Tyre wear

andrew_s · Post by **andrew_s** » 30 Dec 2008, 11:37pm

Mick F wrote:How many times do I have to repeat.

I swap my tyres front-to-back two or three times in their life, This equalises wear, and I can buy a new pair rather than a single tyre.

I don't wear out my tyres. I wear my tyres until they need to be replaced. I want to replace them in pairs. Swapping them round extends their lifespan.

Please understand, I know what I'm doing.

Swapping them round doesn't extend their lifespan. You actually end up spending more.
This is because at the point where you decide one tyre is dead, there will still be a small amount of wear left in the other unless you've been very lucky.

Example
Suppose a tyre lasts 2000 miles on the back and 6000 on the front

front -> back plan
new tyres front and rear
ride 2000 miles, front->back: new front, rear 1/3 worn
ride 1333 miles, front->back: new front, rear 2/9 worn
ride 1556 miles, front->back: new front, rear 1/4 worn (ish)
ride 1500 miles, front->back: new front, rear 1/4 worn

so you end up buying a single new tyre every 1500 miles. You've also got a fairly new tyre on the front all of the time, so handling is better and you've less chance of a nasty tyre related prang.

even wear plan
new tyres front and rear
ride 500 miles, swap: front 3/12 worn, rear 1/12 worn
ride 500 miles, swap: front 4/12 worn, rear 4/12 worn
ride 500 miles, swap: front 7/12 worn, rear 5/12 worn
ride 500 miles, swap: front 9/12 worn, rear 8/12 worn
ride 500 miles, swap: front 11/12 worn, rear 10/12 worn
ride 333 miles: rear wears out, 1/36 of wear left in front but discarded

so you end up buying 2 new tyres every 2833 miles

Beakyboy · Post by **Beakyboy** » 31 Dec 2008, 9:12am

Wow! thats just gone straight over my head!

drossall · Post by **drossall** » 31 Dec 2008, 9:38am

I understand Mick's argument, but I just buy tyres in batches of five and replace them as needed. This keeps them matching without bothering with swapping. In practice I seem to use four of the five on the back. Then I buy another batch, usually the same.

Must admit that matching tyres is not necessarily a priority for me though. I sometimes use a lighter version on the front (say 25 front and 28 rear), often but not always of the same brand.

My MTB came with different and specialised front and rear tyres. Not sure that's necessary on the road, but it does show that matching is not the be-all-and-end-all.

Post by **Mick F** » 31 Dec 2008, 9:51am

Can't argue with the maths!

Still, the idea of spending out on five tyres at once is a good idea, but my way extends the time between purchases of tyres as long as I buy two at a time.

I end up, or at least I have done so far, with two equally worn tyres. Maybe not exactly equally worn, but near enough. They go into my spares bin - I have a couple in there now - as just in case I ruin a tyre, so I'm not without tyres whilst waiting for new 'uns. I hate chucking stuff out!

BTW, I run on Vittoria Rubino Pro 20mm, white-walls.
http://www.ribblecycles.co.uk/productde ... ITTTYRF550

Beakyboy · Post by **Beakyboy** » 31 Dec 2008, 1:34pm

I use and love the Conti's GP 4000S, they have some chilli (con carne!) compound on them. They are superb and grip really well, even in the wettest conditions. The more worn they get the better they seem to grip.

CJ · Post by CJ » 31 Dec 2008, 3:59pm

Mick F wrote:Can't argue with the maths!

Oh but I think you should!

I detect an error in Andrew's illustration of the even wear plan. If you think about it, wear should be even not just at the endpoint but also at every second swap. However at the 4th swap it isn't. He's let the rear tyre accumulate an extra 1/12 of wear before being swapped to the front. It should go like this:

even wear plan
new tyres front and rear
ride 500 miles, swap: front 3/12 worn, rear 1/12 worn
ride 500 miles, swap: front 4/12 worn, rear 4/12 worn
ride 500 miles, swap: front 7/12 worn, rear 5/12 worn
ride 500 miles, swap: front 8/12 worn, rear 8/12 worn
ride 500 miles, swap: front 11/12 worn, rear 9/12 worn
ride 500 miles: both tyres now worn out - begin again

So you actually end up buying 2 new tyres every 3000 miles. That's 1500 miles per tyre whichever way you do it.

Andrew's front -> back plan will nevertheless, actually get more life out of tyres, since the relegation of part-worn tyres to the back ensures that each and every tyre becomes totally worn out (however worn the user thinks that should be) before it's replaced, in spite of the somewhat random nature of tyre wear. This randomness will, on the other hand, ensure that the "even wear plan" never quite manages to achieve it's goal.

Front to back also has the virtue of simplicity. Simply waiting for the back tyre to wear out, then putting its replacement on the front instead, does not require any records of mileage or estimates of tyre life to be made. It's a method that I could safely recommend to any cyclist who uses similar tyres front and rear. So I will!

Post by **Mick F** » 31 Dec 2008, 4:26pm

Ta yet again CJ,
but the maths, though out, wasn't far out albeit with a mistake.

I re-read the post earlier on this afternoon, and although I didn't study it in detail, saw that 1500 miles per tyre should have equaled 3000 miles for two. Andrew said 2833. A gnat's whisker off twice as much.

I like the idea a 5 tyres at a time. I wonder if I can get discount for bulk buying?

Beakyboy · Post by **Beakyboy** » 31 Dec 2008, 4:34pm

Would you still swap the tyres on a unicycle?