designs from assumptions etc a number of years ago, there are bikes out there that suprise you and upset the logic quite easily.

Well I never said my logic wasn't flawed 🙂

i didn't make this clear, but although I'm posting this now, the fastest times on both bikes tended to be set in the summer as you'd expect. It's just that I was looking through the dark recently.

Lets imagine half a pedal stroke.

You start with the right pedal at the top. You press down with increasing force. One effect of this force is to bend the frame in such a way that your foot moves further than it needed to. You did work that didn't move the bike. Instead it stored energy in the frame as elastic potential energy.

But once the force you apply starts to reduce the frame bends back the other way. This means that you foot does less work in the later part of the pedal stroke than it needed to. The energy stored in the frame is returned as useful work

For materials like steel all the work done flexing the material is returned, unless you reach the elastic limit and the frame bends permanently

This is why frames with some bottom bracket flex are not less efficient

Of course frame flex can also affect handling and if people prefer to pedal against a stiff frame then why shouldn't they

I'm clueless when it comes to the technicalities around geometry and positioning that folk are talking about here, but Sanny said [i]"I think the added weight means I just go at a steady pace and feel no need to sprint like a dafty."[/i]

I've been wondering why my new build seems to feel slightly faster on the flat but slightly slower on the climbs than my old bike. I'm beginning to wonder whether, because it feels a bit nippier on the flat, I'm not simply pushing it a bit more and am therefore a little bit tireder when I reach the climbs later on; how to your overall ride times compare?

Anyway, which bike do you prefer riding; 10% isn't much unless you're racing.

It's clearly a psychological thing; a fear of broken carbon fibre. I think you really just need to pedal faster OP, like you do on the steel bike. 10% is quite some difference.

I'm still not totally convinced by all this "steep seat angle climbs better" business. Different people suit different positions, and I also think there is a smidge of marketing bs with lazy designers (wink at jameso but actually aimed at others not him) where longer stays and steep seat angles make it easier to package big wheels and fat tyres without more radical tube shaping.

I'm working on the 3rd iteration of my 29er frame, gradually tweaking the design over the last 8 years. I've got a clean sheet to make whatever I want, but constant features are an unfashionably slack seat angle and very short stays. Works for me or I wouldn't keep making them like that 🙂

Before starting this frame, I've gone out of my way to hire / try a variety of other hardtails. One thing I did notice was the tendency for stiff bb might make it slightly more prone to break climbing traction on the pedal stroke. More flex seemed to be a good thing in smoothing out the torque application at the tyre.

Out of interest what sort of head angle are "Iron Works" using? Mark 2 and mark 3

I've probably said but I think it is all very height dependent. For me short stays and a slack seat tube can have me over the rear axle with little weight on the front wheel.

I think the stiff BB and traction thing makes total sense

Are we saying that the stiff carbon frame on the Dude will transfer more energy per pedalstroke to the tyres, deforming them more and so less energy is propelling the Dude up hills?

In which case tyre pressures on the Dude should be higher than on the ICT, using the same tyres?

Are your times just taken from strava or a similar app? They are not always bob on...

I n r a t s

But op unless you are accounting for your power output or heart rate at least the comparison between the 2 bikes is pretty meaningless.

It really is about power to weight in the main, the rest is detail and unlikely to account for the difference

Sorry to digress, but for my friend mr ampthill:-

Ironworks Mk1 was rigid Singular Hummingbird fork 55mm rake (more than a standard sus fork of the time) and 70 degree head angle, 120mm stem (had to go with long stem for various boring down tube and e-stay related reasons). Frame still alive and now my fixie mudguarded fat slick tyred commuter.

Mk2 was suspension fork corrected 120-130mm travel, 51mm offset and 70 degree sagged (about 69.5 static). 90mm stem so front end correspondingly longer than Mk1.

Mk3 will only be half a degree slacker but about 40-50mm longer (so now 40-50mm stem). I don't like the floppy steering of super slack head angles - prefer the Mondraker Prime R method of longer frame / shorter stem / not crazy slack head. BB drop will be rather low 75mm but I'm not currently pedal clonking 65mm so will give it a try. Frame will be 29 plus capable so don't want bb too high if running bigger tyres.

Mk3 is my prototype for a 29plus I'm making for a tall friend in Portland (trading for a batch of Biciclista jerseys). I'm waiting for his saddle / bar / bb position to throw into CAD - will be interesting to see where the chainstay length and seat angle end.

You're running the same tyres, but are they really the same?

EG there's a huge difference in drag between the 120tpi surly Nate and the 27tpi.

