Excessive tire wear: possible source

[Frankie]

I think I've identified at least a possible source of my excessive tire wear.

After two alignments by my trusted indy mechanic, there was a persistent item that stood out on the alignment report: front caster. Camber and toe are both adjustable and were within spec. But caster was not. Specifically, the right front caster was below spec. This explains why my car consistently pulls to the right even after alignments.

My mechanic and I suspect a front strut rebuild may be in order. I'm particularly interested in the strut mounts. Are they prone to failure? What would be a good source for a rebuild 'kit' (strut mounts, spring pads, nuts, washers, etc)? I plan to retain the original struts as they are OK at 130K miles (no leaks, noises).

[Aitch]

I'm not sure if there is a kit, I just pieced mine together from ECS tuning and FCP Euro.

[Frankie]

I just found these: adjustable front camber/caster plates

Has anyone tried them? I'm hesitating to go back in with stock strut mounts since they may not resolve my caster problem.

[Frankie]

I also found this information on E46 Fanatics:

Effects of Positive Caster
Vehicles usually have some positive caster specified since this promotes directional stability, however, excessive positive caster can cause two problems. The first is that excessive caster will cause a high level of road shock to be transmitted to the driver when the vehicle hits a bump, etc. The second problem is that a tire/wheel assembly with positive caster has a tendency to toe inward when the vehicle is being driven. If one side has more positive caster than the other, this causes it to toe inward with more force than the other side. This will cause a lead or pull to the side with least amount of positive caster.

Effects of Caster on Tire Wear
When set with a substantial amount of caster, the spindle travels in a vertical arc, causing it to move up and down and raise and lower the wheels as the steering wheel is turned. Because of this, camber changes occur. With a high amount of positive caster, the camber changes that occur, especially at low speeds in tight turns, cause the tires to show wear on their shoulders. In high speed cornering, the vehicle tends to continue straight ahead when the steering is initially turned. Due to this, and the amount of camber change that takes place when a spindle travels through its arc of travel, the shoulders of the tires on a vehicle may scrub and wear. When a left turn is made at a fairly high rate of speed with a vehicle which has positive caster, the caster of the left front wheel changes toward positive but the momentum of the vehicle is in a straight ahead direction. This causes the inside of the left front tire to scrub as it is turned. Just the opposite effect takes place on the right wheel as the vehicle is turned left at high speed. The right front wheel's camber will go negative but the outside edge of the tire is scrubbed because of the vehicle's momentum to go straight. On some vehicles setting caster more than +2.5° will cause scrub problems.

[Frankie]

KMAC camber/caster plates from Turner Motorsport installed:

IMG_4036_small.jpg

The front suspension is now fully in spec -- finally.

Front tires replaced too, due to outer shoulder wear:

IMG_4038_small.jpg

Observations on tire tread life (Sport models):

I've never owned a car with such short tread life. I'm getting about a year (12K miles) on rear tires and about twice as much (25K miles) on front tires. This car eats tires for breakfast!

Now that my front suspension is within alignment specs, I'm hoping to get longer tread life, but only time will tell. Meanwhile, I can no longer justify expensive, "high performance" tires for this car (such as Michelin Sports or Continental). Until I see a change in tire wear, the time for budget tires has arrived.

Complicating the matter is the staggered wheel sizes and asymmetric tread patterns on today's tires. This means tires can no longer be effectively rotated, leaving me helpless while I watch my tires wear down. Even worse, the tire manufacturer's warranty is cut in half due to this arrangement. So a 50K mile tread warranty becomes 25K miles. This is something few people talk about.

I'm giving serious consideration to replacing the larger rear wheels with sizes to match the front. This would allow me to at least rotate front-to-back. I'll avoid purchasing a car with staggered tires in the future due to the these practical limitations, which only increase the cost of ownership in exchange for theoretical handling benefits (oversteer reduction only).

I'm also beginning to look enviously at you non-Sport owners, thinking I might prefer a smoother ride and lower ownership costs. But I've sunk too much money into this car now, so I'm committed. I do love the look and features of Sport models. But one should consider these realities when contemplating a Sport model purchase decision.

