Right, i’ve been very tempted to try and buy some speed for a while now and finally broke and bought a disc wheel. It arrived last week, i ordered the same tub as i have on my 82mm rear wheel i’ve used until now. My previous best was 22:59 (@ c280w) on my local 10m TT course (5m out uphill, dead turn 5m back downhill). https://www.strava.com/segments/1404218 . Lately i’ve been doing 23:15 or so on this and other courses @ c260-270w. I fitted the disc for Tuesday night. Conditions were fairly typical and all the other riders times were where you would expect yet i did 24:22 at 270w!?!
I didn’t know what had happened. My minute man (normally 20-30 seconds faster had caught me before the turn and i made barely any inroads to the guy i was chasing.
I thought my power meter cal must have been off. but after looking at my data my HR correlated what i was feeling which is that i was definitely at my limit.
To make sure, i rode the course again today, in broadly similar conditions. All other factors, tyre pressures, skin suit, helmet, shoes etc were the same as the other TT’s (on 82mm and disc wheel). Power and HR were at the same threshold +/-.
Results were the same. +1m odd.
I’ve looked at brake rub, bearing friction, alignment, flex etc and the wheel seems good.
To my mind a disc wheel (even a basic flat one) should be faster than a spoked wheel in any conditions barring possibly straight on brutal cross winds. The weight penalty isn’t huge, especially on the kind of gradient experienced in the test.
So, is it a flywheel type effect?
Is the lack of smooth cadence and flat power curve dumping energy into the wheel that i’m not getting back?
Would a more expensive, lighter stiffer wheel negate some of these losses? Would i still be slower?
Do i have to persevere and find out how to get the best out of it (that’s a big deficit to overturn?
If you can tell me what i’m missing or otherwise make sense of my confusion, please do.
Cheers, Al