It was the same set of wheels on both bikes (I swapped them over when I bought the Dude). The ICT ran 4.8" Jumbo Jim Snakeskin tyres. Again the Dude had the same (as in, just swapped from one bike to the other) tyres for some rides, but on others either the rear or both were swapped for the 4.4" version of the same Jumbo Jim snakeskin tyre. So, for a lot of the rides not only was the Dude lighter overall it had lighter wheels.

It's possible that the 4.8" JJs just roll much better than the (lighter) 4.4" version, but it seems unlikely.

Both bikes ran Surly Bud up front in the winter, but unsurprisingly I wasn't setting my fastest times in the winter.

Although there have been a lot of interesting discussions here, my own view is that it's probably quite simple. I was faster on the ICT because I was trying harder. What I don't understand is why I would consistently try a bit harder on almost every climb on one bike. My current theory is that the lively springy feel of the ICT just makes me want to push a bit more than the stiffer but more "dead" feeling Dude, but it's just a theory and I'm intrigued by the article by Jan Heine.

Other factors that could have an effect:

Chainstays: ICT 450mm Dude 439mm

Cranks: ICT 170mm Dude 175mm

Seat Angle: ICT 72.5 Dude 74

Gearing was 1x11 with a bottom gear of 26/42 on the Dude and 2x10 with a bottom gear of 22/36 on the ICT. So pretty similar with the ICT having a slightly lower bottom gear.

Effective Top Tube: ICT 630mm Dude 642mm

What tyre pressures do you use? The rolling resistance of JJs increases by over 50%, dropping from 20-8PSI   https://www.bicyclerollingresistance.com/fat-bike-reviews/schwalbe-jumbo-jim-snakeskin-2017

On mostly tarmac, I run my 4" JJs at ~25/27PSI (front/rear), with total weight of me (with kit) and Wazoo of ~91KG.

Off-road, I know you probably wouldn't want to run anything like that pressure, but an extra ~10-20% boost to your normal pressures on the Dude might transfer more of your pedalling power to moving you uphill rather than the stiff frame squashing the tyre into the terrain.

Got any Strava segment analysis links comparing the two bikes up a hill?

Effective Top Tube: ICT 630mm Dude 642mm

Why do you keep mentioning this?

If you are in the same position over the bottom bracket, what would it matter?

And different length cranks. Might make a difference of the longer one is actually too long for you to use comfortably.

GCN experiments on stiffness of frames. Sweetspot and grey area come to mind as said above. Suitability of material for one's weight and power?

FWIW I found my relatively stiff carbon hardtail was short on traction. That's where of a lot my energy went as it skipped about.

Ride the Dude, do 5 miles with a few hills and a heart rate monitor. Check your segment times.

Get home, fit the bits to the ICT and do the same, let's see.

No point basing this on "4 months ago, "

2 bikes, same day, same route, same conditions

I guess I keep mentioning top tube because I'm interested to know whether the longer bike, which I prefer descending, is having a negative effect on climbing. I'm looking to replace my trail bike this year and wondering whether to go longer. I can see that position of hips over the BB is crucial but just wonder whether being a bit more stretched out could be causing a loss of power somehow.

Doing the experiment properly would probably never work. There would always be some element of the experiment that could be criticised. As soon as you start to consciously measure the effect you get into the problem that you know which bike you are on and I wouldn't put much faith in a single run anyway. That's why I've not published any segments and have tried to avoid talking about any one climb. What I'm doing is looking at the results from a dozen different climbs then (using veloviewer) looking at the history of all my efforts, which shows time and which bike I'm on. What I like about this approach is that I wasn't thinking about which bike was faster when I did the rides. Most of the time I wasn't even thinking about the segment, just enjoying the ride. So I'm hopefully taking my bias out of the equation. Yes, conditions vary, but it's unlikely that conditions were always better on one bike compared with another. To be clear I'm not placing too much weight on any one climb. It's more that when I look at the spread of all the times with multiple efforts for each bike over multiple segments I'm not (as I'd expect) seeing a clear advantage for the lighter stiffer bike on the climbs. In fact there seems to be a clear advantage for the heavier more flexible bike, which is strange to say the least. I'm not claiming the result is definitive (or even statistically significant) but it's probably as valid as most if the other deeply flawed "experiments" that are done with bikes.

As as for tyre pressures; mine are much lower. I run 8psi in the rear and 6 (sometimes 7) psi in the front as that seems to work best for me on my trails. I might experiment a bit more with that now though.

Crank length is important to me - others, not so much.

Riding position has caught me out a few times.

Check your knee position relative to the pedal spindle and saddle hight with a tape measure.

Even a really small difference has a huge effect. Ever had a slipping seat post? You can feel yourself getting slower and your smoothness, power and cadence go to pot.

With regard to stiffness, I find a little flex helps with smoothness when tired at the end of a long day.  I have to concentrate more with  an ultra stiff frame, which in itself is tiring.

