Outing myself - I'm no lover of a low bottom bracket.

Have you tried shorter cranks? What travel have you got on the front of the A9C?

It's definitely an issue on some tracks. I'm particularly thinking about deeply-carved narrow footpaths or even some doubletrack where the centre line is unrideable. I prefer short cranks in any case.

Low BBs also affect luggage carrying capacity with larger saddlebags. When I was getting Brant to lay out my B+ frame I asked him to make the BB slightly higher for this very reason.

I'll hold my hand up and admit I'm getting far more pedal strikes on my new G1 than my 10year old Helius. Luckily budget meant I just went with the SRAM cranks that came with the groupset.

The first change to the bike is going to be shorter cranks, probably 165. Will be staying away from carbon as well 😀

I definitely noticed it on my Stif Squatch hardtail, despite the shorter cranks. I think I'm getting more of an instinctive feel for technical strike-free climbing over time though. The worst was a narrow carved out path (as per above) in the Peaks near Mam Tor, which had me dabbing a lot! Luckily those are few and far between for me.
On the plus side, for trails and descents I'm feeling more 'in' the bike and berms are noticeably better.

I've come to the conclusion that I would prefer a higher BB for riding The Peak.

Same. Only so many times you can whack a crank on the side of a rutted mountain trail before you start disliking low BBs.

Low BBs suck for any bike that gets pedalled. The only reason they're so prolific is this tedious trend that bike manufacturers have been on towards making the downhill slightly easier/ faster at the expense of rideability and fun on anything not pointing down.

As I said years ago, the inevitable outcome of all this is ebikes. 🙂

Aether 9A here, so the same 40mm drop (330mm height, 289mm at sag of presumably 30%).This is my first LLS bike so nothing to compare to aside from bikes I demoed.

Didn't have an issue per se, just the odd pedal ding on trailside obstacles when descending or pressing the bike up with the base of the pedal when climbing. Many ruts, I figured say 10mm higher still wouldn't be enough. Well come to think of it, it might have been a contributing factor to when I nearly died. I switched to 165mm cranks out of curiosity and it's better. I didn't notice any handling disadvantage.

I have my suspension setup quite poppy trail-centery oriented, with 27% shock sag. If I set it up more for natural rides, I'd have to compromise between comfort/traction and pedal clearance.

It's interesting to see what BB drop some other bikes I think of as designed for particular terrain have:
Bird AM9 - 30mm
Cotic FlareMAX - 32mm
Cotic Jeht - 27mm
Deviate Highlander - 28mm
Ibis Ripmo - 30mm
Pace RC295 - 46mm (just including this one as an outlier I remember)

It's not bothering me, but my next bike will have a drop closer to 30mm.

The LLS thing is definitely better on steeper downhill/enduro trails.

Maybe Hardtails are less effected as I don't really get many on my Hello Dave. So maybe more of a full Sus issue?

On a full Sus bike, I think suspension setup can definitely be a contributor with pedal strikes.
Maybe try adding a token or two to ramp up the suspension towards the end of the stroke.
I think a more linear suspension stroke would result in more pedal strike as the suspension compresses. So the token solution should help counter this.
Or how about installing a angleset headset to steepen the head angle and lift the bike a bit?

Obviously this will affect the overall feel of the bike which is maybe not what you want.

Could it be that you're more of a trail bike rider than an enduro type bike rider?

I've always disliked a low bottom bracket but then I've always pretty much ridden rocky techy stuff in the peak. The last bike I had where I was happy with the bottom bracket height was a Turner 6 Pack back in 2005. 6" of travel on the back end with 26" wheels and a 14" bottom bracket height.

How does that compare to modern stuff? I think it's about -15mm on a modern 29er

I like low BB’s but not too low!

The bb height is more affected by sag than any other aspect of bike geometry. There’s a lot more to it than the number on the geometry chart - there’s also the amount of suspension travel, the range of sag the bike works best at, the anti-squat and how you prefer the suspension to feel.

My 29” full-sus has 27mm drop but I’m running 10mm more fork travel, so that changes it to 24mm drop static. But then I run about 25% sag front and 35% sag rear on 160/157mm travel, which is about 47mm more BB drop sagged, so about 71mm BB drop. On a 29x2.3 tyre that puts me at about 300mm BB height.

