drbob
05-15-02, 03:36 PM
I'm 6-0 172 lbs and was considering changing to carbon cranks. I currently have ultegra 172.5's. Is there any advantage to getting 175's? Any disadvantages?
Road Cycling - 172.5 vs 175 cranks
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Joe Gardner
05-15-02, 03:52 PM
Read this thread: http://www.bikeforums.net/showthread.php?s=&threadid=6719 (Also check out the links that MichaelW has posted in that same thread).
I have 167.5mm cranks on my mtn bike, and 180mm on my road bike. I feel much more comfortable with 180mm cranks. The difference is amazing, I have no idea why i had such small cranks on my mtn bike to start with.
BTW, I'm 6'4" tall, with long legs. YMMV! :)
I have 167.5mm cranks on my mtn bike, and 180mm on my road bike. I feel much more comfortable with 180mm cranks. The difference is amazing, I have no idea why i had such small cranks on my mtn bike to start with.
BTW, I'm 6'4" tall, with long legs. YMMV! :)
RiPHRaPH
05-16-02, 06:48 AM
if you lengthen the crankarms , and lower the seat - what about the clearance issues?!
John E
05-16-02, 08:09 AM
Originally posted by RiPHRaPH
if you lengthen the crankarms , and lower the seat - what about the clearance issues?!
This is generally not a problem unless you pedal through fast turns (or have to, because you ride a fixed gear). If you coast through turns, inside pedal up, you will have no problems on-road. Likewise, you can avoid problems offroad by clearing obstacles with the cranks in a horizontal orientation.
if you lengthen the crankarms , and lower the seat - what about the clearance issues?!
This is generally not a problem unless you pedal through fast turns (or have to, because you ride a fixed gear). If you coast through turns, inside pedal up, you will have no problems on-road. Likewise, you can avoid problems offroad by clearing obstacles with the cranks in a horizontal orientation.
lotek
05-16-02, 09:10 AM
I have 167.5mm cranks on my mtn bike, and 180mm on my road bike.
Joe, this is exactly opposite of the standard notion for
crank length as I have seen it.
Usually you see longer cranks on mountain bike than road
bikes. My understanding of this is that
for mountain bikes where cadence isn't much of an issue
a longer crank gives more leverage to power up hills etc.
On a road bike its more difficult to maintain cadence through the
top of the crank rotation (10 o'clock to 2 o'clck) so less
length translates to higher cadence.
Does 2.5mm make a huge difference? not sure.
If you can maintain cadence with longer cranks you get
the additional leverage plus the benefit of high cadence.
Marty
Joe, this is exactly opposite of the standard notion for
crank length as I have seen it.
Usually you see longer cranks on mountain bike than road
bikes. My understanding of this is that
for mountain bikes where cadence isn't much of an issue
a longer crank gives more leverage to power up hills etc.
On a road bike its more difficult to maintain cadence through the
top of the crank rotation (10 o'clock to 2 o'clck) so less
length translates to higher cadence.
Does 2.5mm make a huge difference? not sure.
If you can maintain cadence with longer cranks you get
the additional leverage plus the benefit of high cadence.
Marty
Joe Gardner
05-16-02, 10:58 AM
Marty, I understand what your saying. I think I have always had the wrong size cranks on my mtn bike, its now 7yrs old, I purchased it when I was just 17yrs old and 5'5" tall :)
The bike is way to small for me now, as are the cranks. I have changed out the stem, and have quit a bit of seat post sticking out as well, to somewhat fit the bike to me.
Overall, my new road bike is a much better fit, and I feel much more comfortable spinning on 180mm cranks then my mtn bikes short 167.5mm cranks. My LBS has some older DuraAce 175.55mm cranks, I may give those a try for a few weeks, to see if it makes a difference.
BTW, on my road bike, I have no problems spinning at 110rpm, but feel most comfortable at 85rpm.
The bike is way to small for me now, as are the cranks. I have changed out the stem, and have quit a bit of seat post sticking out as well, to somewhat fit the bike to me.
Overall, my new road bike is a much better fit, and I feel much more comfortable spinning on 180mm cranks then my mtn bikes short 167.5mm cranks. My LBS has some older DuraAce 175.55mm cranks, I may give those a try for a few weeks, to see if it makes a difference.
BTW, on my road bike, I have no problems spinning at 110rpm, but feel most comfortable at 85rpm.
lotek
05-16-02, 02:51 PM
I found a bunch of different "formulas" for determining
crank length by doing search of Google groups.
The basic "formula" (palms?) is:
L (mm) = 2.16*I (cm)
where L= crank length in mm,
I= inseam measurement in cm.
or:
L = 6.07 * I
where I= inseam measurement in inches
and finally
Edmund Burke, PhD gives these guidelines :
<5'0" 160mm
5'0" - 5'5" 165mm
5'5" - 6'0" 170mm
6'0" - 6'2" 172.5mm
6'2" - 6'4" 175mm
using these formulas I get the following recommendations
based on a 30 inch inseam
1) 164.59
2) 182.1
3) 170
thats really assuring, isn't it?
Marty
crank length by doing search of Google groups.
The basic "formula" (palms?) is:
L (mm) = 2.16*I (cm)
where L= crank length in mm,
I= inseam measurement in cm.
or:
L = 6.07 * I
where I= inseam measurement in inches
and finally
Edmund Burke, PhD gives these guidelines :
<5'0" 160mm
5'0" - 5'5" 165mm
5'5" - 6'0" 170mm
6'0" - 6'2" 172.5mm
6'2" - 6'4" 175mm
using these formulas I get the following recommendations
based on a 30 inch inseam
1) 164.59
2) 182.1
3) 170
thats really assuring, isn't it?
Marty
mikey
05-17-02, 08:12 AM
...and then there's the formula provided here: http://www.peterwhitecycles.com/fitting.htm
Let us know what length that gives you Lotek
Let us know what length that gives you Lotek
Richard D
05-17-02, 09:27 AM
I went from 170 - 175mm cranks on my commuter and noticed a very slight improvement in leverage on hills, but it was so slight it could have been psychological rather than physical...
Richard
Richard
fubar5
05-17-02, 08:52 PM
It depends on your height and your pedal cadence.
poptart
05-20-02, 06:01 PM
Here is my crank length story:
I have 175s on the mountain bikes and they feel fine.
Until recently I've had 170s on the road and tandem. Just started riding 172.5s on the single road bike. I hate to be "princess and the pea" but i *swear* i can feel that my cadence has dropped, especially while climbing, with the 172.5s.
The 172.5s are DuraAce and my 170s are Ultegra. I'm considering going back to the Ultegra thinking the loss of "spin" offsets the weight advantages.
Thoughts?
I have 175s on the mountain bikes and they feel fine.
Until recently I've had 170s on the road and tandem. Just started riding 172.5s on the single road bike. I hate to be "princess and the pea" but i *swear* i can feel that my cadence has dropped, especially while climbing, with the 172.5s.
The 172.5s are DuraAce and my 170s are Ultegra. I'm considering going back to the Ultegra thinking the loss of "spin" offsets the weight advantages.
Thoughts?
MichaelW
05-21-02, 06:02 AM
For a person of your size, a 2.5mm change is fairly minor and both are within the correct size range.
You may want to try a cheaper crank of that size before investing in an expensive one. Going to the larger crank, you may find yourself using a lower cadence and a higher gear. Although we often say pedal at the fastest cadence, really that should read optimum cadence.
You may want to try a cheaper crank of that size before investing in an expensive one. Going to the larger crank, you may find yourself using a lower cadence and a higher gear. Although we often say pedal at the fastest cadence, really that should read optimum cadence.