Talk about Power

Triathlon Forum
1

With things switching away from Speed and HR as a measurement of effort I was wondering if anyone has some experience to “pass on” related to power.

In particular I am interesting in exploring “what” power can bring to the table but there are many, many options. I know people who train with Powertap so I pretty much understand (but am willing to listen to new insight) the up/downs of that option. I am interested if anyone has experience and thoughts of the following:

Ergomo sport - Using the BB to measure

PowerTap - Measuring from the hub

Polar - Chain speed and tension

SRM - Crank

Pros/Cons - Perhaps we could even get Slowman to do a review? :wink:

2

http://www.midweekclub.ca/articles/
Read the first six items and come back with questions. The FAQ is missing some minor details.

3

Thanks for the resource. Perhaps I should have defined my questions a little narrower. I understand the advantages of training with power and the overall concepts. I was thinking more along the line of “If I am going to invest upwards of $1k on a power meter, Does anyone have pros/cons of the specific units described above? impressions? ease of use? service/warranty issues?, etc” I guess I am looking for real life use reviews on where to “invest” my earnings. :wink:

4

I’ve used Polar for six months, SRM for six months (so far) and PowerTap since it came out. The FAQ covers most of the pros/cons pretty well.

Polar may be adequate if you want to measure longer steady state intervals and can tolerate the not knowing if the numbers are ever accurate - just compare yourself to the Polar numbers. The setup issues are ridiculous, check the cyclingforums.com power forum for other users with issues, once you get over that, it’s consistent, unless the sensor moves, then you are back to setup. Also not in the FAQ, when your chain gets heavier from regular use and dirt, your reading goes off!

For their differences, SRM and PowerTap are pretty comparable. PowerTap wheels last from one to three years in the field - there’s some parts and mechanical bits inside the hub that are not user serviceable and the wheel must be returned to the factory. I’ve never been charged for this service but shipping wheels is a slight pain(keep the box!). SRM has rechargeable batteries that are not user serviceable (although intrepid folks have done the replacement on the crank themselves) and must be returned to the factory for service (there’s a service center in Colorado, and Germany). The precision and accuracy of the Amateur model is subject to debate ( I would not get an Amateur as the cost is the same as a powertap with an extra wheel). After regular calibration and checking, SRM and PowerTap are pretty much use and forget about except for charging/changing batteries. For the SRM you have to worry about monitoring the charge in the CPU, for the PowerTap you want to have extra batteries in your kit bag just in case and regularly change the batteries. Each day of use for both PowerTap and SRM one has to reset the CPU’s torque just in case to match temperature conditions and do a sanity check to make sure everything is valid - no torque reading when not pedaling. When something goes wrong - it’s like diagnosing a computer problem. If you have spare parts or friends with the same brand, it helps a lot. Can be frustrating to diagnose without a spare harness or CPU.

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

http://mywebpage.netscape.com/rechung/wattage/

5

SRM:
PRO: VERY accurate (2% for D/A-10 and the other new setups) and is able to be used with any wheelset. Also pretty easy to move between bikes. LONG reputation for quality. Widely considered the “gold standard.”

CON: Expensive. Cannot experiment with different length cranks.

POLAR:
PRO: CHEAPEST. Reasonable accurate, although accuracy may degrade on rough roads.

CON: Pain in the butt to set-up. Cannot be used indoors. Not supposed to be as accurate as others 5%

ERGOMO:
PRO: Can use any wheelset. Can use any Shimano octalink or Campy square-taper crankset, depending on which BB you buy. This means you can experiment with different cranks. Also can try different length cranks. Very accurate, claim 2%, but not sure if this has been validated.

CON: You are wedded to old technology with a separate BB & crank, as the advantages of outboard bearings are clear. Pain in the butt to move between bikes if you want to. Doesn’t have the same longstanding reputation as SRM. The record rate is MUCH slower than SRM. Cadence is only updated every 8 pedal revolutions. SRM you can record as often as every 1/4 of a second.

POWERTAP

PRO: Reasonable price, except if you want to race and train, you may need to buy two of them. Although an “aero cover” makes for a pretty good disc in the rear. Good accuracy. Can use any crankset/experiment with cranklength. New PowerTap Pro SL is pretty light. Very easy to move between bikes.

CON: No way to run a real disc. If you integrate with a durable training wheel, then it’s not so good for racing, and vice versa. Two powertap pros are STILL cheaper than a SRM, so it is not such a bad deal to get like a Mavic Open Pro with a Power Tap for training and a Zipp 808 rear for racing. Older, non-SL powertaps are VERY heavy and also have lousy water-resistance. SL apparently has better water-resistance, but may still not be great.

I have an SRM. The only downsides to it, in my opinion, is that you can’t experiment with different crank-lengths. The price is what it is. If you really use it, I think the difference is justifiable. If budget is your limiter, then buy the one that is in your budget. They are all pretty good. I think the SRM, PowerTap, and Ergomo are a cut above the Polar one, but are also SUBSTANTIALLY more expensive.

SRM is the ne plus ultra. But it may not be worth the extra money for you.

6

I have a SRM and it’s pretty easy to experiment with crank lengths, just $200 and you can pop in a new pair of crank arms, at least with the Campy model. :slight_smile:

The Campy model uses Campy taper bottom brackets but uses standard 130 BCD chainrings.

7

On the older ones I know you can. I have the new D/A-10. I didn’t think changing cranks was possible with this set-up. I could be wrong, though.

8

I’ve got an Ergomo and PT.

Ergomo - pros include fantastic software (cyclingpeaks), use any wheelset, temperature on the display, secondhand units can be had dirt cheap. Cons are big CPU with a lousy mount, not as accurate and needs calibration from time to time (and you really need another power meter if you want an accurate calibration), no interval marking for the CPU (multiple rides tacked together on the display though not when downloading), VERY SLOW downloads

PT - pros include being the gold standard for accuracy (better than SRM), PT Pro CPU is fantastic, multiple recording rates. Cons include locked into wheel choice, lousy software

Best bang for the buck is the PT, but there is the wheel issue. If that doesn’t bother you, I’d go for it. I’ve had mine for 3 years now and have been more than happy with it as well as Cycleops/Graber in terms of support.

9

That reminds me, the SRM CPU is pretty big and can be tricky to mount on some aerobars as the mounting system is not very flexible. PT is more similar to other cycling CPU’s and can be mounted where you want it mostly.