Noahs944

Greetings,
I'm contemplating raising Wilson's suspension (late 944) to gain more ground clearance and get a bit more suspension travel for TSD rallies on country back roads. I won't be flying in the air.
I'd like to do this the most practical way, and in a "reversible" way.
The intended ride height is around 1" above North American standard.
I may or may not increase tire diameter.
Wondering about suggestions you may have.
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The car sits 1.5" lower than oem presently. The following parts are being used presently in the lowered car & in excellent condition and is about the right spring rate for me:
SP250 progressive front springs
28 solid torsion bars
Blue/Yellow Bilstein HD struts/shocks
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My thought are: re-index the torsion bars (because I hate myself LOL) & replace the short front springs with longer springs. I considered the spacers to reset the ride height to oem from Paragon, but think I'd loose out on suspension travel compared to longer springs. Is this correct thinking?

Noahs944

I will update if I make these changes but basically settled my mind on longer 250 lb coils (Hypercoil or Ground Control might be good sources) and probably run without sway bars, at least some of the time. I noticed the car (as it is now, doesn't need f&r sways for any of the driving I have done... but I'm sure autocrossing or track days would change that).

thomasmryan

looking for extra clearance or suppleness? I would go back to stock height and see how it handles the terrain.

(I take my old S class down some crazy logging trails aired down to 25psi but not at a fast pace.)

V2Rocket

tarmac rally or dirt/gravel?
i would think spring rate might vary based on surface (grip)

RoyaleWithCheese

I have been doing rallycross in my car for about a year now on stock suspension and the sway bars removed. Apparently rallycross favors softer suspension, which shows during practice when it's a mix of cars and I'm running competitive times to a couple of the stage-rally prepped awd cars.

This past fall I took the car out to do some stage rally practice and it was immediately apparent that the stock suspension was nowhere close to being up to the task. The original rear bump stops pretty much disintegrated and the crossmember and chassis of the car would dig in hard on any dip in the road or after coming over a crest. An extra inch of clearance may have helped a bit but at the speeds I was going the suspension really needs an overhaul.

So from what I've learned, if it's tight and technical driving you will be doing (0-35mph) you will be fine with factory rate springs and raising it an inch would help reduce bottoming out. If you want to go faster than that I would increase the spring rate a fair bit, get properly valved shocks, make sure you have good bump stops, and add some serious skid plates to smooth the bottom out so it doesn't drag if it does hit the ground. It seems counter-intuitive to run stiff springs on an off-road car but when travelling at high speeds over bumps there is a massive amount of force that the suspension has to resist. I remember reading an interview of a monster-truck driver that said at slow speeds you could feel if the truck ran over a penny, the suspension is so stiff, but it feels soft as can be landing from 20ft in the air.

Noahs944

V2: Dirt/gravel mostly. I love love love my current SP250 / 28mm TB for tarmac, but the car is too low.
Royale w cheese: Exactly my experience. Even with sway bar removed & brand new SACHS then BILSTEIN, the stock susp bottoms out too quickly. Sucks!!!

Noahs944

At slower speeds the stock set up is fine, but once the car gets loaded with gear & navigator, 2 spare wheels it becomes inadequate.

Per vers

A set of bilstein b6 (The long/std. model). And a set of std. hight 968 front springs. Could do the job, maybe ;-)

Van

I've given this some thought - and I wonder if it's possible to modify the front sub frame to relocate the control arm pivots down 2 inches, and then make 2" spacer blocks for the caster mounts. Then see if you can modify the strut housing to take a longer-travel shock, maybe something by Fox, to get extra travel. Pair that with a 175lb spring?

For the rear, getting extra travel will be a challenge, because the lower torsion bar carrier end-cap bolt with the spacer limits the droop travel. I'm wondering how much extra travel you can get by removing just the spacer (or possibly even the bolt?) Of course the torsion bars will need to be re-indexed, but that's not too hard (what's the smallest diameter torsion bars? Base 944? Are 924 ones any smaller?) And, again, I think you'll need a longer travel shock. The thing I worry most about is how much downward travel you can get without over-extending the CV joints. I think one will just have to play around with it a bit and figure it out. (Although I just had an idea... you might be able to make custom offset-hole torsion bar carrier mounts to move the whole assembly down - this will give you space to lower the transmission an inch or so (it'll tilt the engine and torque tube a little, but I wouldn't be concerned) - to reduce the extension of the CV joints.)

Noahs944

Van, I'm loving your ideas here and starting to do some design brainstorming.
TBs: what would you estimate the maximum ride height to be possible by simply re-indexing?
Also, are stock front springs considered 2.5"? How do we measure coil spring size?
THANKS!

Van

With oversized tires, I think you can re-index the rear torsion bars to get 8" of ground clearance.

The stock springs are way over 2.5" ID - they're probably 5 or 6 inches. What you want is like a ground control coilover set for the front struts - it'll have a perch and a threaded collar, and it'll have a top-hat to match. Aftermarket springs are measured in 3 ways: the ID (inner diameter), 944s use either 2.25" or 2.5"; free length, for racing we usually use 8", but I imagine that for your purpose, because you'll have more shock travel, you'll want a 10" or 12" spring; and a rate, this is measured in lbs/in (meaning it takes a certain amount of weight to compress the spring 1" - if it takes 250 lbs to compress 1", it takes 500 lbs to compress 2", etc.).

Springs also have a max compressed length - meaning how short they can compress before the coils touch. I'm sure there's a lot of suspension math you can do, but I'd say that, for your application, you wan the spring to be able to hold at least 2x, maybe 3x, of the car's corner weight at max compression - meaning you land from a jump, you don't want the spring to bottom out. Do be aware of the motion ratio, too - because of the leverage and angle of the strut, the wheel rate is only about 90% of the wheel rate. So, if the corner weight of the car is 750 lbs, 2x that is 1500 lbs. Looking at the Eibach spec chart, a 1000.250.0275 (10" long, 2.5" ID, 275 lb/in) has a 6.23" travel at 1715 lbs. If you go up to a 12" long spring, you get about 7.5" travel out of a 225 lb/in spring (meaning the lighter spring compresses more distance. Can you go even more? I don't know... Go 14" long and now you can get 9.3" inches of travel from 200 lb/in.

For offroad, generally you want as soft as you can go. (But, again, you want to match to your torsion bar rate...)

Noahs944

Man you are smart. Thank you!!

V2Rocket

Van - years ago I recall seeing VW offroaders notching their spring plates to clear that bolt for more clearance.
some would also plate the spring plate with extra sheetmetal on either side to compensate for any lost strength.

the V8 swap kits as you know tend to use a x-member spacer and redrill the control arm mounts to compensate.
you could space the x-member down with strut spacers too but at some point you'll also need a longer steering shaft.

have always wanted to raise my car an inch or so to make it offroad friendly, will watch this thread.

Noahs944

...longer steering shaft. Yeah I was thinking of that. I noticed the steering slip yoke is in the cab, so easy enough to marking "before" the lift & take notice of the extended length. So far, have yet to read about modes on the steer shaft on 911 safari builds.

V2Rocket

Borgeson makes all the parts required for a longer steering shaft if needed.