Tyre Wear

[Ozsko]

Thanks for the offer Brad but I have a full workshop here and a son who is a mechanic, in fact he has encountered it on customer cars but has never been given a good reason for the problem from anyone including the manufacturer. Google wasn't much help either, the Yanks obviously don't encounter it and the Poms have the issue on Landrovers. Interesting that some cars do it and some don't and if the treads are bending why don't the backs do it on a rear wheel drive car, or maybe they do but we never notice. It is also more predominant on the drivers side for some reason. I know that Euro cars have to be aligned differently before being driven in Oz if they are set up to Euro roads in the factory as the road camber is the opposite out here, or that was the reason I was given when we had to do all our Mercedes vans.

Also something else occurs to me, do other Superbs suffer the same wear pattern and if not why is mine doing it? Can anyone check for me please.

[brad]

Thanks for the offer Brad but I have a full workshop here and a son who is a mechanic, in fact he has encountered it on customer cars but has never been given a good reason for the problem from anyone including the manufacturer. Google wasn't much help either, the Yanks obviously don't encounter it and the Poms have the issue on Landrovers. Interesting that some cars do it and some don't and if the treads are bending why don't the backs do it on a rear wheel drive car, or maybe they do but we never notice. It is also more predominant on the drivers side for some reason. I know that Euro cars have to be aligned differently before being driven in Oz if they are set up to Euro roads in the factory as the road camber is the opposite out here, or that was the reason I was given when we had to do all our Mercedes vans. .

They do on RWD as well but it isn't as noticeable because it isn't the steer wheel so the load is spread over the whole width of the tyre.

I also suspect you might have a tiny bit to much toe-out and you might need a bit more camber/caster variation from side-to-side (ie: a fraction more camber or caster on the LHS so that you don't have to steer up the camber all the time).

The Mercedes van thing would have been incorrect specs as the production line computer thingy knows what to set the vehicle at when the car is nominated as RHD & LHD. Mercedes have always been a bit crook for not getting the specs right for AUS. I used to have to make huge changes to the W124(??? 450SEL & the like) to get them to steer straight & not wear the tyres.

The worst of the lot were American sourced vehicles which steadfastly clung to American road spec no matter what. Ford F100s were shockers & unfixable unless you bent some suspension components (I couldn't do them - used to send them to a truck place)

[Ozsko]

Have these cars got front struts? I must have a look, because as you know toe is the only adjustment on strut front ends. Thanks for the info and to those who have taken the time to reply. I will get the toe checked ASAP.

[brad]

toe is the only official adjustment on McPherson struts.
Early commodores used to have an eccentric strut-top that you could add caster & remove camber (or remove caster & remove camber) with (undo three nuts, lift car, spin tophat, lower car, etc).

Subarus have the strut (both front & rear) attached to the hub with 2 bolts. On the front, the top bolt is eccentric & you can adjust camber. On the rear, there's no eccentric but there's enough slop in the bolt holes that you can get almost a degree movement if needed. A lot of other cars are similar (Nissan Bluebird U13 springs to mind).

On the VWs, you can often move the subframe but it will remove camber from one side as it adds to the other.

The other thing I've done is elongate the strut-top holes in the body & make a filler piece to sit in the slot & stop the tophat from moving. If you have to make really long slots then put a washer under the nuts to cover the "butchery" (lots of people freak out when they see things like that).

If your son is a good general mechanic, then it's possible he doesn't know a lot about alignments, steering & suspension (nb: there are some aspects of vehicle repair that I have not & never had a clue beyond the basics taught at TAFE), so it might be worth your while to get somebody like East Coast Suspension (never used them but they are local), Heasemans (I like their work but others hate them), Excellor Steering (if he's still in business), etc to have a look at it.

[Ozsko]

toe is the only official adjustment on McPherson struts.
Early commodores used to have an eccentric strut-top that you could add caster & remove camber (or remove caster & remove camber) with (undo three nuts, lift car, spin tophat, lower car, etc).

Toe is the only adjustment. Cams (eccentrics) as adjusters are a big failure as they move in two planes at once, if for instance you have them at the top of the strut then you change both camber and caster at the same time, bloody stupid idea. If you use them on the inner lower control arm pivot then you change the camber and the height of the arm which effectively changes the roll centre of the front suspension, not much I will admit but it does change, I hate cams with a passion as you might have gathered. I had a VS Statesman and as you know these had serious rear camber issues especially when towing so I asked Mr Pedder what they did about it, they suggested cam adjusters on the trailing arm pivots and when I asked them what they did about the toe when the camber was right the bloke sort of looked at me stunned as he had no answer. A couple of years ago I invented a new type of adjuster for karts which is now in use world wide because the original then used was a cam adjuster and it also changed camber and caster at the same time and this is originally where I grew to hate cam adjusters in suspension or steering. Slotted adjusters properly engineered are OK but I think I will pass for the Superb, it is a family car not a race car.

[brad]

How on earth can an eccentric adjuster attached to the strut change the caster as well as the camber unless you have an A-arm with adjusters at the chassis pivots (like an old Merc)? I'm not questioning you, it's just I can't imagine what you are describing. If you could link me to a diagram or similar please?

Yes, those VS IRS were major fail, even on the later models with the extra link(s).

As you said, these are on family cars, so slight changes in roll centre don't worry most people. People seem much happier with "the adjuster is crap but will do the job" rather than "you'll have to live with tyre scrub / pulling / etc because there is no adjustment"

[Ozsko]

Explaining in words is really difficult, at least for me. The strut top moves in an eccentric fashion and eccentrics are not concentric, clear as mud? Sorry Brad I can't think of any other way to put it. BTW I am talking of a cam adjuster at the top of the strut.

[brad]

OK, now I get you. Like a VB-VL Commodore.

From a practical point of view they were great. IIRC, Commodores came out with about 1.75 degrees of negative camber & equal caster. As the dampers gave out (they'd leak at about 30,000km. I used to do about 5 replacements a week. Got it down to 1hr), the springs would cop a pounding then would sag a bit. This made the camber 2 or more degrees & resulted in shocking inner tyre wear for most drivers. At least you could spin the tops & get the camber back to ~1.25. A little extra caster didn't do any harm either. Also, they didn't slip, unlike a cam on the lower control arm (like a Falcon).

[Ozsko]

Yep, just like the commode, I learned how to change the NS rack bush without removing the rack, must have done a hundred of them.