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Crank length ?(14 posts)

Crank length ?legz
Nov 14, 2001 4:04 PM
My bike set up is comfortable. I have started racing only very recently. I am 40 yrs old. A friend mentioned to me that he thought I should try using shorter cranks.
My inseam is just under 32 inches. My cranks are 172.5
Has anyone had a similar experience ie changing crank length. Will this make a significant difference ?
re: Crank length ?Bad Mojo
Nov 14, 2001 4:31 PM
It depends on your pedaling and body style. If you are a big guy that likes to mash the pedals at low rpms then longer crank arms may be better. If you are a smaller framed person and generally keep a higher rpm then I would suggest shorter crank arms. I have a 31" inseam and am sort of a masher. I prefer 172.5mm for my road bike and 175 for my mountain bike. My commuter road bike has 170s and they feel a bit too short for my tastes. They do spin nicely though. Try to find a friend that has a bike with differnt crank arm lengths than yours and ride his bike. Or, go to your local BS and take a few bikes for a test ride.

Good luck,
Ken
HA!filtersweep
Nov 14, 2001 4:48 PM
I'm resisting my urge to comment... struggling.... it's a losing battle.... crank length?
172.5 is perfect for you alreadyLC
Nov 14, 2001 5:15 PM
it really makes very little difference unless you are very short using very long crank arms.
Same inseam size hereCT1
Nov 14, 2001 8:55 PM
My inseam is 31.75" and I use 170mm cranks. I tried 172.5mm cranks and didn't like them. I felt like I couldn't crank up the speed with them. It's not a huge difference ..... more like a minor subtle thing. You won't notice the difference unless you hop back and forth between bikes with the two cranks lengths.

My guess is that you will feel more comfy racing with the 170's but don't expect a big difference.

JohnG
Look at it this wayDave Hickey
Nov 15, 2001 4:19 AM
Take two credit cards out of your wallet. Stack them on top of each other. That's the difference between 170 and 172.5. Stay with your 172.5
... or this wayAkirasho
Nov 15, 2001 5:51 AM
I recently acquired a set of 172.5 Dura Ace cranks... and was considering selling them because I run 175's... till I compared them side by side... The pic graphically shows how small the difference is (Ultegra is 175... I used the pedal holes as a common point of reference).

Considering the difference in length is about 1.5%, I think I'll hold onto 'em and see for myself if I notice a difference (I've always run 175's on my MTB's, road and bents).

Also, this was mentioned in "Cycling Plus" magazine... I've not researched the site, but here it is for your perusal

http://www.thankstomycranks.com

We abide.

Remain In light.
NotCT1
Nov 15, 2001 6:58 AM
Just measured two CC cards and they are exactly 1.50mm.

However, 2.5mm IS a small difference when it comes to crank length. I think it is just on the verge of detectability. That being said..... in a racing situation small percentages can add up to a measurable cumulative effect.

YMMV
JohnG
But a 5mm difference is pretty detectableRay Sachs
Nov 15, 2001 7:14 AM
I only *THINK* I can tell the difference between 170 and 172.5 cranks - I *KNOW* I can tell the difference between 170 and 175. When I first started cycling, I started with 175s but could never get comfortable until I rode a friends bike that felt instantly better to me (same frame, similar components). Turned out the only major difference between the two was that his had 170 cranks. I switched mine to 170's and suddenly loved the feel of that bike. I've since ridden 175s and have never gotten to like them. But I've tried 172.5s and like them and now have them on a couple of bikes. I think I can tell a slight difference when spinning on the 170s or climbing on the 172.5s, but I doubt I could pass a blind test. But I bet I could tell if you put 175s on my bike.

-Ray
I can't tell the difference between 172.5 and 175dzrider
Nov 15, 2001 7:23 AM
I have 170's on my commuter, 175's on my good bike and 172.5's on my rain and stand bike. I measure my seat height from the top of the pedal to the top of the seat. Some day I'll try 180's just for fun. I can't tell any difference in either cadence or leverage. Somehow my body manages to make them all feel normal.

VeloNews did a few articles on this and either they or I or both were confused by the results of their tests which varied from person to person in unpredictable ways.
but don't forget . . .but don't forget . . .
Nov 15, 2001 7:30 AM
... that we want to produce power with a circular motion, not just by stomping a lever down. Thus you have to look at the differences in circumference, not just radius. Going from 172.5mm to 170mm is a small difference in radius, but it works out to about 16mm difference in circumference. In other words, your foot would have to travel 16mm(about 5/8")less to complete one revolution. That accumulates to a lot of foot travel saved over the length of a ride.

Having said that, I agree with the posts that tell you to keep the cranks you're riding now. I'm a big believer in adaptation and the benefits that come from that. Changing stuff sometimes works out well, but more often it just throws your body a curve.
but don't forget . . .is from (addled) jacques. (nm)jacques
Nov 15, 2001 7:50 AM
Look at it this waykyroadie
Nov 15, 2001 7:36 AM
My twin brother has the same road bike that I have with one difference. His cranks are 170, mine are 172.5. My cadence is always over 90 and sometimes 100+. I try to maintain 70 - 90 even while climbing, unless it is a major climb. One day we swapped bikes on a 50 mile ride. I could not tell any difference at all.
Look at it this wayweiwentg
Nov 17, 2001 6:43 PM
you may or may not believe this. I was shopping for new cranks to replace my shimano tiagaras. gearlink had the campy daytonas on sale - comparing the prices, they were the best value for the money. I asked my mountain biker friend what length I should get, and he said 175. And I'm 5'5" tall - practically midget sized, haha!
at the time I was fairly clueless about sizing. so I got the cranks. eventually (2 faulty bottom brackets and some shipping delays later) they were installed. I was worried that they would be completely the wrong length for me, but my word, they work excellently! I am now using a lot of the smaller cogs on my cassette. for the first time, I managed to keep up with the faster riders during the weekly rides with the local cycling club. I'm bloody impressed. of course,it could partly be due to the fact that I was going from shimano tiagara to campy daytona. the bearings are unbelievably smooth.
so, go to the LBS and test ride a few bikes with different-length cranks - I hope they won't mind. THEN make your decision.