For tire sizes,what does the 87T mean?

87 is the "Service Description" which is another way of saying the load carrying capacity of the tire since that is what it describes. The "T" is the speed rating, or maximum speed capability of the tire.

Now here is where it gets tricky. A tire with a service description of 88T is Euro-metric, not Passenger-Metric like your OE tire. Euro-metric and P-Metric tires are dimensionally interchangable but have, as you can see, different service descriptions (that mean different things actually) and have different inflation requirements.

Let me demonstrate with an example.

At 30 psi a P-Metric "P195/60R15 87T" tire has a load carrying capacity of 1,109 pounds.

At 30 psi a Euro-metric "195/60R15 88T" (notice no "P" in the description) has a load carrying capacity of 1,069 pounds. It might not seem like a lot but multiply that by 4 and you have the weight of an average adult male passenger. With the Euro-metric tire you have to increase the inflation pressure to 32 psi to maintain the same load carrying capacity as a P-metric tire at 30 psi.

Whenever putting on tires of a different description than those that came as original equipment is it critical to match the load carrying capacity of the new tire to that of the original tire at its factory recommended inflation pressure.

If your car specifies a P195/60R15 87T and you switch to a 195/60R15 88T I would recommend visiting page 32 of the link below to determine what inflation pressure you should run. The table lists the load carrying capacity of every tire size and description at different pressures. By cross-referencing the table you can determine the correct pressures for your new tires.

http://www.tiresafety.com/images/Tire%20Replacemen...

I hope that wasn't too much answer for you.

ASE Certified Automotive Service Advisor and self-proclaimed tire guru

my tire size is P195/60R15 87T. What if I got a tire that was 88H ... The 87 indicates the tire load rating, or 1201 pounds "on that tire"...the T .........

The 87 indicates the tire load rating, or 1201 pounds "on that tire"...the T indicates the speed rating, in this case 118 mph.

P195 60r 15