mattaway

i keep my 31x9.5 tsl's at 30 psi, my load range is 45 or 50, don't remember off hand.


i'd say keep your tires between 30 and 35 psi. small trucks like ours don't need 50+ psi, all that does is hurt your back

Matt16

P-metric tires used on cars, minivans, and compact 2wd trucks for a softer ride, better mileage etc. People use them on trucks that aren't used too hard. They don't handle loads well. You can tell a P-metric tire as it will say something like P195/70r14. Light Truck tires built heavier and can't put up with more abuse but don't ride quite as nice. Their sidewalls will read something like LT 31x10.5r15 C. The Letter following the rim diameter is the load range- C, D, E ... this originally designated the number of sidewall plies, but now it just designates the strength of the sidewall and the load capacity (stronger, stiffer sidewall allows a greater load capacity).

My 2wd came with passenger car front tires when I bought it, so its not an unreasonable presumption now is it Abe? They required different pressures than the rears (LT tires), even when I swapped them into the front.

You've spent enough time around cars that it would be a little tough to believe that you believe that passenger car tire sidewalls are as stiff as E-rated truck tires. If the sidewall is stiffer, my experience is that you can run at lower pressures without having a "squishy" ride.

My point is that he asked what pressure he should run a specific tire size at, and eveyone is replying what pressures they run their tires at- be it a r14 2wd tire or a 33x12.5r15- neither of which will need the same pressure as his 265/75r16s... capice?

To the OP: 3rd gens sometimes run these tires as its a little bigger than the stock 265/70r16, but you'd be hard pressed to find many pre '95 truck shod in 265/75r16s simply because they came with 15" rims and most people don't see any reason to change.

clydehatchet

The max psi on the sidewall of any tire is rated per tire. It means that thats the MAXIMUM amount of pressure the tire will hold before it becomes unsafe. By unsafe i mean that the tire COULD blow if you even kicked it. P rated is for a vehicle that is assumed to only be carrying passengers. Load rated is, of course, for vehicles assumed to be carrying a load like a loaded trailer, a cargo area full of mulch or cinder blocks, work equipment, etc. If you are unsure about what psi to run in your tires, refer to what the placard says inside your door despite what size tires you run. If you are aware of the risks of deviating from what the placard says, do what suits you. Never go by what your tire says, thats a liability disclaimer for the companies sake, like, dont throw your radio in the tub, it might hurt you. I run 30 psi in my 33 1250's, the door says 26, I like 30.

Matt16

I think the real "burst pressure" of a tire would be in the hundreds of psi, so kicking a tire at 80psi would be totally safe, but i certainly wouldn't run a tire inflated to that pressure haha

FAR more tires burst because of underinflation than over inflation. The Ford-Firestone thing was pretty much a case of Ford telling owners to run the tire at a really low pressure (to compensate for rubbish suspension) and the Firestone tires could take it. The sidewalls of the tires flexed too much with each rotation of the tire, they heated up and subsequently disintegrated.

sundog kid

Here's how I have always filled my tires, as recommended by an aquaintance who worked for Porsches In house performance specials program.

If the max tire rating, and the suggested psi rating on your door are obviously different, go with the tire rating.

Fill tires to 10% less than the max psi on the side wall of your tire. The max psi is the manufacturers safest allowable, so going 10% less is a sure bet for safety, while still coming close to optimum.

Now this is for street driving. All my performance cars I would run my z rated 40 series rubber at 40psi, when the recommended on side wall was 44-45 max psi.

Porsche suggests 10% less than, so thats what I do.

clydehatchet

obviously the kick reference was an exaggeration, though it has happened several times that i have seen first hand in the shop, and im sure there were underlying instances that lead to the over inflation explosions. Also, if you have ever used a tire changer, the machine will quit pumping when the gauge reads 60 psi. Everyone has their preferences on what to run, i tell customers to go by the door, even though i myself don't. Do what makes you comfortable and maximizes tread life. Good thread, btw, i enjoy a discussion where everyone has an opinion based on plenty of experience and knowledge.

