weird tyre defect [pic added!]

deian · Post by **deian** » 16 Jun 2007, 18:31

Guys,

further to my tracking issue, which i will leave for now because one of my tyres are rumbling...

i got a pair of new tyres for the car last week (to replace the front, but to go on the back), just some cheap ones, so i could put them on the back, and put the back ones on the front...

I took the tyres to ATS and asked them to balance them as I didn't see any weights on them (turns out there was weights, but they were on the inside)... reason i wanted them balancing was they were kind of rumbling/scuffing/vibrating but not the usual vibration you get on higher speeds.

Anyway, the guy at ATS asked my why I wanted to balance tyres that are part worn, and i explained they were on the back (remember this bit for now). He had a look at the left one and said the tyre is no good as it it worn weirdly (still reasonable tread on it, and it's all even across)...

but parts of the inside, like every 1/3 of the sticking out parts of the tyre had worn down at an angle, where as the remaining 2/3 are ok.
Basically it's not smooth running along the tyre (not across), and it's happened on the inside.
I could get a picture if you are all puzzled, but something in the back has caused the tyre to wear down really weirdly.

Any ideas at all?

AndersDK · Post by **AndersDK** » 16 Jun 2007, 19:47

Is it a variant of the feather like pattern you sometimes see on worn tyres ?
This can for no obvious reason happen for the odd make of tyre on the odd make of cars.
Its simply the way the tyre is constructed that can & will not match the way the rear supension works - in some odd combinations.
Or just a bad tyre - moulding, rubber mix etc.

At nearest opportunity you should check the sphere the tyre has been mated with. Could be the wrong type (the dead shocker syndrome known from steel sprung cars).
Also try rock the car violently hard sidewards to try reveal any slack in the rear suspension (weight on wheels).

rory_perrett · Post by **rory_perrett** » 16 Jun 2007, 20:01

I think I might have something similar, but in my case it is the outside edge of the tyre. Got and advisory on the last MOT for uneven wear on nearside rear tyre. Like you there were areas that had worn more than others. Thought it could be because I'd never had them balanced or because the rear discs were shot. As they had done 50,000 miles and were coming up for renewal anyway I wasn't too worried. Changed the rear disks and pads and put the tyres from the front which had done 14,000 miles on the back and the new one on the front (yes I know you are not supposed to as it might lead to oversteer in extreem circumstances). They have done a further 8,000 miles and the same thing seems to be happening to the nearside tyre. I'm begining to wonder if there is a problem with the rear suspension arm bearing. The car is a 1998 2.1 TD Xantia with 207,000 miles on the clock. On my previous BX I had to do thearm bearings every 110,000 - to 120,000 miles, not done the Xantia at all. It doesn't appear to be showing the usual signs (wheels leaning in at the top, creaks and squeaks) but I do keep wondering whether I should be getting round to having a look at them.

deian · Post by **deian** » 16 Jun 2007, 21:06

I was thinking of the rear bearings too, but my wheels don't lean out.. the tyre is a firestone one.

Bit it's funny how it's happened on the inside, which was only balanced. the outside didn't have any weights on them. maybe this has caused the weird problem... don't tyres need balancing side to side as well as around?

but i think anders is right about the tyre not being compatible with the car....
the outer treads have little slits in them (designed like that), 1 slit every 4, and 3 slits every 3. not impressed

Maybe i should put the new tyres on the front for the time being just so nothing wears down on the suspension/steering. Because if it is a problem in the back somewhere then it's going to make my new tyres defect too (not that is matter cos they are cheap manky ones just to save my licence for the time being)

i wish i could afford a set of michelin energy ones...mmmm

anyone interested in a picture? i'll sort one tomorrow, then rory can confirm his problems too

out of interest rory, have your tyres been balanced on the outside, and not on the inside? and are they firestone?

thanks

Post by **philhoward** » 16 Jun 2007, 21:30

It is common to use weights on the inside of the rim; some towards the front and other towards the rear. As long as the balancing machine has been told where the weights will go, it will calculate the weights needed.

