Another thought, position, fit, training, tactics, and equipment are not mutually exclusive concepts. Work them all to get every last bit, but if you don't race then just buy what looks best.

I'm the first guy around town to make this point to my cronies but, in "most situations", the difference won't be that much. However, I suppose it depends how 'wrong' the slow tyres are compared to the fast tyres.

On this Bike Tech Review test, some very slow tyres, such as Conti Ultra Sport, are around 7 to 9w slower than the fastest "race-only" clinchers (with latex tubes), but, like.... who uses Ultra Sports any more?!?! Eeew! Perhaps only the newest of newbies.

http://www.biketechreview.com/tires_old ... g_rev9.pdf

lol, atm I am 260lbs (down from 300 in december) I hammer the bejezus out of my bike. I can maintain 24mph without a problem at all on the flats(with spinergy xaero-lites)(Read as insanely un-aero). Given my shoulder size and relative cross section. I will take any aero benefit I can get. Also no one is mentioning the increase in stiffness of deep section wheels. If a wheel is stiffer it transfers more POWAH!!!! As much as I love my spinergy's for thier comfyness and relatively light weight(1500 grams clincher) The PBO spokes are huge, and the rear wheel does experience a good amount of wrap up (enough to make noise in the 350 watt range). So I am fairly certain I would gain a decent amount of speed everywhere going to a 404 or a ENVE wheel. However I am not everyone, so take with a grain of.....well crack

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[img]<iframe%20height='160'%20width='300'%20frameborder='0'%20allowtransparency='true'%20scrolling='no'%20src='http://app.strava.com/athletes/1677950/activity-summary/ddf436fc1ca509b20d4637cfa80c928da771d2c6'></iframe>[/img]

The info I gave came froma Tour test. The worst performing tyre tested (4 season, some hutchinson tubless efforts and few others) gave power comsumption of about 55W at a high road speed where as the likes of the GP4000S gave a comsumption in the order of around 32W or something like that. Which goes to show which test is closer to reality? I do not know as I have not done emperical testing my self and the only kind of test that means anything.

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www.thecycleclinic.co.uk

Per wheel!

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formerly rruff...

Yes, per wheel, but that's comparing the worst tyres to the absolute fastest and lightest.
Who still hacks around of Schwalbe Stelvios or the old Conti GP 4000? No one, I reckon.

About the worst tyres I see the odd cool riding on their wet day bikes are GP Four Seasons or Gatorskins