Cupped front tires, inside and out, both sides

[joecrna]

Im looking for opinions on what suspension component would most likley lead to cupped front tires on both sides of my Explorer.

Both tires are cupped on the inside and outside edges. I recently replaced all 4 tires, the last set went 100k miles but started to show cupping over the last 10k miles. The new set was installed, the vehicle was aligned and had the thrust angle checked. Now a few months later, the new tires are again showing cupping on both vehicle sides and both sides of each front tire.

Just want some ideas on what suspension parts may be causing this. I'll then add what I have replaced recently and what things have been checked (such as ride hieght). Trying to see if my thinking is correct as I trouble shoot this. 6 months left before 8000 mile trip towing our heavy trailer and several things must be addressed on the Explorer.

 

[corkey]

sounds like not enough air in them to me,, if they are wore on both outside edges..

 

[joecrna]

Good guess but no dice. The tires are BFG Allterrains, a floatation model as oppossed to P metric or LT. They are kept at 50 psi whenever they are on the road and I haven't airred them down for off-roading yet. The old set that went 100,000 miles was maintained this way too. That set only began to cup over the last 10k miles or so. By the way, this truck gets about 35,000 highway miles per year so that means its only cupped tires over the last few months.

 

[joecrna]

I was really think about hard parts since the alignment was recently rechecked also. Like inner and outer tie rod ends. Upper and lower ball joints, control arm bushings, anti roll bar end links or mounts. Shocks, maybe even specific alignment settings; camber, caster, toe.

 

[joecrna]

OK, so no one wants to play. I will probably replace the shocks. They seem a probable cause given the wear patterns. Ball joints have been replaced earlier and show no wear now. Anti-roll bar should have no effect, though one end link is once again loose do to a crushed bushing. control arm bushings are original but show no detectable wear. The shocks are approaching 100k miles but considering they are Bilstein (very thick chroming on shaft) and the million mile warranty I remain unconvinced. No leaks and bounce is normal but than a bounce test on this vehicle is near useless.

 

[Turdle]

Lower control arm bushings. Bet they are floppy. The only way to check em is to unspring them and release them from the knuckle. Once they are isolated from all other components they can be wiggled.

 

[joecrna]

Better to check them than just blindly replace the shocks. Completly unspring them or do the usual put truck on jack stands then half compress the lower control arm/spring assembly with a floor jack?

 

[jaschlum]

Sounds like the shocks to me. Did you replace them? Is it fixed?? Also sounds like ball joints. Furthermore, 50psi is pretty high for the BFG's, especially for an explorer. I recommend running 35-40psi; unless you do any towing.

 

[Naasau]

Sounds like the shocks to me. Did you replace them? Is it fixed?? Also sounds like ball joints. Furthermore, 50psi is pretty high for the BFG's, especially for an explorer. I recommend running 35-40psi; unless you do any towing.

I agree with the shocks, but for psi... I've always gone with the tried and true 'chalk line test'. To me it is the only way to really get a feel for what the pressure should be for that specific tire/wheel/vehicle combo.

 

[joecrna]

Sorry, I failed to update this thread. All front suspension components check out fine. I of coarse do not have a machine to cycle the shocks and check exact jounce and rebound but they appear to be OK. Out of desperation, I measured my ride hieght at all 4 corners and compared this to my documented baseline. The front was sagging (the truck carries a lot of weight) about 3/4" on the right and 1/2" on the left. Adjusted these back up to baseline and no more cupping.

Couldn't see the sag and didn't show up on alignment rack. That did however cure the cupping problem.

As for 50 psi, the BFG's I use are a floatation class tire. Not P metric. Its a fine pressure for them.

 

[Naasau]

Glad to hear you found it! Keep an eye on that ride height, the springs might just be dying slowly... and I've found that once they start to go, it tends to pick up speed pretty damned quick.