Bklyn

I got new cranks put on the old Fuji road bike. Unfortunately, I thought I was getting 170's, and I got 165's. I'm 6-foot-2. I need to get the 170's, don't I?
(The bike at the moment is a singlespeed, but will ultimately be fixed when I get the $ for a new wheel.)

marqueemoon

I'm your height and my KHS came with 165s so I'm rolling with it.

It's not that weird. Going from that bike to my Cross Check with 175s is a little weird though.

Bklyn

Yeah, I didn't notice it when I rode back to work from the LBS. But I called the LBS (City Bikes on 38th St., NYC; can't say enough good things about them), and they told me that I could ride them for a while, and if I didn't like them, they'd swap them out for 170's.

DerekRI

If you can ride them comfortably, I'd say do it.. you can always use some extra ground clearance

iamtim

I swapped out my 170s for 165s; my frame is built for 27" wheels but I'm running 700c, so I felt I needed a little clearance. With the same gear ratio, I can't really tell a difference at all.

For what it's worth, I'm 6'2" as well.

queerpunk

if you like them, keep them.

me, i'm short. 5'5". 5'6" on a low-gravity day. i've been riding on 170s for almost two years and last night i took a new (to me) bike out for a spin with 165s that i put on. oh, it made such a difference, especially when i was low in the drops. with my bike with 170s, i could not get low comfortably - my spin would suffer. on the bike with 165s? huge difference. i am so going to love the crap out of this bike...

bitpartinyrlife

My beater conversion has 170's on it, my track bike has 165's. As far as my pedal stroke, I can't tell the difference, but when I lay that b*tch down in a turn I sure can...(oddly enough both bikes have the same bb height).

Landgolier

I don't remember if it was on here or on some listserv I'm on, but somebody who was futzing around with crank length a lot said you basically never notice if they're too short, only if they're too long. He had some bike with like BMX 150's or 145's on it that he let a bunch of people ride and not a single one remarked about it. My stock line is to get 165's for FG unless you're really, really tall, but if you have a set longer than that and you're not getting pedal strikes and you're not under 5-6, don't worry about it.

chunts

Peter White has a good article about bike fit that talks about crank length. he suggests 18.5% of the distance from top of femur to bottom of heel should be your crank length. in general it sounds like having too long a crank is worse than too short as far as efficiency, but his anecdote was that he switched to longer cranks when he heard that formula and noticed better power.

for fixed you obviously have to worry about clearance a bit more. I'm 6'1" and I put 170s on my new conversion but i'm still waffling if I should have gone with 165s. the clearance is pretty good on my frame though.

mihlbach

The only downside to short cranks is that you get used to that length, which is fine if all you ride is short cranks. But, if you have other bikes with longer cranks, going back and forth from short to long can by irksome. I'm 6'1" and I normally ride 167.5s on my track bike. Its all fine and dandy until I get out my road bike or ssmtb which both have 175s. 175s feel too long after riding my track bike around for weeks on end, and it effects my pedaling efficiency for a while, until I'm able to readjust. I would probably be better off just going with 170s on my track bike and 172.5s on my other bikes.

iamtim

That's a good point... I've got 175s on my roadie and I haven't ridden it once since I put the 165s on my fixie... I might take the roadie out tomorrow. I'll report back if I do and I feel any difference.

NextDollarAfter

I'm 6'3 and currently running 165's and I noticed a difference when I put them on, I haven't had any problems and have been running them for almost a year now.

Retem

I have 170s presently but my net build will be 165 as will be my new cranks for my current build toe overlap if you ask

captsven

The only time I can detect a difference in crank arm length is when you start talking about hills. A longer crank arm will get you up a hill quicker (if all other factors are equal and reasonable esp. gearing) than a shorter one.

I also like the fact that you don't spin out as fast on the downs with longer crank arms.

Shorter crank arms are excellent for sprinting.

fix

I'm 5'8, and I've been thinking about moving to 165s on my road bike. If I do it, I'll tell you how it goes.

cphfxt

To me it was a huge upset when I tried 165, it felt as a kids bike.. Im also 6´6, so that might explain it..
170´s for fixed for me..

Ken Cox

I've read everything available regarding crank length, and I find it inconclusive.

