I’m in the process of building a TT bike. I have all of my parts picked out except for my crank. Here is my dilema. I want to add a power meter to my bike. I can’t afford an SRM, and I’m not crazy about being limited to one wheelset if I choose powertap.
That leaves me with Quarq. Some people make mention that the SRAM S900 crank, FSA crank and Rotor cranks that work with Quarq are not stiff enough.
Here is my question. How important is crank stiffness for a TT bike? I can see it being more important for crit racing where you are constantly sprinting but I’m not sure it’s that important for a TT bike. After all… Michellie Jones won on a SRAM Force crank and many other pro’s have won on FSA cranks.
Let me know what you think.
Thanks
That leaves me with Quarq. Some people make mention that the SRAM S900 crank, FSA crank and Rotor cranks that work with Quarq are not stiff enough.
“Some people” don’t know what the heck they are talking about 
I defy ANY of the “some people” to be able to detect “crank stiffness” difference in a blind test of those cranks mentioned above and whatever other crank they prefer.
Let me know what you think.
I think the CinQo/S900 setup I’ve been using for over 6 months now is PLENTY “stiff” 
I’m in the process of building a TT bike. I have all of my parts picked out except for my crank. Here is my dilema. I want to add a power meter to my bike. I can’t afford an SRM, and I’m not crazy about being limited to one wheelset if I choose powertap.
That leaves me with Quarq. Some people make mention that the SRAM S900 crank, FSA crank and Rotor cranks that work with Quarq are not stiff enough.
Here is my question. How important is crank stiffness for a TT bike? I can see it being more important for crit racing where you are constantly sprinting but I’m not sure it’s that important for a TT bike. After all… Michellie Jones won on a SRAM Force crank and many other pro’s have won on FSA cranks.
Let me know what you think.
Thanks
Crank stiffness is just one element of how much energy you lose between yourself and the wheel, the transmission efficiency. Most cranks are probably adequate on the stiffness front if you are only putting out 150-200 watts. If you are putting out 400 watts it will be a much bigger factor. The people who are putting out the most watts, the track cyclists don’t care much about weight. Stiffness is extremely important to them. They will have heavy stiff frames and heavy stiff cranks, in general, compared to what the weight weenies are using.
That leaves me with Quarq. Some people make mention that the SRAM S900 crank, FSA crank and Rotor cranks that work with Quarq are not stiff enough.
“Some people” don’t know what the heck they are talking about
I defy ANY of the “some people” to be able to detect “crank stiffness” difference in a blind test of those cranks mentioned above and whatever other crank they prefer.
Let me know what you think.
I think the CinQo/S900 setup I’ve been using for over 6 months now is PLENTY “stiff”
I agree that most people would not be able to detect any difference in crank stiffness in a blind test. That doesn’t mean that differences don’t exist though.
So if I’m holding 200-300 watts and not a track cyclist it really doesn’t matter?
So if I’m holding 200-300 watts and not a track cyclist it really doesn’t matter?
'zactly
Even if you were holding higher wattages…it wouldn’t really matter with the S900. It’s not exactly “wimpy”
So if I’m holding 200-300 watts and not a track cyclist it really doesn’t matter?
'zactly
Even if you were holding higher wattages…it wouldn’t really matter with the S900. It’s not exactly “wimpy”
Tom A and I agree on this one. Unless you are going to obsess over a couple of seconds over an IM distance you can ignore this at your power. Total transmission losses are usually only about 2-3%, and most of that is in the chain. We are talking very small stuff here but people here obsess over grams of weight and that is an even smaller time savings.
All of those cranks are more than stiff enough
unless you can TT at over 500 watts average or something
I’m in the process of building a TT bike. I have all of my parts picked out except for my crank. Here is my dilema. I want to add a power meter to my bike. I can’t afford an SRM, and I’m not crazy about being limited to one wheelset if I choose powertap.
That leaves me with Quarq. Some people make mention that the SRAM S900 crank, FSA crank and Rotor cranks that work with Quarq are not stiff enough.
Here is my question. How important is crank stiffness for a TT bike? I can see it being more important for crit racing where you are constantly sprinting but I’m not sure it’s that important for a TT bike. After all… Michellie Jones won on a SRAM Force crank and many other pro’s have won on FSA cranks.
Let me know what you think.
Thanks
Ever wonder why many track spriners who can put out 2000+ watts run square taper BB with Sugino 75 cranks or similar, and the roadies run supposedly “stiffer” integrated cranks???
The situation where crank stiffness comes into play is from a standing start ie high torque.
Making some basic assumptions even at 500 watts at 100rpm the torque is roughly 50Nm or equivalent to about 29 kg on 175mm cranks. At a more realistic for most people figure of 250w this becomes roughly 14.5kg at 100rpm.
So basically for most people especially IM triathletes crank stiffness is a non issue.
Bikesport has a small write up but not much into the science of how crank stiffness contributes to less effective power transfer.
http://www.bikesportmichigan.com/reviews/crank.shtml
My engineering .02$ is that crank stiffness is a T that needs to be crossed last. Just get a set of ultegra cranks and if you don’t fine them stiff enough you also might want to check your mattress for peas.
Thanks again to everyone for their thoughts. You’ve really helped clear things up.