S7 Rear Wheel Camber

[Guest nick coram]

I bought a "finished" S7 a while ago and am discovering how loosely the term can be applied.

 

My question concerns rear wheel camber. The original wheels were the Seria 165s fitted. I have just changed these to 195/50 R15. I am finding that they are wearing on the inside of both wheels very quickly.

 

Looking at the rear wheels they appear to lean inwards at the top so running slightly on the inside edge.

 

How do I correct this?

[Guest Fred2b]

I think on the Sierra the rear wheels are supposed to in at the top, something to do with wheel geometry and vehicle loading.

On the RH this does not apply because it is not nearly as heavy and it can look better if the wheels are vertical and to correct this you need to get shims made up. There was a recent post ( last week I think ) about this subject. They are quite easy to fit but it's getting them made that is the problem.

Regards

Fred

[Guest Peejay]

I'm sue big Jim'll answer this one. might be worth looking on his site

 

http://nw.rhocar.org/

 

Pete

[ibrooks]

The reason for the wheels "leaning in" is that the trailing arms on the Sierra rear suspension do not have an axis at right angles to the length of the car (the two bushes are at different distances down the car). This means that the wheels lean in as the suspension drops. No problem on a Sierra as it spends most of it's time at normal ride height. Your Hood is obviously lower. You have three choices.

 

Either raise the ride height to the same as the Sierra (measure the height of the ends of the subframe on a normal Sierra). This may make you rcar look strange and change the handling characteristics so if you're happy with these choose another option.

 

Live with it - expensive on tyres.

 

Correct the camber - there are several methods. Jim had made some wedge shaped shims which bolted between the hub and the trailing arms to do this job but I beleive they have all gone. You can get the same effect by putting washers between them on the top two bolts (others have done it - hopefully they will reply and tell you what to look for and how it works). Fit Cosworth arms (kerching goes the dealers cash register) these were meant to run lower and the arms had different geometry to compensate but just what the angles were I don't know, maybe not enough (XR4x4's were lower too but I don't know if they had different arms or not as they weren't as different from standard as the Cossies).

 

Iain

[Longboarder]

There is a fourth choice. File this one under not possible but if the semi-trailing arm mounts were at the same height as they are in the sierra the negative camber problem would be solved. However the propshaft would be level with your left shoulder and the diff would be in the boot, not under it!

 

Mr Silly

[ibrooks]

You mean raise the subframe within the body? I suppose it is actually possible as it wouldn't have to be as much higher as you suggest but you'd have to be braver than me to do that much chopping and welding.

 

Iain

[Longboarder]

I wasn't being serious as I'm not brave enough to do it either but it is the technicaly correct solution. The semi-trailing arm mounts should be fixed at roughly the same height off the ground as the wheel centre. This gives upright wheels and minimises lateral movement of the tyre contact patch on suspension travel and thus rear wheel steer.

Does raise another interesting point. If you have a puncture the car will drop onto the wheel rim, 7.5cm on my car. Is there any bit of the car with less ground clearance than that. The front of my car is set up so that it will run on the rim and I should stop with some control. However if I have a rear blow out the cross beam hits the ground and that could be more exciting.

 

Nigel

[Guest Fred2b]

I have also thought of using some big washers on the top two bolts instead of the wedge shaped shims but there are two questions needing answers.

1. Will there be any oil leakage from the half shaft at the wheel end?

2. What thickness washers are needed?

This seems to be the easiest option for us that cannot make wedged shims.

Regards

Fred

[ibrooks]

There won't be any oil leakage as the halfshaft is a "sealed" unit independant of the arm. The only possible leakage is from the diff end where you will have effectively pulled the shaft slightly out of the diff. I think the difference is negligible but again there are Hoodiez out there who have done it who could answer the question better. Come on guys where are you?

 

Iain

[Big Jim]

There's not a problem with the ½ shafts, as they are "sprung" ie, you need to physically push them in against a preload of some kind, this keeps them in the correct place as the hub moves up and down . The problem with fitting washers is, that there is more of a possiblity of getting *bleep*e etc. into the hub bearings, also you don't have the full machined face to carry the loads & stresses but just washer dia's.

[Guest Fred2b]

Jim

I believe you are the one that made up the original batch of shims but have no plans to make anymore.

Do you have any dimensioned drawings available so that I can approach a local engineering firm to possibly getting some made for myself and others in the club?

Regards

Fred

[Big Jim]

go to; http://community.rhocar.org/index.php?s...?showtopic=1197

[Peter Bell]

Fred 2b. (or not), before I discovered 'Jims wonderful shims' I had tried fitting washers and found a shim thickness of 0.035” 0.9mm changes the camber by about 1°. but it is a bit of a bodge and as Jim says the load is just taken on the washer diameter.

Peter.

[Guest nick coram]

How do the other 7 style kits using Sierra back axel like Tiger and Westfield over come this ? Is it possible they have an off the shelf solution (shim) or do their run with the diff in the correct height ?

 

If anyone is considering having some shims made, I would be interested in sharing the cost. These things are usually cheaper the more you have made.

 

Also I am finding that to run 205 tires on the back I need a 5 mill spacer. is ther any limit to the overall thickness of this. I am thinking back to ibrook's last post

[Guest daveg]

All

 

Has anyone thought of talking to Mr Richard?

 

Surely this would be best then he could make them for everyone and possibly include said item in the future kits thus enhancing his product...

 

Dave

my 2p