I was using a 575 up until last year. The 23c GP4000s is a little bit wide for the disc and gives a bit of a lightbulb profile. I found the 22c Bontrager R4 Aero gives slightly better profile. Now whether it matters that much consider the leading edge of the tire was mostly shielded by the frame, I don't know.

How does the Bontrager tire compare to the Conti in crr value?

20mm Supersonic.

Maybe 22mm Attack.

The Supersonic makes me a little nervous due to flatting. Is the Attack better at flat resistance (compared to Supersonic) and faster than the 23mm 4000s?

yes the attack does have a puncture protection belt, and usually has better CRR than the 4000s

and is narrower

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I've been using the 4000s tires with my 555. It's not a bad match, but now that I know about the attack, I'll likely try that next time around.

I put Vittoria Open Course Evo Triathlon on my wife's bike. Latex tubes. Measures right at 22mm. Harder to find anymore but I bought a bunch some time ago. Have always been a fan of Vittoria tires.

It's your rear wheel, I wouldn't worry about it that much. Get a tire that has a good rolling resistance and as much puncture protection as you feel comfortable with. The 23mm 4000S is a good choice. If you are lighter weight, then going smaller to a 20mm GP 4000S would make the wheel slightly more aerodynamic, but at the same time your rolling resistance increases. So it's a give and take. That is why on a rear wheel that is mostly protected by the bike frame, tire width is not as important as on the front wheel.

I have one and they are nice... but aero performance is bad unfortunately.

Also, though the nice Vittoria tires have longer tread life than the Supersonic, I haven't found them to be any better for puncture and cut resistance (maybe even worse)... and they are a good step below the Attack or GP4000.

I'm 180lbs and have run the 20mm Supersonic on my 575 for three years now w/o flatting (michelin latex tubes).

It's safer to run a 23mm 4000s, but not as fast; just depends on your risk tolerance.

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I run the 20mm Supersonics. 808 up front and a Renn 575 out back. Starting the second season with the Conti Supersonics but think I will need to rotate the front to the back soon and put a new one on the front. I find them in as a race only tire great. I've never flatted one in years of racing but have wore them out

Resurrecting this fairly old thread as I have a Renn 555 on it's way to my dirty little eager hands...

I noticed you can buy the Conti GP 4000S in 20mm now, is that the best tire? If it matters it is on my (2012 Classic) P3, so the back wheel is faired.

I race IM when I'm allowed to, so comfort is important. This isn't for 10m TTs, so would I be better with the Attack II, if I can find them - for some reason over in the UK you tend mainly to find them in a Force/Attack pack of two.

Ta,
Rich.

No on the 20mm GP4000. Get Attacks (turn them backward) if you don't like the SS.

Backwards for aero-ness?

Edit to add:

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/kj

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The Crr on the 20mm 4000 is poor compared to the 23. Attack is a good all around choice. Maybe the 21 mm vittoria open tubular roll a bit better or the 20 Conti SS, but you are probably splitting hairs and the 22mm Attack might actually roll better on rough pavement at a slightly lower pressure.

This is what they really look like. Based on SwissSides testing I think you want the grooves oriented more perpendicular to the airflow for high yaw.

Brill, thanks everyone! Mainly just wanted the cool vwhoomph vwhoomph noise from the disc but a bit of speed will be a nice bonus.

;-)

Cheers again, Rich

WHere is the 20 vs 23 RR published? I (probably stupidly) bought a 20 4000S for my 575 renn disc thinking it would be better than the 23 and wanting something longer lasting than the supersonic.

The 22 R4 aero rolled faster than the 20 supersonic in Al Morrison testing I saw, and I have a couple of those, so perhaps that is the better choice for what I currently have on hand. I was saving those for my mass start race wheels though (the front of which is 404 FC and would be used for TT as well).

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I'm the OP. For what it's worth, I bought the 22mm Attacks for my Renn 555. Though I have no comparison, the tire is working well for me.

The 22 R4 aero rolled faster than the 20 supersonic in Al Morrison testing I saw

The R4 was quite a bit worse in my testing. 1 R4, 3 Supersonics.

Do you publish the results online? Apologies if you do and have cited it 100 times. I'm curious to see the difference.

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I didn't publish that one. It's ~.0005 worse than the avg of the 20mm SSs I've tested, so ~.17mph slower.

plus, weren't AFM's published results before the advent of black chili? ie, look at how bad the 4000S did in his testing. 0.284 23mm 4000S with latex tube vs .0251 for 20mm SS

Those are both Black Chili.