I installed 195/65R15 91H tires on my 2000 Accord EX Coupe 4cyl. The sign in the door jamb says that the optimal pressure for original tires ( 195/65R15 89H ) is 29 psi.

Should I adjust the tire pressure to the new load index, and how much?

Thanks!

 

No, I don't think so. All else being equal (which is rarely true) your new tires should be able to tolerate higher load with higher pressure. You aren't adding extra load (compared to your old tires) so don't add extra pressure.

 

Thanks, Jim! What you are saying sounds reasonable, but consider this.

I have read that the load index for all tires is measured at a fixed pressure of 36 psi. So, at this pressure, a 91 load index tire is designed to carry 1356 lbs and a 89 load index tire is designed to carry 1279 lbs. Then, if you take a 91 tire at 36 psi and put only 1279 lbs on it, it will not be pressed against the ground enough to assume its optimal shape for the best traction and tread wear.

Considering the above, I suppose that, to make the 91 load index tires assume the correct shape, maybe I should inflate them by (1279/1356)*29 psi = 27 to 27.5 psi? This is a minor correction, of course, but why not figure it out...

P.S.: even if the load index is measured at not at 36 psi, but at the maximum pressure, still the maximum pressure is 44 psi for both the original new tires.

 

Well, I guess I gotta do some more homework so I understand this...

 

hummm very interesting...keep it going