Ken

Stiffening the front shocks is a good move, just take it in small increments. At a recent autocross, I started to mess with my Koni yellow settings. An 1/8 of a turn made the difference between a loose rear end and a nicely planted car.

smokey

It sounds as if the Konis and sway bars increased the cornering limit to a point where the spin was no longer catchable at the speed you were going. You said the car was handling well up to that point, so the suspension is probably set up right. It may just have been an uncatchable spin. It happens to the best in the world. The better your suspension and tires, the faster you go, and the more uncatchable the spins become. That's why the "both feet in" rule applies at the track, which is where you may want to test in the future. I saw three cars spin on the track in front of me this weekend at Mosport, two of them at about 100 mph. All locked up as soon as it was clear that nothing could be done, and fortunately, no damage. Just my 2 cents ....

smokey

Perry 951,
One other possibility: if the LSD is original and has 120,000 miles on it, it may now be working as an open diff because the plates are worn. Your burn-out tests seem to confirm this. If the LSD is worn out and not functioning, and your new stiff rear sway bar lifted the inside wheel more than your old sway bar, maybe the inside wheel spun, broke traction, and looped you. Have you checked whether your LSD is working within spec? If it's original and well used, it probably requires a rebuild. Loosening the rear bar will help, but without LSD, you'd still have to be careful. Of course, with LSD you'll go faster, but at the limit, both wheels will let go at the same time, so it will be even less catchable. Always a trade-off when you want to go faster. I spun my '62 Ferrari GTE into the gully off Turn 5 at Mosport in 1982 by getting on the throttle too early with no LSD, and I didn't go back to the track for 15 years . Just another 2 cents (Canadian)..

Perry 951

Other than a burnout test and tossing the wheels in the air and observing the rotation, I have not done anything specific to check the LSD. On the burnout, both patches start and end at the same point, so I don't think it slips.

... for what it's worth....

Matt

There's a good clue in your original post to at least part of the problem. You said the car seemed to squat too much, and also said you have the original torsion bars, and Koni Yellow's set to half stiff.

Those shocks are only adjustable in rebound. The compression damping is fixed, so adjusting them only changes the rebound, the rate at which the car comes back up to normal ride height after the rear suspension is compressed.

With too much rebound damping, the rear end will jack itself down and fail to come back up quickly enough. This will lessen rear supension compliance, screw up the ability of your rear tires to respond to the road surface, and generally reduce available traction. With stock torsion bars, half stiff is way too stiff.

You need to start with the shocks adjusted to full soft and take it from there. Those shocks can easily overpower the stock torsion bars. As an example, I've gone through the whole range of adjustments on my car (lighter car, but 29mm torsion bars, more than twice as stiff as stock turbo bars) and anything more than slightly over full soft is too much - the rear suspension begins to lose sensitivity.

I won't rant about the stupidity of exploring your limits on public roads (I mean your limits - the car's limits are far beyond your limits). Please save it for the DE's, when you'll have an instructor in the right seat. The simple fact that you spun and you don't know why makes it really clear that you shouldn't be hanging it out on the street.

Matt

adrial

Matt, I have been running my koni yellows at ~75% stiff on the rear of my car with no handling issues...plenty of autox to test it out too.

Matt

Adrial,

The question is, what do you have to to compare it against? How many setups have you tried, different shocks/torsion bars/springs? How many different cars have you driven or ridden in at real speed?

Coming down a highway ramp at high speed is a lot more like track driving than autox, except it is a lot more dangerous than either.

It is easy to think that a particular setup, even if it's wrong, is fine if it is what you are used to - if it doesn't bite you it'll eventually seem okay. You'll adjust your driving to its shortcomings, and it'll become comfortable to you. The only way to know differently is to try different setups under real conditions. A non-responsive suspension will seem okay until you drive one that is properly set up, then the light bulb will go on. There's no substitute for seat time and informed experimentation.

Matt

adrial

Matt,

I've done a DE at pocono on the south course, so I have a little bit of track experience. You're correct in that I do lack something to compare to. I've driven the car on koni's to 75% stifness and on the bilstein's that the PO put on the car. I dont recall noticing much of a difference between the 2, but at that point I was even less experienced than I am now.

I'm a bit tempted to take them off and crank em down before the next autox this sunday. I wish they were externally adjustable!

You are the first person I've seen in my time on Rennlist that has suggested this. Thanks for your input. (The first person I've seen that said it and left an imprint on me, anyway).

So basically you're saying the if the shock is set to be too stiff, it wont rebound quick enough and the car wont't extend fast enough after going over a bump?

