MOT Failure - Front Springs

[Dekker]

I was told by Chris Franklin at Centre of Gravity that a stock car will not run safely at RS height as the steering links are at the wrong angle ie pointing upwards at the hub end.
This will make steering geometry work against you when the suspension is under further compression thus adding to the pull on the steering causing severe kicks to the steering when going over pot holes and the like as well as much increased tramlining.

Steve has his set at the limit.

It does sound as though your car has had some RS components added, so if they have, RS height would be OK if all of the differences have been added.

It is very wrong to set the ride height by measuring to the wheel arch. It should only be done as per the book to the bolt head on the front lower wishbone and the boss on the rear trailing arm.
There is almost a 5mm difference in wheel arch measurements on my car and no it hasn't been in a shunt, just differences that were normal back in the 90's. I don't know if the robot's that build the new cars have tighter tollerances.

 

[Steve Brookes]

The arch/ground measurement also varies a bit according to fuel load.

I don't think Ian means his ride height was set using arch to ground. Mine wasn't. We've just used those measurements for a rough comparison on this thread to avoid wriggling underneath the car......not that I think Ian has any chance of that with his current settings! []

 

[IanHighfield]

As an aside, and yes Steve and I are using rough numbers to gain on view on how low the car is, I parked on my drive which has a very slight incline, and I could not get the standard 964 wind up jack to go under the front of the sill to get the car up - now that is low ! Had to drive the car up on to a small piece of wood to be able to get the jack under.

Ian

 

[Dekker]

When Chris sets up the suspension it's with 3/4 fuel and your weight in the driving seat.

I had trouble finding a good surface to take measurements and eventually found Sainsbury's carpark was ideal. Caused a few odd looks from the shoppers.

 

[asjasj]

Just for a laugh, checked my front arch measurement...........27"

I have (so far as I know) standard suspension on it but looks like it has sagged a bit at the rear. Would love to replace it all but can't really justify the cost at the mo......

 

[IanHighfield]

Ade - a set of standard Eibach / H&R Lowering springs would sort that out !

Dekker - I note from PET that the Carrera 4 and RS have a different inner track rod to the C2 / Turbo etc. - is that what allows the outer track rod geometry to be corrected for bump steer etc. on the RS ? Not sure if mine are standard or not.

Ian

 

[Steve Brookes]

ORIGINAL: Dekker

When Chris sets up the suspension it's with 3/4 fuel and your weight in the driving seat.

I had trouble finding a good surface to take measurements and eventually found Sainsbury's carpark was ideal. Caused a few odd looks from the shoppers.

It always amuses me when I get those same type of odd looks from people who think I'm putting the shopping inside the engine []

 

[Dekker]

I'm sure that's part of it Ian.

I also wonder if the steering rack is raised also.
Something I vaguely remember hearing of people fixing spacers under the steering rack to compensate.

 

[IanHighfield]

Spoke to Paul at Tuthills and Steve at Jaz today.

Paul had not been able to speak to the right person at Eibach in Leicester, and so we are going to try again on Monday.

I spoke to Steve as he had originally installed the suspension and in fact done the other work and had the car repainted - he is a real enthusiast and currently has a number of requests in to build RS reps ! Rich he mentioede your car is even stiffer.

Steve recalls fitting RS arms to the front (I need to verify) but he was not happy at having to sit the car so low on the street, but Hamish had wanted it this way, as to be honest it is a brilliant car like this on the track. Steve said we should just be able to fit a longer Eibach spring with the same rating (40 Nm) to achieve the desired RS ride height. Tuthill will also investigate the tie rad angle etc. etc. so we should be back on the road at circa RS height next week. Will photo when done.

Ian

p.s. there is also a nice write up by John Glynn in 911PW mag this month on the car (and me).

 

[Dekker]

Photos would be good, especially a side view before and after.

 

[RLambert]

Sorry Ian, only just seen your reply.

I have JRZ, two way adjustables, with Eibach springs

 

[IanHighfield]

Richard

Do you know which Eibach springs you have - Main and Tender or a single progressive ?

Ian

 

[RLambert]

I've got main and tender.

I was hitting the bump stop at the bottom of paddock hill by the way so I'll have to have a look at raising the car 1/2 an inch when I race there.

 

[IanHighfield]

Thanks Richard - any idea what spec of spring - PM me if it is a racer secret

Ian

 

[RLambert]

I don't actually know the specific spring rates, Steve put them on. I do know they aren't super stiff somewhere between RS and CUP.

The attached PDF shows the different rates