I would like only comments on the stock Goodyear tires that come with the xB. I know the suggested tire pressure on the door post says 29 or 30 lbs., but in anticipation of a lengthy 3500 mile round trip, and in an attempt to get the best gas mileage I can- while traveling 60-65 mph, what do you think about increasing the pressure to 34 lbs. Do you thing that would help maximize my fuel mileage? Keep in mind please that comments from other over-sized tire owners and speciality tire owners will not help me. Thank you---PJRACER

p.s. I posted this same question in the wrong forum (tC Owners Lounge) -- sorry for this 69 year old's rookie mistake.

 

I have the stock tires still, and I have run them at 40 psi for a while and everything was fine. Just causes a little stiffer ride. But I have already mellowed my ride with "echo" shocks, but the higher inflation will definitely give you more mpg.

 

Tire pressure is a tradeoff between ride comfort and gas mileage. If you increase the tire pressure, you get better gas mileage at the expense of ride comfort. And this goes the other way when you decrease the pressure. You can increase the pressure of the tire to the maximum that is specified on the tire sidewall and try to improve your gas mileage.

 

Why not just keep it at the Mfgr. recommended pressure.
They had their engineers come up with the optimal pressure for that car.

Just how much extra milage will you get by pumping them up by few psi ? Is it really worth it?

 

I'd be concerned about going much past the recommended 29 psi. The recommendation is indeed a tradeoff between ride comfort and gas mileage, but it is also based upon tire size and vehicle weight. This is why higher tire pressures are often recommended for heavily loaded cars, since the tire sidewall will "squash" down harder due to the loading; the air pressure increase will "push" the center back out to even out the tire loading and hence lower the tire running temperature thus avoiding blowouts.

Running at a significantly higher pressure could be a false economy - you might save a bit on fuel since your tires would have slightly less friction with the road, but you'll wear out your tires faster since the car's weight is now distributed over a smaller area (in the center). The tires' lives will be governed by the higher tire pressure wearing out the center strip of the tread. Similarly, under-inflating is a trick used to increase traction in snow or mud, but comes at the expense of the inner and outer strips of tire tread.