Cranks

[retrogeek]

My first post, I have really enjoyed this site so far.

I started riding in the mid-70's and most everything came with 170's at that time so that is what I rode. I started to experiment with crank length sometime in the early 80's by first trying 172.5's and then 175's. The jump from 170 to 175 wasn't as big a deal as I thought it would be and I used that set-up for maybe 10 years.

I now use 180's on all my bikes and don't think I will change from that. I am 5' 10" with a 35" inseam (long legs and arms for my height). I think that of all the experimentation I have done over the years with riding position and equipment, changing to a longer crank has shown the greatest jump in performance improvement. My cadence on the flats is a consistent 95-110, and on climbs I like to keep between 85-95.

I am a road racer and enjoy climbing the most so that may have a big influence on my crank length choice. But I would still recommend to anyone to at least experiment with longer cranks to see its effect on your riding. Like all changes made to the bike do it with forethought and care. Don't change to a longer crank and go out smashing the pedals to see the difference, it's a good way to injure yourself. I subscribe to Bernard Hinault's method of changing riding position (see his book), take your time, evaluate the effect of the change, let your body (and brain) adjust.

I think the history that J-MAT has given is right on the mark, this is exactly what I have found as well. I have never known anybody to go back to shorter cranks after trying longer lengths, within reason of course.

 

[lesliegee]

I'm a 5'3" woman, with a 27" inseam (short legs, not so short torso), and have no idea what crank length I'm riding. Guess after all this talk, I should check it out.

 

[larry barr]

Originally posted by ArvinC
172.5 Ultegra on my Kestrel.

I have been reading in several bike mags that there is a trend toward longer crank arms for better power.

I have this legnth 'cause it's what came with my bike...but, seem to be doing okay with it.

Go Terps. But what the heck was with that disaster last night. I live in the suburbs of Chicago, drove all the way to Dekalb, only to see them stink up the joint. Fortunately basketball season is not to far behind.

Back on topic, I went to 175. You are right about the trend to longer crank arms, better leverage.

 

[jtfleming]

OK...I need help. Cranks are something that I just don't understand the mechanical relationship on. Bear with me.

I have found difficulty in developing a high cadence at a reasonable gearing level. Granted, most of my training since I have been back on the bike has been for strength, and only when I was satisfied with my leg strength and aerobic performance did I start down-shifting to keep my cadence up.

Now according to the chart, I have a 32 inch inseam, which correlates to a 167.5 crank. My present crank is 175 because I am long in the torso at 6 feet tall, and the model of Specialized bike comes with a 175 for my size.

I am using Shimano 52/42/30 with a rear cassette of 12/25. Will a shorter crank, which I would presumably move at higher revolutions, lose me significant efficiency (in the pure meaning: least effort for the most gain). Would I potentially benefit by shortening my crank, on the presumtion that my cadence is relatively low with the 175.

Anything you can tell me to enlighten me on the dynamics here will be most helpful in allowing me to sleep, because I am laying awake nights trying to figure this one out!

Thanks

 

[guised]

zakeen, usually the largest available (62/63/64cm depending on vendor) but with an enormous seat pin to get the required leg length.

I'm currently having a Chas Roberts custom frame made so hopefully this will go some way to solving my fitment issues. My inside leg (39") is one of the largest they've seen!

Cheers

Dan

 

[ant evans]

If you don't have knee problems, there's nothing much to worry about. What matters is that you can keep going further and faster without doing yourself any damage.

I run 165s. 175s feel impossibly clumsy and slow to me, but then I have short legs (I think 31").

In my opinion, long cranks with short legs raise the risk of injury because your knees bend further. They're designed to transmit maximum effort beyond 120 degrees; we push them from 80. I have the MRI scans to prove that this is a bad thing. But unless you are in the top percentile of athletes, pushing too hard in the wrong gear is also bad (see below).

If you are going to change your crank length, change your gearing accordingly. The difference is small but measurable. Shorter cranks give you less leverage and therefore less torque at the chainring. You need to compensate by running a gear lower, and spinning slightly faster, otherwise your legs )and knees) will have to provide the torque instead of the gearbox. Let the bike do the work.

Unfortunately, small changes are best, and chainrings are an expensive component to change. This is probably the real reason people stick to standard lengths.

 

[jitteringjr]

After having knee surgery, the shorter 172.5s on my new bike feel better than the old 175. Don't they say stronger riders (Ullrich) prefer shorter cranks and high cadence people (Armstrong) prefer longer cranks in general?

 

[retrogeek]

I was going through some old material on this subject and I found a great formula from something Leonard Zinn had written. He stated that you should use cranks that are 21% of your inseam measurement.

For example, my inseam is 86cm.

86 x .21 = 18.06.

This formula shows that for me 180mm cranks would be ideal, which is exactly what I ride, so the formula works for me, try it.

 

[Ted B]

Originally posted by jitteringjr
After having knee surgery, the shorter 172.5s on my new bike feel better than the old 175. Don't they say stronger riders (Ullrich) prefer shorter cranks and high cadence people (Armstrong) prefer longer cranks in general?

FWIW, Cycling News indicated that Ullrich used 177.5mm cranks in the '03 TDF, and was training at a cadence up to around 120.

