Big Dave

Being the optimist, I removed my phone dials with M&S tires and put the much more aesthetically pleasing 17" cups back on my shark.

Before doing so, I had the rubber on the fronts swapped. The tires are directional but over the past 20K miles, they've worn a little more on the inside edge. So, the tires still spin in the correct direction, but the worn edges are on the outside.

Before putting them on the car, with the M&S tires (and with the 17" tires last summer), steering was perfect. This morning I've noticed some significant wandering with every bump in the road. The rears have not been changed at all (ie mounted on the same sides and same directions as last fall).

My question: is my car's wandering caused by the worn edges being on the outside instead of the inside edge? If so, I think I'm going to swap them back and replace them earlier.

Thanks in advance for any replies.

Mark

This is common among certain tire types and even worse with many other tires once they are worn.

I have heard it referred to as "Tram Lining"...they are following grooves/wear in the road itself.

The tires that came with my car did this BADLY. Changing over to new YOKO's cured it...but - as my tires have become worn, it is starting to slowly come back!

It is MOST likley the tire type/overall wear. Switching the wear from inside to out may or may not help.

Big Dave

Mark:

I didn't tramline before when the worn edges were on the inside. It just started now that I moved the worn edges to the outside.

FYI: They're Toyo Proxes FZ4 tires.

Old & New

Can I assume you gave the suspension time to settle after lifting the front end?

Get the front end alignment checked (or D.I.Y.). If they were wearing on the inside, you needed a toe-in adjustment anyway.

Big Dave

The front end had to have settled by the time I got to work - 15 miles over less than perfect roads at 50-60 mph (the same route I travel every weekday).

I know that an alignment is needed, but it's not a significant need right now. The wear on the one edge isn't dramatic after 20K miles, but it's there.

The big factor in my mind is that there was no tramlining at all yesterday with the 16" phone dials.

Old & New

The direction that your toe-in is miscalibrated will give you the feeling you describe (wear on the inside is due to not enough toe-in).

Big Dave

Why didn't I experience the wander (at all) with the narrower, 16" tires? If I didn't just drive 5 months with no problems, I'd be agreeing with you completely. It just doesn't make sense to me that changing the wheels would result in wandering that had nothing to do with the wear patterns on the tires.

I'm obviously not an expert....I'm just fishing for possibilities so I can check all of them.

Ron_H

My car wanders as you have described and we discovered that my tires were wearing on the inside of both fronts in support of what Old&New says: insufficient toe-in. It has been getting progressively worse. Devek also noticed that since it was aligned, the car had dropped considerably, and Marc thinks it is due to "tired" springs which he suggests should be replaced. He raised the height and off I went, but it is still there though less noticeable. Also, the wandering goes away at higher speeds, though the uneven tire wear seems to create an imbalance and vibration at around 90 to 100 mph (not that I would ever drive at that speed, but I heard about it from a menehune that drove my car). The tires on there now are Dunlop SP8000 and I am waiting for to find a deal on cup wheels to switch to new tires, and maybe new springs. I live with it but it is irritating me.

I once had a situation like this on a VW Rabbit that was solved by switching to Michilen tires, from some cheap brand. The diagnosis was that the belts in the front tires were moving around and causing the tires to wander all over the road. Weird. Buy good tires I concluded. Duh!!

Alan

Dave,
My front alignment was a bit off (turned out to be toe and some caster) and my Potenza S-03's wore unevenly and were pretty low on the inside edges.

I had a complete alignment done the correct way (twice!) but until I replaced the tires I could never avoid the car pulling across cambers and tram-lining & wandering in general - it felt awful - actually it almost seemed worse after the alignment was corrected.

Fitting new tires really showed the alignment was perfect after-all (I had been debating this with the shop - they were right).

So you may have to change the tires if they are significantly unevenly worn - OR wait for them to wear flatter - if you can stand it....

I couldn't stand it - but mine were virtually gone anyway

You may be better off just putting them back where they were and later do a tire replacement & alignment check @ the same time.

Alan

Garth S

Dave,
The wear pattern on your 17" tires left you running effectively on two truncated cones vs. two true cylinders. In the orriginal position, the inner radius of the 'cone', being smaller than the outer, tends to direct (it's force vector) to the center when on road irregularities. ie., they wore to a point where they more or less gained stability despite an alignment imperfection. The tires, when new, may have had a bit of the instability you now experience - but these things happen so gradually, they are rarely noticed.
...rarely noticed until the tires are reversed! Now, the greatest load is focused on the larger radius, which in principle shifts the contact patch 'pressure print' to the inside. Any contact with surface irregularities redirects the force 180 deg. - it pulls the vehicle left or right almost at random, a proper PITA.
If you continue to drive with the tires as they are now, in all probability, they will improve (higher effective inner contact pressure = accelerated inner wear), but never become as new. Playing with tire pressures can help - try lowering first.
The winter tires, being narrower and of different internal construction, would wear differently, be less sensitive, and may well not have been flipped left/right as the 17" tires.

Big Dave

I've put them back they way they were. The wandering has improved, but it's still there. I think part of my perception of the problem is that I went from 205/55/16 narrow tires with tall sidewalls back to the 17" tires (225/45/17 front 255/40/17 rear). The ride is rough like I remember it, but the wandering just seems more exaggerated than before.

Either way, I'm going to need new summer tires in the next few months. My rears (Kumho Ecsta Supra 712s) are nearly gone and the fronts (Toyos) are unevenly worn (althought it took 20K+ miles for it to get bad). I still need to lift each corner up to feel if the wheel bearings are loose, and I'll see if the folks hosting the free 928 tech session tomorrow will be willing to check the alignment as part of their presentation.

Thanks for all the replies.

Dave

Old & New

Dave,

Just got back in. What Garth said.

You had tires that were worn and planted in a particular fashion; when you swapped them, the force was distributed differently on the footprint.

Lucky you, getting it looked at - at a tech session! Good timing.

Big Dave

It's not guaranteed yet, since I think they're putting Dennis's Weissach up (they aligned it last year) as a showpiece. Now I know why he painted his headers this month.


If nothing else, I can be used as an example of a car needing an alignment.

toofast928

Dave you have to check;
tire pressure, ride height, ( no lower than 155 mm) and toe in. Directional tires have more of a tendency to follow the crown of the road than non directional tires. Going from 16" to 17" only amplifies the wander.
Sounds like you need tires. Bump steer on the 928 is related to too low ride height. I highly recommend "forced radial balancing"

Geezer

What is "forced radial balancing"?