A Continental GP 5000 Without Friction

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Years ago I rode with a scooter tyre for nine thousand kilometres before it was replaced. It was only replaced because I went to a different garage. Scooter tyres are rated for about 3000 kilometres before they are meant to be replaced. I rode for four thousand kilometres with my GP5000 and several times I noticed that the rear tyre skidded, either when I applied the brakes as I got home, or when I was braking in a descent, but especially when I had to emergency brake in group riding situations more than once.

Yesterday, before the ride, I ran my thumb along the rear tyre and I felt no grip. The tyre wasn’t trying to slow down my finger at all. That’s why I chose to swap out the GP5000 rear tyre for a GP All season tyre. I’m glad I did, because when I had to brake fast when riding as a group, there was a moment where we had to stop fast, and I kept full control. The rear tyre didn’t skid.

Loss of Friction as a Sign of Wear

If you search the web, or ask AI agents when to replace tyres they say "When you get punctures, when the tyre wear indicators are gone, when the thread shows", and more. What they don’t write is "When you notice the tyre skidding more regularly than usual.

When I had a scooter, and when I rode it regularly, I relied on the garage to warn me that the tyres were worn, and to replace them. With an old garage they allowed me to run for 9000 kilometres without swapping the tyre. Visually it looked fine, but three or four times, after rain, the rear tyre skidded out from under me and I fell. I didn’t know, at the time, that falling was due to tyre wear and loss of friction, rather than riding skill.

That’s why, when I noticed the same problem with the bicycle tyre, I knew I had to change the tyre, especially yesterday afternoon two to three hours before the ride. The thumb test is a quick and easy test. If the thumb slides, without sticking, the tyre is degraded. If it sticks the tyre is okay.

And Finally

If, like me, you notice that your rear tyre is starting to skid, when slowing down, check the tread and make sure that it hasn’t become smooth, and stopped gripping. "Over time, and with the repeated heating and cooling cycles from riding, the chemical properties of the rubber change — a process similar to vulcanisation continuing slowly. The rubber compound hardens and becomes less pliable." This quote is from Gemini but Gemini did not attribute its source.

I attributed the skids to the swapping of the brake pads, but now I think it was also related to tyre wear after around 4000km of riding this year.