Extreme inner shoulder tire wear

[IN10SS]

Hi All,
This year I lowered my Z4M on eibachs, installed turner camber washers and aligned to zero toe in the front and slight toe-in in the back. Camber ended up at -2.8 in front and -1.9 in back. I added a strut brace and 12mm spacers in front to widen the track. Looked good and the handling was improved by an incredible amount. I made three trips to the tail of the dragon and had a blast. I ran tire pressure at 33 lbs front and 31 lbs rear. I regularly checked for uneven tire wear, measuring outer grooves and inner grooves with a tread depth gauge. Only slightly more wear at the inner groove and no unusual outer shoulder wear. Then I found this:
Extreme wear on the inner shoulder. Down to the cords so far down the side of the shoulder, it is almost the sidewall. Scared me just to see it, especially when I considered what a tire failure would mean at 120 mph on the skyway.
So, needless to say, I'm looking for a good street alignment set-up instead of maybe a track set-up. I have new tires and wheels installed, and swapped from two washer spacing to one washer in the front. I raised the rear 10mm in hopes that raising it slightly will help decrease some of the negative camber I gained when lowering, and I'm ready to head off to the alignment shop. I'm hoping for some discussion and opinions on what I should shoot for and also if I'll need adjustable rear control arms to achieve it. Also wondering if I may be over inflating tires although nothing found to support this. Finally, am I missing something completely as in a worn part causing this? Car has 51K miles and everything feels tight.

[IN10SS]

Hear is how it is sitting now:

[inTgr8r]

- is that wear in front, or rear?
- how many miles with that setup?
- slight rear toe; do you know the #s ?

I have a more extreme setup than you & have no such wear issues.
worn out bushings are the first thing that comes to mind, but I would expect more cupping.

[IN10SS]

Hi, The tire shown was the left rear. The other rear was almost identical. The fronts were showing bad wear as well. rear toe-in was less than 1/16. All this uneven wear happened within about 4500miles. A dozen hard runs on the dragon, at least 4 skyway runs pushing hard, and numerous trips on hellbender 28. I have gone a couple times a year on my hayabusa for ages and this time my son brought his new GSXR1000. I just want to figure out how to use the rest of the tire so I can go faster (ha ha). Seriously, we both looked over suspension front and rear and saw nothing obvious. If my toe settings were responsible, I'd expect the top of the shoulder to wear rapidly, but only 1/32nd" difference from outermost groove to innermost. It seems as if several guys are running specs at least this extreme, so I'm concerned there are worn parts I'm missing.

[Shipkiller]

...

[inTgr8r]

Originally Posted by IN10SS

Hi, The tire shown was the left rear. The other rear was almost identical. The fronts were showing bad wear as well. rear toe-in was less than 1/16. All this uneven wear happened within about 4500miles. .........
...... It seems as if several guys are running specs at least this extreme, so I'm concerned there are worn parts I'm missing.

Almost guaranteed to be the RTABs

[Arsonism]

Originally Posted by inTgr8r

Almost guaranteed to be the RTABs

Would agree 100%

[IN10SS]

Thanks for the input. Time to replace asap before I waste an alignment. Should I replace with stock parts and use limiters, or is there a better upgrade? What about adjustable control arms: needed or not?

[The HACK]

How often do you track the car?

[IN10SS]

Originally Posted by The HACK

How often do you track the car?

Maybe twice a year. Remaining use is 30% easy country cruising with the wife, 30% getting to the mountains, and 40% very hard mountain driving. So I can't have a track only set-up. I've made the mistake of going too far down the performance only set-up before, but have also conditioned my favorite passenger to expect and enjoy a sporting ride. If it is coming apart, I want the replacement parts to be more performance focused. Thanks!

[inTgr8r]

I went with the R.Eng black poly RTABs which are a little softer than a full out track bush.
They have been great for me on a combined usage car.
I would buy them again.

there is some interesting info on the linked page.

[The HACK]

That's a lot of camber for a car that only sees 2 track weekends a year.

[XMetal]

Originally Posted by The HACK

That's a lot of camber for a car that only sees 2 track weekends a year.

-1.9 in the rear is a lot of camber? Isn't that pretty much close to stock? I believed the picture shown for the excessive wear is for the rear.

