DiskDoctr wrote:
If you don't have a load (towing), try 70 psi in all 4 tires. Sometimes an uprating will bite you because of the higher pressures. The truck may not have enough weight to form the proper tire shape.
This is referred to as 'ballooning' Picture running around on 4 inner tubes and what that would feel like.
If that is your problem, the tires can be ultra-sensitive to road defects and cornering can be uneven/unsteady.
I haven't found a good way to find this problem other than driving. My buddy has a tire shop. We pulled the wheels, rebalanced them (barely any adjustment, but did it from scratch), cleaned and thoroughly inspected wheel assemblies, suspension, etc.
I inspected the tire profile both with and without loading (on a rack or with vehicle's weight, not talking cargo or trailer), and whatever else I could imagine.
No change, nothing found. So we mounted the new fronts (different brand, but same profile and 10ply also) to match up with rears and viola! I can again take a corner quite comfortably on uneven road at 80mph or more. I only stress test that way, I don't drive like that ;)
BTW, this would be at 70psi unloaded. The sidewalls are so much stiffermthan the original P-rated tires, they do not suffer from the overheat/risk that underinflated tires do.
I may go to 72psi all around, as it would be within 10% of max inflation, especially when under load for safety reasons.
ah64id wrote:
It sounds like you took the truck in without a load, 75-80 psi is WAY too much air pressure.
Your sig doesn't say much, other than it's a F-250 XL. Is it 2/4 wheel drive? Diesel? Cab size? Bed length?
I cannot imagine you needing much more than 65 psi in the front, if it's a diesel.
The rears probably only need to be 40-45 psi unless you are towing.
New tires will squirm (my LRG's I have on now have been the worst of any tire, and where broke-in within 200 miles), having them over inflated will make the issue worse and make it last longer as tires need heat cycles to break-in and overinflated tires don't heat up as much.
I would let some air out, and drive it. If that doesn't fix it then talk to the place that sold you the tires. I would also have your aliment checked, but it sounds to me like a combo of new tires and too much air.
Just because they are rated for 80 psi doesn't mean you run them at 80 psi, over inflating tires effects ride, handling, wear, and increases puncture susceptibility.
To the people responding, read the sig. It's an F-250, they DO NOT come with P rated tires from the factory they come with E rated tires..
If you have 3 tires in 265/70R17 a LRB(P), LRD, LRE they ALL carry the same weight at 35 psi. The LRD and LRE carry the same weight at 65 psi.
This is from Toyo, other brands will be very similar.
http://toyotires.com/tires-101/load-and-inflation-tables
For reference the curb weight of a 2008 F-250 CC LB 4x4 Diesel is 7635, front 4756, and rear 2879. Lets assume some people, normal emergency items and gear. 4850/3100. That breaks down to 2425/tire on the front and 1550/tire on the rear. Now reference that Toyo chart.
The front's should be inflated to about 47 psi, so round up to 50. No more air is needed, maybe 55-60 if your going to do a long drive at 70-80 mph.
The rears are actually under the min load at 35 psi, so 35 psi is plenty for 1550 lbs/tire. I would run about 40 for high speed driving.
If the F-250 is gas, or smaller cab/bed, etc then those pressures will be lower.
Your sig doesn't say much, other than it's a F-250 XL. Is it 2/4 wheel drive? Diesel? Cab size? Bed length?
2WD, Gas, Crew Cab, loooong
Thanks, guys. I knew you'd come through for me. I drove it unloaded because I was going to work. Not sure they'd approve of me dragging the Whaleboat to work, even if I could get into the parking deck.
I'll tell DH to try leaking the air out and see how it drives. He wants to take it up to the lake in about 2 weeks, which is only about a 25 min drive. I'll already getting anxious about it--it really is that wonky. If it's gonna take 1000 miles or more to break these babies in, it's gonna be a problem. I cannot drive this tank into Atlanta and all points N-S-E-W as I do home visits all over the state of Georgia. I don't even want my kids to ride in the truck.
