[Closed] Are 29ers worse on slow climbs?

Does the wheel size define all the features of the bike?

Is it actually a fact that at a given speed 29ers are accelerating yet at the same speed a 26" bike isn't?

You'd need to have otherwise identical bikes to even begin to assess this. Once again a kitten had to die needlessly. 🙄

I can see where you're coming from, certainly with the idea that every pedal stroke is an acceleration, but have you considered gearing too?

Especially for you 😉

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I think it can be, especially with heavier wheelsets/tyres- the reasoning seems sound too, once you get down to stumbling speed. I remember toiling a demo Gyro 29 up the fire road at fort william to the wall ride, the whyte 26er felt much easier despite slower tyres. In fact my 224 felt pretty similiar to the gyro! But riding the same bike faster up a hill felt easier than riding the other bikes faster.

(I'm ruling out gearing because I was selecting the gear I wanted in each case. Except on the 224 when I wanted to change down about 8 gears)

johnnystorm - Member

Is it actually a fact that at a given speed 29ers are accelerating yet at the same speed a 26" bike isn't?

Strange question; that's not what he's suggesting

and the fact that, at very low speeds, every pedal stroke is effectively an acceleration.

Isn't it?

No

I'd agree with Mostly. On smooth climbs such as a fire road I just spin along with no noticable difference. On rougher terrain the bonus of the wheels rolling over lumps and bumps easier more then makes up for any sluggishness. I really notice 26" getting stalled on rocks and roots after spending time on 29ers.

johnnystorm - Member

Isn't it?

Nope. Just that the impact of having to constantly "re-accelerate" wheels is going to increase with wheel size and weight.

Though, at the same time a bigger wheel should have more momentum too. But also more wind resistance. But it'd certainly explain the way they felt to me

Either lots of people are in a bad mood (what with it being Monday) or I did a crap job of explaining what I meant (or a bit of both), but thanks for the comments.

I remember toiling a demo Gyro 29 up the fire road at fort william to the wall ride, the whyte 26er felt much easier despite slower tyres. In fact my 224 felt pretty similiar to the gyro! But riding the same bike faster up a hill felt easier than riding the other bikes faster.

Yes, that's exactly what I was trying to get at. If I can keep on top of the 29er then it skips along very nicely, but once I'm spent it seems to be more of a struggle.

Isn't it?

I think.

Probably not ridden my 29er enough to comment, but I think the higher BB on my 29er occasionally causes me a little more wobble when going slowly.

he said every pedal stroke is acceleration (which it is afaik, pedalling up hill you are constantly accelerating) combined with the extra inertia of a 29er means the same effect is felt more on the 29er, no one said you didn't get it on a 26er.

I think.

You think correctly, I think 🙂

The point about the advantages of the bigger wheel on rougher terrain is valid and Northwind's comment about the Gyro has reminded me of my own experiences testing one of these.

There is a short but steep and rocky section on one of my rides that pretty much always defeats me. In fact I've only got up it once and that was when I was testing the Gyro. I came into it with a good bit of speed and just got up it without really thinking. I must have tried it dozens of times since and while I've come close on a few occasions, I've still never repeated the feat.

That one short climb was almost enough to make me buy the Gyro. The reason I didn't has a lot to do with the fact that I failed to get up a long drag that I can usually manage. This is a section that takes anything from 17-20 minutes most days with an average speed below 5mph. Truth be told I often get to the top feeling like death and have given up on more than one occasion, but it just felt even more painful on the Gyro than I expected. But, of course, that may have nothing to do with the size of the wheels, which is why I wanted to hear some other peoples' experiences.

OP I think you're confusing angular acceleration with gravity. Climbing is effectively acceleration against gravity, but the effect of a 29er wheel's extra weight is marginal at best in the context of bike+rider weight. Inertia won't be coming into it unless you are accelerating relative to the ground, which in your scenario sounds unlikely.

What you might be feeling is the effect - due to larger wheels - of riding 12% further per crank revolution compared to a 26er, assuming your gearing is not 29er specific?

edit: I should mention I have a 29er, but do run a 28t ring to compensate for the wheels, as opposed to say a 30t or 32t.

OP I think you're confusing angular acceleration with gravity. Climbing is effectively acceleration against gravity, but the effect of a 29er wheel's extra weight is marginal at best in the context of bike+rider weight. Inertia won't be coming into it unless you are accelerating relative to the ground, which in your scenario sounds unlikely.

Hmmm, that's a very good point.

