Size Change to Conti GP5000 Clinchers?

Has anyone noticed a relative size change in Conti GP5000 clinchers? I just mounted new GP5000s, and they are significantly smaller than previous versions of the same size. Both the 25mm and 28mm now measure less than their advertised width (on DT Swiss R460 rims…18mm internal width), with the 28mm coming in just over 26mm wide.

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Tyre makers seem to be making road tyres with 19-21mm inner rim widths in mind now, not the 15-17mm of the previous generation.

I’m pleased about this to be honest as they’re a lot more true to size, I was fed up of buying tyres that were a lot bigger than advertised (Michelin were especially bad) that then led to clearence problems with mudguards.

Your own GP5000’s will probably gain a millimetre or so as they wear in.

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I agree the new tyres are smaller but in a good way The new 5000s TR measure 29.5mm on 25mm inner width hookless rims. This width is perfect for the 31mm external width.

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Thanks for noticing. I’ll be buying new contis soon and I wasn’t sure what size to get. Definitely gotta go with 28mm now.

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Small world,

I asked this question to Challenge a while back when I noticed their 25mm Strada got quite a bit more narrow on my 18c ID rims after I ordered from a different website. Attached is their response but to paraphrase it appears the ISO standard has been updated to accommodate larger ID wheels that are prevalent so the tire width has been narrowed to make the stamped size accurate to the width of the tire mounted on the new wheels.

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Anecdotally, 32mm GP5k’s used to swell up to a bit over 35mm on my rims and now only sit at about 33.2mm so I’d lean towards believing they adjusted their sizing… but no concrete proof that they have.

Interesting, as 5000s were already notably smaller than 4000 S2s.

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IIRC the 4000 SII s where weird in the sense that the 25s seemed to be oversized and the 23s where seemingly undersized. I vaguely recall the original GP 4000s being narrower across the board but that was ages ago and I’ve never been a big fan/user of Continental road tires.

New GP5000S is indeed narrower than old GP5000 and a 25mm tire now actually measures 25 mm when mounted.

I’m liking the changes. Also much easier to fit than the old GP5000 TR.

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True, 4000 S2 in 25 really was oversized.

This is an interesting development and I was thinking could potentially explain a portion of the degradation in speed bicyclerollingresistance.com found between the 5000 TL and TR.

It’s a great conversation starter (as much about cycling tyres in 2022 can be…), and I have approached a Conti rep for an explanation. Here is an overview of Conti GP5000 and an explanation about widths now.

"Regarding sizing, the GP5000 and new GP5000 S TR are both made to an ETRTO standard, and have had no change since launch.
"Width here can be affected by rim width, with ETRTO suggesting an 18mm internal diameter rim be fitted with a 28mm tyre.
"From the previous generation GP4000s (circa. 2018), The new range is truer to size, whereas the older GP4000 often ran on the larger side.
“Anecdotally,” concludes the Continental rep, “I’ve just fitted up the new S TR in a 32mm on my 20mm internal rims, and these measure bang on 32… I hope this is of some help. The world of tyre/rim width and compatibility is often complex.”