Ride height - Bad geometry?

[tfg50]

new to me 1982 SC.
checking rear ride height and my calcs TB center less WB center leave me with a negative number. That is, my height of the center of the wheel is higher than to center of the torsion bar. Do I need to re-index torsion bar?

[Joe Bob]

Depends on the height to the underside of the lip.

A good benchmark is an alignment and corner balance.

[tfg50]

25" from ground through center of wheel to wheel well lip

[Joe Bob]

Take a look at this thread. Zimmerman is the guru.

911 sc lowered ride height pics & measurements please

[JAR0023]

Originally Posted by tfg50

25" from ground through center of wheel to wheel well lip

That's the ballpark where a ton of "low" cars around here are sitting. Euro height tends to fluctuate based on which expert is posting but you're in definitely in the ballpark. 25" rear/25.5" front give or take. Corner weights are more important that perfect symmetry. Leave it alone and drive it like you stole it. -J

[JAR0023]

BTW, welcome aboard. Nice ride. I dig the blue, but I'm kind of partial. At least now I know what my car might look like if I washed it and added RSR'd Fuchs.

Here's 24.5" rear and 25" front for reference. -J

[stlrj]

Originally Posted by tfg50

Do I need to re-index torsion bar?

The rear bars only need re-indexing if you want to raise it back up to factory European (ROW) specs. for optimum factory geometry.

[gduke2010]

Originally Posted by tfg50

new to me 1982 SC.
checking rear ride height and my calcs TB center less WB center leave me with a negative number. That is, my height of the center of the wheel is higher than to center of the torsion bar. Do I need to re-index torsion bar?

Look at Project 55 Lowering The 911 in Wayne's book 101 Projects for Your Porsche. For an SC the European ride hight should be 16 mm for thr rear and 108 mm for the front. See projec 64 for re-indexing the spline.

I think according to Wayne's book you'd have to re-index the rear torsion bars. Minne is just slightly below Euro ride hight. The previous owner had the car sitting to low and I had to raise it innorder to correct a bump-steer issue on my car.

It's important that you put your car on the scales after adjusting hight. That will make a world of difference. Mine drove like a truck before I had it cornerbalanced and aligned,.

Gary

[javadog]

The answer to your question has three parts.

Do you want to raise the car to the correct height? Correct as in the spec book, not the universal accepted opinion of "correct" which is much lower...

You have adjustable spring plates on that car. They allow a certain range of adjustment before you have to re-index the bars. Since we don't know how they are adjusted at this moment we don't know how much the car can be raised using that adjustment, and we have no idea exactly how low you are, so we can't say one way or the other if you have to readjust the bars.

What you can do is raise the car until you either run out of adjustment or reach the ride height you want. If that adjustment is not enough, then you can either live with a lower ride height or pull the bars and re-index them.

JR

[KTL]

Fender heights may give you the look you desire but it'll make for a poor handling car. On the street, no big deal. If you take your car to the occasional track day, and like to compare laps/times with your friends, you'll be driving a crappy handling car.

Couple of things worth noting IMO

1. Fender lip heights same side to side invite imbalance. My constant fiddling with heights ended up with a car that had a VERY light right rear corner and I could spin the right rear way too easily on corner exit. You are wise to corner-weight it after setting your heights.

2. Front of the 911 is VERY sensitive to height adjustment. If you decide you want to change your front height after your car is aligned, you just screwed up your toe bigtime. Toe will be way out of whack. Also noteworthy is that a considerably lowered car has a lot of bumpsteer (toe change during suspension travel) and that makes for a car that you have to juggle/shuffle the steering wheel when taking fast corners.