Ride Height Decision

[Superman]

I need to make a final decision on ride height. I need to hear from people who actually know. Steve W., Grady C. and Bill V. come to mind, along with others. I am not particularly afraid of bump-steer, but am told I might run out of suspension travel if I go too low.

Car is a '78 SC that I think will tip the scales at about 2400 lbs. 22/29 torsion bars. Late Carrera sways. Fresh Bilstein heavy-duties (cannot afford the right shocks right now). Steering rack spacers. Elephant front bushings, Neatrix rear.

Everything has been assembled and ride height has been temporarily set at 24.0 rear and 24.5 front. Do I settle on this ride height.......or must I increase height another half-inch? Or inch? Or quarter-inch?

[berettafan]

have 22/28 on my '70 and i would suggest you'd have a hard time running out of suspension travel with such a setup.

[Superman]

Originally Posted by berettafan

have 22/28 on my '70 and i would suggest you'd have a hard time running out of suspension travel with such a setup.

I'm not afraid. But I've been told by a reliable expert that 24/24.5 may be too low. Because of lack of suspension travel.

[berettafan]

i would think you'd need to know t-bar info to make that statement. UNLESS the issue is roll center which i understand to be a geometry issue.

[Superman]

I mentioned torsion bars. 22/29. This expert knows what I have. And he seems to think 24" is too low.

[175K911]

FWIW, I'm about the same ride height as you but I've got 23/33 torsions, custom valved Bilsteins with front rods shortened 19mm, weigh just under 2500 lbs. 99% a track car. I can drive it on the street, but this ride height is purely track based, and I'm a whole lot stiffer than you. Before I had the front Bilsteins revalved and rods shortened, I could bounce the car off the internal bump stops on hard bumps in the road, and that's with a 23mm front bar.

I can't imagine you aren't bottoming the shocks up front on a regular basis. If it was me, I'd go up half to three quarters of an inch. But that's just me.

[Vipergrün]

I assume you have cut down the rubber bump stops in the shocks and removed the 10mm spacer at the top of the struts?

[David]

I'd go up a 1/2"

[Paulporsche]

What size wheels and tires do you have?

[sbrown.nw]

Here is what Byron at Tru-line in Bellevue, WA (known local suspension setup expert) set the ride height at after a 4 wheel align, height and corner balance (pre-loaded with driver's weight in car)

front: 24 5/8
rear: 24 1/4



I am running the following tire and rim setup:

17x7.5 - 215/45R17 - 34lbs tire pressure
17x9 - 245/40R17 - 40lbs tire pressure

Car is about 2600lbs with 2/3 tank (no driver). Non-HD shocks and factory tbars.

Scott

[RWebb]

set it a tad high then see how many gas stn. driveways & parking barriers you hit

re-evaluate from there...

[blk911]

Superman,

Another thing to consider is that you lose castor when lowering. I think below about 24.5" in front, you will notice the steering a bit more twitchy. Turn it is great, but very sensitive to steering input. Driving straight line makes you pay more attention or you are changing directions. Not always confidence inspiring.

[stlrj]

Originally Posted by blk911

Superman,

Another thing to consider is that you lose castor when lowering. I think below about 24.5" in front, you will notice the steering a bit more twitchy. Turn it is great, but very sensitive to steering input. Driving straight line makes you pay more attention or you are changing directions. Not always confidence inspiring.

Castor would not change but the additional negative camber would make it twitchy and steer heavy.

[Bill Verburg]

the ride height is fine w/ the bigger t-bars(as long as the tires are clear), bump steer is the concern, you may(likely do) need a tie rod end bumpsteer kit as sold by Elephant & Smart Racing

for street /track 0 pressed toe is good for A/X they run some toe out but this makes the car darty, max castor and camber(unless you use camber plates in which case ~-1.5 - 2* is usually good, rear 0 toe and -1.5 -2* camber is good

[Superman]

I raised the car last night from 24.0 (rear) to 24.5. Now it sounds like I could lower it a tad bit. Perhaps 24.25.

But I have more questions:

What is "pressed" toe?

Camber plates? I may go head and run a tad bit of toe-in in the front, to help control some of that dartyness problem. This will be mostly a street car.

What effect does rear toe have on handling. I'd guess that rear toe out would make the car oversteer more. But I don't know. I have a suspicion that our rear suspensions toe out a bit when the suspension is compressed. Is that a correct guess?

[RWebb]

means w/ wt. on it

[86 911 Targa]

Our stock '86,

25 1/4 Rear

25 7/8 Front

Car looks great, no issues.

Work performed by Johnsons Alignment
in Torrance, CA

[Bill Verburg]

Originally Posted by Superman

I raised the car last night from 24.0 (rear) to 24.5. Now it sounds like I could lower it a tad bit. Perhaps 24.25.

But I have more questions:

What is "pressed" toe?

Camber plates? I may go head and run a tad bit of toe-in in the front, to help control some of that dartyness problem. This will be mostly a street car.

What effect does rear toe have on handling. I'd guess that rear toe out would make the car oversteer more. But I don't know. I have a suspicion that our rear suspensions toe out a bit when the suspension is compressed. Is that a correct guess?

pressed toe - an adjustable rod is used to press the leading edge of the tires apart, simulating what happens on the road. the amount of force is speced @ 15kp(~33lbs)

toe out promotes dartiness, toe in quashs it. 0 pressed is good though for a/x you might want some toe out to promote dartyness

rear toe works just like front most street cars will have a small amount of toe in, toe out promotes dartiness in back, toe in quashes it. 0 is good but again for a/x you may want a small amount of dartiness. The Weissach effect used from 928 &964 up selectively promotes toe out on one side and toe in on the other, steering the rear thru a corner.

yes, toe out in back promotes oversteer and toe does change w/ suspension excursion. But w/ a stiff suppension change is limited, all you can do is set the static #s and live w/ the dynamic ones