I will re-check my height at lunch today, as the numbers I quoted I pulled from my foggy memory from about 6 months ago.

Tim,

There is nothing wrong with the car's attitude or aero package ...

The toe sounds too little in the rear, and marginal -- maybe not enough in front.

The tires may be a problem, too! Have you used those tires on other vehicles and found them satisfactory at high speed?

Warren, I have not used these tires on any of my other cars. My front wheels are set at 1/16 toe-in each or 1/8 total measured at the wheel extremeties. What would you recommend?

Just did a quick check and ride height measures 24.5" rear and 25.125" up front with these 205/55/16 frt and 225/50/16 rears.

From my research, the difference between front and rear bumper measurements should be 0.50 inches, but more accurate measurement methods are available, taking more time to do.

Here's what I'd suggest you do. Buy the Bump steer reduction spacer kit from out hosts, it's just a bit less than $15.00 plus shipping. Installation is very easy, I have one on my car.

After you've installed those parts, take your car in for a first class alignment on a machine that uses laser guidance and can align both front and rear suspensions; both to the car and to each other. I don't know what this costs in your area, but it's still not horrendously expensive. I think the improvement in handling at all speeds will be impressive.

Later, get and install new shocks all around, in my opinion you should install Bilstein Sports at all four corners with your lowered ride height.

Tim,

The front toe-in is probably OK, and I like 3/16" toe-in at the rear. You basically want to assure that the rear tires can NEVER get into a toe-out situation at high speed when the rear end can be jumping around and squatting at 2" - 3" of deflection, or more due to road dips, bumps, 'yumps,' and other imperfections that are magnified at 125+ mph.

I think the next step is a full corner balance and align.

My heights were measured from the ground to the fender arch. There are no local shops with 911 alignment experience as I mentioned earlier. If my steering geometry check shows that I have issues I will make up a couple of spacers on the lathe and install in between the rack and the cross member.

Tim,

I just did a self alignment and corner balance 2 weeks ago. I also replaced spring plate bushings, FR/RR sway bar bushings, ball joints, turbo tie rods, bump steer kit and lowered the car to slightly below euro. I would recommend the bump steer kit. I have zero bump steer now. I had bump steer at US ride height with stock tie rods. (I'm not saying that's whats messing up your handling.)

I haven't tested at high speed yet, I've only managed 80 so far, but the car handles great.

I used bentley's specs of:
Front Toe: +15'+/- 5' - ( I set .25* total toe)
Front camber: 0* +/- 10' - ( I got 0*)
Caster 6*5' +/- 15' (I got 6* LF and 5*50' RF)
Rear Toe: +10'+/- 10' (I set 0 on both sides.)
Rear camber: -1*+/- 10' (I set both to -1*)

I went conservative to reduce tire wear. I just bought S0-3s and don't want to replace them for a few years.

Do you have a way to check caster? My caster was only set at about 5* before I adjusted it. As I understand it, caster controls "on center" feel. Many of the home alignement threads suggest setting caster to the middle of the range, but I had to go to the extreme to get into spec. Middle would have been about 4.5*.

Might be worth a look.

Good luck!

You'll need bolts longer by the thickness of the spacers you make. I think the Weltmeister spacers are 10mm thick, the bolts should be 10.9 grade IIRC.

On a car lowered as much as yours has been, unless it's a european model, the tie rod angularity needs to be reduced, no question.

Pat, if I need longer bolts, not a problem as I can have next day at work thru several vendors.


Never checked caster, only camber and toe.



Thanks a bunch guys for all the input!

Re: 1st high speed SC run = disgust
 

Good call.

Car will do 150 in that set up easy enough....well maybe not because of lack of HP in a SC but the aero package sure will.

Porsche spent a lot of time to get the cars to handle well at speed. C/B, ride height and a few other little things make a BIG difference.

But speed is something you need to get accustomed to. Better done on a track than on a country road as well. Easier to get a feel for the car at speed there. 130 is easy. But if you have never driven past 120 you aren't going to know how the car is suppose to feel.

10 mph does make a difference in feel. I found a signifigant difference between 120 and 130 and then again between 130 and 150 in my car even with better aero packages.

No disrespect intended just something to think about. The SC isn't going to be a "fast" car by today's standards. Factory listed them as 126 top end. If your's hit 130 you were doing well.

Rdane, I do not have alot of high speed experience over 100, but I have seen 135 indicated in my 951 and it felt stable as does about 120 in my 325i until the speed limiter shut it down (which was scary as I thought I had just blown something). Point taken on wreckless street driving. Most of my cars have all received a high speed test at least once while I owned them after getting somewhat sorted out first. I live in a rural farm community with long stretches of open road w/ perfect uncluttered visibility of surrounding areas. I normally do not exceed 85 on these back roads and once I reach civilization, I seldom drive 10mph over posted speed.

My SC was still accelerating (slowly) at this speed. The engine is stock except for Sport SC cams and modified to dual outlet exhaust.

Tim, I saw you fly so I figured you were use to "flying" The 951 is a modern car in comparison to our SCs. That is what the local 951 crowd tells m anyway. 140 isn't a big deal for a good 951.

Brian, I was pulling that figure from "THE ORIGINAL 911" by Morgan and his performance spec sheet on all the cars. CAR and DRIVER said 130 in their 1980 road test on the '80 SC.

I think the turbo tail and front lip were an option on the SC's.

Carrera tail and front lip were an option. The turbo tail has a much wider rubber edge that is also curved.
Plus the turbo tails (and this has no aerodynamic implication) has a wider base that allows the use of an intercooler.

Check the differences in the pictures;

http://forums.pelicanparts.com/uploa...1119464055.jpg


http://forums.pelicanparts.com/uploa...1119464157.jpg

Kinda funny Matteo, When I looked at those two cars you just posted, I thought to myself those are some nice looking cars and the bottom one even looks like mine, then I realized the bottom one was a repost of the photo I took this morning! Doh!!! I think I have been at work too long today!

FWIW,

I'd take your wheels into a shop that uses the Hunter GSP9700 dynamic wheel balancer. Not to sound like a commercial, but this machine is unbelievable.

Their site also has a shop finder so you can find the closest unit.

http://www.gsp9700.com/

I couldn't believe how solid my car felt after they balanced my wheels/tires.

sounds like you're going in a straight line. That's your problem. Find some curves...

Road & Track corrected themselves some years later. The actual top speed should have been listed as 136 MPH. They were able to get an 81 SC to 138 MPH. Incidently, my owner's manual lists 139 MPH.

Check the tire pressures. Also the tires can cause that. That happened to me with a pair of Dunlop tires that I brought. I feel that the rubber compund was really soft compared to the old Dunlop tires. Same brand, size, model and style. Because of that, thank God that I did not crash the car in the highway. I change the tires the next day with Pirelli and no more problems until today.