Tires, my secret sauce formula.

[ZugyNA]

With a Tercel 4WD wagon I get 30 mpg with 1% undersized tires vs 37 mpg with 5% oversized tires.

Part of the difference can be explained by the tire construction and series...the larger ones being 80 series vs 60 series for the smaller.

That's a 23% difference in mpg.

Will be retesting this to see if it still happens that way.

[GasSavers_katman]

Originally Posted by SVOboy

j5e: I think it's been decided on here that the tire doesn't bow out, therefore reducing contact patch, because of high pressure, since the steel belting in the tire prevent the tire from physically growing in size, as the steel doesn't morph enough to make that difference.

Also, some have claimed greater traction with the higher inflation, and a police article has also claimed this to be a fact.

I beg to differ! With 325 50 15 you can see the edge tread lift off the ground with more air. This is not a large tire either. The bigger ones are extremely sensitive to air.

[philmcneal]

Originally Posted by katman

I beg to differ! With 325 50 15 you can see the edge tread lift off the ground with more air. This is not a large tire either. The bigger ones are extremely sensitive to air.

interesting... so what your saying if you have small tires, load the **** up in terms of psi? and if you have something like a suv better not go over sidewall limit?

[GasSavers_katman]

I'm just saying that a wider tire, even with steel, can go concave or convex. On my Tahoe and wife's 99 GMC, side-wall is 44 and I run 55.

[SVOboy]

It seems when I see tires being inflated the poofiness is more of a function of the sidewalls getting stiffer.

I've seen treads tear, they don't stretch, they tear and blow the rubber off them.

[cfg83]

theclencher -

Originally Posted by theclencher

Ummm... yeah. It doesn't seem everybody is being held to the standard Compaq was...

Here's a little something from the leader among tire companies in low rolling resistance (from what I can tell): http://www.michelin.co.uk/uk/pl/pl_juste_pression.jsp

"Under or overinflation of your tyres can be very costly and even dangerous. Mileage performance, comfort, transmission of traction and braking, in fact all elements of tyre performance are affected by their inflation pressure

Under-inflation caused extra flexing to the casing. This causes the tyre to heat up, increases rolling resistance and increases wear. In extreme cases, under-inflation can cause tyre failure.

Over inflation can also reduce mileage potential. It reduces grip and increases irregular wear, in particular on drive axles."

So perhaps going waaay overboard on overinflation isn't all it's cracked up to be?

That's one reason why I am keeping my eye on Michelin Energy tires that are rated at 51 PSI. If I only go to 40 PSI, I should be well within the tire's safety limits and still have good MPG. I think I would lose my fillings at 50 PSI.

CarloSW2

[cfg83]

theclencher -

Originally Posted by theclencher

I was just noticing today how the tires on my Microbus are suffering from overinflation- yes, the center of the tread is wearing much faster than either side. Some on here claim even treadwear, even with massive overinflation above the sidewall rating. If it's true in their case fine but I'm here to tell you it's not true in every case. My suspicion is it's not true in the vast majority of cases. Also note on the Michelin graphs that the performance loss for overinflation is even greater than the performance loss for underinflation! That surprises me.

I am taking my tires in this Sunday for rotation (Just Tires tires). It will be interesting to see what they say. I am thinking of reducing my current 39 PSI to 35-36 to avoid too much lecturing from them.

CarloSW2