correct radial tire inflation pressure

[William F.]

A '67 I bought has Michelin X 205/75/ 15 tires. Sidewall states 35 psi max pressure but what much is correct psi for driving? Coker radials specify 35 psi but would think the Michelins would be run with somewhat less than the max.

[Brian M.]

Re: correct radial tire inflation pressure

I run 30 PSI all around on our 67 small block.

[Gene M.]

Re: correct radial tire inflation pressure

Using BF Goodrich 205 and 215 70 series been at 35 psi.

I would suggest you try the differences and use what you like best.

More pressure stiffens the sidewall.

[Michael H.]

Re: correct radial tire inflation pressure

I run 30 PSI all around on our 67 small block.

I run 30 PSI as well.

[Harry S.]

Re: correct radial tire inflation pressure

I run 32 on my 63 but anything over 30 should be fine.

[Leif A.]

Re: correct radial tire inflation pressure

Michelin 215/70R15 radials on my '67. I like 33 lbs. It truly boils down to personal preference in ride quality. Anything between 30-35 lbs will be safe...try different levels and see what suits you best.

[Jack M.]

Re: correct radial tire inflation pressure

Diamondback states this info in their FAQ's:

A good setting for most applications is 35 psi COLD.

[Duke W.]

Re: correct radial tire inflation pressure

The pressure data placarded on the sidewall is MAXIMUM LOAD AT MAXIMUM COLD PRESSURE, but vehicle manufacturers specify pressure(s) for specific vehicles. Since vintage Corvettes didn't have radial tires as OE we have to set our own recommendations.

Higher pressure causes less heat buildup from flex, lower rolling resistance, and crisper steering response, however higher pressure will also create more high frequency ride harshness. Since Corvettes are relatively light for typical replacement size load capacity they have a lot of what I call "load margin", so they don't need to be run at maximum cold pressure.

It takes some experimentation by each owner to find out what is best, so it depends on road quality, and how you like to drive including typical speeds. I usually recommend starting at 32 and then going up and down from there in 2-4 psi increments to find what works best for you; 32 is good starting point for highway/freeway speeds, but around town going lower is okay if you want a better ride, but I don't recommend going below 26.

If you remember the Ford Explorer/Firestone tire debacle from about 15 years ago, there were three primary causes. Substandard manufacturing practices were certainly a factor, but because the Explorer was built on a truck Frame, Ford specified too low cold inflation pressure to reduce ride harshness, and typical owners don't check and adjust pressure with any discipline. Then they over load their vehicle with low tire pressure and drive 80 MPH on the freeway in hot weather. The result was that many of these low quality, low speed rated tires that lacked the safety of a spiral wrapped nylon cap belt disintegrated, and you know the rest.

A good bead seal and tire should result in no more than 1-2 psi monthly loss, but you have to take into account ambient temperature, which increases TP about one psi for every 10 degrees increase, and vice versa for colder temps. Tire pressure should be checked/corrected monthly when the tires are cold. Typical around town driving in mild to hot weather will increase TP by 2-4 psi and up to about 6-7 psi at 80 MPH freeway speeds on hot days. Hop lapping big race tracks like Willow Springs increases cold pressure by 8-12 psi.

Never bleed down a hot tire with over the maximum pressure placarded on the sidewall. Remember this is the maximum recommended COLD pressure and pressure will increase with driving conditions as outlined above.

Duke

[John S.]

Re: correct radial tire inflation pressure

What Duke said. I personally run 30 lbs in both my C-2s. Seems a good ride and good handling combo.