Autocross Suspension Setup
02-05-2002, 03:17 PM
#1
Burning Brakes
Thread Starter
Autocross Suspension Setup
Hi everyone,
In my quest for a firmer suspension and, more specifically, for a better autocross setup, I have the springs and shocks from the M030 suspension on their way (thanks Rob). The only thing I'm missing from the M030 package is the larger 22 mm front sway bar. The stock bar is 20mm.
As others have noted, the 964 tends to understeer (push) quite a bit during autocross, and I'd like to have just a little bit of oversteer dialed in. What would you recommend that I do with the front sway bar? Leave it alone, put on the 22mm M030 bar, or go with an aftermarket adjustable bar?
I like the idea of an adjustable bar so that I can adjust it for autocross, street, and DE use.
Also, what effect does the front sway bar have on handling? I found an earlier autocross thread, and people said to loosen the front end to neutralize understeer by disconnecting the front sway bar. I always thought that would have the opposite effect- i.e., loosening the front end would make the front end lose grip sooner and add more understeer. Can someone explain this to me?
Thanks for any help.
Drew
92 C2 Coupe
In my quest for a firmer suspension and, more specifically, for a better autocross setup, I have the springs and shocks from the M030 suspension on their way (thanks Rob). The only thing I'm missing from the M030 package is the larger 22 mm front sway bar. The stock bar is 20mm.
As others have noted, the 964 tends to understeer (push) quite a bit during autocross, and I'd like to have just a little bit of oversteer dialed in. What would you recommend that I do with the front sway bar? Leave it alone, put on the 22mm M030 bar, or go with an aftermarket adjustable bar?
I like the idea of an adjustable bar so that I can adjust it for autocross, street, and DE use.
Also, what effect does the front sway bar have on handling? I found an earlier autocross thread, and people said to loosen the front end to neutralize understeer by disconnecting the front sway bar. I always thought that would have the opposite effect- i.e., loosening the front end would make the front end lose grip sooner and add more understeer. Can someone explain this to me?
Thanks for any help.
Drew
92 C2 Coupe
02-05-2002, 04:21 PM
#2
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Drew,
When you lose traction at one end of the car, it is normally because there is too much weight being transferred to that end.
In terms of antiroll bars, if your car has a push, and you stiffen the front bar, you are increasing the amount of weight transferred to the front, which is already over worked, and thus it will push more. So if you have an understeer situation, you either need to soften the front bar, or stiffen the rear bar.
For an oversteer situation, you would either soften the rear bar or stiffen the front bar.
All that is well and good, but then you have to look at high speed vs. low speed handling. As was pointed out by others, disconnecting the front bar is great for low speed corners, but you DO NOT want to do a high speed track event with it disconnected.
From my perspective, I prefer a slight high speed push vs. a high speed oversteer. I also refer a slight low speed oversteer to a low speed understeer. When they back gets lose at high speed, things get really interesting really quickly!
For a really good run down on this, you might try to find a copy of "How to Make Your Car Handle" by Fred Puhn, or perhaps one of the Caroll Smith's books on race car preperation and set-up.
FTR, I will be running my 1st event in the C2 in a few weeks, and will report the results.
Best Regards,
BL
When you lose traction at one end of the car, it is normally because there is too much weight being transferred to that end.
In terms of antiroll bars, if your car has a push, and you stiffen the front bar, you are increasing the amount of weight transferred to the front, which is already over worked, and thus it will push more. So if you have an understeer situation, you either need to soften the front bar, or stiffen the rear bar.
For an oversteer situation, you would either soften the rear bar or stiffen the front bar.
All that is well and good, but then you have to look at high speed vs. low speed handling. As was pointed out by others, disconnecting the front bar is great for low speed corners, but you DO NOT want to do a high speed track event with it disconnected.
From my perspective, I prefer a slight high speed push vs. a high speed oversteer. I also refer a slight low speed oversteer to a low speed understeer. When they back gets lose at high speed, things get really interesting really quickly!
For a really good run down on this, you might try to find a copy of "How to Make Your Car Handle" by Fred Puhn, or perhaps one of the Caroll Smith's books on race car preperation and set-up.
