Lower load rating question

[Corvette Owner]

Originally Posted By: CapriRacer
Originally Posted By: Corvette Owner
.......Also, remember that maximum load ratings are at maximum tire pressure........


Ah.....Mmmmm.....Ah... Actually, No.

You will find info on the sidewall of a tire has 2 forms:

1) Max Load XXXX, Max Pressure YY

These are separate points of reference.

2) Max Load XXXX at YY pressure.

This is a relationship.

Be careful which one you have.


On extra load (XL) tires you will always find one statement:

Maximum load is XXXX at YY maximum pressure.

 

[threeputtpar]

Actually, what I found was that on XL rated tires, the maximum load was attained at 42 psi and any increase in psi up to the maxium of 51 did not increase the tires load capacity.

For standard load tires, the maximum load was achieved at 36 psi.

 

[dparm]

XL is an arbitrary thing, by the way. Usually it applies to 94+ ratings but there are plenty of companies who just don't use the XL moniker but still provide 95, 97, even 100 load ratings. I don't think my 245/40R18 Goodyears say XL but they are rated at 95.

 

[Quattro Pete]

Originally Posted By: dparm
I don't think my 245/40R18 Goodyears say XL but they are rated at 95.

That's a bit odd. Which GY model is it?

For 245/40/18 size, 93 is the standard load rating and 97 is XL.

 

[Hokiefyd]

Originally Posted By: dparm
XL is an arbitrary thing, by the way. Usually it applies to 94+ ratings but there are plenty of companies who just don't use the XL moniker but still provide 95, 97, even 100 load ratings. I don't think my 245/40R18 Goodyears say XL but they are rated at 95.


XL doesn't denote a load index above a certain value. It denotes a load index higher than the "standard" load index for that particular tire size. To my knowledge, the load index is generated based on the contained air volume inside a tire, which is pretty much defined by the tire's nominal size. So you can have a "standard" load of 93, or an XL of 97 (to use Quattro Pete's example above).

 

[Hokiefyd]

Originally Posted By: threeputtpar
For standard load tires, the maximum load was achieved at 36 psi.


This is correct for E-metric tires (or ones with a preceding "P" on the size). If it's a P-metric tire (like P215/70R15 for example), the maximum load is achieved at 35 psi.