I say a 23 vs a 20 on a FC808 gives up 3min in an IM bike leg(specific tires in mind) but most here would not ride that 20 for fear of flatting, they'd run that 23 thinking it is the be all of tires. with an H#, designed for narrow tires, i'd guess it would be worse, but that is only a guess

I run a Continental Supersonic 20mm on the front, although I've also run the 20mm 4000 (no s, but conti says the 20mm black is an "s"), and I've run the 23mm 4000s. I've recorded my fastest times on the supersonic (although that's subjective). However, as far as rolling resistance goes, Tom A. tested all those wheels and I think the 23mm 4000s and supersonic tested the best of the ones I've tried.

Over 112 miles, if 10 seconds aren't going to decide your pay day, I'd run dual 23mm 4000s w/latex. Hope that helps.

Safer how? I have no data showing a safety difference between a 23mm GP4000s vs a 19mm Bonty AW19 on an H3.

How much time difference there is depends on which 19mm, 20mm and 23mm tire's you compare. The difference can be minutes.

How much less safe and less comfy is a 20mm tire of similar construction?

IMHO damn near 0 less safe and comfortable.

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

a nice compromise by the way is the continental attack.

22mm, but really quite a bit smaller than the 23mm 4000S. But it says 22 on it so you won't psychologically worry about. It also has a puncture belt unlike the supersonics which is nice.

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

Yeah, but getting those 21 or less tyres on is a real bastard. Even with a nuclear jackhammer let alone a Pedros lever at the side of the road. I went with twin HED 3s. 22 ZIPP Tangente up front and a Conti GP 4000 outboard.

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http://www.fitspeek.com the Fraser Valley's fitness, wellness, and endurance sports podcast

I'm riding a HED 3-setup for both front and rear. Going with a Conti GP4000 20mm in the front and a Conti GP4000S 23mm on the rear wheel.

/CE

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Next race: IRONMAN Florida

http://www.cetri.se/

Just a quick piggy back on the thread, I was originally planning on a conti attack for the front with my fc808. Will an s-works mondo 21mm be a better option at IMWI?

So I guess the 25mm tire I am running on my Hed Disc is not the best choice?

Narrow or wide? Also the rear is more shielded

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http://RoadID.com/...te/4HC4V-TAFQ9XPJDTX

The strong preference of the HED3 for 19-21mm tires isn't matched by the rest of the Hed lineup. If you have a C2 or rim the 25mm isn't much of a penalty, though 23mm would be a bit better. I'm assuming you don't have one of the brand-new "+" rims.

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The point is, ladies and gentleman, that speed, for lack of a better word, is good. Speed is right, Speed works. Speed clarifies, cuts through, and captures the essence of the evolutionary spirit.

no that is fine.
the old H3 is an especially narrow wheel.
and this mostly is a big deal only on the front wheel

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

Exactly, I bought it used, its the HED jet Disc (I think, 2011 or 2012). It had a 25MM GP 4000 on it, since it was in good shape I left it on this racing season.