172.5 to 170 cranks

roubaixtom

Hi,

Im trying to achieve sightly more setback on my bike with a 74.5 degree seat tube. Would an extra 2.5 off the cranks in theory increase my setback by 2.5mm? Im 5ft9 and potentially think slightly shorter cranks may benefit me anyway.

Will i notice the difference?

cougie

I really doubt it.

852Kompol

Doubt the setback- the opposite end got 2.5mm shorter as well... so its not gonna make much difference that way... if you're after setback than perhaps a setback post? or if you're already all the way back with it maybe a saddle with a longer nose?

lesfirth

Roubaixtom wrote:

Hi,

Im trying to achieve sightly more setback on my bike with a 74.5 degree seat tube. Would an extra 2.5 off the cranks in theory increase my setback by 2.5mm? Im 5ft9 and potentially think slightly shorter cranks may benefit me anyway.

Will i notice the difference?

No. I have 165 cranks on one bike and 170 on another. I can not tell the difference.

ugo.santalucia

I went from 172.5 to 170 as it was the only size available... never noticed any difference

philbar72

no real difference. the race bike has 172.5 and the climbing/ training bike 170. the race bike also runs Q rings, and I notice very little difference.

StillGoing

Roubaixtom wrote:

Hi,

Im trying to achieve sightly more setback on my bike with a 74.5 degree seat tube. Would an extra 2.5 off the cranks in theory increase my setback by 2.5mm? Im 5ft9 and potentially think slightly shorter cranks may benefit me anyway.

Will i notice the difference?

I have 165mm and 170mm and do notice the difference. I have a higher cadence with the 165mm with less tiring.

amrushton

This would be right since 165 must be describing a smaller circle (pi x 165 compared to 170). Also, the seat would have to come up by the equivalent as the leg is less stretched at the bottom of the stroke and you would be pushing a shorter lever

dj58

I went from 172.5 to 170mm on my road bike and could feel the difference, I have been using 170mm on my MTB's for years and when I bought my road bike which came with 172.5mm cranks I could feel the difference straight away. I'm going to try 165mm cranks on my road bike. Whether you would be able to feel the difference in a crank length change only you can say.

crankycrank

Your entire bike fit centers around proper saddle height and setback. Everything else gets adjusted around it. For more setback you need to find a different setback seatpost or saddle to get the right position. Different length cranks can certainly make a difference in pedal stroke comfort for many of us but won't compensate for an ill placed saddle.

bernithebiker

I have a hunch that many riders would be better off on shorter cranks, as many riders tend to have to low a cadence and shorter cranks promote faster pedalling speeds.

I have tried 175, 172.5 and 170 and definitely prefer the 170's. 175's felt awful and gave me knee problems. I may try 167.5 or 165, soon. (I am about 5'7, 8, but have shortish legs).

drlodge

4 years ago I changed from 170mm (old 42/52 Shimano 600EX) to a new Ultegra 172.5mm cranks. Could I notice the difference? Yes, I think so, slightly. I prefer the longer crank as it gives a bit more leverage, if its noticeable at all its going up steep hills where the extra leverage helps a tad.

It is marginal though.