Help! Tyres melting!

[Jabbah]

Having a slight problem with the rear tyres. Recently had them replaced but it was happening with the old ones too. Every time I go over a a bump or dip you can hear the rear tyres scrape on the outside of the arches. Was particularly bad on the trip to Le Mans this weekend with a loaded boot and full tank of petrol. I had tried increasing the height on the suspension but it looks a bit odd when unladen.

Does anyone else have this problem? Might there be a spacer fitted somewhere for the "look"? Is it a geo setup issue (although looks like it would need 3deg camber to clear the lip)? Is this just the way cerbs are and I need to get a higher rated spring or different bump stop? Seems odd as there is a lot of space in the arch, it's just catching the lip. I've seen some cerbs with suspension lowered quite a bit so wheel must go into the arches in some.

My dampers are Protech. Don't know anything more than the make though.

A few pics to help show the problem:





ETA: Wheels are 18" spiders and tyres are standard 255/35/R18 on the rear.

Edited by Jabbah on Tuesday 19th June 12:23

[Tanguero]

If you don't want to set the ride height higher when laden then you will need a higher rated spring.

[Steve_T]

What's the offset on the rear wheels? Should be ET42 all round iirc, but Tuscan rears are ET33. If that's not an issue you're into grinding the arches a little

[ridds]

My money is on incorrect offset rest wheels.

[FarmyardPants]

It does vary from car to car and tyre to tyre (some have squarer shoulders than others) but it looks like you have the 'rear' offset spiders and need the 'front' ones as stated above. I can manage with the rears and some negative camber but as I say it does vary. You could try adjusting the camber which obviously makes a big difference clearance-wise, improves grip to a point and is easy to do, otherwise get some fronts for the extra 9mm.

[Gazzab]

If you look at your spider wheels whilst on the car and if you can see a difference in offset between a front and a rear spider then you've go the wrong wheels. Most Cerbs cant deal with rears on the rear and so have fronts all round.
If you want to be sure then remove the road wheel and it will have front or rear stamped inside it.
If you do have 4 x fronts then your next option is to raise the ride height by adjusting the coilover 'platform'.

[scotty_d]

The gap looks fine when set up correctly fully loaded you should be able to get 2 fingers approx in between tyre and arch. I would check offset's first and then look at what spring loads you are running.

[pmessling]

With out doubt its the offset. I had tuscan rears on mine, they were fine most of the time, but when i went to the Silverstone classic last year with a boot full of camping stuff they rubbed just like the photo shows.

[Storer]

The last thing you want on a road Cerbera is stiffer springs. Many owners have the suspension lowered and the damper too stiff. If you set it as the factory recommended you get much better handling and traction with a car that is a lot less likely to bite but can still be provoked into a tail slide.




Paul

[itiejim]

Storer said:

The last thing you want on a road Cerbera is stiffer springs. Many owners have the suspension lowered and the damper too stiff. If you set it as the factory recommended you get much better handling and traction with a car that is a lot less likely to bite but can still be provoked into a tail slide.
Paul

Whilst increasing the spring rate just to address a the problem of having wheels with the wrong offset is not the answer, I strongly disagree with the above. The experience with my car was that the suspension was well over damped and under sprung. Increasing spring rates greatly improved road holding, predictability and ride quality. I used 500lb front and 450 lb rear springs and really thought that it was the best money I ever spent on the car.

[Tanguero]

itiejim said:

Storer said:

The last thing you want on a road Cerbera is stiffer springs. Many owners have the suspension lowered and the damper too stiff. If you set it as the factory recommended you get much better handling and traction with a car that is a lot less likely to bite but can still be provoked into a tail slide.
Paul

Whilst increasing the spring rate just to address a the problem of having wheels with the wrong offset is not the answer, I strongly disagree with the above. The experience with my car was that the suspension was well over damped and under sprung. Increasing spring rates greatly improved road holding, predictability and ride quality. I used 500lb front and 450 lb rear springs and really thought that it was the best money I ever spent on the car.

I am with itiejim on this one - emphaticaly! Increasing the spring rate hugely improves the handling. I have the same 500/450 springing at Nitrons recommendation and it is a vast improvement on the standard spring rate. To say it will harm the handling is simply incorrect.

[gruffalo]

Tanguero said:

itiejim said:

Storer said:

The last thing you want on a road Cerbera is stiffer springs. Many owners have the suspension lowered and the damper too stiff. If you set it as the factory recommended you get much better handling and traction with a car that is a lot less likely to bite but can still be provoked into a tail slide.
Paul

Whilst increasing the spring rate just to address a the problem of having wheels with the wrong offset is not the answer, I strongly disagree with the above. The experience with my car was that the suspension was well over damped and under sprung. Increasing spring rates greatly improved road holding, predictability and ride quality. I used 500lb front and 450 lb rear springs and really thought that it was the best money I ever spent on the car.

I am with itiejim on this one - emphaticaly! Increasing the spring rate hugely improves the handling. I have the same 500/450 springing at Nitrons recommendation and it is a vast improvement on the standard spring rate. To say it will harm the handling is simply incorrect.

And another one with itiejim here, transformed the ride and handling, do not lower the car though as this does have a hugely negative affect.

[ridds]

Same here

500 front springs, 425 rears, Protech shocks, bump rate wound up a little more on the rear dampers than as supplied, lowered, 19" wheels, raised steering rack and lowered track-rod ends and she handles better than it did when I first got it. Ok the dampers were shot then.

Agree it's certainly not going to be the last thing in B road blasting but if I wanted that I'd buy a Scooby.

[Jabbah]

Thanks guys, some good suggestions there. Is it possible to machine the rear wheels to get rid of the offset or is that not worth it due to cost or safety considerations? Annoyingly even the wheels have a custom paint job so would need to get new ones refurbished... The handling feels like it would benefit from stiffer springs so will look into that too. Any recommendations on where to purchase?

[Gazzab]

Have you checked the offset?
I wouldnt start machining spiders. Not sure its possible as they are quite different moulds etc...

[Brummmie]

A long while since i gave up on the Choccie spiders, but your picture shows a raised edge where the bolts go through, so it looks like you have the wrong offset. So yes you could machine that raised casting off, as thats all the front ones are anyway.
The other option is to decrease the size of the inner arch lip, i had to do this to get 10" rears under mine.

[C1RBY]

Had the same thing at le man just had it lifted at power today.

[ridds]

Brummmie said:

A long while since i gave up on the Choccie spiders, but your picture shows a raised edge where the bolts go through, so it looks like you have the wrong offset. So yes you could machine that raised casting off, as thats all the front ones are anyway.
The other option is to decrease the size of the inner arch lip, i had to do this to get 10" rears under mine.

Did they not use different cores for the wheels? Sure the amount of thread that protrudes would be greatly reduced with the higher offset wheels.

I've looked at doing this on other wheels and the amount of material between the mounting face and the taper seat for the nuts is VERY small!!!

[pmessling]

I looked into getting the Tuscan rears machined but as has been said there isn't enough material before the cone for the nuts so would be very dangerous

[Brummmie]

pmessling said:

I looked into getting the Tuscan rears machined but as has been said there isn't enough material before the cone for the nuts so would be very dangerous

They must countersink them further in then.
Get the linisher on them arches!