XrussianX

Hey guys I was reading thru a few threads on suspension options and it seems like there's quite a bit of them. So my plan is to have a car that feels responsive, has limited body roll but also don't want to be bouncing around thru the streets. And id like a lowered stance. What would u suggest? I'm having trouble understanding the struts thing in the rear, does the rear have no springs? I'd like to budget $1.5-$2k

Dougs951S

Have you never had your car up on jack stands/lift and had a look underneath? The rear of the car does not have struts, it has torsion bars that act like springs and it has gas filled shock absorbers. The front is very standard mcphearson strut setup. What year is your car? If you're looking for a good street setup, do the koni cut-a-strut mod and look at paragon's adjustable ride height kit with something like 300 lb springs, and for the rear I would get a set of bilsteins and have them cut for a circlip, turn them into coilovers with springs in the 450 lb/in range, then run those with racers edge rear shock mounts and do the torsion bar delete. I'd also invest in some thick sway bars if you dont already have them, 951 M030 bars can be gotten fairly cheap. You'll want sway bar braces as well. Finally make sure all your bushings are in good shape. You could easily get all that done for under your budget.

Adjustable ride height: http://www.paragon-products.com/Coil...rhk-nr-xdo.htm
These are the inserts to use with the cut-a-strut rebuild: http://www.paragon-products.com/Koni...-1414s-xdo.htm

rear coilovers: https://rennlist.com/forums/924-931-...-coilover.html

XrussianX

I got the car a few days ago so I haven't had a chance to see under her. I like a really aggressive stance and the streets around my area are very good so scraping won't be a problem. I'm just doing some research before I start buying stuff lol. The car will be 90% street driven but I do enjoy a stiffer ride, I'm 28 so I can still take it. I definitely don't want to change/add things that I wouldn't need to. Thanks

User 52121

You will find lots of opinions. IMO just spend a couple weeks searching and reading. The PO to my car installed the Bilstein "Cup" kit, 450lb springs up front, 350's out back with the stock torsion bars. It's stiff but not unbearable and I'm happy with how it handles. If I were to do it over again, I'd have a tough time not considering the kit that Dougs951S references. I have yet to see someone complain about that route.

Dougs951S

If you want a really trick setup, go with the bilstein rear coilovers I mentioned earlier but instead of cutting your front struts and installing koni sport inserts, get a hold of a pair of EARLY N/A struts. For a street car, these can be slightly modified on the flange where they bolt to the spindle so that they mate to the turbo spindles. You will need a small grinder and some spacers. Then, you can have bolt in coilovers with bilstein inserts in the front, and they can be rebuilt simply be removing the screw cap and dropping in a new insert. Best of both worlds in my opinion.


Jim, are you really running 350# springs in the rear with that high of a front rate? Does your car understeer? I was looking at spring rates for rear coilovers just yesterday and I decided a good rate to match my 300# fronts would be to put the stock T bars back in and run 325# rear springs. I would have thought your car would like rear rates more in the 525-550 lb/in range and that your use of the car would leave you desiring a bit of oversteer, but im no suspension expert. Does your car see much street driving? I'm wanting to go stiffer up front but its my DD and I dont want to have to wear a mouthpiece. I was thinking 375F/425R with stock T bars would be a nice compromise.

XrussianX

Thanks for all the advice. I was looking at the Koni full coilover kit front and back for $1400 but another guy said the Koni shocks won't last long and I should go with blisten. The blistens are $600 more. But if they are that good then I'll bite the bullet and go for it. I hate when I sting and buy the cheaper stuff and then wish I spent a bit more. So if I wanna do full coils and delete the torsions, what spring rates u recommend front and rear for a street semi track setup? Also if my car has sways is it worth getting bigger ones?

User 52121

Hey Doug,

Sorry for bumping an old thread - I actually stumbled back here doing a search for my own spring rates (I knew I posted them here and don't have my notes handy). I don't think I noticed your reply before.

I imagine you've gotten your stuff sorted out but I'll comment anyways.

I agree, it seems like, compared to others here, the 450s seem stiff in the front. My car has some funny handling issues that I'm trying to work out now, and maybe spring rate has something to do with it.

