Guardrail

I'm not?!?!

I see you like extremes. As I stated, the tire should be run near that. 30-40 psi below max recommended psi is asking for trouble.

Patrick Campbell

My tires are good for 5790 lbs (per pair) at 70 PSI. I dont know if his are load range G or H or what but that is a lot of weight either way. The best thing would be to weigh the truck otherwise you are just guessing.

TRCM

Well. my tires are rated for roughly 3100 each at 80 psi.

the rear axle supports 3300 lbs.

3300/4=825

825/3100 * 100 =26.6

So, my tires are carying 27% of their rated capacity.....there fore i should be able to run 27% of the rated pressure, or 22 psi (if you go strictly by the numbers).

I run 35 lbs in each of my rear tires when unloaded, and I get a full contact patch. Any more psi, and I start to run on the center of the tire.

At 60 psi (less than max rated), I am running on ONLY the center 1 1/2" of tread....not good for tire wear, or safety in ANY way.

And Guardrail, the extremes I mentioned are equal to you saying since it is rated for 80 psi, it has to be run at 80 psi. The max psi on the sidewall IS the extreme....the max SAFE pressure to run in the tire.

And you're right, the manufacturers DO know their tires. That's why they list the MAX press, not the best pressure for EVERY vehicle. They do not tell you to run at that psi unless you are carrying that much weight. I'm sure they want you to, so you will need new tires sooner tho.

The absolute best psi to run is the highest you can and still get a FULL contact patch at the tire.

As you go above that ideal psi, you will start to pull the sidewall tread off the road, and that will lead to early tire wear, and a loss of safety margin in wet/snowy weather. The lower below that ideal psi you go, the more the sidewall will bulge out, which will give you worse mpg, and early tire wear, and a mushy sidewall, which is yet another safety issue.


I use to run 18 psi in 39" tall by 15" wide tires on my offroad toy, because that was what got me a full contact patch on the road. the max press on the sidewall was 50 psi.

windyr

I usually run my tires near or at the rated sidewall pressure regardless of the load, The edges still seem to wear out first. I rotate them often to keep the front ones wore off as much as the back ones. I suspect that the roads out here have a few more curves in them. I find would find stability seriously compromised if I worried about what the contact patch looks like standing still! I want my sidewalls to be pretty stiff for responsive and precise handling. I might consider running at 1/2 rated PSI for running on sand below 50mph. I do get reasonable life from my tires, 45-60K depending on the vehicle.

Ford went for contact patch and smooth ride on the Explorer with results we have all heard of.

Jimb

PZM123

THIS GUY HIT THE NAIL ON THE HEAD. Depending on how tall the tread is, it's normal. I put Bridgestone lug tires on the Mack that come with 30/32nd of tread. The lugs will squirm a bit until they wear in. (usually about 3-5000 miles)

I don't understand this whole idea of thinking that the tire manufacturer doesn't know what inflation pressure their tires should be run at. If the tire says 100, it should be run close to that for maximum tread life and performance.

Trying to get a softer ride by decreasing the tire pressure is on of the reasons Ford had a tire blow out issue with the Firestone's.

TRCM

well, do what you want. The tire is rated for a max load at the max pressure.

every car I have ever owned had a lower recommended pressure on the door jamb than the tire was rated for at max load.

they only put the max pressurte/load on the tire because the tire isn't big enough to put on all the pressures for the different loads.

herb

my 03 dually says 65 lbs on the door jam new generals i just had put on say 80. 65 rides good empty 80 rides hard.
probably bump then to 80 when i tow

BearKiller

I am not a Michelin fan, nor am I a big radial fan.

My truck lurched and tryed to follow seams in the road with several brands of radials.

I got to thinking and decided that I never experienced the problem with older trucks that had bias tires on them.

I have spent a fortune on the front-end, replacing the springs even, and it still didn't drive very good.

I put on a set of 10 ply BIAS 7.50-16 and now she drives like a dream.

I was driving an old R-model Mack tri-axle dump a few years back and it had Bias tires on it. It drove as good as you could expect a walking-beam truck to drive. They put ten new radials on it, and you couldn't hold it between the ditches.

My own experience is that less air pressure will actually make squirming worse.

Ramirezh

Biglar, did this ever get resolved for you? I am having the EXACT problem with my new Michelins on my dually. I have to go in and get the front ones replaced. Do I really have to drive it for 3-5000 miles before this crap goes away? Its only been a week, but I was really hoping to go to the track next week, but not if these things are just gonna stay spinning out da hole.

RonP

Man, i love this board. I recently got rid of the wore out BFG rugged trails and had some dueler at revo's put on. I have this exact problem. I have got about 2000 miles on them now and it is much better but the first drive was way different. The tread pattern is much more aggressive and deeper soI guess thats it. They are much better now, but I hope they get a little better yet.

good luck

Ramirezh

2000 miles...geez....I hate to "throw away" money but.....will a good burnout take care of this? This whole fish tailing thing freaks me out...add to that the track issue, I got new tires to avoid just spinning my wheels at launch and now this is happening

biglar

Since I wrote that I've replaced the other 2 tires as well. For the record, I'm running 4 Michelin 245/70R19.5 XDE M/S tires on 19.5" wheels from Rickson on an '02 2500 SRW.

The handling was better after I got all 4 tires the same, but still not as stable as I wanted. Seems to be best at 90 psi front and 80 rear. Softer wasn't good. After reading many recommendations on this forum, I bit the bullet and ordered the DSS stabilizer for the front end. It installed as easily as it was supposed to - about 1 hour with no hassles - and has made a huge difference in the way the truck handles. The sensation at 1st was something like if you put a giant shock absorber on the front end. It goes where I point it and stays there.....within reason. It's not a sports car and won't like it if you yank it from lane to lane. Drive it reasonably, and it handles very well. I've got about 2,000 miles on the DSS now, and can recommend it VEry highly. I'm looking into the locator arm kit now. (can't remember the name of the thing)

Lar.