Your PT vs Rented PT
Hey folks,
A couple threads in the forum got me to thinking about the implications of training on your Powertap and then renting a Powertap race wheel for race day. Of course, our budget recommendation is to just slap a wheelcover on your training wheel -- cheaper and, more importantly, you're absolutely sure that is your PT, your watts, your FTP, from training that's out there with you on race day. The fear being that your PT and your rented PT have a 2% variance between them (within the margin of error of a PT) which could really change things. In other words, worse case is that the rented PT reads a full 2% lower than yours, so your 200w on the dial on race day, on your rented PT, is actually 204w if you were riding your PT. I can tell you that 4-5w to the bad in an Ironman can definitely make a difference.
I called Sawiris just now and he confirmed this is a possibility. I've been on him for years to offer race and PT wheel rental. His solution would be to send him your PT, he puts it and your to be rented PT wheel on a calibration thingy he has, gets both PTs reading the exact same watts, sends you the rented wheel, you race with it, send it back and he sends you the training wheel.
Sounds pretty involved but more importantly I wanted to remind people of this friction point and that's not as simple as renting a PT wheel and racing with it.
For WI I'll likely just slap a cover on my Hed Belgium PT, unless he can hook me up with an 808 + cover...in which case I'd would DEFINITELY do this calibration deal above.
Comments
So, buy the wheel cover from wheelbuilder.com, which is only like $90...that is the recommendation over renting a Zipp rear disk + PT from somewhere like racewheels.com?
I have the DT Swiss rear wheel with the Power Tap built into it, and I am riding a Cervelo P3. I know you aren't necessarily the know-it-all on this, but, have you heard of anyone having trouble with this combo and the rear wheel cover?
I'm saying it's not as simple as renting a PT race wheel to race on, because you can't be 100% certain that the race PT reads EXACTLY the same as your training PT. And, trust me, you want to them to read EXACTLY the same, or as damn close as you could get it. When I last raced IM, IMCDA'08, I did 2-3x RR's, all at 216w Pnorm. I raced at 215-216w Pnorm. I can tell you that, to me, there would be a world of difference between that 216w and an accidently 221-223w. You wouldn't think it would matter that much but, trust us, when have you nose stuck on the dial for months and months you can really tell the difference.
So you want an aero wheel for the aero benefit, obviously. In my experience, a trainer wheel + wheelcover is 99-100% as good as $$$$$$ race wheel...so that solves the aero question.
Weight? A few grams, aero trumps weight in our gig, and I'd be motivated to lose an additional 4-8oz of body weight to save $$$$$$$.
Power consistency, ie, the variance from your PT to a rented PT? That's the variable that you can't measure, control, or account. Sawiris said something about hanging a known weight off the pedal and using that to calibrate between two PT's. I'll ask if that's something that anyone can do or just him, with special equipment.
Stephen,
I've not heard anything about this combination being an issue but I am far from an expert on this. Call wheelbuilder I'm sure they would be able to tell you.
Gordon