Perry 951

Matt.. as I have said multiple times, I am going to AX and DE the car shortly. I have 1800 miles on a 99% mecanically new car.. so it is not broken in enough to go flog it. I'd be the 1st to admit the car has more potential than the driver right now, but, I am a pretty competent driver.

Sure.. the street is not the best place to test something, however, it was a section of road I have driven every day for the last 4 years, has pleanty of room for run off in the event of something like this, I scouted the area before the run, and PLANNED to do it at 2:30am when there was no traffic. I should not have to list my reasoning, but I want all to know this was not a spur of the moment thing.

I asked simply because suspesion setup is not my strong point. There is not a whole lot on these cars I don't know the answers to, but suspension is one.

When I have a chance to get it out in an open parking lot at an AX, I'll bring a jack and stands and have at it.

FormulaOne10

Well, I'll agree that compairison is a terrific thing. The more cars I drive at the track the better, more informed driver I become. However, remember that a car setup doesn't mean anything accept to the person behind the wheel. This concept of engineering subjectivity is especially important when discussing shock absorbers. Some of the top drivers of all time have repeatedly said that there is only so much to be done with shock absorbers and they are really a matter of preference in the end. Mark Donohue, one of the most universal drivers and engineers in racing history came to this exact conclusion. Adrial seems to have found a really good shock setup that works for him...seems fine to me. Now that's not to say he shouldn't try a few different setups up to see what he prefers. However, in the end, no setup shock setup is "wrong" if it feels right to the competent driver.

And I couldn't agree more...there is no substitute for seat time and experimentation.

Rich Sandor

I just wanted to add, when experimenting, it's really, REALLY important to try to only change ONE thing at a time, and test it to see the difference.

When you change more than one aspect of the suspension in one pit stop, you don't know exactly which change has caused the difference in handling.

For me, I went from one set of really bad tires, on 16" rims, with a very neutral street setup, to a new set of tires with a very aggressive camber alignment. And then I got 17" cups with again worn tires. It's hard to say what contributed to what handling characteristic when so many things change at once.

Matt

Think about what you're saying here - that car setup doesn't matter, only driver preference. That would mean that no one car is actally better handling that another, it all comes down to what the driver is comfortable with. In reality, chassis setup makes a huge difference in what the car is capable of. Setup affects balance, how the car handles transitions, what kind of surface the car works best on, what it does under braking, how much grip is ultimately available from the tires, etc. And the fastest setup may not be the most comfortable or reassuring to drive.

I agree that driver preference plays a role in the subtle, final tuning once the car is close to correct, but the basic setup has to be in the ballpark, and it's not a very big park. I am sure Donohue wasn't talking about 20-50% differences in any parameter - at his level, a change of a few percent in spring/shock/swaybar setup is (was) significant, and the differences he was talking about were far smaller than what we are talking about here.

smokey

There is a huge difference between an AX setup and a track setup. A car that rotates easily at 40 mph will be unstable in a 100 mph corner. The stakes are also different.

keith

Brian - You may want to check out my thread in the Autocross section as it develops...

I think basically you need to soften the rear Konis - they probably shouldn't equal the front in rebound resistance. Also, you should be running closer to zero toe or marginally toed-out in the rear, I'm learning, to reduce a snap-loss of traction (exceeding the tire's slip angle).

I, personally believe in levelling the car, which means the rear end comes DOWN from the US spec. Level doorsills, my man.

What is your rear swaybar size? It may be too big.

M758

Keith,
Toe out in the rear will make the car less stable underbraking and more prone to oversteer. It will not help Perry at all.

With respect to suspension set-ups. Both Paul Bloomberg and I run the same suspesion, shocks, springs, sway bars, camber, toe etc. Yet our cars respond differently and we like them differently.

The best suspension set-up is the one that the allows the driver to go the fastest.

Perry needs to spend some time on the Autocross and DE. Better to do this than to mess with the car right now. Autocross and Track set-up are different, but only when you are looking for that last 5% from each. Up to 95% the car and driving skills are really the same.


Also remember that it is possible even with the perfect suspension to mess-up. I have done that and found that a spin or off was 100% driver error rather than car error. It is often too easy for novice drivers to "blame the car" rather the real source of problems. A mistake by the driver. In this case did Perry mess-up or is it a car problem? Well given his relativly netural (on paper) set-up and limited experience in the car i'd vote for driver error. The reality is that he needs to spend more time on the track and he can then learn better what happend. It is VERY difficult for those not there to figure what happend. Heck in my two offs at Turn 9 at Willow Springs this weekend I am still thinking about what I did wrong. Was it old tires or simply driver error. I am thinking driver error, but I could always cathch it before so it has to be the car right? Well probably not. I just messed-up. It happens.