I think Peter White has something valid to say about geared bikes, but not fixed gear bikes; and I have read other formulas regarding crank length based on femur length.

I don't think any geared bike arguments regarding crank length apply to fixed gear bikes.

Dedicated fixed gear track bikes have higher bottom brackets, which works out nice on the street as it precludes pedal strike.

I have a friend who rides a conversion, and he had a pedal strike issue and went to 165mm cranks to minimize it.
He found that his spin improved.

I ride with 170mm cranks on both my fixed and geared bike.
I would like a longer crank arm on my geared bike and I can see an argument for a shorter crank arm on my fixed gear bike.

A shorter crank arm means a smaller radius, which means a smaller circumference, which means a faster spin.

A short crank arm facilitates a faster spin.

170mm minus 165mm equals five millimeters, half of a centimeter.

This makes very little difference in ARM (or MOMENT), but a significant difference in CIRCUMFERENCE (distance/time travelled by the pedal in every rotation).

Half a centimeter in radius equals 1.57 centimeters in circumference.

iamtim

I rode my 175 equipped roadie today after a few weeks of 165 equipped fixie riding. I *could* tell a difference. I felt like my feet were going in HUGE circles in comparison.

mihlbach

I agree completely. The increased ability to spin with shorter cranks is greater than the loss of leverage. When I started with fg I used an old pair of 175s. Then I put on some 170s and I noticed that I could spin faster going downhills, but I didn't notice it being any harder to climb. Now I have 167.5s on my track bike, and again, I've noticed tht it gives me a slightly higher max cadence, but it really doesn't seem to make a difference for acceleration or climbing.

mihlbach

Thats the only problem I have with short cranks on a fixie. When I switch back to the 175s on my roadie or MTB, the circles feel way too huge and my pedal stroke is inefficient until I get readjusted to longer cranks.

stahu

I think your calculations are wrong; 0.5cm in radius equals 3.14 (pi) cm in circumference.
circumference = 2 * pi * r = 2 * pi * 0.5 = pi

so when you pedaling with 80rpm - your one foot travels 2.5m (8ft) more per minute with 170 cranks than with 165.

Ken Cox

I agree.

I multiplied pi times the radius.

I should have multiplied pi times the diameter, or twice the radius.

Two time five mm's equals 10 mm's, or one centimeter.

Pi times one centimeter equals 3.141592 centimeters.

So, following stahu's lead, at 100 rpm, each foot would travel 314 centimeters, or 3.14 meters further with a 170mm crank than with a 165 mm crank.

Both feet, together, would travel 6.28 meters further with a 170 mm crank than with a 165mm crank.

The big thing, though, for someone riding a conversion, involves pedal strike.

When it comes to pedal strike on a road conversion, I think a few millimeters make a huge difference.

WoodsterSS

I hope this is not too far astray of this thread, but I know very little about crank length--only that I was told to get 180's for my ss MTB to facilitate climbing (I'm 6'4). I am looking into a road ss now and I am wondering, is the only issue on the fixed gear one of pedal strike? I will still have many killer hills to climb on the road where I live so, should I keep to the same cranklength since it is not a fixie?

noisebeam

I have been using 170mm on my conversion (11" high BB centerline) and now need to get new cranks for my new Jamis Sputnik (10.85" high BB)

I have generally been happy with 170mm, only had a few minor pedal tap moments. But I do hold back on corners relative to folks I ride with on freewheel bikes.

I can and do spin, I also really enjoy powering up long hills.

This is now an opportunity to switch to 165mm cranks or stick with length I've used. I am 6'2", but more importantly have a long torso, short legs (33.5" 'true' inseam).

165mm seems right for added cornering confidence and spinning, my only concern is the longer hills, the steeper sections. From what I read above (ken cox, mihlbach) the lowered leverage is minimal and the added spin possibility a pleasure.

(I ride 175mm on my now rarely used road bike, I've noticed I get knee pain with it, although fit right)

A safe bet is to stick with 170mm, but I can't pass up this opportunity.

Al

fatbat

That's why i went with 175's on my fixie (+superhigh bb). No sense training the old spin on the fixed gear if i'm just going to totally lose all pedaling form when i switch to the other bikes.