The rates weren't chosen by me - they were chosen by the PO, or, probably more accurately, they were chosen by a local Porsche specialist (they do a LOT of race cars - Midwest Eurosport) for him, and he was using the car exclusively for DE. So I have to imagine they were chosen for a reason.

When I got the car, it had those springs, an open rear diff, and Welt bars set full-soft up front and full-stiff out back.

With this setup, I only autocrossed the car, and it was perfect. Lots of grip in the front, and if I needed more, a quick lift of the throttle was perfect. Under power it tracked right where I wanted it to - but it did light up the inside rear tire if I got on it too soon.

Then I added a limited slip (torque-biasing Guard unit) and the car became VERY tail-happy under power. I softened the rear bar (from full stiff to just shy of halfway) and that made it IMO perfect again - but now with traction in the rear under power.

Then I started DE'ing the car. Car felt pretty good, but if I had a complaint, it was long sweeping turns at maintenance throttle (like, say, the carousel at Road America). It felt like it wanted to understeer if I pushed it hard. At the time I was only running ~2 degrees of camber in the front though, and talking to another, different, local specialist (Fischer Motorsports) he suggested adding more camber. We went to 2.5 (the max I can do without camber plates) and it seemed to help a little. Still not ideal, but it was better. I figured I just needed more camber.

THEN I did a session with David Murry. I'd been doing things like a good little DE student - namely, braking 100% in a straight line. His suggestion was to start trying trail braking - and that's when things went wrong. ANY wheel input on the brakes resulted in the car wanting to spin.

I started playing with the bars again. I stiffened the front bar a bit, to around 25%. That helped, a little. The car didn't want to spin INSTANTLY. Still very twitchy feeling but an improvement. So I went some more - I set the front and rear bars both right in the middle. So I stiffened the front another 25% and softened the rear a tiny smidge to get it in the middle.

Now it handles goofy. :/

Trail braking is ok. But off throttle or maintenance throttle, it understeers. Bad. Get into the throttle, and it starts to tighten up but still leans towards understeer - unless I hit the power just right, then the rear will start to move around. (More like low speed sharp turns where you get the boost "hit" while unwinding the wheel).

So... that's where I'm at. I don't know if it's a spring issue, an alignment issue... *shrug* I also have a rear shock that's got a little bit of slime around the top of the shock, so it's due to be rebuilt or replaced as it seems a seal is starting to leak. I think my plan is to have the shocks in the back redone, then have one of the local specialists just give it a full "once over" with setup. Set the bars, re-align it, do a corner balance, give me their thoughts on current spring rates, etc.

LUCKY DAVE

From the sound of it, you're adding band-aids (bar settings) to address unbalanced spring rates.
Get camber plates asap, these cars need ~4 degrees front, 3 rear as a starting point, then look at tire temperature distribution, tire wear patterns, and track pics of the car under cornering load to fine adjust.
You didn't say anything about tire pressures, they make a lot of difference too. 2 psi can be the difference from hero-to-zero. Ask some local hot shoes that run your track for inflation suggestions.

User 52121

Thanks.

From the photos I have - the car stays relatively flat (side-side) but does generate some squat under power.

Tire pressures - I've tried to just keep that constant, so I know whether or not the bar changes helped or hurt. I only run street tires (Yokohama Neova AD-08), and I aim to stay at 36psi hot all the way around.

I actually have a set of camber plates sitting on the bench in the garage. I know I'm giving up some by not running super aggressive camber. Those will also probably go in this winter. They appear to be a no-name plate, got them for a steal of a price off a friend of mine here who had them kicking around his basement. I noticed that, pretty much every other plate on the market has 4 bolts to lock the adjustment down (2 on each side of the bearing) - these only have 2 (one on each side). Not sure how common it is to have the adjustment move around... but it's given me pause and I haven't installed them yet (well that, and the fact that I also drive the car on the street, and running around with 3+ degrees is going to cook my tires in short order...) I'll probably spur up a separate thread to get opinions on the plates before I install them.

But even without installing the plates - I want to get the balance back in the car.

