Bicycle Mechanics - When to replace tires?

How often do you replace your tires? I've had my bike for a year now. Do you go by miles or by how the tires looks? How do you determine when to replace so as not to push it and have a blow out or replace them way before you need to?

You probably only need to replace them if they're damaged or if they're worn down to the threads.

If you rely on knobby tires, you could probably replace them when the knobs are worn flat and the tire is bald.

Or if the tires are so old that the rubber is no longer rubbery.

Of course, you can replace them if you just get sick of them and want to try something different.

I agree with Shecky. A cut through the casing or seeing threads through worn rubber will get me to replace a tire.

The other time is if a tire is close to those replacement conditions and I'm headed for a long unsupported ride or tour. I'll replace a tire early to avoid problems where I can't fix them or a major tire problem would ruin a trip or an event. The result is I have a couple mostly-worn tires that, in theory, I could remount and use (on my back tire). I haven't done that part yet.

Okay, I've looked them over and I have a couple of spots on the front where it looks like there is a small cut in the front tire where something might be able to get through and puncture. The back tire is worn a little flat in some spots, maybe from the times I rode a trainer. Looks like a trip to the bike shop.

Personally, I wouldn't necessarily replace just for a couple of small cuts, but once I start noticing a number of small ones or some large ones I replace. I guess it's a matter of when I start getting nervous. In my commuting on often trashy urban streets my tires take a pretty good shredding, seldom getting 1000 miles before I decide it's time. I have recently started using Avocet Cross II Kevlar and Specialized Infinity Armadillo tires. These aren't exactly lugged but do have quite a bit of tread thickness. I am hoping to get more miles out of them than the smoother tires I was using.

Small cuts in just the rubber are a tough call. If any of those cuts go through the casing, then I'd change that tire. If I couldn't feel the flat spots while riding, I'd keep using that tire.

Watch for bulging cuts, for rotting sidewalls, and for beads which are tearing through the casing. On a road bike, tyre tread does nothing, so do not necessarily worry if it the road contact surface has been worn smooth.

Also, Sheldon Brown makes a cogent safety argument against rotating your tyres, i.e., putting a well-used rear tyre on the front. I always wear out the rear tyre, then move the front to the rear and buy a new one for the front.