[IN10SS]

Originally Posted by The HACK

That's a lot of camber for a car that only sees 2 track weekends a year.

I guess so. I'm not sure I should (but I will) convey just how hard I push it in the mountains, but I'm willing to give up quite a bit to have it handle the best it can. Some locals who run the dragon are practically a cult club with timed runs when enforcement is low. Not many cars are as suited for that road as ours. Those as nimble are low powered and those more powerful are much bigger. To run fast there is just as intense and less predictable than track work and not very forgiving of mistakes.
With that said, my settings are definitely in the track realm and may not need to be this extreme, which is one reason I'm asking for advice. Plus the rear camber is simply what I ended up with when I lowered the car. Then there is the worn part issue, and finally what settings I shoot for will help decide if I need adjustable lower arms and so forth. Thanks for sharing your thoughts and experience.

[IN10SS]

Originally Posted by XMetal

-1.9 in the rear is a lot of camber? Isn't that pretty much close to stock? I believed the picture shown for the excessive wear is for the rear.

Thanks for your point. I didn't think this was as extreme as the front camber, either. The wear and the angle of wear on the tire is what prompted me to seek help. If the primary culprit is the RTAB's, I may be able to just dial back the camber slightly.
My front tire wear was also right on the inner edge of the tire, just not as extreme. I'm thinking of FCAB upgrades as well after doing a few searches and reading.
The car seems to corner pretty flat, but maybe I need to explore sway bars or end link upgrades too.

[IN10SS]

Originally Posted by inTgr8r

I went with the R.Eng black poly RTABs which are a little softer than a full out track bush.
They have been great for me on a combined usage car.
I would buy them again.
there is some interesting info on the linked page.

Good to know. I've gone with poly bushings in the rear control arms on another vehicle and experienced binding, so I was leery. Tempted but afraid of spherical ball ends transmitting NVH, especially since these are only a foot from the seats. This choice might be just the ticket. Nothing like learning from your first hand experience, so thanks!
I did also find something on B'world that was supposedly a streetable monoball type.
I'm considering putting off replacement until January when I won't miss any chances to drive due to winter weather anyway. So I may go ahead and align the car, see how much negative camber I can dial out and drive easy until then.
I did just buy a new set of pilot super sports and don't want to risk them!

[inTgr8r]

absolutely no binding or noise after a couple of years usage.

I also have poly FCABs and they have been great as well.


BTW...
Envious of your location near those great driving roads.
Some of the best I've ever driven!
Cherohala

[IN10SS]

Originally Posted by inTgr8r

absolutely no binding or noise after a couple of years usage.

Great news

I also have poly FCABs and they have been great as well.

Looks good, too.

BTW...
Envious of your location near those great driving roads.
Some of the best I've ever driven!
Cherohala

Hard to beat a spirited run on the Cherohala Skyway. Sharp curve, accelerate to 130 while passing a Harley, hit the brakes, sharp curve, repeat for next 40 miles only stopping occasionally to admire the view and let your brakes stop smoking.
You're always welcome to come visit again!

[seank]

4 degrees of camber wont make a tire look like that. There is more to the story!

[IN10SS]

Originally Posted by seank

4 degrees of camber wont make a tire look like that. There is more to the story!

I looked over the lateral arms in the rear when I changed my brake lines last spring and didn't see any noticeable play. RTABs are harder to inspect; I assumed they must be good considering the low miles, but the evidence and the experience of the guys here have shown me the error of my ways.
There has to be some serious deflection going on when under heavy load. I'm definitely replacing the RTABs and wanting to add poly bushings to the lateral control arms as well.

[mtrhed]

I've been running the BW spherical rtab's for about 10k miles and really like them. I also did the rear ball joints at same time and rear is very stable now under hard braking/turning. My car is also a back/mnt. road car but driven pretty hard. I run -2 rear camber and have no significant inner wear. Before the sphericals I could really feel the rear end squirming around with the stock bushings after 10k-15k miles.

[IN10SS]

I was hoping someone would post up with some experience with the BW spherical RTABs. I'm leaning that way now. Always liked the idea but worried about harshness. Wondering about lateral control arms. I did also decide to go with poly FCABs in the front. Thanks!