Barrettscv 

I've been using a 175mm double crank with good results. I found a better quality crank at a good price, but the seller only has 172.5mm. should I avoid the shorter crank? 2.5mm isn't much. I'm 5' 11" with a normal build.

Michael

lechat

some will argue that it does. 1/10th of an inch? no fekin' way.

CrossCountry2k7

Yes fekin' way! You should be able to tell the difference in your pedal stroke and it will probably require some saddle height adjustment. For your height I'd say that 172.5 is pretty typical on a road bike, although a lot of people run a little longer on TT rigs. Just make sure to make the necessary fit adjustments so you don't run into problems with your knees or ankles with the change in fit.

tadawdy

yes it matters, though htfuers will say it doesn't. It alters the circle you pedal in. it obviously has the potential to cause more problems if you're thinking about moving to a bigger one, though. Longer crank = more leverage, typically better for turning bigger gears at lower cadence. It has been shown that a shorter crank allows a higher cadence. of course, this is only relevant if if it is relevant to you.

2.5 mm isn't a big jump, but I definitely notice the difference between the 170mm and 175mm on my two bikes. Being a high-cadence guy myself, I prefer the smaller cranks. I'll probably switch out the stock 175 for a 170 when my funds recover.

I do recall seeing a chart that listed inseams and heights related to suggested crank lengths. IIRC, 172.5's were suggested for 5'11" (assuming proportional femur length).

prathmann

Probably not. My bikes have cranks ranging from 165 mm (tandem) to 170 mm (touring & folder) to 175 mm (road). I can hardly notice the difference in that range, so I'm sure I wouldn't notice the difference between 172.5 and 175. You may want to move the seat up a bit to get the same leg extension, but the 1/10" adjustment is pretty small.

RoboChrist

The general consensus is short cranks are better for high cadence, longer better for mashing the big gears

Point

There's a good chance you wouldn't notice 1/10" on your seat height anyway, so my guess is you won't really feel any difference. As for fore and aft, your cleats may be off that far too.

I've gone back and forth from 170 to 175 and to be honest, it doesn't make any difference to me. From 172.5 to 175 is less than 2% difference

10 Wheels

I am 6'-2" and Yes you will notice the difference.

mollusk

If you ride a lot it matters a lot.

I have three road bikes. Two are 175 mm and one is 170 mm that I use as my commuter bike. In REALLY nasty weather (during a tropical storm) I will take the commuter bike out to train and it is a totally different pedal stroke. For the two 175 mm bikes I also find a pedal stroke difference. The Q-factor is different by 1 mm between the two bikes. It was immediately noticeable to me in the first mile that I rode the second bike.

Obrigado

I've been thinking about the opposite change...going from 170 to 172.5

I ride 170 (road) and 175 (commuter), and I definitely notice a larger diameter pedal stroke and lower cadence going from 170 to 175. When tucked in an aero position with 175s, I have a harder time getting power through the top of the pedal stroke, perhaps due to a decreased hip angle or lack of hip flexibility?...as compared to the 170s.

Building up a new bike, I thought of trying out 172.5 cranks to see how they feel. BTW, I'm 5'11" 160lbs about 32" inseam. Most advice online seems to point at 172.5 as a good starting point for my body size.

I spin more than mash, so I feel smaller cranks < 175mm are more suitable for my riding style.

brian416

It probably depends on how much you ride, if you're spending 10+ hours a week on the bike, you'll probably be able to feel the difference. I went to 175s for a year and went back down to 172.5 for this year, for me, it is so much better, I can spin an additional 20+ rpm over longer cranks

lechat

shoe soles have to vary much more than 2.5mm. i doubt that anyone would notice a difference if you swapped their cranks surreptitiously.

CrossCountry2k7

I don't know about you but I ride in the same pair of shoes all the time. I would bet that most people who ride more than 10 hours a week could tell the difference by the time they made it down the block. 2.5 mm is actually a difference of 5 mm in diameter of the pedal circle, so that is pretty significant. If I moved your saddle height 5 mm, you could tell right away, and if you couldn't I bet your knees could after an hour long ride.

Barrettscv 

Thanks for the response.

I'm starting to see an advantage to 172.5mm crank arm length over my current 175mm.

I do like to maintain a faster cadence in the 90-100 rpm range. I completed a 200K last weekend, and often checked to see what cadence I maintained. I was keeping a cadence in this range even when tired on longer rides.

A 172.5mm size may help provide a further improvement in my cadence rate.

Michael

tribble222

Changing the thickness of your shoe's sole is equivalent to changing the height of your seat, not changing the length of your crank. Changing your crank length changes how large a circle you pedal in. I, for one, definitely notice the difference between 170 and 172.5 on my two bikes.

Val23708

I found that switching from 172.5's to 170's help me not kneemy chest when in the drops. its a 5mm difference.

SSSTANG

Wow, the search function paid off.

Both my road bike and my MTB have 175mm cranks. This week I am in Germany and I brought my MTB because the road bike is awaiting parts. It has a 11-19 cassette and whatever the stock chainrings are. Today I hit 41 mph on a short decline with a tailwind but needless to say, I was pedaling my ass off. This got me to thinking about shorter cranks. At about 125 rpm I start bouncing on the seat. My max cadence was 143 rpm the two times I hit 41 mph. What effect would 172 or 170mm cranks have on this situation.

Sorry to hijack.

botto 

slyjackson

YOu know, I went through this and I could not believe that there would be a diffrence. So say that they can't tell, but that depends on your riding type. This is what I noticed.

1. My cadence was smoother
2. Since my cadence was smoother I was more comfortable at a higher rpm.
3. When I stand on the pedals, I can feel the stroke better.

So with this being said my cycling improved as a whole I personally feel. Others may argue this, but I actually feel going from a 175 mm crank to 172.5 has helped me. This is just me, you will have to try the 172.5's yourself and see how they work for you regardless of what others post about the change. just my $.02 worth.

ac29593

I noticed a difference going the opposite way.....from 170s on my first road bike to 172.5's on the new bike when I got it.

I know my cadence very well and know my comfort zone. I like to spin and not use larger gears. When I started using the 172.5's I was uncomfortable and noticed the difference in effort I was putting in trying to maintain the same cadence.

I rode on them for a while since I thought it was due to the fact that I was out of shape from not exercising over the winter rather than the length of the crank since it was such a small difference.

Eventually as I became more fit I figured out it was not the case. I sold the crank set and bought 170s again. I felt the difference right away and will never go back.