I don't think it's gearing. It might have been with the demo Gyro, but I've fitted a 22T granny to my own 29er to give basically the same bottom gear as the 26 (with its 24T granny) and I'm still feeling the same. Maybe it's all just in my head 🙂

Based on the evidence in this thread from Northwind and Roverpig might I suggest it be re-titled as "Are Orange Gyros worse on slow climbs?" 😉

I've fitted a 22T granny to my own 29er to give basically the same bottom gear as the 26 (with its 24T granny)

Are you sure? Standard 26er granny is 22t.

Are you sure? Standard 26er granny is 22t.

Anyway the bike as a package makes more of a difference to me.

i dunno, but i definitely needed the 30t on my 1x 10 29er rather than the 34t i ran on my 26er on local climbs (swinley, surrey hills etc)

No matter what wheel size you ride. "once your spent" at the end of a big day riding is always harder.
Ride more to get fitter and eat more when your out riding.

last 2 doubles I had were 24 or 26 on any bike

Just checked CRC and you're right. Guess I'm still stuck in a converted triple mindset. 😳

Are you sure? Standard 26er granny is 22t.

Nothing's been standard for years as far as gearing goes!

[quote=roverpig ]I put this down to the higher inertia of the larger wheel and the fact that, at very low speeds, every pedal stroke is effectively an acceleration.

A couple of misconceptions on this thread. Firstly the suggestion that climbing is accelerating against gravity - it isn't (I don't think you were suggesting that, but somebody else did).

Yes, you accelerate and decelerate every pedal stroke, but the effect of larger wheels on this is very small - say a 500g rim and a 750g tyre for 2.5kg total rotating weight. 29er wheels are ~10% bigger, hence 250g more rotating weight - in acceleration terms this is equivalent to 500g extra static weight. Yet you and your bike probably weigh 90kg in total, so 500g is only 0.6% extra, and you'd only accelerate 0.6% slower.

The thing is though, accelerating slower is actually an advantage when pedalling at low speeds on a climb, as you also decelerate slower, so the minimum speed will be a little higher with the bigger wheel!

T'was me. A mere over-simplification to try and get the point across. Acceleration = rate of change of velocity. Gravity wants to accelerate you down, so you need to more than overcome it to climb, that's all.

Talking of misconceptions, 29er wheel/tyres generally aren't anywhere near 10% 'bigger' (assume you meant they have more mass).

Also my pedal technique is awsum so I don't accel/decel every stroke. I just waft majestically upwards.

the effect of larger wheels on this is very small - say a 500g rim and a 750g tyre for 2.5kg total rotating weight. 29er wheels are ~10% bigger, hence 250g more rotating weight - in acceleration terms this is equivalent to 500g extra static weight

Thanks. Do you have to factor in the larger radius as well? No you don't do you? It's a long time since I did this stuff but I seem to remember that the lower angular velocity cancels the higher moment of inertia so the angular energy term just looks like the linear energy term, hence your factor of two when considering the effect of wheel weight, right?

Either way, I take your point, the total effect is not going to be more than ~1% which is probably below what any of us could actually detect out on a real trail (with variable conditions, gradient, weather fitness etc).

Guess it's all in my head then 🙂

Assuming you're traveling up the hill at the same speed you don't have to accelerate the wheel as much as the wheel rpm is less, coupled with the negligable extra weight I'd imagine the net benefit is in flavour of the 29er. But that's all academic. It's a while since I've ridden a 26er now but can't recall the move to a 29er made slow climbs any tricker when I moved over. One thing is for sure, they're significantly better in deep mud.

[quote=Rockplough ]Talking of misconceptions, 29er wheel/tyres generally aren't anywhere near 10% 'bigger' (assume you meant they have more mass).

~10% larger diamater, ~10% larger circumference, hence ~10% more mass

A 26" rim is 559 bead seat diameter, a 29" wheel 622, which is about 11% bigger. Fit a 2.25 tyre to each the outer diameters are ~673 and ~736, so the 29er is about 9% bigger in total. ~10% bigger seems a fair approximation.

Ach you know what. I was going to say I'd done some digging on this before buying my 29er and it was more like 5%, but then I was comparing to 650b.

To answer the OPs question with a non technical assessment from my experience between my 29er hardtail on Nobby Nics and 26" Cove Stiffee up exactly the same climb on Conti RQs is it sure felt easier on the 26er! Both bkes weigh near as dammit the same ie within a few pounds of each other so it's not overall bike weight (the Coves a little heavier) I swear it's the wheel inertia of the wagon wheels. I like the 29er for flattish XC rides but still way more prefer 26" all round....

all this is making it sound like 650b is the perfect compromise !!!!!!!!!!!!

It's making it sound like people making excuses for tiredness, good day / bad day , justifying a bike / everything based on some kind of semi-scientific thought processes.

