Technical JTD Tyre Wear - Pointless Wailing

[Steve148]

Hi -

Jacked-up the Stilo tonight to change the front pads, and noticed that the aberrant tyre-wear problem has struck again. Attached pics show a marked sloping wear on the inner edge of each wheel, cutting right down to the carcass strands. There's obviously an overall under-inflation wear pattern, and the new set will run a couple of psi higher, but the inner wear is ridiculous.

I've had this before with Stilo's, and tried wheel alignment without success. I bought some cambered strut bolts last year but found they changed the handling so radically that I was uneasy about them. I think I'm going to have to get them out and ask a four-wheel laser facility to set them up.

Damned annoying - must be costing me 20% of the tyre's overall life-span, never mind the black paint I'll now have to waste on covering the strands for the MOT next week .

 

[john55]

Check your subframe is aligned and you havent got any failed wishbone bushes.
For subframe alignment, jack up the front and crawl underneeth with a tape measure. Make sure the subframe is exactly in the center of the car left to right. Measure from whatever points you find (holes in the chassis rails make good reference points) to points on the subframe. The front subframe is held on with 4 big bolts that have oversize holes with play in them. If you need to move it, slacken off the 4 bolts, but do not remove them, then leaver the subframe across to the correct position.

 

[Argonought]

I've had this before with Stilo's, and tried wheel alignment without success. I bought some cambered strut bolts last year but found they changed the handling so radically that I was uneasy about them. I think I'm going to have to get them out and ask a four-wheel laser facility to set them up.

I like your title (presume you've read the mountain of threads on this topic )

I've always said from the outset that inner front tyre wear has got very little to do with camber.

It's always nice to get generally good 4 wheel alignment (John's suggestion may help here) but what's critical is Toe. Set this to ZERO (dead easy to remember) and fit a set of Pirelli P7's. You do get quite a harsh ride but at least you do get some feedback from the steering

 

[PNL]

There was a dealer service bulletin on this one ..ie realignment of lower arms..

 

[Davren]

The service bulletin (44-01.03) says to loosen the 2 lower arm fixing bolts then lever the arm out then tighten the fixing bolts whilst still holding pressure on the lever.

I can't see what affect that would have. The fixing bolts go through rubber mounting bushes so would just revert to the original position when the lever was removed.

Dave.

 

[PNL]

The service bulletin (44-01.03) says to loosen the 2 lower arm fixing bolts then lever the arm out then tighten the fixing bolts whilst still holding pressure on the lever.

I can't see what affect that would have. The fixing bolts go through rubber mounting bushes so would just revert to the original position when the lever was removed.

Dave.

Dan the man had it done and he said it worked on his car ..

 

[Davren]

If it works that's good but I like to know why and how. The only way I can see this having any affect would be if the mounting holes in the sub frame are bigger than the bolt diameters so the bolts can move about in the holes.

Dave.

 

[PNL]

If it works that's good but I like to know why and how. The only way I can see this having any affect would be if the mounting holes in the sub frame are bigger than the bolt diameters so the bolts can move about in the holes.

Dave.

I wouldnt disagree with you Dave but fiat must have done some thing to correct the problem..now if they fitted new lower arms then fair enough but from what I could understand they just reset the old ones..

 

[Steve148]

Thanks to Davren for posting the bulletin, but there's one rather important point which isn't entirely clear. Hopefully one of the covert Fiat techs can shed light on this?

Fig 2 shows a lever being placed through the hole in the wishbone (I'd wondered why that was there) and force being applied inward. This would force the wishbone outwards to the limit of the bushes. However the text above says "apply a force to the wishbone towards the interior of the car", which suggests the opposite.

Can someone clarify for me please - correct procedure is to slacken bushes and push wishbone INwards or OUTwards before retightening?

I do agree with Davren that it seems intuitively unlikely to work - the forces transmitted through those components will surely be the deciding factor if any 'adjustable' play exists. OTOH, it's simple to try so it can't hurt.

 

[Steve148]

I like your title (presume you've read the mountain of threads on this topic )

Yep, I've posted in the previous threads too. Have done about 150k in 2 JTD Stilo's now, and both of them had this problem. Doesn't help that most of my travel is on curvy, fast roads (boo hoo, poor me).

I'll try the wishbone-levering idea, but I have to admit it seems a bit shonky to me. Levering major components around and tightening bushed fasteners enough to withstand dynamic forces.... . But John55 was recommending this a year ago, so I suppose it's worth a crack.

If not, I'm getting the cam-bolts out again. Last time I fitted them with max offset dialled-in, and the effect on steering was radical & disconcerting. But with a bit more patient trial and error it might be possible to find a happy medium. I probably only need a mm or two of change to counteract the wear trend, and it's only reasonable that I should devote my leisure time to designing a stable suspension system for Fiat.

 

[Davren]

I think the top of the lever is against the inner edge of the wishbone, not in the hole.

The lever's fulcrum point is on the sub frame, therefore, if you push the bottom of the lever towards the middle of the car, the top of the lever and the wishbone will be pushed towards the outside of the car.

Dave.

 

[Steve148]

I think the top of the lever is against the inner edge of the wishbone, not in the hole.

The lever's fulcrum point is on the sub frame, therefore, if you push the bottom of the lever towards the middle of the car, the top of the lever and the wishbone will be pushed towards the outside of the car.

