A commonly occurring problem on my Montero has been with tires developing cupping wear patterns over time, despite regularly being balanced and rotated. It has happened with the set of Dunlops I had, the Pro-Comps, and now the BFGs. The general consensus among knowledgeable tire people is that it's a consistent problem when running oversize tires with an IFS, and sometimes even with stock size tires (early Ford Explorers/Rangers). The first set of tires cupped even though my OME shocks were nearly new at the time, so it's not due to worn shocks. Worn steering/suspension components could be playing a part since it seems I've always got something or other that I've beat the life out of that needs to be replaced.

Anyway, my BFGs have become progressively louder, especially at highway speeds, so I've been thinking about possible solutions to try to level off the uneven tread blocks. The photo somewhat shows how unevenly they have become worn, the darker blocks being the ones making less contact with the road than the lighter ones.



I researched having the tires shaved like racing tires, but the few places that can do that would only shave a brand new tire or couldn't fit a 35" diameter tire on their equipment. Big rig tire shops wouldn't touch them either - embedded gravel in the tires can damage or break the cutting tools on tire "truing" equipment. So, I improvised.

I set up the Montero securely on 4 jackstands, with the tires just off the ground. I started it up, shifted into locked 4 high, locked the rear diff and put it in drive. Using a 14" rasp, I braced one end on a brick on the ground and pressed the rasp against the spinning tread of the tire.



The rasp worked far better than I hoped, taking rubber off fairly quickly. This is one tire after about 15 seconds of "truing".



It turns out that my tires had their worst unevenness on the outer 1/3 of the tread blocks - it was very easy to tell by feel and by sound which areas needed the most attention. I spent about an hour all together, to reach a point where the rasp wasn't bouncing against the surface of the tires but riding smoothly (well, smooth for mud-terrain tires).



I definitely shortened the life-expectancy of the tires a bit with the rubber that I removed.



On driving it afterwards, it was noticeably quieter driving through my neighborhood at low speeds, and on surface streets at medium speeds, but highway noise levels didn't diminish nearly as much as I'd hoped for. I'm thinking that I may try having the tires dismounted and remounted on the wheels so the former inside edges can wear as the outside edges, just to try to create some new wear patterns.

Once you've 'surfaced' all the tires, you might perform the chalk test to find the optimal air pressure for your tires and load? The tires on my wife's GMC have this issue from time to time, some solved by replacing the shock absorbers, some by adjusting the pressure.

Nice work! I'll have to remember that a rasp works nicely. I have found that rotating tires at every oil change keeps the uneven wear down to a minimum. That, and the occasional burnout. <img src="/forums/images/graemlins/smile.gif" alt="" />

How are you rotating your tires? I rotate them like this and my bfgs wear evenly. Swapping sides changes the direction of rotation and improves the wear pattern.
web page

I don't rotate my spare, so the fronts get moved to the rear and the rears swap sides and move to the front.

I rotated my KM1's alternately two ways; front to back/back to front, and an X pattern. Had great results for 30K+ miles, then I got lazy and they cupped right up. <img src="/forums/images/graemlins/lol.gif" alt="" />

<img src="/forums/images/graemlins/cheers.gif" alt="" />

Rotate in an x. seems to help. Plus adjust air pressure a bit. Might help.

Now that your tires have been "retrued" take them to a offroad shop that grooves tires. It's about $70 per tire, if you get them grooved they will quiet down and wear a little better. The theory is that the bigger blocks have to turn and drag part of itself through the turn more than a smaller block, plus better wet traction. Maybe start with the front 2 and see how it works?

Do you know of any shops that do this?