Current consensus is that it doesn't matter THAT much for a rear, but since rear comfort is not that much of an issue for Tri, I'd go for a rim-with matching narrow tire (<=21mm) because of the trailing edge.

Three tires to consider. The Vittoria TLR 23 has probably the lowest Crr but you might lose a watt or two for the width mismatch. The new Conti SS20 tests very close to as fast as the Vittoria TLR in terms of Crr and is probably a touch better for aero, so that pretty makes it the fastest choice. I think the GP TT comes in a 21 and has flat protection strip, but Crr is a bit worse.

can we define terms here? "new" Conti SS... where are we at with Conti's model roll outs?

Also, whose testing?

thx

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Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

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There are at least three different versions of the Conti SS. The first generation had yellow lettering on the sidewall and these tires have a roughly 3 watt higher Crr then the later models. Last time I tried ordering old stock SS 20s on EBay they ended up being the gen 1 tires, so they still aren't there even though I would guess they are 5-6+ years old.

Gen 2 has silver lettering on the sidewall. The casing is noticably softer than the first Gen and these have a Crr very close to the Vittoria TLR.

Gen 3 came out last year. Sidewall lettering is in silver as well and Crr is about equivalent to Gen 2 for the limited number of tires I tested. These appear to have a subtle dual tread compound, though it might be just a change in mold or texture. The problem with Gen 3 is they installed wider by about 5%. This makes them less than ideal for the old H3 because they install at 21mm and change, which makes them wider than the 105% rule that Zipp put out years ago. That look pretty badass on a H3+ though.

I plan to get the calipers out and measure the resulting shape and see how the Gen 3 SS and TLR compared on the 25mm HED and Flo wheels. I probably need to go back and look at The Flo and Tom A windtunnel tests as well.

there is unfortunately a "Gen 4".... Conti SS tires that look like GP TT tires... I have a whole batch of them.

Curious, are you located in the US?

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Eric Reid AeroFit | Instagram Portfolio
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“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”

Another generation would be a PITA,... Unless they are faster and/or narrower. So is this a new tire for this year? I haven't actually seen a GP TT yet, so my interpretation of the Gen 3 and 4 could be confused.

Ya I am in Northern Colorado. The land of beer and bongs.

i was told it was a branding issue for north american customers... nobody knew how to install or use the SS so when one of us orders an SS from a US IP, we get a rebadged TT. Not sure if that's still the case.

they are NOT narrow... 23mm "SS" (ie. GPTT) is wider than my Zipp 808 Firecrest brake tracks... barely OK on my NSW wheel.

Best tire for still remains the SS, which is OK on Firecrest and perfect on NSW.

FWIW, Corsa Speed TLR look pretty narrow on my NSWs... coming in at the listed 23mm.

Finally, I would love to see some aero testing on the Corsa Speeds... I"m sure the SS is faster when you include Crr and CdA.

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Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”

Gerlach has the TLR aero tested on his blog page. I can’t remember the comparison tire (most likely some version of a SS, given his history with that tire), but the TLR was a watt or two behind. I am guessing the TLR must still come out ahead for a lot of application because you see Grill and the he other CTT guys running them as front tires. I also saw a picture of Amber Neban in Velonews using a kiss-matched tire combo with a TLR in front. Maybe you could get Jim Manton to comment on that

A rebadg d GPTT would be interesting I think I got my new SS 20s from Europe, but I can’t remember for sure. I am waiting for a snowy weekend to do some more roller testing

I was hoping to get some SS's for next season, and I'm in Utah. Any idea how to get the gen 3 tires in the US?

I just picked up a 20mm GP4000s II on eBay for $38 for my narrow rear disc wheel.

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Madison photographer Timothy Hughes | Instagram

where are you finding GP TTs in 21? I've looked and conti says it only comes in 23 and 25.

I've had bad luck with punctures - punctured a vittoria corsa (NOT corsa speed version) tubular in a race and a Force tubular rear this year, which makes me think maybe ultra fast and thing race tyres might not be all that good- So I'm hesitant to run the SS 700x20c on the rear. Would I be losing alot if I went GP4000SII 700x20c on the rear?

not sure that my issue is still a thing... Rob Gray ordered some recently and received Gen 3 or its equivalent tires.

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Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”

You might see you can return those. RRuff tested them and posted about a really high Crr. Being a skeptic and thinking that maybe Conti had changed the casing or compound to match the current GP 4000s in the 23 or 25 width, I ordered one to test. They look like the perfect tire for the HED 3, but they are total Crr turds. RRuff was right, they don’t roll anything like the 23s. Sorry

Oh bummer. I figured the black Chili compound was a no-brainer.

I've been running a 23mm GP4000s II and will probably just keep that on.

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Madison photographer Timothy Hughes | Instagram