Currently running 175 XTRs on my Five Evo and they're hitting everything (its a prototype frame so I think it has a slightly lower BB than production versions). Was about to hit the button on some 165s but then Hope (and now Middleburn by the look of it) are doing the 155s... Anyone jumped that far yet and has some real life experience of 155s? Will be used for general trail riding - I'm not riding up actual mountains week in, week out - in fact nothing I often ride has proper lung busting climbs, mostly more gentle, longer ones.
I think all the current thinking is that shorter is better (admittedly I'm speaking from a roadie/gravel perspective).
https://bikepacking.com/gear/crank-length-test/
I'd be very tempted but having stockpiled bikes over the last few years and regularly rotating between 4 of them it would become an expensive business!
It will make pedaling up hills a bit harder, but if you have gear range to spare as it is then you should be fine.
It will make pedaling up hills a bit harder
Only if you're already at the limit of your gears I think? i.e. shortening cranks might just require lower gears to compensate. The experiment above seems to suggest they're climbing just as efficiently (from memory, I just skim read before I posted it this time)
It will make pedaling up hills a bit harder
Yeah, I can never get my head past the fact that with shorter length, you have less leverage and therefore are reducing your mechanical advantage. 1st day of leverage school that one.
Science innit.
Having said that, I've not read the article and if you have gear range to spare(does anyone have spare gear range?) and never find yourself at the limit of gradient, then I suppose there is no loss of advantage.
Wouldn't bother me on an eeb so much.
Yeah, gears are just ratios of torque at the BB and freehub (gross oversimplification obviously) do if you reduce crank length you just need to adjust the ratio back in your favour with the gear ratios.
This leaves you able to spin easier circles with a generally more favourable position at the hips and lower risk of pedal strike.
I think the challenge is adjusting to higher cadences.
OOH! 155mm Middleburns - while they don't actually seem to be available, that's a good thing as it means I haven't bought any. Yet.
Short cranks are the way forward. No idea why the industry has stuck to 175mm as a standard for so long.
I have just gone from 172.5mm to 175mm (Ribble's cheap GRX).
I noticed the difference. I had to drop my saddle!
I bought 155 Hopes for the eBike to reduce pedal strikes. Does that admirably, and helps being more 'spinny'. 175s on both other bikes.
Negatives:
I do notice, and miss, 'out of the saddle' long crank torque though. I can't really get my legs/knees to do that properly with wee cranks yet. Most odd.
I also found long descending, with feet 40mm closer together, absolutely f'ing knacked my knees. That has however, after 6 months, now passed. Also v odd.
YMMV, all IMHE etc etc etc
They market the 155 ones as E Bike cranks don't they? I'm not aware of anyone who's running 155's on a normal bike. I went from 175 to 165 on mine and I can't tell any real difference apart from them hitting the ground less.
Never tried 155mm cranks but I had 165mm on my last full suss bike and 175mm on my hardtail.
I didn't notice any difference in how they pedalled when swapping between the two.
They initially did the 155s for eBikes then thought why not try them on regular cranks. Turns out they're quite good
It's my next upgrade
Not tried 155s yet but have run 165s on all my MTBs for a while now. My road bike though has 175s on it and the difference is really noticeable. Not so much in terms of gearing and torque, but just comfort. I find the longer cranks much harder on my knees, hips and lower back - presumably from having my knees come up to that slightly more acute angle at the top of the pedal stroke. Overcoming the 'TDC' of the crank action feels like it puts more strain on those joints.
Properly intrigued by the idea of 155s now.
It will make pedaling up hills a bit harder
Yeah, I can never get my head past the fact that with shorter length, you have less leverage and therefore are reducing your mechanical advantage. 1st day of leverage school that one.
Science innit.
But the shorter lever is compensated for (when seated, at least) by the fact that you're not bending your legs as much. I found that I was one-to-two gears higher riding up a given bit of hill with 152mm cranks than when using 175s.
