It's always useful whenever you switch PMs to have 2 head units to see how the new power meter compares to the old one. Obviously going to a Powertap limits your rear wheel selection, which is the biggest drawback to using one.

As far as missing anything from power data, the Powertap actually produces better data than Vectors, so you might be getting an upgrade there.

Nick,

Awesome. I should be all set as I have a training wheel and a race wheel with Powertap, hoping they can be calibrated to match.
Interesting on the data quality.

They either will pretty much match or not. You can't change the torque slope of a Powertap hub so you're stuck with what you get. That said, Powertap hubs have a very good reputation in terms of precision and accuracy.

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Genetics load the gun, lifestyle pulls the trigger.

Your FTP will get lower.

The Powertap GS hub is available for $400, but it's SRAM/Shimano and 24 hole only. With a Flo 60 or 90 rim, a wheel cover and Sapim CX-Ray spokes, you could built a very nice race wheel for under $1200.

Why will it go down, just because of where it measures?

Yea, it's place in the drivetrain. I'd guess maybe 2-4% depending on how clean you keep your stuff.

Really? I sure hope they are similar. If not the race wheel is not worth it then.

I think there's a mis-understanding here. Your power will not go down with the Powertap. The Powertap is a bit more accurate that the pedal PMs. As the previous poster said, the Powertap will likely read 2-4% lower than the pedals. The situation is somewhat analogous to measuring an engines horsepower at the engine or at the rear wheels. The engine produces the same power. The test point produces 2 different numbers.

New units seem to be super consistent so I wouldn't worry about it.

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Genetics load the gun, lifestyle pulls the trigger.

If you like the Vectors, and they are working for you, why switch? Is it just because the new wheel has a PowerTap? Is the PowerTap up to date or as new as the Vector? As others have said, there will be differences, you just have to figure out what they are. It doesn't mean you are any stronger or weaker, just that the new PM likely reads differently.

Do you get L/R metrics on hub based PM's? If not seems like a step backwards.

hmm, but is it? where is power the most "accurate" and reflective of your body's work? at the pedals, which are closer to the "source?" or at the hub...?

i'm really just messing around here. but seriously, if your FTP on the Vectors is 300, your FTP on the PT will likely be like 285-290 or something. But what you are doing is no different, it's just the fact that the power is being measured further downstream.


What do you even do with those numbers?

My 2 cents: I went from two Powertap rear wheels (racing and training) to a P2M crank powermeter and there was less than a 1% difference between the two. I did a few rides using both PM's and it was something like 268 on the Powertap and 270 on the P2M, which is pretty much negligible. Not quite sure how Vector to Powertap compares though.

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Perfect, hope I have same experience. My concern isn't the drop from Vector to Powertap, it is between the 2 power tap units, I will have one on 808, and currently have one on my race wheel which is a disk, but I never have used, just used pedals 100% of time.

Why? What do you do with that? L/R metrics are really just "entertainment purposes only" type of data...

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