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Profile tweak

Posted: Sat May 30, 2009 5:09 pm
by jkallo
I have a good profile, a brand new set of wheels that I'd like to ride tomorrow, and the spot where I usually do my coast downs is unavailable (charity run/walk). I'll do the proper coast downs on Monday and apply them to the ride file, but would anyone care to suggest how I might tweak my current profile to get reasonable numbers on the bike tomorrow?

Old wheels/tires: aero aluminum ~30mm clinchers with pretty normal rubber (vittoria rubino slicks)

New wheels/tires: 50mm carbon deep dish tubulars, non-flat spokes, schwable tires

I am guessing I am going to be gaining aerodynamics and a bit less friction right?

Re: Profile tweak

Posted: Sat May 30, 2009 6:23 pm
by rruff
From the information you've given I can't tell if the new wheels will have lower aero drag or friction compared to the old. Schwalbes are not noted for low Crr, and you say the spokes on the new wheels are non-flat... what shape are they exactly, and what is the spoke count? And what spokes and count are on your old wheels?

Anyway, we are really just nit-picking. If your profile is good, you should get very reasonable numbers by leaving it the same. Any difference in CdA or Crr would be quite small.

Re: Profile tweak

Posted: Sat May 30, 2009 6:55 pm
by R Mc
a terminology quibble first:

Are you serving pizza on your wheels? Or, is the rear wheel so atypical that it requires a deep dishing to fit the cassette?

Although lots of people, for some unknown reason, persist in calling deep-section rims "deep-dish", it's really not a good term.

Experience:

I've ridden both dt 1.1 rims and Flashpoint 60s in the last year with the ibike. Aero for the flashpoints: 244; aero for dts: 254. Friction for fps (with Hutchinson Fusion2 tubeless): 6.179, crr: .0067; Friction for dts: 7.63; crr: 6.5 (also hutchinson tubeless).

Re: Profile tweak

Posted: Sat May 30, 2009 10:20 pm
by jkallo
The term "deep-dish" was delivered tongue in cheek. As in "I ride in chicago so I ride deep dish rims" :-)

Thanks to you both for the input.