C5x7 extreme tyre wear at rear

[aerodynamica]

Hi all, I found the rear tyres on the c5 have excess wear on the inner shoulder as though the toe is excessive. These are 3 year old tyres and have done about 19k miles.

Checked just now with the track ace and the rear shows as being 30 degree minutes toe out at the rear. It's a bit toe out but I wouldn't have thought that was very excessive (?) What is it supposed to be?
Given that there is no toe adjustment at the rear I wondered if a suspension bush or two had gone.
I have had a quick look and a go at each rubber bushing with a pry bar and none seem particularly movable.

I do notice that there as a bit of camber at the rear - compared with the occasional Peugeot 407 I see that has the same subframe, arms and hubs - that could contribute to inner shoulder wear but wouldn't have considered it excessive and actually I would think excess camber would show up as a collapsed arm bush anyway ,(of course I may have missed it)

Any ideas about this?

[GiveMeABreak]

For reference:

X7 Rear Axle Geometry

Checking Values
Tyres	225/60 R 16
“	225/55 R 17
“	245/45 R 18
“	245/40 R 19
Camber (not adjustable)	-1°16' ± 0°30'
Thrust angle	0° ± 0°30'
Tracking at the axle (adjustable)	0°34' ± 0°09'
Camber dissymmetry	± 0°30'

Rear Axle

Rear Hub	Rear Suspension Geometry

[aerodynamica]

Hi Marc, thanks. According to that the toe is correct. Not measured the camber angle yet

[Svod]

Hi,
I was salso struggling with this and there is a solution. I made a new center piece for 517847 (front adjustable arm for toe) and made the rar arm adjustable too. This way you are able to adjust also the rear camber.

[wurlycorner]

Nice modification to resolve it - did you get to the bottom of what you thought might be the original cause (which couldn't be fixed because no adjustment)?

[Svod]

I replaced all the rubber components in the rear suspension, but the camber was still out of tolerance. The car continued to wear both rear tyres on the inner edge and felt unstable—especially when cornering and hitting a pothole, where it would become noticeably 'jumpy'.

Even after fitting brand new rear arms (item number 2 in the "Rear Suspension Geometry" diagram), fully refurbishing the rear axle, installing new spheres, and setting the correct ride height, the issue remained unchanged.

What caused it? I believe the most likely reason is material fatigue in the entire rear axle assembly. Over time, the structural integrity may have weakened to the point where alignment issues couldn't be resolved through standard refurbishment. But these are only my thoughts.

As a result, I decided to approach it differently—similar to how some other car brands naturally address this OEM. Nowadays, whenever I refurbish a rear axle, I install these by default.

[Kees]

A dealer here in the Netherlands, make the same modification.

[Svod]

I have made a bunch of them if anyone interested. Solid steel, zinc plated.

[Paul-R]

Couldn't see on the photo but are the threads matched LH and RH? Did you make the LH and RH nut assemblies and then weld them onto the remains of the old tie bars?

Excellent bit of work BTW.

[Svod]

Tie bar is brand new and have L+R thread. The way I finish it is that I use older 'front' adjustable nuts with new silentblocks, or brand new front adjustables (PN 517847) from which i remove the center bar and insert new one. I also install new nut securing bolts from stainless steel with hexagonal head.

[Kees]

I like to get a pair of them, will you send them to the Netherlands?

[Svod]

Have some. Shipping to Netherlands should not be problem. PM me.

[aerodynamica]

Hi,
I was salso struggling with this and there is a solution. I made a new center piece for 517847 (front adjustable arm for toe) and made the rar arm adjustable too. This way you are able to adjust also the rear camber.

That's very impressive

[aerodynamica]

It's a great piece of work there. Did you ever find out what really makes the camber go so bad? I kind of thought it was the upper arm rubber bushes compressing inward and the lower ones pulling outward over time.

[Svod]

Thank you! I had a similar opinion on this. Unfortunatelly when i changed the silentblocks on the upper arms (with all other ones on the rear) it help just little bit. Camber was still out of the tolerance. Thing is that when alignment guy was setting the toe it changes also the camber. So there were 2 options: make a compromise between camber and toe on rear, or make camber adjustable too. It takes little bit more time to set the rear properly now as camber influences toe and vice versa, but the change when riding is noticeable.