My 29” hardtail has 64mm BB drop but I’m running 20mm more fork travel so that’s about 58mm drop static. 160mm fork sagged 25% drops the BB about 13mm giving me about 71mm BB drop again, and about 300mm BB height.

My previous hardtail was about 6mm lower and running cranks 5mm longer (I’m on 165mm on both bikes now). It wasn’t so much the pedal strikes as the chainring clearance on teetery things or the clearance in ruts/gulleys.

Very low BB heights are awesome on groomed trails and often great on natural trails that are steep enough that you don’t need to pedal. Also I swear too low a BB makes the back of a hardtail harsher because of how your feet pull the rear wheel into bumps.

Just checked out the geometry chart for my Hello Dave and it's BB drop is 50mm 😱

Checked my Scalpel SE and its 32mm stock, I have since added an angleset to slacken the H/A so will be lower now but not sure exactly without measuring.

I always felt that the Scalpel felt a bit tall when riding which the angleset has now countered. So maybe 35-40mm BB drop might be the best compromise for general trail riding?

Some interesting reading on bike geometry here ....

https://www.singletracks.com/mtb-gear/quick-question-how-does-bottom-bracket-height-affect-my-mountain-bikes-handling/

Could it be that you’re more of a trail bike rider than an enduro type bike rider?

Oh, very much so - but then again so is my bike (Bird Aether 9c). To be fair when it was first launched it was marketed as 'trail centre specific' or words to that effect and that a more all day natural bike would have had longer chainstays and higher BB and hints that such a bike might be on the drawing board. I'm guessing there are no plans for that bike to be made at the moments and the Aether 9c is now marketed as more of a do it all trail bike....although nothing has changed about it in a physical sense.

Yes I'm sure a few tweaks would improve it (for me). I could go from 170 to 165 cranks and I could play around with the shock. I use(d) a shockwiz to set it up, which did involve reducing the pressure from my own attempts which will have compounded the issue. It's clearly better than me at setting up bikes as it does feel better for the changes it suggested. And it's not like I went from no pedal strikes to lots after taking its advice. A token is not a bad idea - but my all seeing shockwiz master might not approve!

My OP was less of a cry for help sorting my current bike. Tweak it or leave it - it's staying for the foreseeable. It was more a comment that the low bit of LLS might be what a lot of us 'think' we might want (or are told we want) but in reality for (some) amateur level riders, in the real world which is not all downhill it might be a hindrance not a benefit.

“ Just checked out the geometry chart for my Hello Dave and it’s BB drop is 50mm 😱”

That’s quite a high BB for a 29” hardtail nowadays.

To compare BB heights between different travel bikes (with the same size wheels), you need to add about a quarter of the rear travel to the BB drop.

So my full-sus and hardtail have the same size wheels and same size forks and the same BB height at sag - but the former has 24mm BB drop and the latter 58mm BB drop.

Definitely of the low BB camp.

Saracen Zenith LSL is 70mm drop
Marino custom rigid SS is 74mm drop
Sentinel is 29mm static, but sagged would be approx 73/4 I guess?

Just checked out the geometry chart for my Hello Dave and it’s BB drop is 50mm 😱

Those are rookie numbers.

- Rå .410 rider - static 80mm BB drop.

Pedal strikes haven’t been an issue, but then there aren’t an abundance of rocky climbs round ‘ere. Am running 165 cranks though. Feels great.

Bird AM9 – 30mm
Cotic FlareMAX – 32mm
Cotic Jeht – 27mm

these bikes all have different amounts of rear travel. the more travel you have the more bb drop that you need to accommodate the travel for a given amount of bb height at full compression.

i moved from 175mm to 165. really helped with pedal clearance. it was a shame to remove the 175 crank, i’d had it for a long time. first generation xt hollow tech 2, and it was silver.

edit: i recall that cotic, even in the longshot era have taller BB’s than other bikes. i don’t know if their suspension models all have the same bb drop at compression or at a given sag.

edit edit: starling have recently revised their geo. the bb drop was reduced, but then the travel increased on the murmur. no idea if the reduction in bb drop was to alter the handling or to accommodate the extra travel (or if i have the wrong end of the stick and that i’m talking total bollocks - as opposed to semi-bollocks which is my usual position)

the more travel you have the more bb drop that you need to accommodate the travel for a given amount of bb height at full compression.

