Aside from the fact that the crank arm is a little longer.
How will this affect my time trial, cadence, power output, etc? And how long does it usually take to get used to this kind of change?
you probably wont notice much difference. Your leverage may be better, depending on your leg length, so a little more power output. I did finf when I went from 175 to 180 my RPM went down a bit so my power stayed the same. After about 2-3 months, my rpms went back to where they used to (ave 90-95) and my power went up about 5 watts.
You should have to lower your saddle height by 2.5mm, since your pedal will now be 2.5mm further away from you at the bottom of the pedal stroke. Likewise, at the top of your pedal stroke, your knee will now be 5mm higher than normal. This might affect you if you have bad knees, since you’ll be coming over the top at a more acute knee angle.
Then again, it also could affect you if you have a gut - your knee could be banging into it every stroke.
You should have to lower your saddle height by 2.5mm, since your pedal will now be 2.5mm further away from you at the bottom of the pedal stroke. Likewise, at the top of your pedal stroke, your knee will now be 5mm higher than normal. This might affect you if you have bad knees, since you’ll be coming over the top at a more acute knee angle.
why would it be 2.5mm further away at the bottom and 5mm closer at the top? the crank is 2.5mm longer.
Saddle down 2.5mm
Crank up 2.5mm
equals 5mm
.
I will be absolutely, and utterly in disbelief if you notice anything. As others have said, you may have to lower your saddle just slightly…As far as other parameters, IMHO, 2.5mm simply isn’t enough to notice. Maybe if you made a 5mm jump, but not a 2.5, just too little.
I agree. I bet you couldn’t tell if it was a blind test. Only way you will notice a difference is because you’re looking for it.
I used to ride 175s when it was the thing to do.
Then I noticed one had cracked and so I put on a 170 crank I had lying round. Couldnt tell the difference, and I forgot about it afterwards. I rode months before I got it replaced.
What is your inseam?
34.5 inches
.
I went from 175 on my road bike to 172.5 on my TT bike and really I don’t think I could tell the difference. ALthough, I don’t know for sure since i have yet to get back on a bike with 175 cranks. In the back of my mind I’m always wondering if the 175 will make me a little faster.
As others have pointed out, I think there is something to be said for shorter cranks on a TT bike. Maybe with shoter cranks you can get lower and thus become more aero.
crank circum- inches at feet at diff in length-mm inches ferance 90 rpm 90 rpm ft per minute 170 6.6929 42.05417 3784.875 315.4063 -4.63833 172.5 6.791325 42.67261 3840.535 320.0446 0 175 6.88975 43.29106 3896.195 324.6829 4.638327 180 7.0866 44.52794 4007.515 333.9596 9.276655
The advantage of high cadence over pushing big gears slower for a triathlete is his legs aren’t cooked getting off the bike.
Based on a statistical population of two people, I’ll even contend that if you spin at 90 rpm, you don’t even need to include bricks in your training regimen. That is why I went with the 90rpm in the above.
The 1st column is the most popularly discussed crank lengths.
column 2 is converted to inches because that is how I picture distances.
column 3 is how far your foot travels in one revolution in inches (2-Pi-R)
column 4 is foot travel after 90 revs in inches
column 5 is in feet. (how far your foot travels if you stretched all those circles into a straight line)
column 6 is the diff from standard 172.5 in feet.
All of this is for one minute. If you multiply by 60 minutes, you see how these numbers are really accumulative.
You may not be able to feel a differance, but it is surely there.
My conclusion: Since high cadence is king if you run after the ride, a shorter crank arm helps you. Where it bites you, is if you are riding up a hill with the little ring up front and the biggest ring on back and you still doubt if you can make it. Then you would love to have the extra leverage of a longer crank arm.