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 (https://www.turnermotorsport.com/p-389661-front-adjustable-cambercaster-plates-e39-540m5-e38-740-kmac-stage-1-street/)

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:

605571

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

Front tires replaced too, due to outer shoulder wear:

605570

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. :confused

[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?

641691

[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 (https://www.bimmerforums.com/forum/showthread.php?2380668-Decided-Sport-model-not-for-me), 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.

[Frankie]

...I think I'm getting more than 15k out of the tires...


...I usually burn through the rears in two summers - 10-15k miles

That's outrageously low mileage (especially for non-Sports) and only confirms my experience.

My point of reference is my trusty E39 with standard suspension. I've been getting 45K+ miles during the 7 years I've owner her. Hell, my old E36 saw similar tread life. My 'heavy' E31 would get 15K(R)/25K(F). But I can't get even this much out of my 740. BMW's really aren't so different from other cars that tire life should be problematic (M-cars excluded). It's clear to me BMW engineers sacrificed tread life on the alter of 'sport' with the E38 Sport.

Since my 740 is a daily driver, I easily see 12-14K/year...requiring new tires annually. This is unacceptable for my purposes.

[clarkitect]

Yeah I agree it is crazy low. Mine is a sport. I had an E39 sport and that wore out tires pretty fast too, at least on the rears. But being able to rotate the tires made a big difference - front to back, then side to side with the rears, switching wheels to keep the same rotation.

40k miles now with my E38 and I am on my third set of rear summer tires (one set was new but a few years old, those burned out quick), and second set of winter rears. I even had them use non-sport spec in the rear alignment.

So, yeah, I guess your basic premise is correct. But oh well, is what it is. Maybe going to a square set up would help.

[Ruskii]

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.

Car does not pull and tracks true. I am going to visit the shop that did my alignment tomorrow, and ask them to check the front. I also had them rebalance front wheels at the same time they did all wheel alignment -- maybe that's a factor to my right front excess wear (bad balance?). Tires have only 14K on them. :(

[nmlss2006]

Frankie,
if you recall we had the discussion back when I was having issues. I will keep this to the point: at the time I was skeptical that that amount of cross-caster could cause any tire wear and it seems that my skepticism has been validated.

I know for a fact that E38s with sport suspension from the factory did not go through a set of tires in 25k km, that is to say 15kmi. Twice that would be relatively normal, depending on a lot of factors. The difference in angles is not even remotely sufficient to have a material effect on wear (that is to say, 5% maybe?).

Driving habits, of course, count for a lot, but if you're going through rear tires in 10kmi on the street in the US... I think you may want to change them. It's not the car's fault and no, that is not normal either.

As a further point of reference, I used to go through a set of tires every ~40kmi on the M5, back when speed limits didn't matter in Europe. The last set of tires has lasted one-and-a-half times that. BMW suspension, especially the E38/E39 kind, wears tires very smoothly - when it works.

A very old mechanic a long time ago said that the best way to deal with these cars alignment is to NOT touch the factory settings. So far, in my experience, he is distressingly accurate.

[racer2086]

Grasping at straws here...Maybe try a different brand/type of tire? The E38 is a heavy car, so it requires a high load index tire. I run Firestone Firehawk Indy 500 Tires. The front is 101W and rear is 103W load rating. The wear rating is a 340. Not super soft, not super hard. Not sure if the load index plays a factor in the wear of the tires. The treadwear number (340 in my case) surely does...

[ShiftPoint]

I know this is a somewhat old thread, but I have some information to add to it.

Back in September of 2018, I bought a set of Sumitomo's for my 2001 740i sport. The HTR A/S P02's. This was at 136k miles. I replaced all of my front suspension aside from the struts and sway bar links before I bought the new tires. I didn't touch the rear suspension. Turns out the rear suspension was worn-out as well. I didn't know that until after I got the new tires...

The old tires didn't seem to have any signs of damage due to failing suspension parts or an out of spec alignment. They were just old and starting to crack. This car was a rescue lol. I was in California and it was in Michigan. I didn't even know if it ran when I bought it. None of the tires matched, one rear was on the front and the other rear was in the trunk... still had a few original spark plugs lol.

Anyways, I ordered the rear suspension parts and figured I'd park it for the winter and get back to it when spring came around... However, my plans were ruined in November. I ended up having to drive out to California from Detroit with around 600lbs of stuff on the already worn-out rear suspension and my new tires... you can imagine how thrilled I was lol.

I had to drive through a blizzard, literally at least 6 inches of snow at 65mph wit practically no visibility. I was at the edge of my seat trying to see the road. I had to turn the headlights off and drive with just the fog lights on just to see where I was going to some degree. I still couldn't see where the edge of the road was... there were no guard rails. Ended up following a tractor-trailer to a small town and got a room for the night.