I think you've got that the wrong way around. Full on downhil rigs have less unsagged BB drop than most 'progressive' trail bikes. Perhaps you meant BB height not BB drop.

I read the Starling Bikes blog about why low BB are not responsible for pedal strikes. . Interesting. As I said in my OP I suspected technique has a big part to play in why I get them. But I'm really talking about when pedalling is unavoidable - like a techy uphill or a deeply rutted track/path. If it was merely a matter of keeping your cranks flat and pumping a bit someone might have to have a word with gravity for me as it's not playing ball.

I think you’ve got that the wrong way around. Full on downhil rigs have less unsagged BB drop

i’m not sure about dh bikes, but i do know that i have completely confused myself! i’m my defence it’s the morning where i live 😅 but less bb drop equals more bb height.

Starling... not responsible, no, but a contributing factor to making them more likely.

To compare BB heights between different travel bikes (with the same size wheels), you need to add about a quarter of the rear travel to the BB drop.

Forgot about that! Adding 30% of the travel matches Bird's spec sheet quite closely, so I'll apply that to some of the others as they don't quote sagged geometry:

Bird Aether 9 - 81mm at sag (spec sheet)
Bird AM9 - 78mm at sag (spec sheet)
Cotic FlareMAX – 70mm at sag
Cotic Jeht – 70mm at sag
Deviate Highlander – 70mm at sag

I remember Pole did a bike with 3mm BB drop (static).

twistedpencil

I’ll hold my hand up and admit I’m getting far more pedal strikes on my new G1 than my 10year old Helius.

You can pick your BB height on the G1, a set of seatstay mutators will cost you less than new cranks.

Cheers @honourablegeorge

I really should have known that shouldn't I?!  Looking to mullet the bike for the Alps, so an email to Marcus to see what he suggests might be in order 😀

Cool, you'd be changing the same part for mulleting it, as you need higher bb for smaller wheel (and maybe looking to shorten chainstay also,those are more expensive)... they have a bunch of different options. My frame came with a mullet chips, not tried it yet. Marcel will sort you out.

One of the reasons I often keep my shock set to the firmest setting, on the compression damping, whilst pedalling, is that it increases the bottom bracket height.

FYI my bike has 40mm off bottom bracket drop and 130mm of rear travel. It could Probably do with some tokens

Short cranks 165mm, skinny pedals, 10mm longer fork, slightly reduced shock sag and still think my BB is a tad low. You're far from alone.

“It could Probably do with some tokens”

Generally adding tokens lowers the sagged BB height because it allows you to run more sag without the bike bottoming out too hard. Fewer tokens tends to both decrease sag and increase midstroke support, both of which tend to raise the sagged BB height and the static ride height.

Regarding pedalling, if anti-squat is sufficiently far enough above 100% (how far will will depend on your height and weight and pedalling style), the rear end jacks itself up as you pedal. If anti-squat is too low the BB will squat as you pedal, costing you pedal clearance. Swapping to a smaller chainring will increase anti-squat (and chainring clearance) so it’s a win-win if your BB feels too low.

How many of the pedal strike afflicted are running big ol' platform pedals?

Seems less of an issue for me on my (often complained about for a low BB Stumpy) but I use relatively low profile SPDs...

For a couple of years now I've wondered how LLS is too LLS...
I'm of the view that LLS is generally a good thing, but too much, like many things in life, can ruin things...

Hmmm...

Banshee state the bottom bracket drop for a V3.2 Rune is 10mm in low or 2mm in the high setting with a 170mm fork.

iI've got a 180mm fork & run th drop out chips in the high setting, so that should be around 0mm BB drop. A quick measure with a bit of string confirms it.

My V2 Spitfire had a horribly low BB judging by the pedal strikes I got on that.

Nice little tool here for playing around with changes to your bike - unsurprisingly it's not possible to input it for different Geometron mutators, but it does most other things: https://www.bike-stats.de/

Not sure what counts as low these days. I'm happy with a 335mm BB height on my 155 rear travel 29er Geometron with 170 cranks. I was unsure about trying 165 cranks but the Hopes I use claim to give extra clearance due to the design of the crank ends (and I can see what they mean).

I've got a longer shock and 650b rear wheel to mullet it and add 20mm more rear travel. However, the static BB height only increases by 6mm despite 20mm more rear travel. A 340ish BB height for 175mm rear travel sounds low to me...

