Accuracy of computrainer.

kclw said:

Does anybody have a computrainer and other power device? Has anybody measured the accuracy of their computrainner?

I have heard that is variation from computrainne to comptrainner.

I have a computrainer and 2 powertaps - all agree with each other within 3 watts in step tests from 100watts to 400watts. I have a problem with the load generator and was given a new one - second one gave identical readings to the first. IMO a very accurate device.

kclw said:

Does anybody have a computrainer and other power device? Has anybody measured the accuracy of their computrainner?

I have heard that is variation from computrainne to comptrainner.

well all devices have some variation - it's a question of whether it's significant or not. There were three CT"s bought here in fall 2002 on a group purchase. About a year later, I'd become addicted to power and bought a PT Pro. I performed numerous step tests with the PT against my CT in ergo mode and over several months confirmed that the CT was extremely repeatable and extremely linear wrt the PT but it's slope was low by 1.045. I tested the other two units less rigorously (single day, multiple step tests) and found ratios of 1.05 and 1.08.

Yes I did check my PT's torque before this series of tests 🙂

After some wailing, knashing of teeth and initial denial from Racermate, a procedure was devised that allowed slope adjustment of the CT to match one's PM of choice. I performed that on the three CT's (took about an hour for each), rechecked the step test a couple of times and left them there. I have confirmed mine numerous times since that and it's still within 1% of my PT Pro power. I added an external cooling fan when I found that my longer L4 intervals caused the CT power to significantly droop or drift lower over time. With that addition, the CT and PT agree to within 1% even up to three hour tempo rides that I've done this winter.

I have not tested new units but from reports across the net, it sounds like they are much closer than our's right out of the box. In any case, given you can easily use your own or borrow a PT wheel/harness to test and adjust, I see no issue with CT accuracy.

So with the addition of a small fan to the base kit (cost about $15 CAD), I'd highly recommend the CT as a linear, repeatbable and accurate training device. I think I have close 1000+ hrs on mine and the bearings are still smooth.