[JaxChris]

Norm is right, the side track is dead. Only thing I'd care to see in here anymore is more information on the deformation rates of runflats at partial supporting pressures. Point of the thread was to get a consensus as to whether or not deflating your tires for the drag strip has an increased wear impact on the runflat side walls over traditional tire compounds.

Thanks everyone.

[Norm Peterson]

I'll see what I can find out.

But FWIW, accumulated fatigue effects aren't likely to be anything visible to your eyes unless some of the sidewall cords have actually failed. Should that be the case, I'm guessing you'd see a "bubble", which would be your clue that the last run you made was the last run or high speed drive that that particular tire should ever make.


Norm

[Fraxum]

I would not bother "bagging" your runflats below 25 PSI. But going to 25 will help your 60s. Now with my M6 SS I can get a 1.9 something 2 out of 3 times. At 35 PSI I could not get below 2.0.

[Norm Peterson]

What I found out is that yes, it's a fatigue issue, at least to a point. Should the inflation pressure drop so far that the inner side of the upper sidewall actually touches the inner side of the lower sidewall (i.e. the tire has completely collapsed onto itself), a different failure mechanism appears. That's a scrubbing action, because the two points that are in contact with each other are rotating at slightly different speeds (this is a difference in linear, or circumferential, speeds, not rpm). The educated guess I was able to dig up is that a tire can transition between these failure modes at as high as about 50% inflation.

The difference between RF's and non-RF's is that while the life of a non-RF tire being operated in the rubbing mode may last on the order of feet to perhaps single-digit miles, the RF is good for tens to maybe hundreds of miles, depending on the circumstances of the moment.

But in their current state of development, RF tires pay for their extended zero-pressure mobility with reduced fatigue life at pressures sufficient to keep internal rubbing contact from happening. At least that's how I read what I've found so far. I'm asking for further clarification.

As I suspected, less pressure = faster accumulation of fatigue damage, which is something that cannot be reversed, recovered from, or "undone". What I didn't know was that there aren't any tools to judge the extent of internal damage on a RF tire, like there can be with non-RF's (rub marks outside, rubber dust inside, etc.).


Norm