Just purchased new s-ram groupset bargain price so was limited to 170mm crank size. Not been a problem riding new bike but have had 165mm cranks on previous bikes .Currently have a Tifosi cx trake bike which i use on road with a 165mm Miche Primato set-up. Dose 5mm make a difference to riding ? I know about the bb height issue from track to road so small is better for track conversions to prevent pedal strike plus if you ride a small size frame then small is better for strike . 165 BETTER SPINNING 170 FASTER ?
165mm or 170mm chainset ????
- Thread starter hatch69
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GrasB
Veteran
- Location
- Nr Cambridge
If you go for longer cranks your power band moves in terms of rpm the following table shows this -
My optimal power range is 1.8-2.3m/s based on real word data taken on 160, 165, 172.5 & 175mm cranks - the rpm changes but the power production doesn't. So you just increase the rpm a bit more to produce the same power, any half decent rider will automatically settle on the same peddle velocity after an adaption period. The only thing is you might find you want to jump from a 12-27t cassette to an 11-26t.
My optimal power range is 1.8-2.3m/s based on real word data taken on 160, 165, 172.5 & 175mm cranks - the rpm changes but the power production doesn't. So you just increase the rpm a bit more to produce the same power, any half decent rider will automatically settle on the same peddle velocity after an adaption period. The only thing is you might find you want to jump from a 12-27t cassette to an 11-26t.
HJ
Cycling in Scotland
- Location
- Auld Reekie
This topic has been moved to Know How by the admin team.
If you go for longer cranks your power band moves in terms of rpm the following table shows this -
My optimal power range is 1.8-2.3m/s based on real word data taken on 160, 165, 172.5 & 175mm cranks - the rpm changes but the power production doesn't. So you just increase the rpm a bit more to produce the same power, any half decent rider will automatically settle on the same peddle velocity after an adaption period. The only thing is you might find you want to jump from a 12-27t cassette to an 11-26t.
Felt no change with the 170mm cranks . The chart baffles me not clued up on this type of data ! My cassette is 11- 26 so all been well will not upgrade chainset till next year . Would like to try 160mm cranks but the majority of major brands are limited in this regard ! Thanks for info 
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GrasB
Veteran
- Location
- Nr Cambridge
I bet your legs have noticed. If you have a trip computer that records cadence you'll see a slight trend towards a lower cadence over time. But just ride unless you're having problems with them.Felt no change with the 170mm cranks . The chart baffles me not clued up on this type of data ! My cassette is 11- 26 so all been well will not upgrade chainset till next year . Would like to try 160mm cranks but the majority of major brands are limited in this regard ! Thanks for info
02GF74
Über Member
all the chart is saying that to maintain same pedal speed, you need to pedal faster on sorter cranks, or pedal slower using longer ones.
imagine 3 cars driving at 30 mph on a 3 lane roundabout - the lanes represent crank length.
as they are all going same speed, 30 mph, the car in the inner lane makes more laps, in say, a minute than the other two, likewise the car in the middle lane makes more laps than the one in the outer lane. laps per minute equate to rpm.
simples.
now back to bike. on the road there will be a pedalling rate (cadence) that is optimum for power output for any given cyclist - tall and heavily built cyclists (sprinters)will have a lower cadence than smaller and or spindly built cyclist (climbers). this is for two reason - for the same power output, the heavier cyclist can get that at lower rpm plus being heavier, they are not going to be able to move their legs as faster as a lighter legged cyclists. there is more to it thant that but that is the gist of it.
D
Deleted member 1258
Guest
I have 165's on the fixed and 172.5 on the geared bike, when I'm riding they don't feel any different. What the 165's do on the fixed is make spinning down hill easier, I started with 170's on the fixed and the only difference I can notice between the two is the easier descending. At 5' 6" I'm a short arse though.
Saddle bum
Über Member
- Location
- Kent
For years, the standard crank length was 6-3/4 inch, which is 171.5mm. For folk between about 5' 5" up to 5' 10" this was more than adequate. For some reason the continentals, adopted 170mm as the standard, which in my opinion is too short.
At 5' 8" and I take 30" trousers, I always use 172.5mm cranks.
At 5' 8" and I take 30" trousers, I always use 172.5mm cranks.
e-rider
Banned member
- Location
- South West
I always use 175 becasue I'm tall - if I ride 170 I don't like it!
Never tried 172.5 but if I did I probably wont notice the difference, perhaps.
So what im saying is: you can notice 5mm; but ive never tried a 2.5mm jump
Never tried 172.5 but if I did I probably wont notice the difference, perhaps.
So what im saying is: you can notice 5mm; but ive never tried a 2.5mm jump
No reason for 165mm just thought as small 5" 5 165mm would be about right when upgrading bike. Probably been riding old type sizing anyhow . All the bikes i 've ever had as a child would not know the crank lengths. The info on here suggests that they were 171.5mm so 1 think a difference of 5- 6mm either way in my experience makes not noticable difference. Thought about crank length after read a article on crank lengths which confused me . Started thinking was using wrong size as article was saying with the chart that my crank length should be about 150mm ??? Somthing to do with height x inseam x ?? also saying due to manufactures limitations on crank length lots of people would be ridinG with wrong crank lengths !HAPPY WITH 165MM 0R 170MM
GrasB
Veteran
- Location
- Nr Cambridge
I ride across a huge range of crank sizes... I produce the same maximal power & I produce the same power at a given effort level. I seem to be recommended something between 155mm & 160mm cranks.. doesn't stop be being incredibly effective on 175mm cranks, I'd love to try 177.5mm cranks but I worked out I'd need a 81 deg seat tube to get the leg/ankle angles I like... I'm not going to spend several £100/£1000 on a custom stem or frame to try that out.