Dave.

Yes, I think you're right - it's actually going in behind the rear edge (not poised to go through the hole). The question would be unchanged though - eg whether we're aiming to force the assembly outwards or inwards. Thanks for clarifying that it's outwards, Dave.

I must admit I'm even more puzzled now though. Forcing the lower assembly outwards will maximise the negative camber, which would increase loading on the innermost edge of the tyre. Maybe camber isn't relevant, as Argonought suggests, but I can't see how that change would help.

(and this is the point at which I usually just give up and buy some new tyres - thus the 'pointless wailing').....

 

[Davren]

The only other difference I can see is that this document says set the toe in to 0° whereas eLEARN says set it to -1°, i.e. 1° toe out.

Perhaps some garages and tyre fitters still have it listed as, and set it to, the original specification of -1°.

Dave.

 

[Argonought]

The only other difference I can see is that this document says set the toe in to 0° whereas eLEARN says set it to -1°, i.e. 1° toe out.

Perhaps some garages and tyre fitters still have it listed as, and set it to, the original specification of -1°.

Dave.

Interesting post there Dave

As you'll note from my earlier post I came to that conclusion and didn't even read the bulletin although I thought the allowed range of toe was 0° to -0°09'

Negative toe will tend to increase inner tyre wear and for that reason I had mine set to exactly 0° (straight ahead)

I don't seem to have any problem wear issues on my P7's and remember I still drive the early 02 model.

I only thing I will say is mine is very camber sensitive and tends to 'tramline' a bit (it's the same in France so that proves the geometry is good) but then this is only an issue at low speeds anyway - and you do tend to get used to it.

Oddly enough I can still feel a bit of feathering on the front tyres (when dragging a finger across) so the set-up is certainly not perfect but this doesn't seem to translate to heavy wear (not on P7's anyway) which is pretty good considering I drive mine very enthusiastically on the curves and hate using the brakes. :devil:

 

[Morty Mort]

There is only one thing that has worked with my 2002 model: Oldschool front manual alignment.

I've had several high tech laser / optics attached and aligned for several hours altogether. Didn't work. Done the sevice bulletin... thought it worked, but it didn't. 4-wheel alignment, front wheel alignment and so on.

So until I went to an independent garage that did it the oldschool way with an adjustable steel bar/rod inbetween the front wheels (from beneath with the steering wheel centered. They found the alignment to be some millimeters out, which they cured by turning the track rod ends. And this was one month after a 4-wheel laser alignment which was set to 0,0.

And it's been perfect ever since.

Now I'm on Vredestein Ultrac 215/45R17 and it doesn't even tramline!!! :slayer:

 

[Argonought]

There is only one thing that has worked with my 2002 model: Oldschool front manual alignment.

They all use the same principal so something seems rather odd there

Either alignment is correct or it isn't.

Sure, defects within the suspension may allow the tracking to change from one minute to the next (and also remember some companies may be using the wrong data) but I fail to see how the car can put itself right.

I would have gone back to the first company and asked them to check it again (many will do this for free once you've already paid) as I'd want to know what's going on.

 

[ivan73]

There is only one thing that has worked with my 2002 model: Oldschool front manual alignment.

I've had several high tech laser / optics attached and aligned for several hours altogether. Didn't work. Done the sevice bulletin... thought it worked, but it didn't. 4-wheel alignment, front wheel alignment and so on.

So until I went to an independent garage that did it the oldschool way with an adjustable steel bar/rod inbetween the front wheels (from beneath with the steering wheel centered. They found the alignment to be some millimeters out, which they cured by turning the track rod ends. And this was one month after a 4-wheel laser alignment which was set to 0,0.

And it's been perfect ever since.

Now I'm on Vredestein Ultrac 215/45R17 and it doesn't even tramline!!! :slayer:

What do you mean by "tramline"?

 

[PNL]

What do you mean by "tramline"?

The car will follow ruts and camber of the road..:bang:

 

[Morty Mort]

They all use the same principal so something seems rather odd there

Either alignment is correct or it isn't.

Well, yes and I also got the paperwork afterwards, stating correct values.

Sure, defects within the suspension may allow the tracking to change from one minute to the next (and also remember some companies may be using the wrong data) but I fail to see how the car can put itself right.

The car has been checked for slack and play on several garages, where I have been present and watched while they were working. I have also done crowbar testing myself. The only way I can find the Stilo suspension to alter itself is at the top mounts. They aren't fixed to the body at all.

Lets say you drive pretty fast (not important) doing a left curve. A large hole in the road appears, and you have no time or place to avoid it. Left wheel drops into the hole and the suspension does its job - propably. Most of the forces are on the right front wheel, but the anti roll bar will force the left front wheel down to keep traction. Wheen the suspension drops it might loosen the 5 mm play (it has about 5 mm clearance, try opening the bonnet when the car is parked) and twist some degrees before it settles again when it hits the asphalt. So when you are back on track on the straight road, the "camber" adjustment of the top mount has moved. And it might do it again over and over again. This is just a theory... Feedback anyone?

I would have gone back to the first company and asked them to check it again (many will do this for free once you've already paid) as I'd want to know what's going on.

Not a big point as it has been fine for a year now.

 

[Morty Mort]

The car will follow ruts and camber of the road..:bang:

And it usually gets worse the wider tires you put on. :bang: