anixi

Hi All,

I'd like to upgrade my 105 crankset, but, the question is what should a 6' rider with short legs, 30" inseam, use at the minimum?

I'm scoping out deals, one of which has 165mm crank-arms. I'm concerned that it's too short. Please let me know what you all think.

Thanks!

10 Wheels

165 should be good.

Cranks arms are a personal choice item.

r0ckh0und 

I have a 30" inseam and am quite comfortable riding 170mm arms. The 165mm might be a good choice for a beginner but for a seasoned rider I would suggest the 170mm.

obrentharris 

Crank arm length is pretty subjective. If there is a formula that puts you in the ballpark I'm pretty sure that it will be based on length of femur rather than length of entire leg. Like top tube length and handlebar drop a lot seems to be based on factors other than just length of body parts; factors like flexibility, muscle mass, weight, leg speed.

I can only offer you anecdotal evidence from my own experience. I have a 34" inseam. I am accustomed to using 172.5s and 175s. I have experimented with crank arm lengths ranging from 165 to 185. The 165's felt definitely peculiar, like I was pedaling with my ankles instead of my legs. The 185s stayed on the bike for a few months because I thought I might get used to them. I couldn't decide whether they seemed awkward only because I was used to spinning smaller circles with smaller cranks. In the end I took them off. But I am not a finely calibrated instrument (or a "very sensitive guy") because I really can't tell the difference between 172.5 and 175. I'm not even sure I can tell the difference between 170 and 175. If you put me on a bike and asked me to tell you how long the cranks are I would probably be hard-pressed to give you a correct answer between these three sizes.

Not very helpful huh? My guess is that you will be happy with either 165 or 170.
Brent

anixi

Thanks for the help guys. I've got a short femur, especially hard to fit me using the KOPS method. I'm not saying that KOPS is either good or evil, it's just that I'm getting feedback like "You need a custom frame" because of my short femur.

I'll try the 165 crankset and see if it makes up for my issue, shouldn't hurt eh? BTW, I've been using 175 for a long time, it's not working out for my knees so well...

ironwood

What do you mean by inseam? Is that your pant leg length or the distance from the floor to your pubic bone? For years I used 170mm cranks, but recently put 165mm cranks on a 1983 Trek 630 that I converted to 650b. I did this because the bike has a rather low BB. I don't notice much difference. But I'm 5'8, at least in the morning. According to some charts put out by TA, 167.5mm cranks would be my optimum length.

For some riders crank length isn't important, they can adjust to most, but I know someone about your height who insists on 171mm cranks, not 1mm less nor 1.5 mm more.

Paramount1973 

I have seen research that indicates crank length only matters in the far extremes. 170mm seems to be a happy medium.

repechage

That is an important consideration.

This I think comes down to fit overall. There are plenty of elements that can cause knee problems. My suggestion is to locate a fitter with a good reputation for the non racer.
Flexibility, cleat position (if you ride with street shoes or sneakers, the bending of your foot over the pedal can make a huge difference), saddle position all can have a bearing on how you should be on the bike and knee pain or lack thereof.
There is more than I mentioned too.
As knee replacement eventually is possible but not desired, spend some cash, then buy the crank that is best. And don't forget "Q" factor either.
For me, the "Q" factor at the pedals is not the issue, but the width of the crank set at the BB axle. Everyone is different is the point I am attempting to make quickly.

John E

I have 165s on the Peugeot, 170s on everything else. (Trouser inseam = 30".) Works for me.

poprad

From my experience it's pretty immaterial in the scheme of setup as long as the pedal deck to saddle contact points distances remain the same. Think about it; the percentage difference between 165 and 170? So tiny I doubt many of us could tell. In fact, I'd bet a paycheck if you changed the cranks to an identical model 5mm different in either direction you'd be hard pressed to even notice if no one told you.

I'd put 'em on and forget them.

obrentharris 

I think the comments by repechage are so important! If you are experiencing knee pain it's very important to get to the bottom of it. (says the guy who has already gone under the knife for a torn meniscus) And there are several possible causes: I suspect that saddle position and the accompanying leg extension probably are a much bigger factor than 5 mm of crank length. But you're doing the right thing trying to get to the cause of your knee problems. Take care of yourself!
Brent

Goosecheck 

I have a 30" inseam. 3 of my bikes have 170's. One of my bikes has 175's. No problems. This is a relatively minor issue to be concerned with unless you want to unnecessarily make it one. 165 or 170 is good. Go ride!

rhm

Going from 170 to 165, or even 175 to 165, will hardly be noticeable and will benefit your knees. I've been picking up shorter crank arms whenever possible, and the shortest you can get for most models is 165. I have 160s on two bikes.

