Leon Speed

Here are the alignment values as done by a Porsche shop today. To my untrained eye it looks pretty good, and within spec (excaept for the front caster which seems a bit below spec). What do you think?

Front
Caster
Left was +3d.22' is +3d.22'
Right was +3d.12' is +3d.12'

Camber
Left was -0d.31' is -0d.39'
Right was -0d.34' is -0d.27'

Toe
Left was -0d.04' is +0d.07'
Right was -0d.04' is +0d.07'

Rear
Camber
Left was -0d.44' is -0d.39'
Right was -0d.47' is -0d.41'

Toe
Left was +0d.12' is +0d.13'
Right was -0d.14' is +0d.14'


The car handles definitely better, less nervous, less tramlining. I guess because of the changes to the toe?

Herman K

That looks good what was the last time before this and what is th ride height?

MVG

Leon Speed

Hoi Herman,

No idea when it was last done; I have the car 2 years now and it's a first for me. This was after changing the upper A-arms and shocks all around recently.

Ride height:
Front 170 mm
Rear 178 mm

Groeten

Aryan

RKD in OKC

Hmmm, my Porsche dealer was able to get the left and right to match right on the money.

Richter12x2

Yeah, it looks like the camber on the right front was better before they messed with it. Either way, it's close enough to not be concerned about, it just makes me wonder why they felt the need to change it.

pcar928fan

as long as they didn't jack the car off the ground or even take the weight off the wheels you should be ok...all bets are off if they jacked that bad boy up! Happens less often now, but even many Porsche dealerships didn't/don't know how to properly align 928's... You will know in about 2k miles with completely destroyed front tires if they did lift it!

AO

Looks like the tech made things a tiny bit worse except for the front toe.

Front
Caster: He obviously didn't change anything here. But you're still slightly out of spec. Spec is 3° 30' +30' (3° 30' to 4°)
Camber: You're were already in spec, but he made it worse side-to-side. Spec is -30' ±10' (-40' to -20')
Toe: You're barely in spec here - I would have gone a bit more toe. Spec is (per wheel) 7.5' +2.5' (7.5' to 10')

Rear
Camber: You're spot on here - usually, one of the side is way off. Spec is -40' ±10' (-50' to -30')
Toe: Again, you're barely in spec here, but this time it's on the other end of the scale. Looks liek he probably didn't do anything here. The value adjsuted a bit from changing the camber. Spec for each wheel is 10' ± 5' (-5' to -15')

To sum up, I think he could have done better on front camber and given you a little more toe on the front, but overall it should work for you.

Leon Speed

Thanks for the replies guys

Exactly to spec?

Haaa! You know, when I went to the dealership I asked them if they had any experience with alignments on a 928, the service manager looked almost offended I told him, just checking because sometimes these cars get jacked off the ground and then it won't work. He said, don't worry, it is our own product. Uh-huh But..they had the correct machine and I watched some of the work - I could walk around as I pleased, that was nice.

I don't know. I didn't quiz him on it, and studied the results when I came home. Hindsight: if they would let me use the machine, I would stop until perfectly on spec!!!

I am indeed not happy with the front caster and camber values. The front caster value is weird, hard to imagine it wasn't adjusted. Front camber got worse side-to-side, maybe a result of messing with the other axes? Spec for toe is a little confusing, one side is 7' (thus it would be in spec), but together spec is 15' (then it is not within spec).

The tech said the rear axle was fine, and that he didn't need to change much.


I would be happier with caster and camber settings closer each side. But that is just from looking at numbers. I don't have a feeling for what is good and how much variance from spec is bad. But, again, looking at the numbers, I am not worried and I am glad you agree!

I have to read up on alignment, but maybe you can help me with your experience a little bit more here: what would it do to handling if I were to have a little bit more toe-in and caster and camber closer each side? Or: what negative characteristics should I experience when I leave it like this? I drove 500 kms today and still noticed some tramlining (maybe due to new and wider tires) and a tendency to keep going straight when veered of course (no automatic return to the middle of the lane).

Btw: Rennlist rules! Let me rephrase that: 928 forum rules!!

AO

In my experience, a little more (I mean it... just a tiny bit) toe will improve handeling while driving a bit, but I think you'll notice it even more under braking. Under hard braking you're front wheels will want to toe out, so if you can prevent this from happening by running a bit more toe, it will handel better. This largely depends on the condition of your front suspension. Your report that the car wants to track straight is a good thing in my opinion.