NYChopshop

Porsches run lower profile tires much faster than light trucks do. They have much less sidewall than we do as well. All of the softness in the suspension play is therefore in the struts, as even the springs are firm. Road vehicles graduated from bias ply tires with firmer sidewalls to radials with softer sidewalls because during cornering, the radials' sidewalls will flex a lot allowing more of the tread to actually contact the road surface. The very nature of low profile tires is extremely different than almost anything with a nice juicy sidewall. On a light truck like ours on the road, a p-rated passenger tire will give you a softer ride and better traction. Off the road, they become more of a liability being very easy to tear. Jacking up the air pressure will firm up a tire so that it provides less friction, allowing the drivetrain to move more freely at high speeds and get better gas mileage. Porsche, and rightly so, does not give out recommendations for tire pressure for any reason other than high speed performance - as in, don't even think about bumps, pot holes, or speed bumps! Your vehicle was designed to work with a specific tire pressure (and has it posted on your truck) for a very good reason. IT ISNT A PORCHE! Load to what your door says. If you are having wearing or handling issues, add some more air.

NYChopshop

right! If anyone has mounted a tire on a wheel, you know that you arent supposed to (and some machines won't even let you) load more than 40psi before the bead seats lest there be a catastrophic failure. Then, you fill the tire up to about 50psi and reduce pressure to a recommended operating range. It is then that the wheel and tire are balanced. Anyhow, I'm almost positive the shop that balanced your tire did it at the manufacturer's recommended pressure. Also, any sort of dry rot in the sidewall that would have been fine otherwise, or puncture in the tread that would have just made you go flat could result in catastrophic failure instead. Yesterday I saw a tire get overfilled (jackass kid put a tire filler straight up to the 150psi compressor) and it blew the sidewall straight out sitting on the ground, throwing rotten rubber all over the room and scaring the sam hell out of four classes of ASE master certified technicians in training.

mattaway

most tires seat at under 20 psi, but i've seated the bead on quite a few tires with 60+ psi and nothing has ever happened.... not saying i feel "safe" doing that, but sometimes it's the only way to get the damn things to seat. damn stubborn tires!

vandert

I run 35 around town and go up to 42 for road trips and it helps on the milage;-) But 35 will wear more evenly

91Toyota

Dang! I run 28psi on my swampers. I did the chalk test lots of times and just couldn't get them to wear even with ~35 psi or so. Oh well.

pb4ugotobed

Actually, Toyota recommends you use NO MORE than 10psi to seat the beads. They REALLY push this. You get a much better quality mount and will get a lower road force variation.

I'm sure you're thinking "bulls**t" but honestly, 99.9% of the time it can be done. Lube the tire good, and lube the rim as well over the safety beads. I've seated anything from your standard camry wheel to my 33" swampers, and 22" lo pro tires at or under 10psi. The only time you really have an issue with it, is when the tire was one of those on the bottom of the stack and squashed down to almost nothing and you have to use the cheetah to get it started. by the time the cheetah blows, you're already over 10psi.

I'd stay close to what the door plackard says. Obviously you're gonna have to adjust for load, modifications, etc. But I'd stay close to where it says to be. In my swampers, I run 35psi.

clydehatchet

Ha, yeah, it seems that most of the tires i put on are from the bottom of the stack, or have been taped together from shipping, thats when i like to take the valve core out, it makes my job quicker. I nearly piss myself when i have to put in 80 psi just to seat a bead, I have seen them blow the rim to pieces though. Not a fun time.

ThatGuy1295

You guys put air inside the tires?

maachine

tires on my bicycle are rated at like 55. i run 35psi in them all the time

TNRabbit

I run 40 psi front & 30 in the rear WITH NO LOAD.

I get best wear that way. YMMV, but keep an eye on how your tires are wearing & adjust from there.

n16ht5

85psi is probably the max LOAD rating, not PSI. I bet they could go to 120 and not blow without a problem.

most tires say:

max LOAD at XXpsi

this means that the tire will be the safest at XX psi under a heavy load. If you go under you will have too much sidewall flex and heat up the tire. More pressure and you will overpressure the tire.

I always fill up higher than the door panel. Less rolling resistance, flex, deterioration. Usually 35-40psi on my runners.

redbayredneck

I personally use Water, that way it sinks to the bottom of the mud hole and gets traction.

On a serious note: I run 32 PSI in 3 of my tires, I fill the other tire to 40 psi because it leaks and I'll catch it at 20 psi in a couple days and have to refill it.

Team420

I run all my vehicles between 30-32psi... but... heres a lil something to set some guidelines.

http://www.tirepressurecalculator.com/

erock13

I always run mine between 30-35, for comfort, wear, and safety.. Just start from the placard and determine whats best for you.. at 80 psi, have fun stopping in time and replacing your tire after the center tread wore out in 20k miles.. not too mention how hard that ride would be..