9six4

This a great thread. I'll need to set up my car soon and this information is excellent. Thanks to all who have posted.

robt964

The tasty looking camber / caster gauge has arrived



This may seem like a luxury purchase (238quid) but it still works out more cost effective than taking the car back for a long (3hrs) explorative geo session to find the missing caster - AND I get to keep the tool. I'll only need the tracking checked afterwards to correct me moving the subframe forward.
So that's a job for Bank holiday Monday sorted

John McM

A tasty piece of equipment. You are taking this to another level. Here is my track focused geo set up. Works well for me.

ras62

Rob, have you done the corner weighting?

BertoSpid

Mine (964 RS Style, road .. to go... track use )

robt964

>Rob, have you done the corner weighting?

No not yet, no point until you've got the suspension in the right ballpark that you want.

ras62

Fair point, I was thinking in reference to the rear ride height that seems high in comparison to the front for RS settings. For the caster issue it maybe worth swapping over the bottom ball joints with their eccentrics bolts to see if you can get to the bottom of why there is a lack of cater on one side?

Ravioliv

I am also hesitating to tune my alignement on my stock C2 that I use 50% fast road 50% track. Stock tyres and suspension.
My tyres are using relatively evenly even on track but especially at the rear the outer edge is showing some signs of faster wear.....which would indicate need of a bit of camber.
Looking at RS specs, and also your track set ups, this seems to be rather straight forward...
- standard toe
- more negative camber ( here the extent varies significantly )
- increase caster

I am not sure about why you guys push that much the caster....what is searched that way?
Camber, ok makes sense but not sure extreme values are needed...why RS specs is not enough?

I am quite cautious in the approach because I like the way standard set up allows to make the car slide....and I don t want a rear that is stuck and getting some increased understeer.....which apparently is the tendency between a C2 and a RS....

But more than alignement, I think the biggest factor is ride height and stance between front and rear.....considering I don t intent to replace the shocks and springs, does anybody know by how much it is possible to lower the car using the stock coil overs? -2cm? ( knowing RS is - 4cm if I am correct....?
thanks, great thread by the way!

robt964

A little update...
I got the front of the car in the air with the wheels off last weekend to have a snoop around the front subframe to see if there is any scope to shift it about a little to increase the RHS caster (It's maxed out at just over 3 degrees where as the LHS will go up to 4.2)

Looking at the witness marks on the chassis where the subframe bolts to, it appears to be in exactly the same place it was before. I don't have any geo settings from the car before the strip so i can only assume its always been like this and always had max caster of 3.# degrees.

Anyway, as the subframe is slotted where the bolts go through I recon I can loosen it up and then tap it forwards as much as it'll go to increase the caster. So that I can quantify any gains I make and ensure both sides of the car are equal I need to mount my new caster/camber gauge on the wheel to take measurements. A quick search around revealed these to be way too expensive (200quid+) for what they are, so I thought I'd make one up.

30 quids worth of ali off ebay and 3hrs work had me this.



Plastic feet so as not to scratch the wheels. 80mm x 10mm x 500mm main plate, 15mm square section for the arms, 80mm x 10mm x 100mm steel plate.



Steel plate in the middle so that the magnet on the gauge can attach. At present the 'arms' are positioned for my 17inch wheels. I'll later slot this hole in the base so that the arm can be slid up and down to suit different wheel sizes (I intend to later use 18inch wheels)



All ready for action Just need some dry weather now.

Jcx

Brilliant!

robt964

I finally got round to having a whole day to spend on the car and thought I'd try and tackle my front caster problem. The issue is that the LHS can be adjusted upto 4.2 degrees but the RHS maxes out at 3.2, so the guys who did the alignment had to set them both to 3.2. Having read many sources on this site I understand the car benefits from as much caster as you can get with 4 degrees being a minimum.
First off I checked out the positioning of the front subframe as it has a degree of adjustment to shuffle about. After many hours laying on the ground under the car, taking measurements from different datums, cross checking, triangulating etc I'm absolutely certain the subframe is true. I did more checking and proved that the pivot points on the outboard end of the lower wishbones (the threaded stud which the lower balljoint pivots about to provide caster adjustment) were also correctly located (the RHS was actually 2mm further rearward than the LHS, but this would not be sufficient to knock 1degree of the max available caster). So that all looks good. That pretty much just leaves the uprights and the positioning of the shock tops. I spent a while going over the uprights but could see nothing bent. I'd be extremely surprised since the whole suspension has been apart, blasted, recoated etc and any damage would've been spotted earlier. The top mounts of the shocks are non-adjustable and locate firmly so aside from the actual chassis drillings / holes being in the wrong place it also looks good. I couldn't find any datum to use to check the correct location of the chassis top mount positions relative with each other.
I'm kind of stumped here
The bottom ballpoint on the RHS is swung fully forward to give it the max available caster. The LHS is only half way through its travel to bring it equal.
The caster adjustment cam swings the outer end of the joint forward to increase caster and pulls it back to decrease. All this operates cleanly. To increase the RHS caster by a further degree would require the lower pivot point to be approx 1cm further forward from where it is or the top mount location 1cm further back :S - I just can't for the life of me see where the misalignment originates. Anybody else come across this before?

ras62

Its worth checking both bottom ball joints are the same and not one from a 993 also eccentric bolt and fixing bolts are the same. Second post on this link could possibly explain the problem.

http://forums.pelicanparts.com/porsc...uspension.html

robt964

Thanks ras62. Both bottom joints are the 964 items that I replaced as part of the rebuild. The difference in lower balljoint position (full forward on the RHS and slightly rearward on the LHS) is so markedly different you'd expect the root cause to be blatantly obvious. I'm 99.9% certain the subframe and lower wishbones are true and correctly positioned...

alexjc4

You have check the front subframe and lower arms are square but have you confirmed the subframe is aligned with the body?

robt964

>You have check the front subframe and lower arms are square but have you confirmed the subframe is aligned with the body?

I checked that the front subframe was aligned and square with respect to the rear suspension. I did this by comparing measurements diagonally accross the car from the rear trailing arm outer joints on the chassis to the pivot studs on the outer ends of the front wishbones. (ie RR->FL & RL->FR) and then again but on the same side of the car (ie RR->FR & RL->FL) to triangulate.

In terms of positioning against the body, thats kind of out of my control right? That is the relationship of the shock top mount WRT the subframe? That, I unfortunately couldn't measure for lack of a reliable datum. The frame does visibly sit square within the body. I guess if the shock tops were removed and pulled to one side, a plumb line could be hung directly through the centre of the hole, a measure could be taken between the line and the outer pivot stud on the lower wishbone. I could then compare this measurement left / right hmmm