 

[kb1d]

Hi Guys,
I have been using 175 Dura Ace cranks and I am installing 175 Rotor Cranks on my 26/20 T-Bone by Reynolds Weld Lab recumbent. My x-seam is 47"
...Marc

 

[Cipher]

175 Ultegra. (The formula's say I should use 172.5's, and I've tried them, but I just don't feel comfortable on 'em).

 

[JAPANic]

This thread has been very interesting for me...

I got my first bike from my brother back in May, and have been riding hard ever since.

My brother is much talller than me and the bike he gave me has 175mm crank arms and according to the chart posted earlier, my inside leg measurment is only 72 cm, so should I bother switching down and buying new cranks or wait a year, where I plan on getting a whole new bike????

My medial ligaments in my knees are pretty sore after a ride, and I will blame this on the huge cranks I'm trying to turn.

I'm still a beginner and this pain may go away the more I ride or it could get worse. It may not even be related to the cranks and continue even after changing.

I suggested to my local cycle shop that I may like to get some 165mm and he said that 170 would be fine, but he seems to have just pulled that figure from the standard size manual and doesn't want to listen to my explanation that smaller may be much better.....

What would you do?

 

[Halflin]

I have 172.5mm Ultegra cranks on my Casati training bike but I have 175mm FSA Team Issue on my Giant TCR composite. I like the 175mm better because I can sprint better with them. I'm 5'10/ 165 lbs and I seem to do better on the larger cranks.

Half

 

[Spider1977]

I have 175mm Shimano 105 cranks on a 53-39 cog.

 

[JAPANic]

I have 175mm Shimano 105 cranks on a 53-39 cog.[QUOTE/]

So do I, but I'm only 172cm tall and my inner leg measurement is only 72cm so turning the 175s are killing me!!!

Have been looking at getting some smaller cranks on Yahoo auctions... 167.5s

So are these triple cogs for wimps? Should I stick to standard cogs?

(I'm a beginner)....

 

[larry barr]

Originally posted by JAPANic

I have 175mm Shimano 105 cranks on a 53-39 cog.[QUOTE/]

So do I, but I'm only 172cm tall and my inner leg measurement is only 72cm so turning the 175s are killing me!!!

Have been looking at getting some smaller cranks on Yahoo auctions... 167.5s

So are these triple cogs for wimps? Should I stick to standard cogs?

(I'm a beginner)....

Lots of debate on triples. I don't ride them, but I also live in the flatlands of the midwest. I leave it up to personal preference and do not judge. It is all about what works for you. I can still remember when getting a ten speed was the bomb, now I ride Record 10.

 

[Ted B]

Originally posted by JAPANic /i]

I have 175mm Shimano 105 cranks on a 53-39 cog. So do I, but I'm only 172cm tall and my inner leg measurement is only 72cm so turning the 175s are killing me!!!
Have been looking at getting some smaller cranks on Yahoo auctions... 167.5s
So are these triple cogs for wimps? Should I stick to standard cogs?
(I'm a beginner)....

I wouldn't consider triples for 'wimps', but chances are you won't need it.

If the 175s are killing you, I suggest you go to a 170mm or 167.5mm.

 

[brindy]

Originally posted by steve
Hi guys

What size cranks does everyone ride? Why do you like them?

Mine are 172.5mm campy chorus cranks, i'm happy to swap them for a set of any 175mm cranks that are in good condition.

Why are you changing?

 

[retrogeek]

It seems as if this thread is really generating a lot of interest. I think this is good because in my view choice of crank length is the most overlooked aspect of proper bike fitting.

I am from the "proportionalist" camp in that I feel that crank length should be determined as a proportion of your inseam length. Seems logical to me, but the traditionalist camp have a hard time moving beyond 175mm for even the tallest of riders, and below 165-170mm for the shortest.

Perhaps this is due to marketing constraints. It would be very difficult for Campy and Shimano to offer crank lengths from 150mm to 200mm, and for frame builders to vary bottom bracket heights as well. Perhaps for the majority of riders this 170-175mm range is satisfactory, but if you race or are a serious recreational rider you should experiment and find out how much difference the "right" crank length can be.

If you are really interested in hearing all sides of this debate go to Google and type "Crank Length" in the search field and you will get access to web pages that very clearly itemize and detail out every facet of this argument, from both sides of the issue. Both Kirby Palm and Andrew Bradley (I hope I got their names right) have web pages that can be accessed, along with other more traditional sources.

As I stated earlier I ride 180mm as a general rule, but go up to 190mm cranks for time trials and rides in the mountains, I have a 34.5" inseam. I feel that if you have the funds experimenting with crank length can be a very eye opening experience.

 

[oldbobcat]

If I remember, both Hinault and Lemond suffered from occasional knee inflamation. Their director, Guimard, was the first to advocate the longer cranks, bigger gears, and sitting farther behind the crank spindle. The proportions of Lemond bikes reflect this philosopy, but Gregs's leg length was pretty average for his height, too. Using the old standard, Lemond might have been on 172.5s and Hinault on 170s. Merckx, who is about 6' and not as lanky as Gimondi, used 175s on the road as a pro. When I learned of this, I moved up to 175s. My climbing improved considerably, but my sprint lost a bit of its snap. Casual riders (people who are not senior racers) might want to stick to shorter lengths just to avoid injury.