Paul Aston has been testing much higher bottom bracket heights on his custom bikes. IIRC he says that low bottom brackets helped handling when bikes were short and steep, now they're getting much longer (front and rear centre) and slacker, there's no longer the need for such low bb's to compensate for poor geometry in other areas.

MTB geometry trends giveth, and MTB geometry trends taketh away.

No sooner had they figured out that anyone over 5ft10 didn't want a 20" frame with a saddle over the rear wheel and a misally 1" more reach than the medium. Than they crippled us with short cranks.

On a related note: My new bike has a nicely on trend seat angle (and it's offset forward to clear the rear wheel), but if you do accidentally sit down on the 170mm dropped saddle you can't push up again because your hip/knee/ankle/pedal mechanics are inverted, makes it more of a very weak kicking motion with your quad, rather than a push with your glute. So the trend to have ever shorter seatubes and longer droppers also has a practical limit that's definitely been exceeded.

How many of the pedal strike afflicted are running big ol’ platform pedals?

I once smashed a Time Atac so hard it broke the binding, faceplanting off the subsequent drop-off left me unable to ride for nearly 3 years!

I think the bigger advantage with SPD's is the lack of pins means they tend to get a glancing blow and then slide better, and (unless it's that one unlucky occasion) your feet remain attached and the bike just lifts up and hops a bit as it's unweighted. Whereas bouncing a flat pedal off something tends to bounce your foot off. I probably smash both into stuff equally, it's just lower consequence on SPD's.

Maybe Hardtails are less effected as I don’t really get many on my Hello Dave. So maybe more of a full Sus issue?

As above, adding tokens will actually lower the BB on pedaling sections.

The FS bit is sort of true though, hardtails have always had a BB height in the region of 275-300mm, which in 29er terms is about -65 to -85 (the Dave isn't actually all that low, which is probably a good thing as if it was it would be even more stable and reluctant to turn). It's also consistent. I can ride upto something and know if I've got clearance. Whereas on the FS if I climb upto a step it'll look fine, then I'll unweight the fork over it (which means compressing the rear), then the BB is now 2" lower than I'm imagining just as I'm pushing down hardest on the pedal.

Nothing to do with how gnarr you are, if anything the FS (and the more travel it has) forces you to be a little more passive because to make it without striking the pedal you need to just adopt a steady cadence and let the bike soak up the step rather than bouncing the bike up and using technique rather than fitness like you would a hardtail.

there's no reason that lower bbs actually "improve" handling. Counterintuitively they make a bike less stable than a higher bb. Thing is, lots of folks ride trails where pedal strikes are a complete non-issue, and as its a trend I guess manufacturers will follow it

I definitely have more pedal strikes when I switch to flats. More the width rather than the height/depth that seems to be the issue for me.

Paul Aston has been testing much higher bottom bracket heights on his custom bikes. IIRC he says that low bottom brackets helped handling when bikes were short and steep, now they’re getting much longer (front and rear centre) and slacker, there’s no longer the need for such low bb’s to compensate for poor geometry in other areas.

that seems to match the logic that pole are applying on their Voima ebike which is seriously long and has a very high BB (and is also the ugliest bike I have ever seen).

I'm happy with a full suss BB height of around 335mm (unsagged) - dont think I'd want it much lower.

I'm in the same boat but Im on an Aether7, had an Aeris before and never had as many pedal strikes as the 7. Not sure if was a mind thing but changed shorter cranks and thinner pedals (flats) ,increased front travel to 150mm but have not rode the bike since it threw me out the front door last June. Big Pedal strike and out the front I went, rupturing elbow tendons which I'm still having issues with.. Just started back now but on a 29er hardtail. I'm not keen on getting back on the Aether for fear of more of the same.

This thread is really missing Geex with his "if you pedal strike you are weak and have no talent / learn to ratchet" world view.

This thread is really missing Geex with his “if you pedal strike you are weak and have no talent / learn to ratchet” world view.

Didn't he......

As I said years ago, the inevitable outcome of all this is ebikes. 🙂

“there’s no reason that lower bbs actually “improve” handling. Counterintuitively they make a bike less stable than a higher bb.”

I’ve read quite a few claims of this over the years and none of them make any convincing arguments with solid maths behind them. If you extrapolate the lowering of BBS to the point that your feet are barely above the contact patch then you can see that your destabilising forces exert barely any torque to lean the bike.

