Campag Bora clinchers on a Colnago C60 - tyre size/clearance

[Lugan]

It's not recommended to use 23mm on new Bora's. The rim itself is 23mm, therefore you must use a 25mm tire to prevent that the tire comes of from the rim.

I don't think that's true. I use 23c GP4000S on mine and after thousands of kilometers they work very well.

[cmcdonnell]

As Lugan said, 23mm's fit better and can be treated as 25mm. Mine newest GP4000II 23 mm's come up as 25.2 mm. I tried a 25 mm last year and they looked huge and lightbulby and measured 27 mm. The outside rim of the current Bora 17C Clinchers is 24.2 so 23mm tyres will give the best fit. Aero data suggests a tyre should be no wider than the widest point of the rim (narrower is actually better apparently). Also I can say that a 23mm tyre on my Bora's feels like a 25 mm tyre on my 15C Shamals.