why would....
 

my buddies Power tap read about 60 watts more on flat ground than mine...we are the same weight and were doing the same speed.

we did intervals today and he was consistently +/-60 watts higher. the only difference was he was on bontrager x-lites and i was on Zipp 303's...they aren't that freaking aero that much i know.

what gives..

ps..i am new to the Powertap thing.

My guess would be zero offset.

Is your body position identical? (Are you more aero than he?)

Does Ben use a higher cadence than you?

zero offset or more likely body aerodynamics coupled with rolling resistance.

not really..we were both within 5 rpm's or so of each other.

actually he is smaller and more aero than me....hmm...must be offset...cause mine drops right to zero the second i take power out..

i'll have to knock that out...any advice on how to do that?, is the zero torque reset thing enough?

I'd just start by making sure they are both zeroed. Go to the watts line by hitting mode, hold down select til it flashes, hold select until it reads zero, release and press again til it turns solid. I have had 3 powertaps and I could zero one, put on another wheel and it read 12 watts differently. Saris seems to think this is normal and is one of the reasons I feel more comfortable with the SRM where you can determine the slope and set it yourself.