And if you really want to try an ultra stiff road frame, try one of the older bonded aluminium examples. Just solid,  incredibly distracting after a couple of hours.

That 'Planing' article is weird.
Why measure power? it seems to suggest that putting out more power is a good thing. Surely you want a frame to use less power to go the same speed. Measuring power is measuring effort isn't it? So it took more effort?

So is the conclusion that the flexier frame somehow made it easier for the rider to expend more effort?

I must be missing something.

I can see that position of hips over the BB is crucial

It's not crucial. Afterall, it's constantly changing as it depends on the gradient you're riding up.

Ignore any comments regarding knee position, saddle position etc. Spoken by people who've got no further than MBUK bike fit articles.

Very funny, but both wrong and unhelpful.

☺

It’s not crucial. Afterall, it’s constantly changing as it depends on the gradient you’re riding up

Exactly. The basic idea behind Keith Bontrager's 'KOPS - Debunking the Myth' essay, worth a read for anyone that cares enough about all this stuff.

As as for tyre pressures; mine are much lower. I run 8psi in the rear and 6 (sometimes 7) psi in the front as that seems to work best for me on my trails. I might experiment a bit more with that now though.

Don't add more air based on that rolling resistance website test. The drum they use is so smooth it's of zero use to tell you anything about how a tyre works off-road. Having a constant for all tested tyres is fair enough but it just tells you that a fat bike tyre is a better on a track/tarmac at 30psi than 6psi ... no 5hit  : )

I don't think anyone has mentioned KOPS?

Relative position is important.

In this case, the two crank lengths complicate the matter somewhat, but everyone has a seat position and crank length that is best for them.

"That ‘Planing’ article is weird."

Indeed so, but it definitely ties in with my experience. Although, that's on lightweight racing bikes which is a somewhat different kettle of fish.

The planing article is just weird. I did try googling frame flex and efficiency. I did see that Greg Lemond was a believer, apparently.

But the bold claim that the more flexible frame allows 15% more output can't be true. I mean did Sky and British Cycling really miss something that big

Bring it back to a small % then maybe. It is certainly true that when I was allowed out on a rigid titanium mountain bike (when rigid was normal) it did pedal beautifully. Boy was that bike bendy round the bottom bracket. But at the moment I can't see why a bendy bike should allow us to output more power

Because it smooths out the pedal stroke, allowing and encouraging a more efficient action?

"if you don’t think frame flex is an issue, try this: Grab your frame and pull hard on the bb, see it flex.  Now do this once a second for five minutes, reckon you’ll get tired?  You’ll have used up a noticeable amount of energy, and gone nowhere."

No, the energy does go back into the drivetrain. Losses will be negligible, just so small you could not measure it and not the reason for the OP's apparently loss of performance.

https://www.globalcyclingnetwork.com/video/are-you-faster-on-a-stiffer-bike

Anyway its all academic in the OP's can as he's stressed a few times he climbs seated, so no or minimal frame flex and the forces are all in line.

The fastest times up climbs in the TDF have been clocked on steel 'flexi' bikes. OK the riders were all doped upto the eyeballs, but they probably are today. But modern technology advances of modern bikes (stiffer and lighter than ever before) and better understanding than ever before in the science of human performance still has not delivered someone up, say Alpe D'huez any quicker than the old steel bikes of the '90's. You can't get away forth fact it is 99.9% about the engine and not the bike.

I think even seated I'm flexing the frame a fair bit. The steel bike certainty feels more "springy". It's the first thing I notice when I jump on it after riding the carbon fibre one for a while. That surprises me given how big the wheels are and the low pressures I'm running. I'd expect frame material to be largely irrelevant when it comes to the feel of a fat bike.

I can accept that frame flex might not be as bad a thing as I thought.  I've always believed that stiffness was key for climbing. Maybe the losses aren't as bad as I thought though and maybe it does smooth out the power delivery a bit. But I still can't see how I can be faster on the more flexible bike.  No slower, yes I could buy that. But faster means I'm putting out more power and I still can't see how a bit of flex is making me work harder. I suspect that's what's happening though and it's why I put "psychology" in the title. For some reason that I don't understand I think I just work harder on the ICT.

There are two climbs that I've only ever managed to get up on the rigid fat bike. Never managed either of them on any of my hardtail or full suss bikes (although I'm sure lots of fitter people have). I'd cleared both of them on the ICT, but in both cases on my first attempt (different days) on the Dude I just gave up before the top. In both cases I went back out again the following week and forced myself to ride up them, so I know I can. I'm sure it's psychological and may have nothing to do with the bike (just the was I felt on the day) but there seems to be a bit of a pattern of me just not wanting to push myself as hard on the Dude.