[asianvenom]

Your strut mount is possible for throwing out your allegnment if all other suspension parts are not damage. Strut mounts and bearings for the front are cheap and easy to swap out. Wore suspension parts can and will throw off your alignment. #1 tire killer will be your toe, excessive toe out will eat tires like butter. As for adjustable camber plate is not necessary, I have adjuster camber, but not like others, I use my adjuster camber for MORE negative camber in the front not less, without any issues. My front camber are 2.3 degs negative and I just went thru a set of all season cont dws with 45k miles.

[lewvirg]

Your strut mount is possible for throwing out your allegnment if all other suspension parts are not damage. Strut mounts and bearings for the front are cheap and easy to swap out. Wore suspension parts can and will throw off your alignment. #1 tire killer will be your toe, excessive toe out will eat tires like butter. As for adjustable camber plate is not necessary, I have adjuster camber, but not like others, I use my adjuster camber for MORE negative camber in the front not less, without any issues. My front camber are 2.3 degs negative and I just went thru a set of all season cont dws with 45k miles.

How long have you had your plates? I was looking into this a few years ago - and IIRC there were some posts about the weight of the front end ruining plates: kmac and one other brand?

[shanecarmaster1]

I am happy for your solution, so don't take this the wrong way, but I do wonder about what else is at play here. My camber has always been a solid -1 degrees in the front for both, with caster at a solid +6.5 on both sides. I don't drive on worn suspension. I'm wondering - have you replaced everything? I'm doubtful about the e38 needing camber plates so badly unless you wanted a specific spec.

[RIboater]

Something to keep in mind is that BMW considers their cars to be performance oriented. So the caster/camber of both front in rear are factory spec for performance, at the expense of tire wear. Can't have it both ways. Like you, and others, having the car in spec chews through (expensive) tires. Last time I put a new set of tires on I told my mechanic I do NOT want factory spec. We set up the car with a very standard spec, basically flattened out the rears to not rider on the inner edge and pulled in the fronts, and my tires are lasting at least twice as long.

[shanecarmaster1]

Something to keep in mind is that BMW considers their cars to be performance oriented. So the caster/camber of both front in rear are factory spec for performance, at the expense of tire wear. Can't have it both ways. Like you, and others, having the car in spec chews through (expensive) tires. Last time I put a new set of tires on I told my mechanic I do NOT want factory spec. We set up the car with a very standard spec, basically flattened out the rears to not rider on the inner edge and pulled in the fronts, and my tires are lasting at least twice as long.

Interesting. I run extremely aggressive alignment specs and don't wear through them quickly. I drive the poopy out of it, too. I wonder what's at play here.

[Frankie]

Alignment specs between Sport and non-Sport are identical except for two: front caster & camber. And those are within .2 degrees of each other (with Sport being the more "aggressive"). These two specs are not adjustable. While my camber was OK, the problem was caster. My alignment now satisfies both Sport and non-Sport specs:

Original (L/R):

• caster: 5.5/5.1 (out-of-spec)
• camber: -0.8/-0.5

Now (L/R):

• caster: 5.8/6.0
• camber: -0.3/-0.3

I must conclude frame warping or damage under previous ownership caused the out-of-spec caster. I considered simply replacing the upper strut mounts, however, what if that wasn't enough? Therefore, I went with KMAC to resolve it once and for all.

But I'm also experiencing alot of rear wear even though I've always been in spec. I get nice, even wear -- but the tread is gone in a year (12K miles). I'm then forced to call upon the tire manufacturer's mileage warranty to help subsidize replacements. But without the ability to rotate, I must cash-in before 1/2 the mileage warranty has passed. As it stands now, I'm getting only 1/4 of the expected mileage.

[chucknorium]

Lower the tire pressure in the back. How much you run now?

[Frankie]

The installation of KMAC camber/caster plates to correct a slightly out-of-spec front caster condition has solved all my premature tire wear problems! No more outer tire wear! No more rapidly vanishing rear tire tread! My car drives straight and true, and feels happy.

