When do tyres 'wear out'?

[Chris S]

Does anybody know when bicycle tyres should be changed?

You know when car tyres have to be changed because the tread is worn down to the bars between the grooves. (My) Bicycle tyres don't have these.

Also am I correct in thinking that the height and width of bicycle tyres (above the rim) is usually the same?

 

[rusky]

I would say when there are large slits in the tyre or when the sidewalls have become perished & cracked.

As for size, that all depends on the tyre & rim width.

 

[swee'pea99]

For road tyres, they talk about 'squaring off' - ie, when you get them and pump them up, look in line with the rim and the profile of the tyre will be a semi-circle, give or take. When it's worn, the top of that semi-circle will be flat rather than rounded. Then it's time to change. So they say. Personally, I look for that and also just general condition - how many slits (and how bad), are there little chunks missing, that sort of thing. I don't think there's any such thing as a definitive rule...the frequency of visits from You Know Who is also an indication of time for a change.

 

[Sambu]

on mine there's a little dimple in the tyre. when thats gone you need new ones apparently.

 

[Fab Foodie]

Tyres are worn out (or need changing) when...

They start getting a lot of P*unctures
When you can see the casing through the rubber
When the rubber is perished
When they're badly cut
When they start to handle badly (if very squared at the rear for example).
When you fancy the latest version in a new funky colour...

 

[zacklaws]

When the rim starts clanking on the road!

I've just had to change my rear as it was almost down to the inner lamminate in a couple of spots, but mainly because I found I lost all grip when I stood to pedal on the flat to accelerate and my back wheel would spin momentarily, which is what I think exposed the inner laminate in a couple of places as the rubber seemed ripped off.

 

[HLaB]

Tyres are worn out (or need changing) when...

They start getting a lot of P*unctures
When you can see the casing through the rubber
When the rubber is perished
When they're badly cut
When they start to handle badly (if very squared at the rear for example).
When you fancy the latest version in a new funky colour...

Thats a good list. Sheldon does a good list IMO which agrees with 90% of that

Tire Wear-When should you replace your tires?

Many cyclists waste money replacing perfectly functional tires simply because they're old, or may have discolored sidewalls. If you just want new tires because the old ones look grotty, it's your money, but if you are mainly concerned with safety/function, there are only two reasons for replacing old tires:

1. When the tread is worn so thin that you start getting a lot of flats from small pieces of glass and the like, or the fabric shows through the rubber.
2. When the tire's fabric has been damaged, so that the tire has a lumpy, irregular appearance somewhere, or the tube bulges through the tire.

Cracks in the tread are harmless. Small punctures in the tire such as are typically caused by nails, tacks, thorns or glas slivers are also harmless to the tire, since the tire doesn't need to be air-tight. Gum-wall tires sometimes get unsightly blistering on the sidewalls from ozone damage. (This is frequently caused by storing the bike near a furnace--the powerful electric motors in typical furnaces can put a fair amount of ozone into the air.) This blistering is ugly, but doesn't actually compromise the safety/reliability of the tire in the least.

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I'll add what I don't think anyone else has said but I'd be a wee bit more cautious/ vigilant when it comes to the front tyre. Failure of the rear whilst cycling is usually control able whereas failure of the front is dangerously less so.

 

[Garz]

For me when I have had a few punctures in a row or if I notice large gashes that super-glue wont fix.

 

[Crankarm]

When the tyre fails and the inner tube goes bang?

 

[threefingerjoe]

I usually run tyres until the AIR is showing!