I have a '86 911. I junked the torsion bars and have Bilstein coilovers. I run 550lb/700lb springs (f/r) and I have the thickest, most adjustable sway bars that Smart Racing makes. (31mm front/27mm rear) Older 911's like a really stiff front bar. Just to give you an idea of the difference a mm makes, I had the biggest WEVO bars before (I think 22/28mm like you mentioned). Now, full soft on my Smart Racing bars is probably close to full stiff on the WEVO bars.

Now that you know the equipment, depending on the track, all I adjust are the sway bars and I really focus more on the rear. The only track that usually requires me to go to the front bar and spring rates is Sebring. The reason for that is that I want to soften the whole car up a bit. Not really change the handling characteristics per say but just soften the whole thing up. Think turn 17 in a 22 year old car on the edge of the grip circle....

If I had adjustable shocks on the '86, I could fiddle less with springs/sway and go after my adjustability a bit more with the bump/rebound/pressure as I can in 3 way shocks on the Cup Car.

Some people may disagree with what I'm about to say and that's what makes competitive racing what it is relative to car setup but ... I like to have my car stiff to the point of a bit of initial understeer at corner entry and at apex and then a bit of throttle oversteer just past the apex through corner exit. In other words, I want to go as fast as I can upon entry without getting into trouble, be on the edge of the grip circle at apex without being twitchy and have the ability to have the car respond to throttle steering with minimal steering wheel input on my way out.

Back to the competitive nature of setup....Guess what, everyone drives different. Everyone does braking, steering input, throttle different. So, you have to fiind the right set up for how YOU feel comfortable. Some people would get in my car and think the car is WAY too twitchy. Some would get in and think it's too soft. This board is all about getting suggestions, not mandates (except when it comes to a stiff front bar on a 911 ).

 

Actually...

2mm is worth about 80lbs. Not huge but not nuthin neither. If you said that 1mm = 40lbs.+/-, you could then gauge a bit. If it is only a "small" increase, I would be probably try it and see. As a for-instance, I did not notice any substantive balance difference going up 100lbs on front springs. I did notice a nice decrease in roll.

 

Suspension is a system, don't monkey with bits of it. You need 23mm torsion bars up front 31 in the rear, custom valved Bilsteins and the big @as smart racing bars front and rear. Then put the right alignment on it taking into consideration the tires you are running. From there, do a couple of DE's at a track you know well and adjust the bars starting with the rear at full soft and playing with the front bar until you get what you want. If that doesn't work, move to the rear bar.

 

one shade tree weekend wrench's method. I look at sway bars as a necessary evil. My reasoning is they reduce independence in the independent suspension. I look to set up with as little bar front and rear as possible. I take bar out as a first step.

Sways reduce body roll by making the inside wheel work against the outside wheel. Its best to have each wheel do its own thing for max mechanical grip. That said most cars have to have them based on the suspension systems used and COG.
Sways are for fine tuning not correcting poor setups. I see some just starting out track junkies add bigger sways I think partly as they are a weekend driveway add on. A stiff sway setup can make a softly sprung car feel real good at low G on the street but a twitchy evil beast when loaded up in hard cornering. Adding adjustable bars is good if you have stock non adjustable but more bar might not be better if its rate is higher than the spring rate range. They have to go hand in hand.

Within reasonable ranges adding bar to one end does not decrease total grip it shifts it. More front grip due to the front wheels being more able to do their own thing = less rear grip as the added body roll is twisting the rear bar more adding to its effective rate. Any change to one end does influence the other end. I think that ading in too much bar does decreas total grip when the bar range is not in line with the spring rate range. Again my own ideas and not based on knowing anything of a learned nature.

My own simpleton busted knuckle rules for sways. The goal is as little overall bar as will work. Less bar is better all things considered. More spring rate = less bar needed other things the same. Higher effective sway bar rate at one in one end reduces the effective rate in the other end. I use the 50% rule for adjusting. Don't dither around with little .25 inch moves when roughing in. Set at half the range and test. Put it in the middle and test. Move 1/2 to the end you think it needs. If better then half of the half and so on until a small movement makes the car go from better to worse. If worse try the other side of ½ range. Set the more important end where you want it and dial the other to it within reason. Try not to end up with both ends tight. If you are all the way or nearly full in on both ends you are correcting for another problem and need to rethink the overall setup. Out-out is the way to fine tune both ends together not in-in. Note all your settings when you get them where you like them!

 

Streak -- don't bother with the 30mm T-bar -- go straight to the 33mm with 23mm front and definitely get your shocks revalved or the car will not brake in a straight line on any track we drive. Not enough rebound in the rear.

 

Yup, same here.

 

Arrrgh! Someone will have to buy a few houses for that to happen

Shocks will probably be next though.

So it sounds like I should expect the rear to move more than the current set up so to start with, goto full soft in the rear and adjust from there.

 

Excellent description!!!

 

If you have adjustable sways one thing you can do is to just move them around. Run a session then change them and run again. See what the car feels like as you adjust them. For all the evils of sway bars they are very valuable in the fact they can be used to quickly change the balance. Now if you need to run a bar "full stiff" for any reason you probably should add more spring rate and then try to back the sway bar stiffness out.

Last race a couple weeks ago I made a 5mm swaybar adjustment (moved my end 5mm stiffer) and got a major improvement in balance. Very very significant improvement as I achieve some balance that I did not have earlier.

 

Definitely -- I had Billstein Sports all around when I had 22/28 combination. Then I switched to 31mm rears and the back end was bit of a handful when braking, particularly at the end of the back straight at Mid Ohio. I ordered the new shocks and T-bars at the same time but only the T-bars came in on time. So I switched to 33mm without changing the shocks. Big mistake. First event, Mid Ohio. it was a religous experience. Sally was not a happy camper. I did warn her to give herself at least an additional five feet to the edge of the track. I changed to the JRZ and dialed that problem right out.

 

That is two Yup's I like a bit of understeer its all a matter of tast, I just think it makes the car more predictable at the limit.

 

Exactly!

 

Even guys who can drive, like Randy Pobst, say the same thing for the same reasons.

 

Gives more control to the feet too. Brake to set the nose and move grip forward and gas to rotate.