ShakeNBake

Yep - I mis spoke, I just did a little exercise and I don't see it impacting caster - the manifestation of the impact of caster yes, but not the caster measurement.

ExMB

RSS shim set

Compare that to individual shim pricing.

jphughan

Thanks! That's not bad at all, especially since one set might cover my alignment needs for all four corners. I'm going to drive the car on its current alignment for a while, but if understeer bothers me on track or eats up the outsides of my tires too quickly, I'll definitely go this route.

orthojoe

I doubt you'll need shims in the rear for what you are looking for. Be aware, at least on the gt3, the rear shims are a different shape than the front

ExMB

No need to worry. Its confirmed that shim shape is the same F & R on the GT4.

orthojoe

Nice!

m3irish

If you go to a lower offset wheel the caster is the same, however the outer edge of the tire will reach out further forward when turning the wheel. I believe this is what Shake was trying to get at.

4carl

Changing offset can cause a wheel to rub but it doesn't change the alignment geometry . carl

ShakeNBake

Depends what you call Geometry...

Scrub Radius is affected, position of the tire in the wheel well is affected....

m3irish

Did I stutter? 😜

4carl

True changing the front track does change the scrub radius but it really doesn't affect caster/ camber or toe. I guess it comes down to the definition . Carl

4carl

Sorry...carl

Yomi

Necroposting...

My owner's manual page 224 is consistent with images I can find on other threads. It shows:

OEM specs from the manual[/B]
Front camber: -1° 30' +/- 3'
Front toe-in (total): +2' +/- 2'
Rear camber: -1° 30'+/- 5'
Rear toe (per wheel): +10' +/- 2'[/B]

How did you do the degrees to inches conversion?


It seems my GT4 is limited to -1.3 deg front, -1.2 deg rear before toe limits. I'm really surprised the max limits are reached at the factory settings, and especially that the limits for camber are so low on a track-oriented car.

jphughan

Those aren't inches; camber is never expressed in inches to my knowledge, although I suppose it could be if you really wanted to. I just couldn't be bothered to find the degree circle that you did, so I used " for degrees (yes, I know that's technically seconds) and the correct ' for minutes. I did however convert from degrees and minutes to degrees with decimal since that's what you typically see on an alignment rack and how people tend to discuss their setups anyway -- 60 minutes in a degree, so 30 minutes is 0.5 degrees. Toe on the other hand CAN be expressed in inches, for which there is a conversion if you know your tire specs and some trigonometry (or have a website do it for you), but expressing toe in minutes is generally preferred because it doesn't depend on the tires you're running, whereas if you have a toe target expressed in inches, you'd have to take the tires you're running into account.

Your GT4's alignment limits are the lowest I've seen yet, though. Is your ride height maybe maxed out?

sgreer78

So I’m pretty irritated. I can only get -1.2° on the left rear of my GT4 with stock parts while keeping 1/16” toe-in per side. I cannot add the toe arms due to rules of parking lot racing. Left can get all I need and more, but that does me no good. Ride heights are set to the publicized “lowest Porsche recommended”. I could lower, however much like my e92 m3’s rod bearings, the strut tower issues make me hesitant to go beyond those numbers. Nothing looks off underneath, subframe looks centered, etc. is this just quirky car crap that makes no sense or....

Any tricks here to get to at least the OE spec of -1.5°?

Thanks for any help!