The only situation where you will wish for longer crank arms is when you need to muscle your way over an obstacle at low speed, I.e. off road or in snow or sand.

anixi

Thanks everyone for their input. If I do get the 165s I'll find someone to help me dial the bike in around them.

lotekmod

I'm 5'9" with a 30" pants inseam, 32.5" cycling inseam. I have 165mm cranks on one road bike, 170mm on another road bike, and 175mm on three mountain bikes. I don't notice the crank arm difference at all switching between bikes. The difference in handlebar width and drop, frame geometry, tires, etc are much bigger factors I do notice, but never the crank arm length.

ThermionicScott 

I've got a cycling inseam of about 32.5" and use 165mm cranks on the fixed-gear, 170mm on everything else. The big thing is to make sure your leg extension is correct at the bottom of the stroke.

I doubt that 165mm would be too short in your case.

Wildwood 

2nd this opinion. 175s were my length until rode shorter and found it didn't matter much - if at all noticible in 5mm increments.

Q-factor gives me more notice when I ride my only road triple.

noglider 

The trend in the market is to go longer, and I don't particularly like it. I don't know WHY I can feel the difference, but I can. I also have short legs, and I prefer short cranks. With 175's, my knee ends up too high on the upstroke. For knee longevity, I'd guess it's better to spin than to mash, and I'm working on increasing my cadence so my knees last me a good, long time. They're already hurting, and I've been mashing too much.

My McLean racing bike has 167.5's, which is weird, but it works. I've been snatching up 165mm arms lately, too. I might even try some shorter.

cdale4ever 

+100

I've always used 170's on the road. Tried 172.5 & 175, but they just don't FEEL right. Can't really quantify it, but it is what it is. As many others have said, it's very much a personal preference. BTW - my pants inseam is 34. Overall fit of the frame and saddle adjustment (both height and fore-aft) are probably more important for reducing knee issues. Many moons ago, I began having sharp pain under one kneecap. Made a 1/8" saddle height adjustment only, pain went away and never returned. It can take a while and many adjustments, but once you get it right, you'll know. You'll definitely know if it's wrong! Good luck!

Bill Kapaun

I have a bad knee with limited range of motion. Not real bad, but limited.
165mm cranks were a godsend for me.
175mm 60 RPM Too much knee pain to ride.
170mm 80 RPM Some pain.
165mm 85 RPM Pain free Did a 70 mile day on my hybrid with these.
160mm 82 RPM Too short. Felt like I was on a kids tricycle.
I'm a 65 yo., about 5-11", 220-240 lbs. & emphysema.
The shorter cranks also work better with the emphysema, running a close ratio cassette and "spinning a narrow cadence range.

DMC707

I have used 170's on the road for 2 decades -- switched to a bike that came with 172.5's and hated them after 5 rides -- went back to 170's.

I don't know why it matters -- I ride my mountain bike more than road and it wears 175's and im good with those -

perhaps its the spin im still trying to cultivate in the roadie

jimmuller 

Okay, I'll chime in too.

I've ridden mostly 170. I have one bike with 165, I can imagine that I feel the difference, but just barely and it's probably only my imagination. I ended up putting that crank on the bike with the lowest BB. I have 172.5 on one bike, and I can't tell the difference. If I switched between the 165 and the 172.5 I could maybe feel the difference.

My sweetie/tandem stoker is only 5'2". We run 140 on the stoker's crank. With a longer crank she would be hip soreness. The short crank fixed it.

The point being, a small difference will make a very small difference. If you want a big difference you need a big difference.

Glennfordx4

I have had some problems with my knees also & I have always used 170 & 175's & have been wanting to try a pair of 165's & see if it would help with the pain ( I'm 6ft w/32" inseam). I think once I get a little better conditioned I may be able to go back to a longer crank, just been out of the saddle a little to long lately.

Glenn

anixi

Yeah, you've got the same proportions as myself. The bike fitter I went to put me on a 63cm frame to get the top tube to fit my long torso, but, it was a chore to get on and off the silly thing! Custom frame is what I'd get "if I were a rich man" yadda-yadda...

Glennfordx4

My Centurion Elite RS is 59cm x 59cm and I need a 130mm stem to be comfortable on it & I am with the exception of my knees bothering me most of the time. I would love a 600EX crankset in 165 to try on it, I really think that would help. My MTB that I set up for street riding isn't as bad and that has 175's on it, I ride this the most.

Glenn