Tyre wear - What's it telling me?

[gatch]

I had read that it is the tire carcass flexing that creates the heat. Makes sense to me..

Though, is that correct ?

[steveyb]

I had read that it is the tire carcass flexing that creates the heat. Makes sense to me..

Though, is that correct ?

Typically that is correct, but of course is not the full story.
Heat is caused by friction, be it friction between solid surfaces rubbing against one another (e.g. tyre vs road), or by molecules clashing against one another as they are forced to move by something (e.g. a flexing tyre).
Flexion of the tyre causes the air (or nitrogen and anything else) that is inside the tyre to be squeezed and released thousands of times per second as the tyre rotates. The more flexible the carcass the faster and more extensive will be this sqeezing and hence the greater will be the rate and extent of heating. This is what causes the tyre pressure to rise as it heats up due to the expansion of a gas as it absorbs heat. Different gases expand at different rates and different amounts, hence the trend of using Nitrogen gas (N), to inflate tyres. No oxygen, no CO2, no water, just N, so you get one constant expansion rate.
Flexion of the tread area of the tyre also contributes to this heating (i.e. tread blocks on road tyres and rain tyres) in addition to their water dispersion and surface interlocking properties.
Spinning up tyres of course also creates heating by creation of increased friction, hence the formation of smoke (i.e. burning rubber) from a spinning tyre.
There will of course be a maximum above which the black body radiation and heat conduction of the tyre/wheel unit will match the heating provided but this will differ for any tyre/wheel combination and environmental temperature/weather condition.

[gatch]

Typically that is correct, but of course is not the full story.

Thanks for that. Makes sense.

Moral of the story. If you aren't using warmers, make the most of your "warm up" lap.

[Robert Taylor]

Thanks for that. Makes sense.

Moral of the story. If you aren't using warmers, make the most of your "warm up" lap.

Not entirely, the more specific the tyre is to racing the more carefully it has to be heat cycled. Not only prior to every race, but also after each race.

[Robert Taylor]

Just to continue this tire thing. I recently spent a day at manfield running a new BT 002 ST on the rear of a gsxr 750. Day was around 15 degrees. I was not using tire warmers and had the rear set at 30 psi, took a couple of laps to warm up and then did another dozen laps. When I came in the tire was absolutely shredded. I was told it was cold tearing so next time out I dropped it to 28psi. Went out and did the same routine, came back in and the tire is still shredded. So, should I have dropped it even further. By the way, I have looked at the Dave Moss video, excellent information. Is there any truth to the story of being able to reverse rear tires to tidy them up, sounds a bit iffy to me.

Many tyre problems are not the fault of the tyre itself Eg:

1) Is your tyre pressure gauge accurate within half a psi? Many are woeful

2) Are you adding air from a compressor source that is full of moisture leading to an abnormal pressure rise when hot?

3) What peak temperature are your tyre warmers actually heating the tyres to?

4) Is the suspension setup correct for your weight and the carcass construction and characteristic of the tyre you are using? MANY TYRE PROBLEMS ARE ACTUALLY CREATED BY INADEQUATE SUSPENSION SETUP. EVEN A HIGH END AFTERMARKET SHOCK HAS TO BE SPRUNG AND VALVED CORRECTLY

5) Are you monitoring track temperature and selecting compounds suitable for the conditions? If the track is cold are you lowering tyre pressures and firming up the settings to manipulate some heat into the tyres?

etc etc.......

[gatch]

Not entirely, the more specific the tyre is to racing the more carefully it has to be heat cycled. Not only prior to every race, but also after each race.

I'm using dunlop a12h, on an nc30. With forks and rs250 shock that your company has fiddled with.

[sugilite:Me]

Interesting thread dredge. About the reversing tyre thing, if it has ripped (cold sheared), My experience is, that will only work if you catch the tearing before it gets to bad (bout only 3 to 4 laps worth on a superbike). Catch it in time (and it's easy to tell when it is happening during practice/qualifying) then reversing the tyre to rip it straight definitely works. If the tears have gone on too long/deep, throw the tyre away.