best tyres on front or rear?

Normally, I'd put the best tires on the front, for stopping and steering. But a Miata tends to wear the rear tires faster than the fronts--about twice as fast, in my case--so I'd start them on the rear. Rotate all-season tires front-to-rear at every other oil change (6000 miles), summer performance tires every oil change (3000 miles).

I agree totally Lanny, the 2 to 1 wear ratio on the rear tires makes me wonder if a person with sticky tires wouldn't do better to avoid rotating tires and do a replace two deal putting them in the back and come out a bit ahead. I suppose it all balances out because on the next tire interval you'd be looking at a full set to replace.

Chris

92BB&T

I used to subscribe to that theory. But with sticky performance tires, there's another factor to consider: heat cycling turns them hard and slippery after a year or two. Better to rotate so they'll all wear out before they lose too much grip and tramlining makes you crazy.

Besides, isn't there always some new tire you'd like to try? :-)

Lanny Chambers wrote in:

Hmmmm.... that's getting to be a really tough choice, 4 new tires or fill the gas tank?

Just filled my '94 BRG yesterday... at 85 cents a litre (up in Canada, eh ! ) it came to $35. new tires installed would equal about 12 fill-ups. I wouldn't use that much gas in the Miata all summer.

Still a lot of smiles per dollar !

Pete

Simply Pete wrote in:

Wait a month and calculate again. :-(

I've never heard this before -- that heat cycling causes performance tires to deteriorate. Do you have any links on the subject?

I've had good luck with putting the two new tires on the front and the 'best two,' usually the old front tires, remounted in the rear. That gives me good rubber in the front. When the rears are shot, I'll buy two more, have them put in the front, and the 'best two' mounted in the rear. It combines rotation with economy.

It is standard knowledge.

Haney, P, (2003) "The Racing and High Performance Tire." TV Motorsport and SAE, co-publishers. p. 141

Leon

Try a search at miataforum.com. Summer HP tires are never the same the next spring (I have another car for snow, so I don't swap tires for winter). I can't tell you if it's the cold, or simply the extra months. Some blame it on too many heat cycles. Everyone notices the effect.

The driven wheels should always have the better tires. All things being equal the older, more worn tires are more likely to come loose when you hit them with torque are an inoportune moment such as the nice ruts in the cloverleaf during a rainstorm.

I have a distinct skepticism about "standard knowledge" that doesn't come with some form of references.

I'll see if I can find a copy, thanks. :-)

My concern is more about loss of steering control in the event of a blowout or sudden loss of tire pressure. I prefer to have the best rubber in front -- that's the end that's steering -- to assure steering control.

That said, I don't let the rears get to the point where the tread is nonexistent. If the concern is 'coming loose,' the tires must be in good shape. My driving involves lots of high-speed freeway stuff -- and a blowout at speed is a concern. That's why I want the best 'blowout prevention' on the front.

Leon

Interesting, but all it's talking about are race tires, which are a very different question from street tires.

There is *one* reference to heat cycles and tires on miata.net and that

-- aga " Subsequent heat cycles do not cause any detriment to the performance of the tire. It is still possible to overheat heat-cycled tires. Assuming you don't do any other permanent damage to them and give them the minimum of 24 hrs. to relax afterwards, they should be fine for later use."

Absolutely, race tires are made of rubber, while street tires are just made of rubber. :)

As the description I posted says, even race tires can be designed to not lose too much effectiveness over heat cycles over the life of the tire. No doubt by losing a bit of the peak performance that would be possible otherwise.

So I would agree even high performance street tires would be unlikely to lose much effectiveness that way. What someone might be able to *notice*, I have no clue.

I have no doubt in my mind that the mentioned noticed deteriorations after a couple of years are due to time factors as noted, (spontaneous and ozone, light, etc, induced continued vulcanization.)

In fact, I strongly suspect the absolutely dangerous tires on Bozo when I bought it were at least in part due to him having stood on a dealers lot for a year or so.

Leon

Come to think of it, noticing a *difference* between new and heat cycled/aged tires on the car at the same time might be easier.

Leon

You looked in the wrong place, Alan. Go to:

Enter "heat cycle" and leave the other options at their defaults. You should find ~97 forum threads discussing heat cycling of tires, mostly NOT concerning racing tires. That's about as close to "common knowledge" as you'll find.

My intuition, FWIW, is that it's far easier to accidentally heat cycle a performance street tire than a dedicated racing tire, since the latter are designed for extreme high-temperature use, and are kept at optimum temperature for a greater part of their duty cycles, rather than being heated and cooled repeatedly like street tires. Many racing tires see only one or two cycles before they're discarded. A street tire may see hundreds, and thousands more partial cycles without the benefit of full cooling between.