A possibility on the tyres...if you look on the inside can you see the words "Outside" anywhere..? Some tyres are only to be fitted one way (nothing to do with uni-directional tyres) as they are harder one way than the other to cope with cornering forces. As Firestone are "old pattern" Bridgestone, they started doing this quite a few years ago and these patterns may have filtered down to the Firestone brand.

Uneven wear (bits of wear here and there) can also be caused by worn dampers. I've seen a lot of cars going down the motorway with one wheel bouncing around like a good 'un! With no damper, the wheel will bounce around at a specific resonant frequency such that the tyre will contact in only a few certain spots causing accelerated wear.

rory_perrett · Post by **rory_perrett** » 16 Jun 2007, 21:49

I'm using Goodyear Hydragrip, the previous rears were Goodyear Ventura I think.

Rear Spheres are GSF units which have been on 3 years and 63,000 miles. Irrationally I wouldn't have expected a citroen hydro suspension to behave like a faulty conventional damper although I must admit the tyrewear is of that nature.

deian · Post by **deian** » 16 Jun 2007, 22:41

Well before anything (as planned) I will put 2 new centre spheres, an accumulator sphere and anti-sink, as well as two drop links and hydraflush the car. It should then be a different car then prepared for new tyres. For the time being, I think i'll swap the tyres over front/back. I'll have a proper check of the back suspension tomorrow.

It's quite shocking how the tyre can affect the ride. It spoils it quite a bit, not as much as having to hold the steering wheel off centre because of bad tracking... grrrrrrrr!

Thanks for the input, it's certainly an insight into the peculiarities of the tyre vs. car relationship (rocky

).

Mandrake · Post by **Mandrake** » 16 Jun 2007, 22:51

I'm surprised nobody has mentioned rear suspension arm bearings being a possible reason for unusual wear on the inside edge of rear tyres ?

Are you sure the rear arm bearings aren't worn and that the rear wheels aren't leaning in ? The rear wheels should only have 1.5 degrees of negative camber (which is barely visible to the eye) so if they look like they're leaning in at the back they may need doing...

Also as Anders says - some tyres just don't like Citroen suspension and the way it moves... could just be a cheap/incompatible tyre... I'd quite like to see a picture of what you're talking about out of interest...

Regards,
Simon

alan s · Post by **alan s** » 16 Jun 2007, 23:40

When my BX16V needed rear arm bearings, the wheels didn't go negative camber. I only spotted the problem when I had one of my sons driving it, and as I have to open the gate to our property and close it again as soon as a car comes in to keep animals inside, I watched it drive over a hump in the gateway at which time the rear wheel moved back as he went over it and then back forward as it came over the other side of the hump, yet to the eye it was all straight even when the suspension was jacked to the top and someone stood 20 or so feet behind the vehicle, so they don't always ahve to lean outwards at the bottom. When pulled out, the bearings were so bad we had thoughts that we may have to replace the entire arms but we managed to fill and do some machining that cured it once and for all time.
I'd suggest taking the weight off the wheels and trying to move the rear arms in all directions to see if there's any movement.
I have seen trucks "scallop" tyres when run constantly empty and that's a weird one too. A round tyre with semi circular pieces worn out of the tread face at about 6 - 8 inch intervals.

Alan S

Brian UK · Post by **Brian UK** » 16 Jun 2007, 23:50

Well, just to put the cat amongst the pidgeons,
I had the same problem with both back tyres on the 307SW. Had been getting a rumbling for a bit, and thought it was the wheel bearing. But noticed the uneven radial wear when I was spinning the wheel.
Now on the 307 there is a solid (sort of) back axle, so no radius arms, and no spheres etc. Also both suspension dampers are fine.
It is possible that the wheels were out of balance, old tyres can go out of balance, even though they were balanced when new. I suppose it is also possible that the rear discs were grabbing a bit, but I cannot feel it when braking.
They were Michelin tyres too.

