Looks like I'm lining up a fresh set of GP TTs for the race season.

Yeah you can buy a 25c GPTT.

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Timothy Winslow

That's interesting. I didn't notice both sizes on the Conti site last month when looking for specs for the new GP SS. I can't imagine how wide the 25c mounts up. Maybe similar to 24c and 26c Spec TC.

Conti now has 23c and 25c sizes in the GP TT and have labeled the Attack III/Force III at 23/25 when vII were listed as 22/24. It will be interesting to see how the 20c and 23c GP Supersonics test and measure mounted. Reports from those on ST that have had them in hand say they look like the GP TT casing and tread.

Presumably the same tire without the Vectran breaker layer.

It is looking that way. I'm just not sure what the 20c GP SS is with a Vectran breaker. Attack III? Or is 20c/23c GP SS really 23c/25c :(

"If you mean rank order, I think you keep forgetting he tests clinchers with butyl tubes and I test with latex."

i know he uses butyl. all things equal, swapping latex for butyl keeps the rank order the same except standard clinchers catch up or overtake tubeless and tubulars.

but on second look yours appear pretty consistent with his. enough at least for you each to validate each other pretty well.

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Dan Empfield
aka Slowman

From my roller tests, I recall that butyl tubes were a bit of an equalizer. They didn't change the rank, but they kept the really good and the really bad tires from standing out as much.

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My latest book: "Out of the Melting Pot, Into the Fire" is on sale on Amazon and at other online and local booksellers

Thanks. That's my takeaway as well.

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http://bikeblather.blogspot.com/

The effect of adding a fixed bias...percent differences are reduced ;-)

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http://bikeblather.blogspot.com/

Is there a difference between brands of latex tubes? One that matches up "best" with a Conti GP TT 23c, for example?

There's no many choices, but Vittoria and Challenge work well for me.

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http://bikeblather.blogspot.com/

What Alan and I both found was that the smaller Michelin tubes (18-20c) had slightly lower CRR than the wider ones ones (22-23c). I have found Challenge and Vittoria tubes to be less reliable than the Michelins.

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My latest book: "Out of the Melting Pot, Into the Fire" is on sale on Amazon and at other online and local booksellers

Thank you for sharing the additional data.

My experience with the Michelins was just the opposite...they tended to "dry up" and fail on me.

Also, I think Michelin stopped making latex tubes a couple of years ago...

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http://bikeblather.blogspot.com/

I bought a couple when I was in France last summer.

New Old Stock (NOS)?

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http://bikeblather.blogspot.com/

There was a group of old ladies with boxes full of NOS 22/23 Michelin latex tubes in a couple valve lengths at a swap meet in Madison, WI about a couple weeks ago. $8 a piece, 3 for $20. They still had most of them left at the end of the day. Part of me thought it was too good to be true so I only grabbed 3. I totally forgot about them until right now.

Edit 1: Thanks for the new roller test results!! Very cool info!!

Edit 2: These are the tubes. Maybe they are not that "old" stock if they are still available.

Someone yell at me if I am wrong, but aren't the Knight 95s pretty damn wide? Like on the order of 28mm or something around there? Wouldn't you be much better off, from an aero perspective, with a wider tire than a 20mm Supersonic, even if the Crr is a bit more? If I recall correctly, Ben Hoffman ran a 25mm up front and 28mm on the rear in Kona a year or two ago.

Thanks for the new results. What is the biggest tire you can test on a 700c rim? There seem to be diminishing returns (aero hit vs improved CRR) beyond 26mm or so, but I would be really curious to see how some of the 30mm+ offerings roll.

Also my lbs (Palo Alto Bicycle) sells Bontrager latex tubes. It is the only place I have EVER seen that stocks latex tubes.

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/kj

http://kjmcawesome.tumblr.com/

They're definitely wide, but I'm wondering if the 23C Supersonics wouldn't work better than the TTs of the same width. I'd expect that the internal width of the Knights would bow a 23 out to 25-6, and that a 25C would likely end up wider than the rim - a thing we are supposed to be watching out for as it negatively affects aero.

That's kind of why I'm curious about the 1w between the TT and Supersonic, but I think the 20 got compared to a 23, which isn't a fair fight.

https://www.bike24.de/...earch=Michelin+latex

How long ago was this experience? Michelin quality varied a lot over the years and many quit using them. The Vittoria latex tubes have proven to be very consistent and reliable the last several years for me.

I do have a newer Michelin that I'm using with my Zipp disc only because they offer a 36mm valve stem while Vittoria only makes 52mm valve stems now. The shorter stem provides better inflation clearance.

One major shortcoming of the Michelins is they do not make latex tubes with removable valve cores. I prefer RVC valve stem extensions for deep wheels. Many latex tube users are also using sealant in their race tube/tire set ups and RVCs work well for sealant installation.

I can go pretty large on the 700C since my "all-road" bike has a power meter on it too ;-)

My 700C wheels for that now have 32C tires, but I could probably go as high as 38 or so...the limit ends up being the chainstay bridge location (it's a frame that was orignally designed around 26" MTB wheels).

The question I get into though when beginning to test wider tires is what to use as a test pressure...120psi isn't going to be a good idea ;-)

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http://bikeblather.blogspot.com/

Tom--if you do stick with 120psi with wide rims, please (a) wear protective gear; and (b) take videos.

Well, I've already developed a lower pressure protocol for wider road tires on wider rims...but even that is 100psi. The idea is was to choose a pressure that gave a roller Crr that was equivalent to what I get at 120psi on the Mavic Open Pro.

But, if I go to even wider tires...yeah...it can start getting dangerous. I've had 27C cotton casing tires not be able to stay on the Mavic Open Pro at 120 psi since the beads are "rounder"...

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http://bikeblather.blogspot.com/