Looking For Tire Pressue Advice

[blacksambo]

Just mounted 4 new Michelin LTX M/S 2's on my '99, 255x70rx16's. Any ideas on tire pressue would be welcome. Not going off road, just looking for best mileage, ride etc. Many Thanks.

[etlsport]

with wider tire, you actually want to decrease your tire pressure to keep load ratings the same. of course most folks actually increase with larger tires.

the best thing you can do is to inflate to factory pressure (should say what it is on the inside of the drivers door jamb. i know the 00 and 01s with 18 inch wheels specify 29psi. i dont know if the 99s are the same with the 16 inch wheels

once you are at factory pressure, take a grease pen or piece of chalk and draw lines across the tread on all 4 tires. drive straight 50 feet or so and check to see how the lines have worn off. if the line wore in the centers of the tread, you have too much pressure. if the line wore more towards the edges, you dont have enough pressure. if it wears on only one side or the other, you likely have an alignment issue to address

there is probably a 5-7 psi range where the wear will be even, at that point it is personal preference, more pressure will increase ride stiffness and steering response. less pressure will give a more comfortable ride

whatever you do, do not exceed the pressure printed on the side of the tire. some folks will tell you to inflate the tires to the pressure printed on the tire. this is a mistake and will almost without a doubt result in uneven wear

[vt_maverick]

But... increased pressure results in a smaller cross-section, thereby reducing friction and improving fuel economy. This is why so-called "hyper-milers" over-inflate their tires. As Eric said, over-inflation can be dangerous if the cross-section is reduced too far, so it's really not something you probably want to do.

[blacksambo]

Thanks, I'll do the grease pencil test he suggested. The door jam says 29lbs but that was for a 245x70r x16. These are 255 and made to carry more weight, I'm guessing I should go up not down in pressure??

[etlsport]

although your tires are rated for more weight, you arent actually carrying any more weight are you?

If thats the case, you can go lower with your pressure. 29 psi means every square inch of tire exerts 29 pounds of pressure on anything that contacts it. Your tires contact with the road is around 3-4 inches x the width of your tire.

Your new tires are 10mm (about 1/3 inch)wider than stock so your contact patch becomes larger and less pressure is needed to achieve the same force exerted on the rosd.