mythbusters tests tyre / tire pressure

[Frank Lee]

Abused tires can separate with "normal" psi.

[NHRABill]

I am sure you are right Frank alternators don't spin bearings by doing the speed limit either (same car) That New York Northway is pretty quiet when you head up to Lake George in the fall. I learned to slow down after that tire issue years back it helped me grow up, it was one of the worst experiences I ever had in a car. I have seen many treads laying on the side of the road from tractor trailers, never thought I have one coming off of a tire on a 1991 Chevy Lumina. I blamed the psi of the tire but I know the other factors helped it on its way.

[SentraSE-R]

It's really not fair of you to blame overinflation for any of the tire problems you described, Bill. I've experienced two blowouts, a tread separation, wheel-hopping, spinouts, and other maladies with normally-inflated tires.

Plus, inflation to sidewall maximum is not overinflation. It is operating within normal parameters.

[CapriRacer]

Originally Posted by Frank Lee

Among EMers, you alone are reporting the only tread separation from max psi.

Frank,

I have been cataloging the problems being reported by folks who inflated their tires over the placard pressure and NHRABill is not alone. Here's one:

Tire stores - CleanMPG Forums

So it isn't like they are completely unknown.

[SentraSE-R]

There's no way tire inflation will cause a tread bubble in a properly manufactured tire. There's simply no relationship or cause/effect rationale possible. You're crying "Wolf" where wolves don't exist.

[Thymeclock]

Originally Posted by fidalgoman

The difficulty is not so much keeping the pressure even side to side but what about front to back and it's effect on oversteer/understeer. Many factors such as static vehicle balance, spring rates, changing payload, etc determine handling characteristics. Tires slightly low and soft promotes good ride and tends to mush the vehicles handling making it docile to drive. Anybody who's played with tire pressures a bit knows how quickly things can change. Wet vs. dry handling etc. Snow is an area where hard tires make good skis. Wet as well can be an issue if inflation pressures are too high or too low. It's not one way or another and you couldn't possibly expect your local tire store to know how to balance your vehicle under all driving conditions and thus the rule of thumb tire pressures.

All I know is running in the forties makes the ride a little bit harsh, improves fuel economy, and stiffens up the cars responsiveness. On soft surfaces like sand and snow, softer makes the tires conform more and have a lot better traction. More pressure can be good until it is too much then it's very bad if traction is diminished too much. Too hard to facilitate low rolling resistance can be as bad as too skinny and loss of directional control. Baby steps. Each car is different.

This is well said as both handling and ride are affected by over-inflation.

More than a decade ago I bought an 89 Celica convertible from a private seller. I test drove the car and loved it but I thought it handled a bit oddly. My mechanic inspected it before I bought it and found everything to be OK. But at highway speeds the handling was spooky: uncomfortably unpredictable. Driving it just didn't feel right. After owning it for a day or two I checked the tires and found the tire pressures were close to 50 PSI. I reduced the pressure to about 38 and what a difference it made! It handled just great. I enjoyed the car for 16 years and recently sold it, with it still going strong.

So no, higher pressure is not always better, and it might even be unsafe. And yes, the much harsher ride that comes with over-inflated tires might not make you a happy camper, either.

[NHRABill]

Originally Posted by SentraSE-R

There's no way tire inflation will cause a tread bubble in a properly manufactured tire. There's simply no relationship or cause/effect rationale possible. You're crying "Wolf" where wolves don't exist.

You are starting to sound like an insurance company... there is as much proof that overinflation can cause tread separation as there is proof that a poorly made tire (Firestone) is the reason or in Fords case a poorly designed car.

When bad things happen under one setup, it is nice to know. If you still feel that the setup is not the problem then that is your decision as long as you understand that it is your responsibility because you are informed.

I never claimed that overinflation will make your car tires to separate or explode I simply stated caution in making that decision. My experiences were just that Mine. This is what slowed me down in life and made me think twice about being cheap on something as important as tires. Read the entire thread formulate your own opinion and go from there to the unique setup that each one of us has. Much information on this forum does not apply to my vehicles but I listen read and use it to figure out what might work. Just because it does not support a particular persons situation does not mean the information is wrong.

[vacationtime247]

Hate blowin' tires. Always seems to happen at the most inconvenient times too. On the highway, middle of the night, in the rain or snow, with no spare and cell phone problems.

Still fill my tires up to 40-45 psi. Haven't had one blow for a while. My own fault for not replacing the last one that did. As far as overinflating causing increased failure rates? If one goes it would have gone anyway, IMO.
VT247

[CapriRacer]

Originally Posted by SentraSE-R

There's no way tire inflation will cause a tread bubble in a properly manufactured tire. There's simply no relationship or cause/effect rationale possible. You're crying "Wolf" where wolves don't exist.

I'm going to be very careful in the wording here because it is obvious that
my words are being mis-interpreted.

I am not saying that high inflation pressures are CAUSING tread bubbles,
but I am saying that it is possible that high inflation pressures may be
more prone to certain types of damage and that damage may lead to
separations and blow outs. Also be aware that I am not saying the tires
inflated to - oh, let's call it placard pressure - are immune to these
types of conditions. It's a matter of degree. People should not be
surprised to hear that tires blowout or separate at both placard pressure
as well as pressures above placard.

So here's the scenario.

When a tire is inflated, the cords within the tire are put into tension.
The higher the inflation pressure, the more that tension is. If the tire
is rolling down the road and encounters an object - and for this
illustration let's use a pyramid with a blunt (not a sharp) point - then as
the tire rolls over the pyramid, the tire envelopes the pyramid, conforming
- more or less - to the shape of the pyramid. The plies in the tire are
bent backwards and the innermost ply recieves more tension because of the
bend. That could result in breaking a cord (or cords). Obviously if the
cords starts off with higher tension (because of higher inflation
pressure), it is more likely to break.

If the number of cords broken is enough, the tire will not be able to
contain the inflation pressure and the tire will rapidly decompress
(Blowout!). However, if only a few cords are damaged, the tire would not fail immediately, but would have a weak spot, and that area would flex more, and eventually create a separation.

Obvious the speed the tire encounters the pyramid is going to have an
effect on how many cords are broken in this scenario - higher speed =
higher force. It should also be obvious that the size of the pyramid would
also have an effect.

What I am trying to point out is that separations and blowouts can occur at
both placard pressures and higher than placard pressure, but higher
inflation pressure will make the tire more prone to this.

[Fat Charlie]

Originally Posted by SentraSE-R

There's no way tire inflation will cause a tread bubble in a properly manufactured tire. There's simply no relationship or cause/effect rationale possible. You're crying "Wolf" where wolves don't exist.

Using tires will cause tread separation and blowouts. The amount of air you put into them can affect this in some way. Your vehicle's weight and suspension settings can also affect this. Road conditions and driving style can affect this. Why on Earth would you pick out one of these factors of tire wear and announce that it does not affect the tires?