I don’t think anyone has mentioned KOPS?

No, but they did mention seat angle and climbing efficiency, it's all related. KOPS is based around seat angle and pedal efficiency on the flat and the way it varies in climbing is what Bontrager's article was about.

I guess I keep mentioning top tube because I’m interested to know whether the longer bike, which I prefer descending, is having a negative effect on climbing.

ETT has no bearing on how stretched out you are. Reach is the dimension you should be looking for. Given that your saddle position isn't different between the two frames.

I thought ETT was the important number when sitting down. It always used to be in my road riding days. Reach matters more when standing of course, but if I'm sitting down and the ETT is longer then surely I have to bend forwards more to reach the bars (assuming the same bar height and stem length of course).

Nope.

You position the saddle relative to the bottom bracket.

Seat tube angle is irrelevant to your position. It's also irrelevant to how much you need to bend forwards. (unless you go from one extreme to another and the range of saddle positions is compromised, which is unlikely in this case.)

It wasn't really important on road bikes either. Except for the fact that any comparably sized/frame would broadly have the same seat tube angle. Everything I've ever had (50 at least) has been between 73 and 73.5.

My current and recent mtbs range from 71 to 75. All cross country bikes.

Ett is irrelevant.

Unless you don't understand how to measure up a bike fit and transfer it from one bike to another

You’ve lost fitness. Or you’re not trying as hard as before.

OK, I get where you are coming from now. Thanks. You obviously feel that position of the saddle relative to the BB is key. I'm not sure I agree. Mind you, I spent a few years riding round on a recumbent ! I'm not going to argue the point though. You may well be right and if you can set the saddle in the same position relative to the BB on all your bikes then I can see why seat angle and ETT are irrelevant to you.

Positioning your saddle relative ONLY to the BB means all you can say is how far apart they are.  I assume we mean in terms of vertical distance above and horizontally behind?  (as some suggested up there, using gravity as a reference is arbitrary and fairly meaningless for seated pedalling efficiency (I'm guessing within at least 5-10 degrees either way - recumbent different in that they seem to have backrests to push against))

I'm not a fit expert or a racer but if I cared I'd want to position my saddle, BB and grips all relative to each other for best pedalling on a road bike (or for seated pedalling generally, I guess).  "Fixing" those 3 points relative to each other should allow for a constant level of angle of bend at your back & pelvis, that you've arrived at [s]by many painstaking hours of turbo-based power testing.[/s]

[s]I suppose you might then choose to set the flatness of your back or whatever while still in that optimised "triangle" by, say, pushing saddle forwards and grips a bit forward and lower (or saddle back and grips up&back) and then confirm that it's all optimal by extensive aero and than timed-ride testing of that position and some others just to be sure you're still correct[/s]

... by luck with a bike that you really felt comfy & were fast on

Seat tube angle is clearly relevant to this but yes it can often be "corrected for" by sliding the saddle (unless you've also got combinations of layback on the 2 seatposts that exagerrate the differences between the frames).

ETT isn't totally irrelevant as long as you accept that it also needs saddle position (layback & rails), stem length/rise, bar width/rise and fork+headtube length before it really means anything.  Most of those lengths and rises can be altered to get the fit you want, of course.

I'm a "meh" on crank length but seems it affects some people (and of course would alter the position of your saddle relative to your BB)

A Dude you say?
Have you taken to wearing a heavy cardigan and drinking white russians?

This really is getting down to mbuk level bike fitting now.

I'm out.

This really is getting down to mbuk level bike fitting now.

I’m out.

or you could be more helpful and say what you know?

We seem to have gone down a bit of a bike fitting dead end here. It was kind of fun to think about these things back in my roadie days, but I fail to see the relevance to mountain biking. I'm not interested in getting the most aerodynamic position on the bike and things like stem length, bar width and bar height are set to give me the steering feel I want (mainly for descending) based on the head angle etc. Since I was already running a 35mm stem on the ICT, moving to the longer Dude was going to give me a more stretched out climbing position unless I did things that messed up the feel I wanted on the way down.

There is far less consensus on the ideal geometry for a mountain bike and the whole point (for me) of trying different geometries is to see the effect. If I buy a bike with a steeper seat angle and a longer reach it's because I want to see the effect of being in a different position. Adjusting all my contact points to give exactly the same setup as my previous bike would make the exercise pointless (for me).

Getting back to my original point, I was interested to see whether a steeper seat angle and a more stretched out position might have been causing the slower climbing times, given that steeper seat angles are often marketed as a way to improve climbing. The fact that I could have compensated for the steeper seat angle by sliding my saddle back is true, but I didn't because I wanted to see the effect of being further forwards.