I couldn't be more impressed with these tires after that... or so I thought...

When I arrived, I had to reorder the rear suspension parts. I heard that you couldn't do the wheel alignment yourself... they say it takes at least 3 guys and a donkey and even then, you'll never get the alignment close enough not to ruin your tires befire yout make it out of your garage... Naturally, I accepted the challenge lol. I figured I replaced the front and aligned it myself, so how hard could the rear possibly be?...lol....

I replaced the rear suspension by myself and set the alignment back exactly where it was. I'm almost at the 8k mile mark since I bought my tires.

This leads me to believe that you folks who are somehow managing to only get 10k miles out of your tires, are doing something horribly wrong. I see some people saying they drive pretty hard... my tires pretty much see track conditions whenever I drive...

Before I replace the rear suspension parts, the rear inner edges were worn as if the wheels were at a 45 degree angle. After I replaced the rear suspension parts, that worn-out part of the tires didn't even come in contact with the pavement. Much more even tread usage. The front tires are almost like new still.

My front sway bar link on the driver side came apart at some point, so I just removed that link, thus leaving the sway bar disconnected. I'm going to order new links, just haven't gotten around to it. I'll likely replace them before I get the new rear tires. That way, there will be no excuses not to do the wheel alignment this time.

An important thing to note... I see a lot of people talking about the Michelin pilot sport a/s 3's, but not many people actually comparing the specs. They have a tread wear rating of 500, same as mine. Max load rating of 1,708lbs, which is actually not as high as mine at 1,929lbs. The traction is rated at AA where mine are rated at A. Temperature ratings are both A, and they both have the same tread depth. However, the Michelin's have a Y speed rating where mine have a W speed rating...

I've never hit 160mph in an e38, how about you? Do you intend on taking curves at 100+mph where 40mph is recommended? I do, and I have. With no front sway bar and on my own wheel alignment.

That being said, I cannot justify buying the Michelin's, especially considering how fast they will wear vs the performance. My car has had a lot of problems, but traction was never one. If I did have traction problems, the first thing I'd do is investigate how much abuse the transmission is willing to put up with. If I liked what I found out, I'd then invest in a set of Mikey Thompson Street Comp tires... tread life will be sacrificed to the speed gods. But these have a better contact patch, softer compound, and aren't as expensive as the Michelin's.

Think about it this way... the less you have to use your brakes, the less fuel you use (because you won't have to get back up to speed) and the less often you have to replace brake pads and rotors lol.

Seriously though, when I get my new tires and alignment, I'm going to take it easy on them and report back. I'm not sure where my adventure will take me next, but for now, I'm in the mountains and thus it's only so easy I'll be able to go on them lol. Place an imaginary egg under the accelerator and pick lines that put the least amount of stress on the tires.

This new style of driving will actually be good training for the track. Extending the tire life results in fewer pit stops and thus an overall higher average speed. I'll definitely have to put some more thought into this new driving style.

[Thresher]

I know this is a somewhat old thread, but I have some information to add to it.


I will chime in too. I've had my E38 for about two years now. Shortly after purchase in June 2018 I replaced all 4 tires with Pirelli Cinturato Strada Sport AS tires. These tires are rated 500/AA/A. I've been very happy with how the tires handle but the rear tires barely managed to get 15,xxx miles on them before I had to replace them two weeks ago while the front ones are still fine and have about 1/2 of their tread life still left. A year ago I replaced two tension struts, four control arms, two rear guide links, front sway bar bushings and had the car aligned. The alignment shop reported the existing alignment was near excellent and only minor tweaks were done. Both of the rear tires had even treadwear and proper inflation. Like Frankie's original posts on this thread, I'm left wondering what to make of this.

The tire shop I purchased them from in 2018 was kind and offered a $125 per tire mileage warranty credit on a new pair of the same tires. It will be interesting to see how the replacement tires perform over the next 1-2 years as I only put about 8,000 miles on the car in a year. Prior to replacing the rear tires I made note of the DOT plant code for comparison with the new tires. Both the old and new tires had the same plant code, which when I looked it up was for the Pirelli factory in Guanajuato, Mexico.

FWIW, the remaining suspension components that I haven't touched yet are the front strut mounts, front EDC struts, the rear EDC w/SLS shocks, and rear sway bar bushings and the 4 springs. Front strut mounts and rear sway bar bushings should be easy to do; the struts and shocks are a different matter (i.e., $$$$) as I would like to keep the EDC and SLS functionality. Car has been based in California its entire life so has virtually no rust -- that gives me confidence in the springs still being in great shape and not deteriorating.