For comparison - my Lemons car. '86 944, base car. Stock springs up front, original TB's out back. Front shocks may be original, not sure - but they're nothing special. They work. Rear shocks were shot, so we replaced them with Autozone specials. We added 944 Turbo sway bars (not M030). And the car handles AWESOME. The balance is perfect. I didn't realize it until I drove it, and my Turbo, back to back at a DE a few months ago. I want my Turbo to handle like the Lemons car. Overall balance leans, very slightly, towards oversteer. Good bite up front on turn in, can trail brake nice and deep. Come in way too hot (to where it starts to plow) on entry - lift the throttle, nose bites. Carry a lot of speed and the tail gets light - add throttle... rear of the car "sits down" and bites. Makes it easy to grab the car by the scruff and throw it around. On a short ~1.9mi track (Blackhawk Farms) I was only 2s off the Turbo pace in the Lemons car.

Trying to get my car back to this level of balance.

LUCKY DAVE

Jim, your description of the car's behavior (I just read it again carefully) sounds like not enough spring rate in the rear, and long, soft springs with a lot of preload (the stock tb setup in other words). Squat under drivetrain load unloads the front making the car run wide, (trying to wheelie) excessive rear suspension extension under braking makes the rear squirrely as it unloads, and the car is unstable during constant load turns because the center of effort is moving around seemingly at random as the rear suspension strokes through more travel than the front - changing alignment in the process.
Does this sound about right?
If so, FIRST address the rear spring rate, (or soften the front) to get back the balance and get your shocks valved to match the spring rates. Alignment and bar settings are fine tuning, you'll never get it to work right if the spring rate is off in the first place.

User 52121

For the most part, yes. I don't think I'd describe the car as "unstable" in constant state turns. It just runs out of front grip. Another way to describe it - I don't think I could spin my car in the carousel at RA unless I really, really, tried hard to do it. It would more likely just plow off to the outside. (By comparison, my Lemons car feels neutral/balanced, with either both ends of the car sliding evenly, or the rear doing a hair more slide than the front... easily correctable with some opposite lock and throttle).

Makes sense. Suspension setup for cars is still very much a mystery, though I'm learning. I was pretty good at setting up my motorcycles back in my racing days though so I understand what you're saying here - springs are the core. Get the spring rates wrong and you'll never get it to handle right. I'm just not sure how much sway bars can compensate (bikes don't have swaybars!)

Since the car was originally set up by a local shop with a good reputation for building race cars (most of the PCA Club Racing guys in the Chicago region have their cars maintained by Eurosport), I took their baseline hardware choice as "gold" and figured I could tune it out with the bars. But maybe their spring rate choice needs to be re-visited.

I very much appreciate your feedback. I will take it with me when I go talk to Eurosport about the shock rebuild on my car and see what they think about making some changes to the springs. Since I do drive the car on the street, if the choice was "stiffer rear" or "softer front" I'd probably choose the softer front. I can live with a little mushiness, as long as I get the balance back. The Lemons car practically drags the rocker panels on the ground in hard turns - but it's very easy to drive it at the limit. I'm ultimately just trying to have fun in the Turbo, not win races... so balance and easy-to-drive is more important.

Though I guess, if I'm going to have the rear shocks rebuilt - I can have them re-valved for stiffer springs at the same time (vs. paying extra to have the fronts re-valved for the softer springs...) Hmmm.

jmj951

This is one way to keep other things constant while trying to focus on sway bars, but it's not the order I would take. Tire pressures and camber need to be optimized for each setup you try, or you'll never really know if you hit the right setup.

Tire pressure should be optimized for each course you visit, for each setup change you make. You need a tire pyrometer (preferably with a metal probe) to measure the temperature across each of the four tires immediately following each run. You'll then follow an iterative process of adjusting pressure and camber (and if available, downforce to balance front vs rear temps) to optimize the setup such that you have approximately a ten degree delta from the outer edge to the inner edge of each tire (increasing towards the inner edge), and if possible depending on the course, a fairly even temp between all the tires. The 944 can reach a very impressive balance. If you want to be really scientific about it, start each run with the same amount of fuel (assuming all the run durations are equal) to ensure the fuel load change throughout the day doesn't skew the results.

LUCKY DAVE

In that case think of your car as having a 1.0 kg spring and gold valves with a stiff washer stack in the Ohlins forks, and a Honda Trail 90 setup in back.
A little unbalanced.....

User 52121

Ummm ok that's getting a little extreme.

450s up front with 350s+TB's out back isn't going to be THAT far off

LUCKY DAVE

Oh yeah,...just having a laugh or two.....