How tall are you and what size cranks do you ride?
 

I'm 5'8" with a 31" cycling inseam.

I ride 165mm on my 54cm (CT) single speed
I ride 170mm on my 51cm (CC) road bike
I ride 175mm on my 17" hardtail

Maybe I'm doing it wrong, but I can't tell the difference.

The reason I'm asking.....I'm going to upgrade the road bike. Thinking about 165s. But not sure what other folks my height ride.

Been cycling a long time. Started on my first serious road bike having 165s, the bike was a 21" (54cm). Got an additional bike a 56cm with 170s, I could tell gthe difference, the 165s felt short when I used the bike ocassionally. other bikes aquired used happen to have 170s (some shorter) My last bike, a brand new special order has 172.5s and I can't really sense the difference. Mountain bikes have longer arms in each respective frame size.
I'd wrestled with the decission whether to go with 172.5s or 175s. One seller I'd asked, right-off rec. the 170s, given my 5'10" ht.. 82.? inseam and rel. short legs (short femurs). The place I ordered the bike from told me "your choice", no recs. One member here in the forums had said one thing, very casually , " my knees go up too high" with my new 175s. That answered that.
Trends have changed; M.bikes have influenced ideas in longer lengths.
30 yrs ago bikes your size and mine; med. to med-lg., 54cm to 56cm as a matter of course came with 165s, 23" or 58cm or so with 170s etc..
20 years ago, they went-up-a -notch. Now it's over the top... trends.
Stay with what you know, besides, spinning is better (I suck at spinning)

Six foot one (and a quarter inch). 33 inch inseam.

I ride a:

- 19" mtb with 175 crank arms
- 58 CC 'cross bike with 172.5 arms*
- 58 CC road bike with 175 arms

* That just happened to be the length of the crank arms on a 105 crankset I picked up used

This thread gets done up every two weeks. Do a search for similar criteria.

I did a search & felt two weeks is too long for a thread like this. Most "I'm a n00b, what bike should I get" threads appear once a week, so here's my attempt to make this a weekly topic of discussion as well.

I saw some just now; one was a silly "let's take a poll" type which always ends weird. others were in tandom and touring. Others are just plain TOO old. Besides, it sure beats "what's the best chain lube"

6'5"
165's

5'5"

165's on all my bikes. I can ride 167.5 or 170 with little to know problem. But when I turn crankarms longer than 170, my knees begin to hurt after long or hard efforts. As far as performance (speed, watts, cadence), little to no difference with respect to crankarm length.

Im no rocket scientist at all about bike fit and bike geometry etc......but with a proper bike fit, as far as your knee in relation to the center of your pedal, shouldn't it be the same no matter which crank arm you have?

34 in inseam; 175 mm.

6'5"
180

I'm about the same size as you (the OP), and my bikes are set up very similarly to yours. 175s on the MTB, 170 road, and 165 FG. I find 175 uncomfortable on road bikes.

6'2, 175mm. Tried 172.5, and hated it. I really didn't expect much difference, but it was huge.

6'0 and recently switched from 175 to 170 and can tell a huge difference. The whole fit of the bike changed for me and I'm looking to go back. Anyone that says there's no difference doesn't spend enough time in the saddle. :innocent:

Your knee has to bend more with a longer crank. You also tend to pedal at a slower cadence with a longer crank that is also harder on knees.

I'm 5'7 and use
165 SS is easy to a get a high cadence,
175 is on a MTB for extra leverage on steep climbs.
170 and 172.5 are on road bikes.
Different tools for different jobs.

5 9 and use 175. I never used anything else. It came stock.

5'9" 31.5 riding inseam 170mm cranks

6' 32" inseam 172.5mm cranks

6'1" 34" inseam, and I ride 175mm, 172.5mm, and 170mm on different bikes.

Can't honestly say I see a whole lot of difference particularly between the 175mm, and 172.5mm

I'm nearly 5' 11" with a 32+ inseam. Just switched from 175 to 170. (175 was what came on my used road bike when I got it.) The 170s are definitely what I need. The 175s were contributing to some minor knee pain. And it is harder to spin with longer crankarms.

If one thinks about it, the longer the crankarm, the bigger the pedaling circle. The bigger the pedaling circle, the more possible stress on knees. And the harder it is to pedal at a high cadence.

My LBS guy is 6' 2" or so. He uses 172.5 crankarms. He used to race back in the day, so he has lots of experience. He's tried everything up to 180, and prefers 172.5. He says it's all about pedaling at a cadence of 100-120. Too long a crankarm tends to prevent this.

6'4"
175

I'm about the same size as you. I use 170s on my road bikes; 165s on my fixed gear. I can't tell any real difference between the two, but the shorter arms on the fixed gear help prevent pedal strike in corners.

5'8" 31.5" inseam

170mm cranks on my BMC
172.5mm cranks on my Orbea

5'8" 32" inseam

170mm & 172.5mm

6 feet, don't remember my inseam. 175 on one road bike and the MTB, 172.5 on the other road bike.

And I've noticed a TON of difference between the 175 and the 172.5. My comfortable cadence goes up about 10 rpm, and my power goes up with it. Part of that's probably the completely different bike, but I think part of it is the crank length as well.

I didn't expect to see a difference, but my feelings led me to believe otherwise.