I've heard owners complain of front outer tire wear. Obtain an alignment and ask for the resulting spec sheet. Look for ANY out-of-spec condition. Many shops will simply align your car as close as possible, then take your money saying "It's done". They won't volunteer the fact that they couldn't align it to spec. Our 20+ year old cars may not align correctly anymore without help.

[racer2086]

Frankie, if you have 130k on your original struts, you should replace them along with all mounting hardware. They are toast at those miles. Oil may not be leaking, but if you took the springs off and pushed them down with your finger, they'd easily collapse without a fight. And they probably wouldn't spring back at all. That's exactly what my originals at 170k did. You would be amazed at the ride difference.

Like you said, there is either frame damage or worn parts (struts and mounts) causing your alignment issues. The plates should not be needed to get within spec.

I also don't think the numbers you posted were off that much to cause the wear you were seeing, but who knows. Not to mention, the positive caster increased and the negative camber decreased. Both of those things should wear the outside more.

[Ruskii]

Hey Frankie, do you have updates after a year? I am getting excess outside tire wear on th front wheels, especially passenger side. I've replaced all suspensions and steering parts except struts/shocks and mounts.

[Frankie]

After a little over a year, I'm disappointed to announce that excessive tire wear is still with me.

It's unbelievable. Tread life is still shorter than any car I've ever owned. After less than 15K miles, I need new tires again. Rear tire wear is mostly even across the tread. But front tire wear is still excessive on the outer shoulder -- but it's less bad than before. I'm sure that if I went another 2-3K miles, I'd be looking at the steel belts on the front.

As I previously mentioned, the installation of caster/camber plates allowed my tech to achieve perfect alignment, which has completely eliminated the right-pulling tendency. The car drives beautifully, tracking straight and true.

In disgust and in preparation for my new tire purchase, I had my tech thoroughly re-inspect the suspension (just yesterday). He said the alignment was perfect, and found no faults in the suspension components. He did remark that tire pressure was low and could cause outer shoulder wear in front. He suggested 36-38psi, while mine was showing about 30psi. Nevertheless, this doesn't explain the wear issue overall. My tech is baffled.

While some suggest new struts, my tech (whom I trust) looked at them with nothing but praise. I think it's forum lore to focus on struts and their effects. In my experience, struts are the last thing to fail on a suspension. Case in point, I replaced front struts on my E39 which were leaking oil at 165K miles. Afterwards, I could discern absolutely no difference in ride quality...or tire wear. I'm not about to throw $2500 in struts at the car in the hope it will make a difference.

Bottom line:

I think it's going to be a fact of life with E38 Sport ownership that new tires will be required every 12-15 months. Is it just Sport models that eat tires for breakfast? Given the staggered sizes, tire rotation is limited. And their larger sizes increase replacement costs. This is a serious drawback and the main factor behind my unhappiness with Sport model ownership. I'm still searching for a special non-Sport E38 as a replacement.

[RIboater2]

You say the rear wear seems to be solved, so if front outer wear is still an issue, it's because the toe "in spec" is too aggressive. You do want some toe in, or the car would wander on the highway, but spec is too much. Low tire pressure could be part of it. You'll get more friction on the outer edge when turning. But also keep in mind that spec is based on the standard 225 50 16 tires all around. Having the 235 50 18 up front, being wider, is another reason "spec" is a problem for toe in.

[racer2086]

Guys, post up your full alignment numbers. Should not be experiencing extreme shoulder wear on the front tires, sport or non-sport.

[740ilDuke]

You can replace the front struts for about $275 then whatever installation is.

I've been running Continental Eco tires that were only available for the front (M-Pars) in
OE size that are 60k mile tires, they are in remarkable shape after 25k miles. The rears
I got about 22k out of and they had the inside wear. So, I dropped the $450 for
Continentals. I've owned it for 5 years and never aligned it since it's always driven
great. Now I have to align it since the centerlink/idlers where just replaced.