Buy the bike you want / like, ride said bike etc

From personal experience solely of my 29er, I will go with the ability to roll over stuff vs the fact that it's bottom gear is significantly higher than anything on my 26ers. It is good for maintaining speed better up a hill if you hit it hard at the bottom and get out of the saddle to "hoof" it.

If you are an efficient pedaller who pedals circles then you will keep moving at the same speed so no slowing down or speeding up = no acceleration . If , on the other hand ,you just stomp on one pedal after the other you will have a very inefficient pedal stroke and will be constantly accelerating and decelerating during the pedal stroke .

Yeah, been talking about how slow I find them from very slow speeds for years. Hence finally giving it one last go with light wheels along with light non-tubeless tyres, only to find that I like the acceleration from very slow speeds on silly climbs far more on my 26" wheels. I've mentioned before about putting short bursts in from near standing starts to get up over some bigger rocky stuff on climbs and for the time being, I'll stick with smaller wheels.

It is good for maintaining speed better up a hill if you hit it hard at the bottom and get out of the saddle to "hoof" it.

[quote=martinxyz ]I like the acceleration from very slow speeds on silly climbs far more on my 26" wheels.

You can detect <1% difference? 😯

I've mentioned before about putting short bursts in from near standing starts to get up over some bigger rocky stuff on climbs and for the time being, I'll stick with smaller wheels.

I've ridden a few bikes from all wheel sizes and TBH the whole 29r is 26 is etc. is not that useful, from what I've seen & ridden the complete package makes more of a difference than the wheel size, my 29r is better climbing even over the slow & rocky stuff due to is being more of an XC bike than my 26" bike and a hell of a lot better than my 26" DH bike.

It kind of goes back to the bit where it's really hard to tell how a bike rides from a bit of paper.

The only difference I can really notice between 26 and 29 inch wheels is the pivot point of the front axle.

Didn't that bikeradar test prove that 29ers are just better at everything?

Are they better at being fun?

The only difference I can really notice between 26 and 29 inch wheels is the pivot point of the front axle.

[quote=Stevet1 ]Are they better at being fun?

I don't have a formula for that 🙁

Do you have to factor in the larger radius as well?

Yes. At a factor^2.

I think i did the calc before, think it came out along the lines of a 29er wheel having a 25% (from memory, could be a little out) larger moment of inertia than a 26" wheel. So in a very naive way, any mass you have in the rim/tyre area, feels like 25% more on a 29er when accelerating per unit mass.

An example, take a 400g 29er rim, it would take as much effort to spin up as a 500g 26er rim, from and to the same angular velocities.

But then you have to factor in the fact the larger diameter of a 29er gives a larger linear velocity (rolling speed) per unit of angular velocity vs a 26" wheel, ie a 29er wheel will be rotating slower than a 26 at the same rolling speed, therefore you don't have to angularly accelerate a 29er wheel as much as a 26 to get from/to the same rolling speed. I have a feeling this will cancel out a majority of that 25% figure i stated above.

I think it actually does just come down to the fact a 29er wheel is simply heavier cos it's bigger, i think someone else did some mass stuff as a proportion of rider weight, it makes naff all difference. The 29" wheel size isn't the cause.

completely subjective non-scientific input from someone who rode 29er exclusively for 18 months and recently tried 26 wheels again (after riding them for 20+ years previously).

I stand up more climbing on the 29er as each pedal stroke really seems to drag me up more than the 26er - it is noticeable. On the smaller wheels I will tend to focus more on smoothing out pedal strokes from the saddle. Perversely I use higher gears on the big bike almost never using the small chainring. My local training loop is dispatched in 10 minutes less on the 29er. But I really have to wrestle the 29er about and doing manuals is just took much hard work, the 26 bikes feel zippier and I am building a new one to make the most of this trait.

I only ride hardtails on flats and have to climb pretty steep hills on every ride locally. I also don't have lungs like Indurain but I do have legs like Hoy - well not quite, but I am sure physiology and technique play a part in the experience too. I.E another random could come along on the same bikes and same trails and find it completely different.

I just realized that's a long winded way of just repeating what has already been said - sod the physics and the rhetoric.

I have a feeling this will cancel out a majority of that 25% figure i stated above.

Yes, I think it cancels out exactly (if I'm remembering this correctly), so the energy required to accelerate a wheel up to some velocity is just the mass of the wheel multiplied by the square of the velocity and is independent of radius. The energy required to accelerate all the non-rotating bits to the same velocity is 1/2 mass times velocity squared of course, hence the rule of thumb that rotating mass is twice as important as the stuff that doesn't rotate.

Well, that's how I remember it anyway. Either way the difference between a 26 and a 29 inch wheel is probably below what any of us could detect.

Perversely I use higher gears on the big bike almost never using the small chainring.