I had a bike with very adjustable geometry and I consistently found that lower BB heights were more stable.

I think the high bb improving handling thing is based to be analogous to a pendulum, like picturing balancing a broom on your fingertip....Long broom is harder to keep in one spot, but it's movements are slower, so more opportunity to micro-adjust and correct, plus the micro-adjustments will be naturally diluted, meaning it's harder to over-correct and mess it up. Now balance a much shorter broom with the same mass in the head on your finger tip, it should be inherently more stable, it probably is, but unless it's perfectly balanced, it's going to move quickly making correction back to balance more challenging. It's a relative speed of movement thing to me, something might be more unstable, but if it's movements are slower, hence easier to correct, it will feel more "stable", where what is probably meant is "sense of safety through predictability",

Higher BB will make it easier to initiate a lean and probably better for carving open turns a LLS bike is good for since it will feel more settled. Maybe that's it, higher BB giving you a sense of more stability, but is it actually stability? Isn't it predictability, can't these be different things?

Same analogy applies to manuals and can be quite clearly be felt, short CS is easier to get up but requires more management, a longer chainstay is harder to get up, but requires less management.

I'm not a physicist and I haven't got time to read every post here, but in my experience low BBs clearly = stuck to the ground-ness and higher BBs = easy to move around-ness.

Is that the same as stability or not?

Since bikes got longer, I've not been such a stickler for a low BB, but I still don't want a high one. And maybe the average has got lower anyway?

The balancing a broom analogy is probably pretty close. The trouble when things get really low is the bike doesn't seem to want to move at all. So if you find yourself off the line you want to be on the amount of counter steer required to bring it back is exponentially higher than it would be.

Well come to think of it, it might have been a contributing factor to when I nearly died

have not rode the bike since it threw me out the front door last June. Big Pedal strike and out the front I went, rupturing elbow tendons which I’m still having issues with

Damn those Bird Aethers and their low BBs!

I found pedals are having much bigger impact on pedal strikes - latest super wide flats, vs say trad little m520. Only time been an issue on my Birds has been when on flats, don't recall any strikes when running spds.

Probably noticed more as only started to use flats when I got my first Bird,  had been a solid SPD user since they came out.

“ I think the high bb improving handling thing is based to be analogous to a pendulum, like picturing balancing a broom on your fingertip”

That’s the analogy I’ve heard but having tried to look at it lots of different ways with my physics brain it still doesn’t stack up. If you want a better analogy that actually works, make some stilts with the foot pegs at different heights. You’ll quickly come to realise that the higher your feet are off the ground, the harder it is to balance on the stilts.

The only vaguely valid argument claiming high BB’s increase stability is the rather backwards approach that a less stable bike is more responsive to rider input and therefore easier to stabilise if it’s in an unstable state. Similar to the argument that less slack bikes handle better because they’re more responsive.

Thankfully the MTB world has realised that more stable is often better so we’re now riding things shaped more like motocross bikes and less like road bikes.

The bb height is more affected by sag than any other aspect of bike geometry

&

…pedals are having much bigger impact on pedal strikes – latest super wide flats, vs say trad little m520

There’s the answer 👆

I have a Cotic Jeht & an Orange Stage Evo. It’s have the same length cranks & very similar size flat pedals etc. The Jeht has a BB drop of 27mm whereas the Stage evo is quoted as 50mm. Static BB height on the Cotic is about 34.5cm whereas the Orange is 32cm

I have no more pedal strikes with the Orange than the Cotic.

The reason I think sag & pedals are the main reason is because of the sheer number of riders I see with waaaaaay too soft rear suspension (especially e-bikes). I reckon most of the rider is see must be running in excess of 50% sag. It’s amazing; I think these people must buy their bike & then don’t touch it from the moment they’ve walked out the shop door.

I rode SPDs for years & returned to flats about 10 years ago. What I noticed is that flats had not only become much thinner, the platform size felt like it had virtually doubled (I used to ride Shimano DX bmx pedals & DMR v10 & now have Hope & Burgtec flats). Funnily enough, the only time I was conscious of pedals strikes was when I returned to flats.

Now I’m not saying that this is the case with absolutely everyone, but my personal experience echoes those above who feel it isn’t BB height that cause pedal strike.