Caster affects the cars ability to keep the steering straight. I don't mean to track straight - that's toe. I'm not saying this correctly. When you're turning the car, if you let go of the wheel, the car wants to straighten out... that's a function of caster. Make sense? You're little off, but probably not enough to notice.

Camber can affect turn in, oversteer, understeer, and the general feel of the car. Because your front right has less camber, you will probably notice a tendancy for the car to understeer (car doesn't turn) more in left hand turns than right. Now this all depends on how hard you push the car.

Leon Speed

Ok so if under hard breaking the wheels want to toe out, the car will pull to one side or the other, or become nervous. I didn't experience that yet, but have to do some more field tests

I understand what your saying about caster. I'll have to test that some more too.

As for understeering in left hand turns your are absolutely right on the money! Today going in long left hand turns at about 220 kmh I felt the front jump to the side slightly. Not a nice feeling!

Now I know what to look/feel for, I see some more field test coming up

Thanks for the help!

Richter12x2

Looking at the chart, your numbers are so close to nil I doubt you'd notice any substantial characteristics in any direction, but the way to feel it is this -

Camber - increased negative camber is the degrees your wheels are in at the top with respect to ground - so your tires sit like this /---\ (viewed from front of car). Negative camber means you have slightly less contact area running straight (which isn't bad, because it also reduces rolling resistance) in order to pick up grip in corners (when you turn left, the weight shifts right, and forces the wheel to straighten up). Generally you're not going to feel it unless you're 2 degrees or better, and most people can only feel differences of 4 degrees. I run 2 degrees negative camber on my cars if I can get it, because it improves the handling a bit and doesn't wear the tires too badly.

Toe-in - tires look like /---\ when viewed from the TOP. As I understand it, you want toe to be neutral (which yours would be) to maybe a bit of toe in - toe in tends help the car's steering return to center, and helps a bit on turn in to a corner (again, as I understand it.) I would think toe out would be undesirable (again, your tenth of a degree or whatever is negligible so I wouldn't worry about it) due to the fact that you would be shifting weight AWAY from the tire that's going in the direction you want in a corner (your opposite tire is going to be pointed MORE away from the corner, again, by degrees).

Caster - is like dynamic Camber - it's essentially the rake angle of the struts. (Canting toward the front or back of wheel centerline in degrees). It affects the handling of your car in a corner, but it's not as straightforward to tune as Camber or Toe.

And with wide tires, tramlining is a way of life.

RKD in OKC

Yes, mine were set to spec on the aggressive side of the specs. Example: front camber at -0° 40' with the spec being -40' to -20'.

What I was talking about in my previous post was that my alignment guy spent enough time on the car to get the left and right the exactly the same for each measurement. Example: Front left camber -40', Front right camber =40'. as opposed to your -39' and =27'. i know it is just splitting hairs, but heck why not do it right eh? It was my local dealership and they replaced some part in the rear to be able to get both rears the same and at the aggressive side of the spec.

Bill Ball

My car is very sensitive to side-to-side differences and the Porsche spec wants them close anyway. I think they should be spot-on too. It takes more iterations, but it's not that hard.

Leon Speed

Maybe I was going a bit fast when I felt the understeer

Aha, makes sense. I really should test some more on the twisties and note how the car handles.

Umm..is negative toe in or out?

Boy isn't that the truth. When I went from 205 front to 255 and 255 to 285 rear I got pulled all over the place - since new struts and A-arms, it is much better, but still there somewhat.

I agree. I am somewhat dissapointed they didn't get it completely on the dime. Has to be perfect!

RKD in OKC

Picking my GTS up this afternoon from a more aggressive alignment. It's not the dealer this time as the dealer was very very reluctant to go out of factory spec. Front camber -1.6, rear -.9, also toe front and rear both to as close to zero without being zero and still get the most negative camber they could. Forgot what he said he put the caster at. The settings were nowhere near where the dealer's print out said the were a year ago.

They spent 5 hours tweaking to get both sides exactly the same and said I had way too much toe in both front and rear. Car was understeering horribly at the limits. Took it for an "is this better" drive and it feels right on the money now. Mid-turn as I increase speed the rear complains first then the front, then it goes 4 wheel drift. When want to tighten up the turn I just lift slightly on the throttle and the fronts grab better and it rotates without losing the 4 wheel drift. Add throttle back to make turn radius bigger while still in 4 wheel drift. Before it was understeering and I had to lift almost violently to get rotation and the rotation came from the rear getting light and letting go instead of front gripping a little and tucking in. We'll see how it does Sunday at the races!