4 New Tires installed but different specs? - 986 Forum - The Community for Porsche Boxster & Cayman Owners

BYprodriver · 03-30-2018, 04:45 PM

Quote:

Originally Posted by thstone

A little further explanation:

The tire load index specifies the maximum weight that a tire can carry (per the tire manufacturer). The same model/size of a tire can have different load indexes (like 95 vs 101) because the tire construction is slightly different between the two tires. Back in the old days, this usually meant they the two tires had a different number of plies but that's not really true in modern tires where the strength of an individual ply can vary.

The load index difference within a tire model/size has little effect on tire performance factors like grip, wear, or handling so it is highly doubtful that you will notice any difference in those characteristics between a 95 and a 101 load index tire.

The reason why using 95 or 101 load index tires on your Boxster doesn't matter is because neither of those tires is anywhere near their maximum load capacity when installed on a Boxster.

101 index = 1819 lbs/tire x 4 tires = 7,276 lbs total weight (car + passengers + cargo)
95 index = 1521 lbs/tire x 4 tires = 6,084 lbs total weight

For example: If two heavyweight people were to take a trip in a Boxster with 500 lbs of luggage each, the total weight would be something like: 3,200 lbs car + two x 300 lb passengers + 1,000 lb luggage/cargo = 4,800 lbs. This is still substantially less than 6,084 lbs or 7,276 lbs so it doesn't matter which set of tires (or mix of 95 or 101 load index tires) is on the car.

You'd have to fill both trunks with cement to get the total weight anywhere near the load index maximums!

All of this is dependent upon adequate air pressure to support the load also.