We probably should have a FAQ, the current tire load ratings are relatively new but is been around for a while.
Before LRs there were "ply ratings" (PR) and had nothing to do with the actual number of plies but related to the sidewall and tread "strength" of a tire.
The "load" of a tire relates to its section volume and the inflation pressure: the larger the volume and the higher the pressure, the greater the load it can carry without deforming.
Tires also have a speed rating. ST (special trailer) tires are rated at a maximum of 65 mph. If you can increase the pressure needed for the anticipated load by 5 psi you can usually go a bit faster. 65 with a loaded rig is fine for me.
Some tires have a different rating, the Kumho 857 is a "Q" tire meaning it is rated for 99 mph. Typical passenger car tires are S or T though for track day you might want a W, or Z depending on your maximum speed expectations. In the US, cars in recent years have been limited to the speed rating of the OEM tires. For my Reattae it is 125 mph.
Back at load ratings: in the beginning ('60s) tires were mostly rated as "2 ply rating" and were limited to 32 psi. As time went by standard tire inflations increased to 36 psi. Those early tires would probably be Load Range A if such existed.
Today many tires are unmarked. If so they are consided "standard load" and may be inflated to 36 psi. Some are marked Extra Load (XL) and may be inflated to 41 psi.
The might be called LRB but aren't.
So now we get into the Load Ranges which replaced Ply Ratings but mean the same and are really pressure ratings.
LRC - 6PR - 50psi
LRD - 8PR - 65 psi
LRE -10PR - 80 psi
More psi=more pounds.
BTW while the extra strength of an "E" is nice, you really do not want to subject anything to 80 psi, particularly withough shocks.
__________________
Looking for a 24/17 in or near Florida.
|