need some alignment help

[Shaun 69 E]

Just got my barn find 73T inspected, ride height set and new tires on the car. Ready for an alignment and tons of fun this summer. This morning I took it to the local Firestone who I've used for a lot for other cars, armed with Wayne's 101 book with the alignment project bookmarked and my 84+ Carrera Bentley manual. We talked about the books, the suspension (all newly rehabed), their Hunter machine has the specs, and I left feeling like it was in good hands.

got it back 2 hours later and have driven around for the past few hours having a great time, but I think the specs can be much better. Here's what they did:

Front
Camber: -.8 and -.9
Caster: 6.7 and 6.1 (they wrote: caster is not adjustable on the measurement printout)
Toe: .15 and .13


Rear
Camber: -.4 and -.6
Toe: .1 and .07

Here's what the car has:
19/26 bars
front 205/55 SO3's on 7x15 cookie cutters
Rear 225/50 SO3's on 7x15 cookie cutters

Ride height:
LF: 24.5
LR: 24

RF: 24.5
RR: 24

The rear quarter fenderwell lips are ground down and rolled over. The right rear I have contact/scuffing on accelerating through a left turn and in/out of drive inclines. the left is fine.

the right rear tire does look like it's coming out of the well more than the left.

So here's the net-net: other than the tire contact, the car drives great. Really solid, very planted, especially given the new tires and it's cold today. No, I didn't push it, but it just felt right. I got the "alignment for a lifetime" deal so I can keep bringing it back until they get it right. The Firestone guys were eager to please and if I bring them back specs, they'll set the car up.

What specs should I give them? What do I tell them about the front caster?

here's the car




here's their printout

[joetiii]

Shaun,

I tried to get more aggressive alignment in my car last year. At Chuck Morelands recommendation I tried:

F Camber 1 neg

F Toe 1/6inch toe in per side

F Castor 6.5 degrees positive

R Camber 1.75 neg

R Toe 0 degrees

The most they could get in the left rear was -1 camber so I'm -1 all around. Car handles better on the autocross but I am sending it back to have the left rear eccentric drilled out out for more negative rear camber.

More negative in the rear should help fender clearance issues I think.

[Shaun 69 E]

Hey, thanks Joe. I lowered the car a little more and ended up -1.2 in the front and -1.7 in the rear. results are here:

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

it handles like it's on rails. there's an off-camber downhill, very similar to the one before the straight at Lime Rock, it's tighter but a smaller decline, that's I've been having a lot of fun on here. Sort of scary how fast this slow little car can go through it.

With the -1.7 and shaved fender wells, I'm fine with the 225s. Considering buying another pair and storing since they are becoming so scarce.

hope you've been well,

S

[304065]

For street driving I wouldn't go any more aggressive than you have at the moment. With the relatively soft 19/26 combo you will probably get a lot of body roll, particularly given the extreme steering angle changes of AX, but unless you're rolling the thing up on the door handles that much negative is a good tradeoff between improved orthogonality (I have hit my vocabulary bonus target for the day!) in the corners and braking performance, particularly if the car is also used for street driving.

Caster? As much as you can get, just make it the same side-to-side.

I can tell you have AX on the brain. . . for years my Carrera never had carpets on the drivers side . . .

[Tom F.]

Shaun,

What Joe said. I would add that I wouldn't go much lower. I had problems with hitting bump stops at 23-5/8 on the rear ride height. I was running 26 mm rear torsion bars, too.

I got rid of the 26 mm. I didn't like the 19/26 combination, but you should probably experiment, see what you like. I went with 19/24.1 in my 71 with a 3.0 engine. I have 16/18 sway bars, which I definitely like.

Will we see you at Devens this summer?

Tom

[Flieger]

How does one know when one is hitting the bump stops? I have stock 19/23mm solid torsion bars (Weltmeister 22mm anti-sway bars) and many people tell me "you must be hitting the bump stops alot". The ride is somewhat harsh, but I thought that would be due to the old rubber bushings. The car weighs about 2000 pounds without a driver. Is there a way to diagnose bump stops coming into play?

[911pcars]

How does one know when one is hitting the bump stops? I have stock 19/23mm solid torsion bars (Weltmeister 22mm anti-sway bars) and many people tell me "you must be hitting the bump stops alot". The ride is somewhat harsh, but I thought that would be due to the old rubber bushings. The car weighs about 2000 pounds without a driver. Is there a way to diagnose bump stops coming into play?

Your ride harshness might be due to the 22mm sway bars. Your shocks? I'd suggest 21/27 TBs or thereabouts. The heavier springs will provide more stability w/o a large increase in ride harshness.

Sherwood

[Flieger]

Thanks. I am hoping the new monoballs and A-arm bearings will help some. At least it will not squeak. The sways are probably most of the harshness but it does seem "crashy" over sharp, high frequency bumps in a straight line, when the sways are not working. New torsion bars are not in the budget for this suspension project. Those will have to wait.

I do not think I am hitting bump stops so I guess if it feels alright, why worry?

[Tom F.]

How does one know when one is hitting the bump stops? I have stock 19/23mm solid torsion bars (Weltmeister 22mm anti-sway bars) and many people tell me "you must be hitting the bump stops alot". The ride is somewhat harsh, but I thought that would be due to the old rubber bushings. The car weighs about 2000 pounds without a driver. Is there a way to diagnose bump stops coming into play?

You're right. I should have said that "I believe that I was hitting the bump stops." I say this because the handling of my car would change abruptly. I judged (and sensed) that this was happening because I was running out of suspension travel, but I don't have measuring devices on my car to tell me when I'm hitting the bump stops. The problem was noticeable in turns. Of course, it could have just been bad driving on my part. I believe that a lot of what we amateurs struggle with is finding suspension setups that make us feel more confident about our driving, subjectively. These are not necessarily the best suspension settings to go the fastest.

If you look on Rennlist and Pelican, you will find lots of excellent advice from the pros (Steve Weiner, Peter Zimmermann, John Walker, and probably some others that I don't recall now) about how to set up your 911 for better handling. It's worth spending some time searching and reading what they have to say.

[Flieger]

If I do the zip tie trick to measure suspension travel, what kind of measurement can I do to find out if the bump stop is coming into play? Maybe measure from the zip tie to the spindle collar and see if it is more than a minimum?