Having said that, I did notice the change when honking out the saddle, and I eventually decided 160mm was the best compromise for me - short enough to address the knee pain issues I had, but long enough to not feel too odd out of the saddle. That was on a HT; having moved to FS I would probably err on the shorter side, as I pedal sat-down much more.
The 152s are still in use on my recumbent.
“It will make pedaling up hills a bit harder”
It will mean you need to adjust your gearing but it won’t make pedalling up hills harder if your gearing range is appropriate - for many people it’ll make uphills easier and downhills better too.
I now have 165mm cranks on both my ebike and my singlespeed hardtail - and I have pretty long legs!
“Uphills harder”
If you use the same gear ratio.
If you use a smaller gear, it’ll be just as easy.
Plus, in theory at least, shorter cranks should be easier to spin to higher revs, so anything you lose in leverage you get back in revs.
I've not read all the data designed to make us adopt yet another new standard yet.
However, imagine pedaling with 125mm cranks, then 100mm cranks. 50mm cranks.
. I'm to be convinced that shorter is better...
I think it best to think of foot speed. Use the same gear at the same bike speed you'll have the same cadence and therefore with shorter cranks your pedals will moving around the path described by the cranks at a slower speed. Therefore there will be more torque to compensate to generate the same power. Want the same foot speed and torque that you had with your longer cranks and you'll need to drop a gear and increase your cadence.
I got into shorter cranks to help with a dodgy hip because they reduce the occluded angle at the top of the stroke. 5mm off your crank means your saddle needs to go up by 5mm to have the same pedal to saddle distance. At the top of your stoke your pedal is 5mm lower than it was but your saddle 5mm higher therefore opening up a 10mm lower knee in comparison to your chest. Might seem a marginal difference, but it was the difference between riding and not riding for me.
I love short cranks. I’ve always had 160 or 165 and when it's upgrade time I’ll probably go for a set of 155 Hope cranks.
martymac
Full Member
“Uphills harder”
If you use the same gear ratio.
I literally said unless he has gear range to spare.
“ I literally said unless he has gear range to spare.”
You don’t need gear range to spare - if you swap to shorter cranks you should simultaneously change to a smaller chainring, unless your bike was under-geared before.
It’s like changing wheel sizes - you want to keep the ratios of foot speed and tyre speed the same - the crank length and tyre diameter are non-shifting parts of your transmission.
Not always possible to go smaller chainring.
I'm on 28t on a couple of my MTBs already.
I went from a 32t (Oval) chainring and 175mm cranks on my old bike to a 30t chainring with 170mm cranks on my new bike.
I definitely noticed a difference when climbing at first, and had a tendency to ride it in a lower gear at a similar cadence, so slower overall.
As I've got used to it, it's not a problem any more, and I'd go down to 165mm and a 28t chainring next to reduce pedal strikes.
I think it depends a lot on fitness. The more I ride, the less I notice it. Last year, when I was riding less because of bike mechanical issues (hence the new bike), and took the new bike to the Alps after riding it once at home, I definitely felt like I was suffering on the climbs.
Cheers all. Food for thought... just don't want to shell out on 165s and wish I'd gone for 155s but then don't want to go straight to 155s and for my knees to explode 😀
Your knees will be fine with 155 unless your gearing is too high - the reduced range of movement is much easier on your joints.
How long are your legs?
I went from 175mm to 170mm then to 165mm and love them, not sure about a leap to 155mm without trying them somehow.
Yeah, i've done 175, to 170 and now 165 on all my "good" bikes. Far prefer them, both for biomechanics, leg speed and ground clearance (less of a concern on the road bikes!)
But, Just got a new big bike, and the pedal strikes are horrendous, it's still got the stock 175s on it, it's even got a higher nominal bottom bracket than my other FS, even with sag etc taken into account.
I'll be looking for some 160s come payday.
And a 28 (got a 32 on there now)