Mandrake · Post by **Mandrake** » 17 Jun 2007, 01:28

Hi Alan,

alan s wrote:When my BX16V needed rear arm bearings, the wheels didn't go negative camber. I only spotted the problem when I had one of my sons driving it, and as I have to open the gate to our property and close it again as soon as a car comes in to keep animals inside, I watched it drive over a hump in the gateway at which time the rear wheel moved back as he went over it and then back forward as it came over the other side of the hump, yet to the eye it was all straight even when the suspension was jacked to the top and someone stood 20 or so feet behind the vehicle, so they don't always ahve to lean outwards at the bottom. When pulled out, the bearings were so bad we had thoughts that we may have to replace the entire arms but we managed to fill and do some machining that cured it once and for all time.

Interesting that they can fail without the symptomatic negative camber. Since mine have visible negative camber does that mean they are possibly even further gone than the ones you replaced ?

Did you notice any symptoms in the ride and handling ? Or was it a case of it getting worse so gradually that you didn't notice it until they were replaced and things suddenly got better ?

The reason why I suggested looking for visible negative camber is because there needs to be quite a bit for the inside edge of the tyre to wear unusually...

I'd suggest taking the weight off the wheels and trying to move the rear arms in all directions to see if there's any movement.

I'm not sure how the rollbar is connected on the BX, but on the Xantia it has a Y-shaped fork on the end of the rollbar with two big bolts onto the arm - and it seems that if you jack the car up and let the wheels hang down, even if there was slack in the bearings the rollbar connection would prevent you being able to detect any slack in the bearings...

I'll be doing the bearings on mine soon so I guess I'll see...

I have seen trucks "scallop" tyres when run constantly empty and that's a weird one too. A round tyre with semi circular pieces worn out of the tread face at about 6 - 8 inch intervals.
Alan S

Perhaps in the truck case its due to the tyres bouncing all the time when the suspension is unladden ? Stiff bouncy suspension surely can't be good for tyres...

Another possibility is a very out of balance wheel, which would cause the wheel rim to bounce on the tyre slightly each revolution...(maybe)

Regards,
Simon

Post by **philhoward** » 17 Jun 2007, 06:34

alan s wrote:When my BX16V needed rear arm bearings, the wheels didn't go negative camber. I only spotted the problem when I had one of my sons driving it, and as I have to open the gate to our property and close it again as soon as a car comes in to keep animals inside, I watched it drive over a hump in the gateway at which time the rear wheel moved back as he went over it and then back forward as it came over the other side of the hump, yet to the eye it was all straight even when the suspension was jacked to the top and someone stood 20 or so feet behind the vehicle, so they don't always ahve to lean outwards at the bottom.

Not exactly the same suspension system, but when the bearings went on my ZX there was no camber change evident, but the wheel had moved sideways and kept rubbing the wheel arch.

alan s · Post by **alan s** » 17 Jun 2007, 10:57

It seems to me that when they go, there's no guarantee that they will lean in at the top.
The problem was suspected when I discovered it didn't handle corners as it should have as the wheels moving to and fro gave it a kind of weird rear wheel steering which meant thet the rear wheels weren't tracking in sync with the front when cornering.
One corner near me was a bit hairy at 80 kph before they were fixed and is no problem at 120 after.

Alan S

deian · Post by **deian** » 17 Jun 2007, 11:52

whats the best way to test the rear suspension arms?

suspension up or down or normal?
wheels on or off?
all the back off the ground?

as the defect tyres are now on the front i can jack up the front and drive the car, being an automatic with cruise control it's quite handy to diagnose knocking/rumbling problems... scary if the stands would collapse and the car shoots off ahead though!!

your inputs are interesting, i will get some pictures done today, and if a video is possible one of them too.

thanks

alan s · Post by **alan s** » 17 Jun 2007, 11:57

Best system I've seen is suspension set at normal but car up on trolley jacks and axle stands with wheels off the ground. Remove the road wheels after first testing them vertically.
A jemmy bar between the arms and rear subframes and pressure applied that way to see if there's any wear movement.

Alan S