Tire cupping, front suspension issues?

[92-SR5]

Ok, so I am a little stumped on this one. I am noticing that my front tires are wearing a lot more on the inside vs the outside. The cupping isn't horrible yet, just enough to notice when you look at it closely. I had an alignment about two months ago when I put my BJ spacers in. At that same time I replaced my ball joints and idler arm.

Note: It drives great, no pulling to the side, vibrations, no noises. When I jack the front up and check the front end there is no slop when I'm moving the tires different directions.

The reasons that I can think of that are causing this are....

1. The guy who did the alignment probably sees hondas/passenger cars all day and doesn't know jack about lifted 4x4s.

2. Would bad shocks cause this? My front shocks (KYB) probably have 20-25k miles on them.


I'm just a little stumped on this one. I am going to have an alignment done on it tomorrow by a guy who I trust. I just thought I would pick your brains on possible other reasons.

 

[mikebontoft]

you're under-inflated.

edit: hmm... perhaps our definitions of "cupping" are different. I went off the title. sorry.

What is your description of the inside and outside of the tire? Inside being the edge of the tire closest to the frame, or inside being the center of the tread? The first one is my description.

Depending on what you mean... there's two things I can tell you: If the center of the tread is cupping in from wear, then it's over inflated.

If you mean the same as my description, then I'm assuming they are getting scalloped. Looking at your avatar, you have a wider track than stock with aftermarket wheels. You have now changed your scrub radius. This is not correctable with an alignment. Only going back to stock wheels will fix it. Just the way it is.

Make sense?

 

[KidVermicious]

If we're talking about the inside edge of the tire, it could be your camber out of whack, too.

 

[mikebontoft]

If we're talking about the inside edge of the tire, it could be your camber out of whack, too.

While it wouldn't help, I suspect if camber is anywhere out of spec on his, it's probably too positive based on what a balljoint spacer does.

That spacer could potentially shift your scrub radius as well. To describe it easily, if you took a stick and lined it up so it points from the upper balljoint, through the lower balljoint (suspension pivot points) and to the bottom of the tire, you have your scrub radius. To ensure even wear, you want that "stick" to end up in the center of the tread.

When you add aftermarket wheels that widen the track, or change the height of the tire, you will change that contact point. On yours, I am absolutely willing to bet your contact patch is to the inside of the tread (closest to the frame, to clarify). Instead of distributing the weight over more tread while turning, it is all concentrated on that inside edge and effectively chewing it up.


On a side note, unless the toe is set pretty far out and there is a good amount of negative camber, it shouldn't be cupping the tires...it would just feather that inside edge.

Post up your alignment printout if you still get one, but I believe it's fine.

 

[KidVermicious]

To describe it easily, if you took a stick and lined it up so it points from the upper balljoint, through the lower balljoint (suspension pivot points) and to the bottom of the tire, you have your scrub radius. To ensure even wear, you want that "stick" to end up in the center of the tread.

I think you're describing this wrong. A line through the ball joints on an IFS 4Runner is nowhere near the centerline of the tire, even stock size with stock rims. The ball joints sit just outside the wheel, which mimimizes scrub radius but doesn't eliminate it. Obviously scrub gets worse the farther out you push your tires, but guys everywhere run ball joint spacers and wheel spacers or low-backspace wheels (I did) and don't get excessive wear on the inside edge. If that's what Cory has, my money is on his camber out of whack, either due to a poor alignment or ball joint wear.

 

[mikebontoft]

I think you're describing this wrong. A line through the ball joints on an IFS 4Runner is nowhere near the centerline of the tire, even stock size with stock rims. The ball joints sit just outside the wheel, which mimimizes scrub radius but doesn't eliminate it. Obviously scrub gets worse the farther out you push your tires, but guys everywhere run ball joint spacers and wheel spacers or low-backspace wheels (I did) and don't get excessive wear on the inside edge. If that's what Cory has, my money is on his camber out of whack, either due to a poor alignment or ball joint wear.

I'm not. In a perfect tire-wearing world, the contact patch will be in the center. Most passenger trucks inherently have a scrub radius to the inside of the tire anyway.

If there's any interest, I could pull a wheel later today and show where my contact patch should be... actually, even better: I could probably see both balljoints and just take picture on the ground. Add a line on the computer and see where that is.

My guess is it's not excessive wear though. It doesn't sound like it. Accelerated, maybe. I'm still willing to bet the camber is either correct or slightly more positive than it should be.... but I'm being competitive and I'd love to see who is right, if either is.

Alignments and electrical are my favorite things... followed by engines of course!

 

[foonanas]

I had some crazy wear on my BFG's(inside of tire cupping and bald closest to the frame) and when I had them replaced Saturday they told me due to my lift they could not get the alignment right.. my camber was maxed out.. from what they told me..

 

[92-SR5]

[MENTION=2454]mike[/MENTION], I am meaning inside of the tire as in the side closest to the frame. I know it is not a tire pressure issue. I check that regularly and run 30-32psi when driving on the street.

I'm thinking it has too much negative camber, we will see what the alignment guy says today.

http://www.mikesauto.net/PosNegCamber.gif

 

[92-SR5]

I think you're describing this wrong. A line through the ball joints on an IFS 4Runner is nowhere near the centerline of the tire, even stock size with stock rims. The ball joints sit just outside the wheel, which mimimizes scrub radius but doesn't eliminate it. Obviously scrub gets worse the farther out you push your tires, but guys everywhere run ball joint spacers and wheel spacers or low-backspace wheels (I did) and don't get excessive wear on the inside edge. If that's what Cory has, my money is on his camber out of whack, either due to a poor alignment or ball joint wear.

I'm thinking (hoping) it is an alignment issue. I'd be pissed if it is my ball joints considering I have brand new Moogs BJs on it.

 

[mikebontoft]

I know it's not tire pressure. That's what I said at first but I didn't think it through at all. Hopefully you read the other part as well...

 

[92-SR5]

Well the results are in....

The guy who did the alignment did not know what the hell he was doing. Caster and camber were WAY off. The guy did not even tighten the sleeves on the tie rods!
I'm pissed, I want to go back there and ***** but that isn't going to get me anywhere.
At least it is all good now.

 

[mikebontoft]

do you have the alignment print out? Caster is still a non tire wearing angle... curious to see what camber was then.

 

[92-SR5]

I don't have a printout. I remember him saying that the camber was about 4 degrees off.
I should have got a print out but I was running late for work.

 

[mikebontoft]

damn. 4 degrees is pretty intense. wonder what exactly it was. Positive or negative.

this is 4 degrees of negative camber. When you said you had an alignment and it drove great, I didn't expect it to be that bad. I was expecting something more around one negative degree or less, but this.....nah. You better believe it will do that. I'd say next time I'll just wait until I see the actual car.

I don't blame you for being pissed at the guy though. He didn't do shit, or made it worse. That sounds like the worst post alignment I've ever heard of.

Because I found this cool picture. This is four degrees of negative camber. (on a little car of course, but it has upper and lower control arms).

 

[92-SR5]

Yeah it's weird. It really didn't look bad.
The worst part is the "owner" of the shop did the original alignment. Out of all employees, he should know better than to send out a vehicle to a customer that doesn't have everything tightened down.

 

[mikebontoft]

Yeah, that's pretty bad. Hopefully it was a one time mistake for the sake of his other customers.