It’s not just Formula One cars that suffer from tyre blisters…
The Continental GP4000s on the road bike have been getting a bit battered since the more powerful Dura Ace brake callipers were fitted last year. I’m not convinced it is actually blistering, but locking up the rear wheel isn’t doing these tyres any good.
What happens to a tyre during build up to blistering, is that the chemical composition of the outer casing, begins to change, usually due to too much heat. Road debris is however another common cause. This can rip little chunks of rubber out of the tyre, especially when friction (generated under braking) makes the tyre hot and therefore very soft and easily damaged.
These are often mistaken for blisters, because the visual evidence is similar. Real blisters occur when the tyre gets hot and the outer rubber begins to melt and crumble apart. This usually happens in small areas and the rubber can bubble. This can look like a blister and after it occurs, rubber begins to chunk off and leave little holes in the tyre.
R O T H A R . C O M 
Those 2 little holes are present from new on GP4000s 🙂
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Rubbish! It’s my powerful sprinting off the lights and breakneck stopping style doing that to ’em.
Seriously of course you’re right, they’re the wear indicators in the casing. When the holes disappear, the tire is worn past its useful life. Unfortunately like the tyres on at the moment riding around Manchester usually means they’re sliced and cut up before the tyre wears out.
That said they’re great tyres. Typically, as a tyres gets older they harden and lose grip. The GP4000’s still feel nearly as supple and grippy as when they were fitted.
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