Standard Load Index

[maxnix]

Why are there two different load standards for some sizes and not others? For 245/45-17, the indices are 93 and 89. For 305/45-17, the two load standards are 102 and 109.

Why do just some particular sizes have two indices, and not all? And if they all did, what would be the point of the indices anyway?

[Grant@tirerack]

Many of the newer tires are being offered with higher load ratings. In many cases, the tire company is still making standard load tires in a given size but a vehicle maker may require an extra load tire for a specific car ('03 Acura 3.2 TL-S is a prime example). The Michelin Pilot HX MXM4 in the stock P215/50-17 is the only XL tire made in that size. This gives the car makers more options for fitments when a car needs a higer load rating than other vehicles using the same tire size.

[szh]

Hi, Grant!

Have and Chet finalized the stuff on the load tables to post them here? If needed, I can help with some other format ...

Z

[SmithSR]

http://www.tiresafety.com/size...adlim"The Metric System is very similar to the P-Metric System, except in terms of load carrying capacity. Load carrying capacities of Metric and P-Metric tires are sometimes not the same, even for two tires of the same size designation"

[Q45tech]

The problem with load index is that it declines with age. [as the internal structure degrades from stress....filaments/steels stretch and break.Oem know this and coupled with the need for softer compounds to look good in magazine test, things work out well as the tires wear out fast. Say by 20-25,000 miles.

Whether a harder compound tire can meet the load index testing above 20k is unknown. Since very few tires are tested beyond 8,000 miles or 100 hours of use.

Always buy more load index than the minimal factory standards if you plan on using tires longer.

[Grant@tirerack]

A lot of tires are coming out with a higher max pressure so you can up the pressure. That will help a little to slow down the eventual breakdown of the tire's internals. Most new tires have a max pressure of over 35psi which used to be the standard.