Helpful info here. Ill be watching to decide how to align my iL.

[KinkedChrome]

Unless you install caster/camber plates or the strut is bent, struts will not affect caster. If it is truly a caster issue, i would investigate the thrust arm. Maybe it is out of spec in length or perhaps the bushing or ball joint are wore out.

This bmw suspension is unique in that the lower control of the strut is done with 2 ball joints instead of one. One from the horizontal control arm, and one from the thrust arm. So even if your alignment is within spec when the car is static on the rack, there is room for it to go out of whack when your driving on the road if the ball joints or bushings on either part are worn.

Do you get any vibration at all at 40-50mph? Or any shuddering under low speed braking?

[Ruskii]

Here is my sheet as of 01-Aug-2018. I am having excessive outside wear on the front right tire. Tie rods and center link replaced last year; all 4 control arms replaced this past summer, hence the alignment.

Should the outside tire wear be in correlation with to too much toe-in, i.e. negative degree? I have 0.12 positive degree, so toe-out, right (or am I getting them confused)? And why would the right tire be wearing out faster than the left one?

Alignment 01Aug2018.jpg

[racer2086]

Positive toe is toe-in. Those numbers look quite great actually. Does your car pull to one side? I could see you scrubbing the outer of the front right if the car had a pull and you had to steer-left compensate to keep it straight. That pull could happen as a result of tires, rather than alignment, which in your case looks great.

[Frankie]

You say the rear wear seems to be solved, so if front outer wear is still an issue, it's because the toe "in spec" is too aggressive.

Actually (maybe I wasn't clear), I'm still seeing magically disappearing tread on all four tires. If that wasn't enough, both front & rear exhibit shoulder balding.

The alignment 'spec' is per factory, so it can't be considered too 'aggressive'. Furthermore, as previously mentioned, alignment specs between Sport and non-Sport are identical except for two: front caster & camber. And those are within .2 degrees of each other (with Sport being the more "aggressive").

...Continental Eco tires...are in remarkable shape after 25k miles. The rears
I got about 22k out of and they had the inside wear...

It's apparent that non-Sport owners are getting somewhat better tread life -- about 2x more -- which is still pathetic, and well below anything I've ever seen.

Do you get any vibration at all at 40-50mph? Or any shuddering under low speed braking?

Nope.

======================

CONCLUSIONS

As of today, I have in-hand two expert opinions. The conclusions are: "normal vehicle function" for E38 Sport models. There's nothing wrong with my suspension or alignment. Learn to live with tire life between 12-15K miles for Sports and maybe twice that for non-Sports, or move on. This issue easily adds $700+ to annual maintenance expenses, and should serve as an advisory to anyone planning E38 Sport ownership.

I consider this matter closed.

For reasons here and in this thread, I will move on with sadness and regret, and am actively searching for a special E39 with standard suspension.

[racer2086]

I feel like 12-15k is low even for the E38. The rears wear faster than the fronts on my car. I have a non-sport E38 that has been lowered and placed on Bilsteins all around, so it's stiffer and lower than a sport. I don't get premature wear of any of my tires. I have to look in my log book, but I think I'm getting more than 15k out of the tires.

But there is no BMW that you buy that isn't going to go through tires "fast". And I put that in quotes because I'm not sure what you're comparing it with. If you want 80k miles out of your tires, buy a Toyota. My dad's M3 will go through rears on his car in a little over 10k miles. BMWs are performance cars, which generally get softer compound tires installed and will wear them faster.

[clarkitect]

Agreed, that seems like very short life for the fronts. I usually burn through the rears in two summers - 10-15k miles. Fronts have the ability to last twice as long at least, but I usually do all four at once.

BUT I did just notice that my fronts are now wearing on the outside edges - a new fact- never did this before. I also noticed the front has started rattling over bumps now. Suspension refresh has 35k miles now, the only thing I did not do is the front struts. Pretty sure the mounts are shot but hope to jack it up for some triage this weekend. Not sure if there is a relation here.