Tires, Camber, UCAs, and wear

[Brian_B]

So I'm asking for advice before I take my Bronco in.

I've got 38x11.5R17 Nitto Ridge Grapplers. I have about ... 25k miles on them. I rotate them frequently - every 3-5k miles.

I just noticed that my tires are wearing unevenly. The inner edge, on all 5 tires, is about 7/32". The outer edge is at 13/32". It's a fairly linear slope between the two (the middle right at 9/32"). My novice research seems to point to excessive negative camber. All 5 tires show the same pattern, to about the same degree.

Last fall I installed some alignment cams. Got an alignment after that. Everything looked good, but Caster Camber was slightly out : -0.5° on both tires. Shop said nothing to really worry about. I did have the 38's on for that alignment.

I have a little bit of adjustment left on the cams, they are not maxed, but they are close to maxed.

I poked around up underneath the front end - everything seems tight, nothing obviously bent, no play in the ball joints or anything, no loose nuts - no smoking gun.

When I bought my Bronco it had an RC 2.5" lift on it from the dealer, which came with the RC forged UCAs. I didn't know any better or worse at the time, and I didn't get the stock UCAs. I also have the Pro Comp coil overs, and they have around 60k miles on them. I haven't had any issues with them or noticed anything that has significantly changed, but worn suspension could be a potential cause here - but I don't see any striping or cupping or anything which would more so point to a worn shock or spring. I also installed my re-geared m210 FDU this winter. Not sure that would have too much effect on tire wear by itself, but just looking at things that have changed. Not really enough miles on the FDU yet to have affected all 5 tires though, I think.

I plan on taking it back into the alignment shop to see what they can see, but thought I would ask the experts around here for some advice. Not sure if the RC UCAs are enough to get the caster in running 38's. If I go in and pay for a re-alignment, I get 30 days of re-alignment service if it is the UCAs and I have to replace them.

When I ran 35s, I got about 50k miles out of a set of MT Baja Legends, and they wore pretty evenly the entire way down. I do have the original alignment from after installing the Pro Comps somewhere, but I think it was about the same negative caster.

Is this one of those things where - eh, you run big tires, you pay the big tire tax.. or should I chase trying to correct it?

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[Oldhippie]

Caster has little effect on tire wear (tracking/steering yes) compared to toe or camber…I think it is more to do with larger tire diameter needing less toe/camber than stock…a good alignment shop can get it right (not just to stock spec)…good luck!

 

[Valhalla]

I'd get it checked, but the big tire thing can be some of it in my opinion. Most of it will be as hippie said, toe. My 82 I ran almost zero toe.

 

[Brian_B]

Caster has little effect on tire wear (tracking/steering yes) compared to toe or camber…I think it is more to do with larger tire diameter needing less toe/camber than stock…a good alignment shop can get it right (not just to stock spec)…good luck!

You are on the right path.

Where I said caster was out, i meant camber.

 

[Fordified1]

I don’t know if this helps but my 35’s wore evenly with these alignment settings. My son did the alignment. I have not had it re—aligned since installing the 37’s a few weeks ago. I should because we have off-roaded it a few times and replaced the diff and one lower control arm. ( I just marked the cams and installed it exactly like it was). Drives exactly the same and I did check the toe with a tape measure. (hey NASCAR does it lol).
Edit: I also asked him to set my caster angle to the limit of acceptable factory spec and he did. This is with stock control arms. Eibach coilovers. Non-Sasquatch.

 

[Oldhippie]

You are on the right path.

Where I said caster was out, i meant camber.

well incorrect camber can indeed wear tires unevenly side to side…likely the issue…

 

[Brian_B]

So here's what the shop said:

Camber had drifted down to -0.8°, but just about everything had drifted by the same amount. Supervisor says he sees that when suspensions settle or start to get old.

My Pro Comps have been on there for around 60,000 miles, and I haven't made any adjustments to them in a really long time. The tires themselves for around 25k. I did change out to the m210 this winter (and did have the alignment redone following that install), but that shouldn't have too much affect on the suspension. It's possible the coil overs are just starting to get ... maybe not worn out, but worn down.

He re-aligned it, got it not exactly perfect, but pretty good - good enough that I felt comfortable running with it with tires that are over halfway done anyway. Both sides are at max adjustment for camber now though, so any additional adjustment I'll need new UCAs.

So I guess, when I get another new set of tires, I'll do new UCAs, consider suspension in general, and get the alignment redone with the new rubber.

 

[Oldhippie]

I would think about getting uca now rather than later since ya are gonna need them anyway with your lift…might get a few extra miles out of your current tires ...anyway glad ya got it figured out…glad to hear ya got some miles on those procomps without troubles…

 

[Snacktime]

I set my camber with a digital gauge from harbor freight. Eyeball my alignment and adjust it as needed based on tire wear. 99% of alignment places have no clue what they are doing besides making the computer number green.

 

[Brian_B]

I set my camber with a digital gauge from harbor freight. Eyeball my alignment and adjust it as needed based on tire wear. 99% of alignment places have no clue what they are doing besides making the computer number green.

I admit I have no idea how to do this… yet.

 

[Valhalla]

Glad you got it figured sir!

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