SpyderLegend

You can find my thread was the first one about 718 gt4/spyder alignment... I also took pictures before installing the stuff.
Also, strut mounts were already "inward" from factory for maximum negative camber. With 16mm shims I reached about -2°10' front camber and +10°15 caster if I recall correctly

toy4speed

Late to the thread, but my 2021 GT4 had 7mm shims installed in the front LCAs.

wizee

One missing from this list:

5 mm shim 996 341 543 99

Reedy

Yes my GT4 came with shims installed both front and rear. The strut tops were at max camber and with the shim it took the front to 1.7 degrees of camber.

TRZ06

I have discovered that as you add more shims to the LCA, it increases either bump steer OR changes the geometry of the suspension, as it makes the steering wheel jerky when navigating imperfections in the road. It isn't a tramlining thing, more of the steering wheel just moving/reacting to the road surface more in your hands. It is a little unsettling and can get annoying at times.

I am at -2.5F with the top mount maxed out and with shims on the LCA for the rest and it is noticeable. Not annoyed enough by it though to lose the amount of lateral grip you get with the settings by reducing the camber/number of shims

ExMB

That is called a caster increase. Surprised that someone like you who is so in tune with the suspension and set up doesn't know this and compensate for it.

TRZ06

I did the caster correction with Thrust arm bushings, however the increased movement of the steering wheel is still present. So something else is being altered to some degree. Not quite sure what it is, but it is enough to feel different.

My caster has been corrected to stock settings of 9.2

wizee

Hmm, maybe it's just the difference in feel without the rubber bushings that the caster pucks delete. Not sure what else could change the steering feel with stock-like caster. There are some nice diagrams showing the geometry changes of adding shims here: https://rennlist.com/forums/gt4-spyd...l#post14406496

Adjustable thrust arms (like those offered by BBi) could be a better choice than caster pucks because they allow fine adjustment of caster.

TRZ06

Yeah, that is my thinking as well, either the solid puck is filtering out that isolation that was present stock, and/or the amount of negative camber is keeping enough of the contact patch off the ground during straight line driving.

I have reduced that feeling quite a bit by upping the compression/rebound settings on the MCS dampers, but the wheel still feels more "alive" from stock form. It is only annoying on extreme roads now and not on all roads. So, at this point it is not enough to spend additional money figuring out or altering my alignment settings.

I thought about doing a bump steer sweep, but the costs of that are too much for an unknown result.

I went with the Elephant Thrust Arm Bushings, which are infinitely adjustable.

jwr9152

If you changed your toe, it can make it feel that way also.

ronbauer

My 2021 GT4 came stock with 7mm shims in the front, but the strut tops were not pushed all the way in from the factory. We added another 7mm shim to each side, pushed the strut tops in and lowered the car slightly, resulting in -2.7 degrees of camber. Rides and drives great, and is amazing in both autocross and during the one track day I did.

Ron

enduro

Yep, results of more toe out could be described like @TRZ06 is indicating, tho I think he's knowledgeable enough to know this so maybe he his effect is different. Either way, my new alignment & parts are also doing it. The car 'wanders' a lot more; I attributed it to the toe out I dialed in, and I expected the effect. Mine also has the caster corrected back to 9.2°.

enduro

FWIW, my factory alignment actually had 11.4 min per side toe in up front.

wizee

Woah, that’s a lot of toe in for the front. I thought the spec was 2 minutes toe in per side (4 minutes total) for the front.

TRZ06

You are correct, I am aware of this. I am not running toe out in the front. I am actually running a decent amount of toe in to keep the car from wandering and being darty, since it is a street car.

I have seen toe measured two different ways and I do not know how it translates into minutes, but my front toe settings are listed as .05" each side, for a total of .1" of toe in. That is how it reads on my alignment sheet.