Power Meter (Power Tap) Basics

Here is a link to a discussion we had about it a couple weeks ago and many of your questions are answered there.

http://www.beginnertriathlete.com/discussion/forums/thread-view.asp... love training with power and I think it can really help your cycling if you use the information you gather.

1. PowerTap, Ergomo and SRM (in order from least to most expensive). They all have about the same accuracy. PowerTap may be a bit less dependable (esp. in the rain).

2. All can be installed pretty easilly (Ergomo requires instalation of bottom bracket, SRM is a crank install)

3. Not sure what you mean by different sizes. Powertap is a hub--it can be built into a 650 or 700c wheel). Ergomo is a bottom bracket--I believe it comes in square-taper or Isis-drive. You'll need cranks to match. SRM is a crankset--you'll need an appropriate BB).

4. New wheel: you can have a PowerTap hub built onto an existing rim, as long as the spoke count matches that of the hub. The others don't utilize a wheel).

5. Indoor or outdoor.

6. Sure you can race on them. The Ergomo and SRM have the advantage of being able to be used with any wheelset. For the PowerTap, you can build it onto a race wheel, or use a disc cover.

7. Probably as safe as anything to buy on E-Bay.

8. A few other options: iBike (I don't recommend it because it only infers power from a bunch or other inputs (namely wind resistance, which is extremely variable. So it's not very accurate. Also, can't use it inside. Polar has a power unit that infers power from chain tension and speed. Supposed to be pretty tricky to set up. There's a new power meter (Quarq) that's wireless and mounts to the crank spider. On par price wise with the SRM (expensive).

edit: link for a discussion of the Quarq PM: http://www.bikeradar.com/road/news/article/interbike-quarq-power-meter-real-bike-computer-12672

The other kind that run4yrlif didn't mention is Polar makes one that measure the vibration of your chain. Setup is definitely harder than the others - you need to know the weight or weigh your chain, and measure the distance (I think) between your rear wheel hub and your cranks.

There is a good review, a few years old, at

http://www.biketechreview.com/archive/pm_review.htm

Good luck!

tom 

The other thing is that apparently there is a book by Andrew Coggan and somebody else about racing & training with a powermeter. Don't know the exact title, but it's something like that. I have heard that is a very good investment if you're gettign a powermeter, since it's keyt hat you use the information it gives you in a smart manner - otherwise it's a huge waste of money.

tom 

I mentioned it...see #8.

Jim - I stand corrected!!!

tom