FTR, I will be running my 1st event in the C2 in a few weeks, and will report the results.
Best Regards,
BL
02-05-2002, 04:27 PM
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One point I forgot to mention....
Antiroll bars can also help by reducing the amount of camber change that happens as the car rolls onto its suspension. In some cars, a stiffer front bar actually improves handling because it prevents the outside front wheel from gaining positive camber in, and thus keeps the tire tread more squarely aligned to the road.
I don't know enough about the Porsche suspension to say if this is a problem of not.
On my past vehicles, my Miata with a double wishbone front, did not have a camber problem, so the bigger front bar created more push due to the weight transfer issue. Other cars with poor camber compensation may like a bigger front bar.
BL
Antiroll bars can also help by reducing the amount of camber change that happens as the car rolls onto its suspension. In some cars, a stiffer front bar actually improves handling because it prevents the outside front wheel from gaining positive camber in, and thus keeps the tire tread more squarely aligned to the road.
I don't know enough about the Porsche suspension to say if this is a problem of not.
On my past vehicles, my Miata with a double wishbone front, did not have a camber problem, so the bigger front bar created more push due to the weight transfer issue. Other cars with poor camber compensation may like a bigger front bar.
BL
02-05-2002, 04:58 PM
#4
Technical Specialist
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Drew,
For adjustable anti-roll or sway bars, you can install a 24mm Porsche RS adjustable bar up front. The rear RS adjustable bar is 18mm, which may not be big enough. There are aftermarket rear adjustable bars in the 21-24mm range by Weltmeister and TRG, amongst others. I installed the Porsche 24mm bar up front and the Weltmeister 21mm bar in back. Track season kicks off at the end of March so I'll know how that combo works then.
For adjustable anti-roll or sway bars, you can install a 24mm Porsche RS adjustable bar up front. The rear RS adjustable bar is 18mm, which may not be big enough. There are aftermarket rear adjustable bars in the 21-24mm range by Weltmeister and TRG, amongst others. I installed the Porsche 24mm bar up front and the Weltmeister 21mm bar in back. Track season kicks off at the end of March so I'll know how that combo works then.
02-05-2002, 06:01 PM
#5
Rennlist Member
Drew:
Note that Bill is talking about setup for track rather than autox. A 24mm front bar will make your car push like a pig in tight turns. The OE 20mm bar you have now will induce less push than the 22mm M030 bar. For reasons that Brian notes above, an 18mm bar might even be better. I have an adjustable bar that I removed because the softest setting was still too stiff for autoxing. The OE 22mm bar is on now, but I disconnect it for autoxing. If your car still pushes with your 20mm bar, try disconnecting the down link on one side. That will induce some oversteer, so you'd need to adjust your throttle application habits on the course to avoid falling behind in your steering and thrilling spectators.
Note that Bill is talking about setup for track rather than autox. A 24mm front bar will make your car push like a pig in tight turns. The OE 20mm bar you have now will induce less push than the 22mm M030 bar. For reasons that Brian notes above, an 18mm bar might even be better. I have an adjustable bar that I removed because the softest setting was still too stiff for autoxing. The OE 22mm bar is on now, but I disconnect it for autoxing. If your car still pushes with your 20mm bar, try disconnecting the down link on one side. That will induce some oversteer, so you'd need to adjust your throttle application habits on the course to avoid falling behind in your steering and thrilling spectators.
02-06-2002, 02:59 AM
#6
Race Car
Jim hit the nail right on the head, Drew is in search of optimal suspension for Autocrossing...quite different from a full scale track.
My opinion would be to use your factory swaybar, 20mm as it is now. If you want better handling for other occasions, get the 22mm or the 24mm and either disconnect the bar for Autocrossing, as I do or at least have it on the softest setting.
If all you are interested in is an Autocross setup, I would keep it simple and stay with the bar you have in place already (20mm).
My opinion would be to use your factory swaybar, 20mm as it is now. If you want better handling for other occasions, get the 22mm or the 24mm and either disconnect the bar for Autocrossing, as I do or at least have it on the softest setting.
If all you are interested in is an Autocross setup, I would keep it simple and stay with the bar you have in place already (20mm).
