Tyre Wear

[Ozsko]

P Zeros @ 28000K with plenty of tread left. Mostly driven on open roads between 100 - 120KPH, very little suburban driving at all. The tread blocks on the front tyres are higher at the front of each block than the back, tapered so to speak and only on the inside of the tyre. Has anyone had camber issues? I was looking for a noisy tyre and when I running my hands over the tyres I noticed it. On asking the so called tyre experts all I got was blank looks for my trouble. They have been always set to the factory pressures with a Longacre digital gauge (verrrryyyy expensive) so the pressures should not be a problem. Has anyone else noticed this issue? I will put a camber gauge on it tomorrow and see what it reads but then I don't know what the stock figures are.

[wai]

For the driven wheels, as they drive, the tread blocks are "bent" forward so the rear of the treads will have the greatest wear. Tyre pressures are not going to do much as this is more a function of the tread pattern and driving habits. For non-driven wheels, the pattern would be reversed somewhat as those wheels will be braking in the main. This is one reason why tyres are "rotated". It attempts to even out the wear.

As you have noticed, this will not be the same over the width of the tread either and will depend on the camber. Again, setting up suspension is a compromise as it has to cover all situations. Even if you get the tread perfectly flat when straight ahead, castor changes things when the front wheels are turned as now the effective camber changes everything.

All you can do is make sure that the wheels are correctly aligned and then look at rotating the tyres. The tyres should remain on the same side as radials do not like being driven in the opposite direction.

[Ozsko]

As you point out caster is the big culprit on how much the camber changes when the road wheels move away from centre but I can't see it being the culprit here. As for the tread blocks bending I have not noticed this having the same effect on the other two FWD cars I have. If other Superb owners had the same tyre wear I would say it is generic to the car and not worry about it.

[wai]

For what it's worth, on my Torana I used to run Michelin XZX and MX tyres which had a very pronounced zig-zag tread pattern and this uneven front to rear wear was always there on the rear (drive) tyres. On the front, it was was not this uneven wear, however the outside edge would always wear down first even though it had something like 0.5 to 1 degree of negative camber. The negative camber should have seen the inside wear first, so this was more to do with cornering wear than normal straight ahead wear.

On my Hiace, all the tyres had more or less ciircumferential grooves and as a result there was no such uneven wear, but again, even though there was neutral to a very slight negative camber, the outside edge on the front tyres would always wear more than the inside. The first ones (Goodyear) did not last too long and were replaced because the tread delaminated (an acknowledged production fault), but because I was only driving around 5,000 km per year, it was outside the warranty period and so I had to get new tyres at my cost. From that point on I used Toyo tyres (HO2 and HO8 ).

Again this shows that cornering is much more significant than straight driving, and you do not have to be driving hard for such wear patterns.

I would get around 60,000 km from a set of tyres.

I do know that many tyre retailers do not necessarily have the correct information on camber and castor. When I got my first set of Toyo HO2's fitted, Tyrepower did a wheel alignment and found it way out, even though the wheels were aligned at the last dealer service only around 3 months earlier. It was not anything I had done, but a major amount of adjustment had to be made to overcome what had been done at the previous wheel alignment.

[K1W1]

The tread blocks on the front tyres are higher at the front of each block than the back, tapered so to speak and only on the inside of the tyre.

It's referred to as castellating if you are talking to a tyre person that's how you describe the problem.

[Ozsko]

For what it's worth, on my Torana I used to run Michelin XZX and MX tyres which had a very pronounced zig-zag tread pattern and this uneven front to rear wear was always there on the rear (drive) tyres. On the front, it was was not this uneven wear, however the outside edge would always wear down first even though it had something like 0.5 to 1 degree of negative camber. The negative camber should have seen the inside wear first, so this was more to do with cornering wear than normal straight ahead wear.



That is from the influence of caster. Too much caster and the tyres/wheels get camber gain when cornering and the outside edges wear evenly on both tyres. Caster helps to keep the car from wandering and helps return the steering to centre when straightening up from a turn or corner.

[Ozsko]

It's referred to as castellating if you are talking to a tyre person that's how you describe the problem.

What causes it?

[wai]

What causes it?The bending of the tread blocks.

[brad]

All you can do is make sure that the wheels are correctly aligned and then look at rotating the tyres. The tyres should remain on the same side as radials do not like being driven in the opposite direction.
Agree with everything else you wrote but the above is old school thought from the '80s when quality control in the manufacturing process was pretty lousy & "dirty" steel in the belts stopped the rubber bonding to the belts properly. This caused excessive belt slip in the drive tyre which when reversed caused tread separation. Goodyear were worst for it but Dunlop were a close second.

Quite a few of the manufacturers recommend cross-rotation (and hence reversal of rotation direction). Of course, if you have symmmeical/directional tyres, then you have no choice. Reversing the rotation direction also serves to make the tyre a bit quieter for a while.

To the OP: If your Superb is FWD & the tyres don't have direction arrows stamped in sidewalls then it won't hurt to x-rotate them. The driven wheel needs an opportunity to normalise the stresses of being the driven wheel, so unfortunately, that has to stay on the same side & go straight to the back. The rears can be crossed over: LR to RF & RR to LF. Personally, I like to do this every 7500-10,000km but if you've manged 28,000km without a rotation then every 15,000km will do at a pinch.

If you want to wander up to Blakehurst, Id be happy to have a look at them & we can break out the jack, jackstands & rattle gun & do the job quick & easy

Tire Tech Information - Tire Rotation Instructions (http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=43)
Trivett Tyres - Tyre Tips (http://www.trivetttyres.com.au/Tyre-Tips-76.aspx)

[brad]

The first ones (Goodyear) did not last too long and were replaced because the tread delaminated (an acknowledged production fault), but because I was only driving around 5,000 km per year, it was outside the warranty period and so I had to get new tyres at my cost. .
Goodyear tyres (and most of the other major brands) have a life of tread, pro-rata warranty for any manufacturing faults. Most Goodyear tyres come with 10/32nds of tread. If the tyre has 5/32nd left &t gets a seppo then you'll get 50% off the RRP of the new tyre. The only problem is that RRP is about 50% more than street price plus they'll try & hit you for fit/valve/balance, so once you get to about 4/32nd you are better off financially buying at street price rather than making a claim. Also, you'll find that the Goodyear branded outlets (single brand stores) are more inclined to know about & give you a claim whereas the multibrand guys try & avoid going through the claims process (they are less likely to be successful as well). What they generally do is tell you there is no claim & then put it through for themselves.

We were very honest at our shop & knew all the batch numbers that were faulty. We'd check the s/nos on all the cars that came in & could offer new tyres at a warranty prices (we would do it cheap as possible) before a fault had appeared. Customers were pretty happy if we could offer them new tyres at a good price & it counted towards our monthly sales quota - so win/win.

[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.