170mm & 172.5mm cranks on Audaxy bikes

[nsew]

Is it a 26” wheel bike with a lowish bottom bracket? Then yes, you’re 5mm closer to bottoming out peddling over kerbs, rough ground and cornering. If it’s a high bottom bracket and 26” you’ll be ok. Larger wheels will be fine.

[Greystoke]

It's a 26" wheel bike.
No danger of toe overlap with longer cranks and I've not hit the pedals on the floor with the existing setup... perhaps I'll not really notice any difference....

[mattheus]

5mm doesn't seem much. I have a bike with longer cranks than t'others, and I quickly stop noticing the difference after hopping on.

But I've only ever ridden day-long (or longer) rides on the "correct" cranks, and don't plan to change that (currently).

If your cranks (and/or saddle height) are already slightly off optimal, then 5mm could easily be the final straw.

[531colin]

... perhaps I'll not really notice any difference....

If this thread shows anything, it shows that some people don't like different crank lengths, and some don't notice.....the trouble is you won't know whether or not the difference in crank length will bother you until you have spent your money and fitted the different cranks (and probably a different BB bearing to go with them).

.......... why can't I buy cheap 22-32-44 170mm crankset to replace my current 28-38-48 170mm set? All I can buy is 175mm.
It's a MTB drop bar tourer.
Would I notice a difference with the longer cranks?

And added to that, assuming your current front mech. is designed for 10 tooth difference between middle and big chainring, it might not work well with 12 T difference.

Can you fit smaller chainrings to the existing chainset?

[Blondie]

I recently picked up a bike from a forum member. My attention was distracted by the series number (5603 rather than 5703 I had hoped for) to the extent that I failed to notice that the cranks on the bike I’ve just bought are 172.5mm rather than my usual 170mm. Similar questions have been asked before, typically about, say, swapping between road bike and MTB, but these bikes are very similar (the main difference being the far superior frame material of my latest acquisition).

I’m still playing about with saddle height/angle and stem length and can’t seem to find a set up I’m quite happy with. I’ll persevere, but I’m wondering if I’ll just get used to the longer cranks as I use the newer bike more often - or maybe it’s not the crank length but just a fit issue. Anyone with a similar experience? I’m 5’8” with approx 29.5” inseam.

Interestingly I am 172.5cm (5,8) with a 79cm (31ish) inseem - I have a 165cm crank arm, it's made a massive difference to my AVG speed over audax distances. I only trialled it after a bike fit explained 170mm was borderline the right size.

How much difference to your average speed?

[nomm]

I recently picked up a bike from a forum member. My attention was distracted by the series number (5603 rather than 5703 I had hoped for) to the extent that I failed to notice that the cranks on the bike I’ve just bought are 172.5mm rather than my usual 170mm. Similar questions have been asked before, typically about, say, swapping between road bike and MTB, but these bikes are very similar (the main difference being the far superior frame material of my latest acquisition).

I’m still playing about with saddle height/angle and stem length and can’t seem to find a set up I’m quite happy with. I’ll persevere, but I’m wondering if I’ll just get used to the longer cranks as I use the newer bike more often - or maybe it’s not the crank length but just a fit issue. Anyone with a similar experience? I’m 5’8” with approx 29.5” inseam.

Interestingly I am 172.5cm (5,8) with a 79cm (31ish) inseem - I have a 165cm crank arm, it's made a massive difference to my AVG speed over audax distances. I only trialled it after a bike fit explained 170mm was borderline the right size.

How much difference to your average speed?

3-5mph on 60-100+km rides, I would say I am at my avg/lower end of fitness atm

[Blondie]

Wow, a shorter crank made you that much faster. Who would have thought?

[nomm]

Wow, a shorter crank made you that much faster. Who would have thought?

I can't quite tell if you are being sarcastic, but I've compared the numbers from rides. My current set up is also heavier by 1+KG. and due to lock down I've done less riding.

Having said that I did use rollers for the first time during the Jan-March winter - but only for 30-45 min stints 1-3 times a week, maybe 3/4 weeks a month avg. But then again I was commuting less, not playing football etc

I would say it just feels less fatiguing going a bit faster, over distance - or its all in my head...or legs

[Blondie]

Not sarcasm just amazement. I would not have thought crank length made that big a difference to average speeds. But clearly the shorter cranks are allowing you to put out significantly more power through the drivetrain.

[keyboardmonkey]

Just an update that I shuffled around cranksets and put the 172.5mm cranks on another bike for the highly technical reason that they match the shiny brake calipers on that bike. I can honestly say that I can find no observable difference when switching between bikes. Thanks again for all the input, gang.