zx tyre wear

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pauljacey
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zx tyre wear

Post by pauljacey »

Recently acquired zx had uneven tyre wear on outside shouder of both rear wheels.
Replaced tyres at Kwick Fit (who said that they were legal) they thought that the tyres were maybe on the front at some time when the tracking was out. They also said that they can't check the tracking on almost all citroen cars, which I find surprising.
Should I check anything as I don't want to ruin my new tyres.
gjb02
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Post by gjb02 »

Check the camber on the rear wheels. Look at the rear of the car from a few metres behind the car. If the wheels are like this:
/----\ Trailing arm bearings gone.
[----] OK, Tyres probably worn badly on front and moved to rear.
The illustrations are exaggerated but you get the idea. Check the inner arches for tyres rub as well. The coating may have been rubbed off the sides. If there is a shiny metal patch it's definately the rear arm bearings.
If you have a tow bar chances are is it the trailing arm bearings in the rear beam. The extra loads of towing speed up rear arm wear.
pauljacey
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Post by pauljacey »

Thanks for that.
Can the wheels go the other way, \-----/ as the wear was on the outside shoulder of the tyre?
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Kowalski
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Post by Kowalski »

The rear wheels can't do that.
Niek
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Post by Niek »

I have the same thing on my xm. New tyres (Goodyear Hydragrip) which are very good (maybe not for this car though [xx(]) although maybe a bit noisy. The rear ones wore excessively on the outside, so much as a matter of fact that the outside is now almost down to the minimum whereas the inside is almost brand new. I jacked the rear up to check for play but found none, the arm bearings are also still good (actually installing some worn bearings might cause the tyres to wear the inside out as well. lasting a little longer [xx(]). I then took the thing over to the specialist who told me that the profile on these tyres just don't work on the car. They start 'cupping' (in dutch) and this causes them to wear unevenly...
Put them on the front recently to try to get a little more life out of them. I guess I'll have to learn to live with the awful noise they now produce untill they are really gone. (Michelin next time...)
AlWilliams
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Post by AlWilliams »

What condition are the front tires in, or were they new when you aquired the ZX?
It's possible the last owner drove like a madman so wore down the outside edges on the tires, do the side walls looked scrubbed?
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Kowalski
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Post by Kowalski »

My newer Xantia eats the inside shoulders of the tyres if driven hard, the older one eats the outside shoulders. Driven gently both seem to wear the centre of the tyre more quickly than the shoulders. Invariably my tyres get the shoulders worn off and the centres wear too and I'm left with two stripes of good tread whilst the centre and shoulders become illegal.
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Post by oilyspanner »

My old BX used to plane the outer shoulders off the tyres when it was on 165s, changing to 185s or 195s has drastically improved grip and tyre life, looks rather better too.
Stewart
pauljacey
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Post by pauljacey »

Thanks for all your postings.
To answer a few questions.
I have had the car for 2 weeks. It was given to my by a mate who is emigrating to Australia. The car was owned from new by his father, they are careful drivers but my mate is mechanically challenged (is that too P.C.?) and forgetful, his girlfriend reminded him that they put 2 new tyres on the front at it's last service.
Last night I found a receipt from 1998 for new tyres and TRACKING. The garage told me the worn tyres (on the back) were made in 1998, so that fits with them starting life on the front when the tracking was out. Unfortunately, my mates dad is off in South America on an extended holiday and is unavailable for comment.
There is no excessive tyre noise and no obviously worn areas of bodywork in the wheel arches.
The tyres from the back look straight [-----]
Thanks again guys
ItDontGo
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Post by ItDontGo »

The edges of tyres wear out because of the toe settings force them to constantly corner more so than because they run at an angle. The rear on a BX should have some negative camber anyway so will never be perfectly |----|
If you imagine the front wheel of a car turning it right the tread of the tyre will be offset towards the right relative to where it would be if the car was going straight ahead. Obviously this will mean the left hand edge will be more heavily loaded than the right hand edge as the left edge will tend towards the centre of the tyre and right edge will move towards not touching the road.
Now if there is too much toe-in on the left this effectively will be like constant right hand cornering and hence the outer edge will be worn. Similarly the outer edge on the right will wear as there will also be toe-in here to make the car go straight.
On the rear of the car there needs to be some toe-in for stability. If you imagine a rear wheel going over a bump it will grip better than the other one as it will instantaneously have more of a load on it than the un-bumped wheel. So if there is some toe-in here then it will make the back of the car turn in a direction which will transfer load onto the unloaded wheel.
For example if it was the left going over the bump it will steer the car towards the left which transfers weight to the right and hence will put more weight on the wheel which is trying to turn the car right - and hence cancels out the affect of the bump.
So all cars need some toe-in on the rear. However too much will wear the edges and will take power. When the rear bearings wear there will be a tendency for the car to develop more toe in either direction. I expect Citroen would have made sure that you get more toe-in as this is a lot more stable that toe-out and hence you may see more wear on the outside.
You need toe as it is impossible to make a car with no play in the suspension. Also on the front you can control the turn-in rate by pre-loading the tyres with some toe-in or if you want a bit if a slower response toe-out.
wilkobob
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Post by wilkobob »

I cant see why you should have problems with the tracking? All the tyre places in my local town, Retford, can do the tracking on a ZX. Im very supprised you are having problems.
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