SRM or Power Tap?

luv2ride

What do you recommend SRM or Power Tap and why. Or is there another wattage measuring device that you like that I haven't mentioned that you like.
Your Friend in Cycling
alder

__________________

RapDaddyo

If you search this forum, you'll find lots of discussion of this topic. To net it out, I think the SRM Pro is the gold standard PM device, but it's pricey and a bit high-maintenance (periodic re-calibration). The PT Pro and SL are almost equally accurate (and certainly sufficiently accurate for 99% of us), but still not cheap. The Polar is a bit less consistent, but is clearly the cheapest alternative. I went with PT SL and I would make the same decision today.

beerco

Why do you think that the Power Tap products are not as accurate as the SRM pro?

RapDaddyo

I don't know that the PT products are less accurate, but I do recall that there is a systematic difference in the watts as reported by SRM Pro vs. PT. But, as to accuracy, for normal training and racing purposes I don't think there is a practical advantage of one over the other. I think the differences are a function of where in the drivetrain the power is being measured. I think the SRM Amateur is definitely less accurate because of the number of strain gauges used.

beerco

Ah. Your first post makes it seem like you thought they were.

RapDaddyo

Actually, while I can't point to any test data to support this (although there may be such data), my own personal view is that any differences between the SRM Pro and the PT units are not due to accuracy/inaccuracy but rather what is being measured (crank vs. hub). But, as a cyclist I can't come up with a good reason to choose one over the other due to such differences. But, as to the SRM Amateur and Polar units, I think there is a distinct difference in accuracy due to the underlying measurement methodology and technology. In the case of the SRM Amateur, I think 2 strain gauges is clearly a less accurate methodology than 4 strain gauges. In the case of the Polar, I am suspicious about the accuracy of the Polar measurement methodology through the full range of power measurement circumstances (e.g., accelerations, gears, constant vs. variable application of power).