Weird Tire Wear
 

Had to crawl under the SDL today to pull the starter motor (whole store in itself) and noticed a weird wear pattern to the very outside edge of the front left tire (see picture).

I'm sure this is a suspension issue, but I'm not sure what it is.

Important facts about the car:

- 1986 300SDL (W126)

- Tires are new as of the Thursday before Thanksgiving. ~500 miles since installed. Yokohama Avid Touring-S if it makes any difference to anyone (Very quiet and smooth tires too, btw).

- Shocks are gone. They'll be replaced in a couple of weeks when I return from a trip

- Car drives straight and doesn't pull. Can take your hands off the wheel and car keeps going in a straight line, doesn't waver or pull under braking either.

- No other tire on the car shows any wear patterns. Look closely at this one and you can see it is ONLY the weird wear pattern that is worn, rest of the tire is normal and even the worn part has no feathering (which is what is really confusing me).

I'm sure this is some sort of suspension problem, where do I need to be looking? Besides shocks...

That type of scalloping on one side usually indicates worn dampers. The shocks are blown and aren't resisting the springs oscillations well enough, so the tire is skipping on the road a little. Should resolve with fresh dampers.

I think, lol.

That would largely make sense since these shocks are G.O.N.E. They're Bilstein HD's, but no telling how old they are (sat in a field for 10 years and couldn't have done them any good!). Certainly pushing down one corner of the car makes the whole thing wiggle around like a bowl of jello. Also have driven the car a hundred miles or so at 50mph or so over the last few days. The shocks in the front are the worst and with the crown in the road (seems to be exaggerated around here for some reason), it does kind of make sense.

In my mind, it's probably a good idea to take the car in for an alignment after replacing the shocks anyway, even though it isn't pulling or having sloppy steering.

I suggest you look at a chassis manual before making any decisions....
our cars make ' non standard ' wear patterns .. there are pictures in the chassis manual...
You might also need shocks or whatever..
but the wear on the outside may be standard given the design of the suspension..

That looks like worn shock wear pattern, but in any case no reason not to put new ones on. Its really a safety issue.;)

Looks like you ran over something hot and it scorched the tire. looks like gouging rather than wear marks. My opinion.

Good Call. I just checked out section 40-0104 in the Chassis manual and it explicitly points out the wear pattern on the outside shoulder.

Of particular interest is the section noting causes of increased tire wear. Point 2 is lifting off the gas in turns causing increased shoulder wear, especially on the front wheels. With bad shocks, this is just part of life in turns, the "scrubbing" makes sense now that I think about it. Point 4 mentions a "normal" saw-tooth wear pattern with certain types of tires, especially on the front axle.

I think what I'm going to do is rotate front/rear tires after replacing the shocks and observe the wear pattern. With the new shocks, the suspension geometry should be a bit better anyway, it seems like changes in geometry are a major cause of tire wear on these cars.

The chassis manual suggests a criss-cross rotation every 5000-10000Km (roughly 3-6K Miles). I'm spoiled by newer cars that suggest every 10K miles ;)

Are you by any chance in the habit of turning the steering wheel and then pressing the go pedal?

How are your Lower Ball Joints and lower bushings?

My SDL...Way back when I was getting similar cupping I re-balanced tires, new shocks, and criss-cross rotated the tires. Cupping came back.

With the recent new tire install I replaced the lower ball joints, and lower bushings. Shocks are kind of shot @ 80k or so miles. I've got about 10,000 miles on the new tires with no cupping wear.

Over the years I found that cupping is usually a function of poor tire balance i.e. lost weight etc., compounded by worn suspension parts.

Scrapes?
 

Just looked at the photo in a different photo viewer. Those tread marks look more like scrapes or some sort or tire compound deterioration vs suspension wear related.


Is it on both front tires?

Lower ball joints have very little time on them. I assume they were replaced shortly before the car was parked. Boots are rotten, but the joints (and everything else in the front end) is very tight with no play. The ball joints are on the list of things to do this spring when it warms up (and the time changes back to allow the working class to have a life after work). I could replace the boots, but if I'm going that far I'll just replace the things. I'd be willing to bet they're Uro crap anyway since the boots didn't hold up.

I agree that the tire wear looks weird, that's why I'm here asking about it. The Chassis manual does mention that "open shoulder" tires will experience unusual wear patterns, so that may just be how these particular tires wear on this car. The only tire showing that wear pattern is front left.

Agree that looking at the picture on a real monitor (versus my phone) the wear looks less like cupping or other wear and more like damage of some sort. Odd.

For the benefit of others, this isn't shock or alignment wear, it is physical damage to the tire caused by an outside source. It isn't alignment as the outer tread blocks are even all the way across and the right hand tread nubs are still visible on the tire surface. ( not the nubs on the side wall, the ones near the first groove. )

Since the wear is only in a localized area per the description and the sidewall is a bit beat up, I vote for driving off a sharp curb or metal object. Take a look at the top band of serrations just below the side tread block ( not the serrations where the Yokohama name is ) the area just above the serrations is scraped. See red lined attached pic but you might have to refer to the original for clarity.

If the wear was all the way around, I would have voted for something on the body rubbing the tire like a screw from a mud flap or some other item in the wheel well.

In any event, the cuts are only a 32 or so deep and will go away as the tire wears.

The sidewall is fine. The apparent "beaten up" look is an artifact of the camera. In real life, it looks like it just left the factory.

The unusual wear is all the way around the tire in the same localized area. Between yesterday and today I've put about 65 miles on the car and the unusual wear pattern is no worse than it was when the picture was taken.

With the amount of suspension movement going on, it is entirely possible that the tire rubbed on something. Not sure if the suspension can travel enough to make it rub on the body. As it is, it doesn't appear to have progressed any in the last 65 or so miles.

When the new shocks make it on and I rotate Front and Rear on that side, we'll see if it comes back!

With the marks all the way around not just on the area pictured, the damage came from:

Something sharp in the body.

Something during the spin balancing process. Perhaps spin balancer guard rubbing, a balancer that has a bad brake and the operator used something as a brake to stop the tire ( like the wheel weight hammer / puller.)

It is highly unlikely this occurred during tire mounting as the cuts are in groups of 3 and 4 like a single point of contact was run across the tread trying to make a "bolt" thread.

In any event, with the wheels on the ground turn the steering in one direction and carefully look for possible contact points, even those 3 or so inches away to account for suspension compression. I'd also look at the center of the fender opening for something sharp.

If nothing is found and none of the cuts are deeper than a 32 or so just keep driving, I don't know that contacting the tire shop will produce much of a result for the effort involved in going back to them.