Gus

I have maxed out my caster adjustment and would like to obtain a little more than the 4+ degrees I currently have.
I am not sure what adjustment increase the Wevo uprights allow. Right now I am as far forward as possible with the stock setting. The tire were rubbing on the front fender lip at the seam between bumper and fender - modified and fixed, but how can you obtain more caster without moving the tire further forward.
From looking at the options it appears that the top shock mounting location needs to be modified to allow the shock to be moved to the rear. I need to modify the top mount anyway to allow for more clearance for the camber adjustment plate. The adjustment allen bolt heads are hitting the mount tower sheet metal and restricting the amount of negative camber I can set. So am going to have to enlarge this area anyway .
What have others done to obtain more caster???

Vandit

Someone on here recently posted some top mounts that have caster adjustment. I forget what brand. Maybe ground control?

EDIT: here, found it. Ground Control top mounts
https://rennlist.com/forums/964-foru...rut-brace.html

I would think that with the provisions on the control arm plus these plates, you should be able to really crank on the caster. Plus since you're adjusting it from the top, the added caster should not move the tire forward in the arch. It'll actually move it backward.

porsche mania

More caster can be had by slotting the subframe holes or by modifying the control arm bushes. Either one is easy to do and there is a lot more adjustment to be had by doing either of these.

Vandit

When you say slot the subframe, you're talking about slotting the longitudinal members and the member where the rack mounts? Cause the rack passes through the longitutinals so moving them independently might cause a problem.

Any more details on modding the control arm bushings?

kos11-12

Good point Gus,
I wander how much can be achieved with the CG camber plates...
How much more caster can someone obtain by modifying the actual set up,
Mine is at 4.20 deg.

964tit

Interesting that you all want more caster. I'm thinking I'd like a little less (ie. bring the angle more to the vertical) to make the steering a bit more alert.

Vandit

I don't want to turn this thread into a geometry debate, but lots of alignment discussion, including caster, can be found in this other thread.

https://rennlist.com/forums/964-foru...and-setup.html

provoste

Just an FYI, 991GT3 and GT4 OE caster range is 9.5-10.5.

Yes, really.

porsche mania

Unfortunately, in that thread rob never gets to the bottom of why he cant get enough caster on one side of his car. I had the same problem on my car so had to explore the options mentioned in my post above.

Gus

In looking at caster - the more you have the greater the negative camber is on turn in, providing better cornering. It is interesting that the GT3 is 9 and GT4 higher, which reinforces my search for more caster. In the post on the CG camber plate with caster adjustment I believe it was stated the only a 2 degree increase could be obtained. This means that the shock tower needs to really be modified to reach higher numbers. So some restructuring is going to have to be done. So, if anyone has taken this step please provide input. Thks

porsche mania

Yes i mean the longditudinals, the nominal amount you need to slot them to get a big change in caster would in my opinion have a very small effect on the rack position.
As for the control arm bushing ive seen it done on a set with poly bushes fitted. These were shaved by a couple of mm on the leading edge and a washer put at the back to make up the difference.

porsche mania

I went from 3.5 to 4.5 caster both sides on my car and its much more of a work out in slow corners on the track and thats with 205 tyres on the front. Going anywhere near as high as gt3 caster and i think it would be a real struggle! Im wondering if gt3 and gt4 have much more leverage on the front hubs to make it work, either that or its the power steering they have thats doing all the work?
Vandit, Back to my previous comment regarding moving longditudinals. If your moving both then the rack stays true, only one needs moving when you have an inbalance that cant be adjusted out.

Gus

If you modify the longdtudinals or poly bushings you are going to move the axle further forward which only increases the issue that I currently have - minimum clearance forward of the front wheel on the axle centerline. From looking at the position and settings that I have (4.2 caster at max adjustment) the best modification would be at the strut/shock top mount. What I have not calculated is how much the mount position can be moved to the rear and can it be moved enough to make that modification worth while. I am going to pull some lines and numbers today. Trying to figure out what a ½ inch reward move increases caster degree setting. Need this to obtain degree of modification to tower mount location.
Reference the GC camber caster unit - need to really understand maximum settings that the GC unit will allow. How much farther reward can you move the top shock mount location over its stock position?

porsche mania

Sorry, i assumed you had just run out of adjustment and not clearance at the front of the wheel. With 4.5 caster i think my wheels could go forward around 5mm more before id have issues. With the top mounts on my car i can see how you could easily adapt them for quite a lot more caster without modifying the shock tower, it would mean running monoballs though. The black plate that the monoball mount slots into is just that, a flat plate that you could easily make another with the desired caster.

Gus

Ok - I did a NON-Scientific string pul just to see what kind of numbers I would come up with. Here is a run down of what I did to get some rough figures.
First I ran a string up from the center line of the wheel, suing axle as a center line. Then I ran a string down from the center top of my front shock tower and intersected this on the axle line or center of the wheel hub.
This gave me an angel difference from a straight vertical ( measured with level ) and the angel to the shock tower - Which when measured with a protractor was around 3 to 3.5 degrees. The distance difference between the center line of the axle ( vertical ) and the angel to the shock was roughly 3/4 inch. So ball park figure - with a CASTER of 4.2 degrees and an angle difference of 3 degrees that works out to 1.4 degrees of caster for every 1/4 inch backwards movement. Granted this is not a laser operation and is only and extrapolation of figures obtained from manual measurements. But at least it is a starting point me to figure out how far back I need to move the center line of the shock tower to obtain better
Caster. Will probably pull this several times and on both sides to see how close the combined measurements are, then take an average.
Here are some pictures so you can understand what I have done .
Addict - Like the IDEA of remaking the Camber Plate bottom flat plate to obtain more caster - This maybe the easiest and first step.