Another suspension upgrade question

[jakermc]

Yes, I have searched the archives, but I have a specific handling issue to address.

First the car. Its an '83 SC with a Euro 3.2 Carerra engine, 930 brakes, and a stock suspension other than turbo tie rods. It weighed about 2500 pounds before the addition of the 930 brakes. Car sits at Euro ride height but has not been corner balanced yet (will do that after the next round of upgrades). Tires are Toyo RA1 (205 in front, 245 in rear) on 7x9x16 wheels. The car is used almost 100% on the track.

Now the handling issues. The car is loose, even by 911 standards. Entering turns I need to stay on the throttle nearly 100% to keep the back end from swinging around. I've adjusted my driving to compensate and I have gotten use to it, but I know my lap times could be quicker with more neutral handling. I let my instuctor take the car for a 30 minute session so I could data log his driving as a benchmark for myself, and he had the same feedback about the set-up.

What to do next:

Tire pressures - I come off the track and measure 33 or 34F and 36R in most cases. Sometimes hotter, but a similar difference between the f/r. What adjustments should I make here?

Torsion Bars - What would be a good f/r combo for this set-up and handling tendency? I will later switch from stock bumpers to figerglass so weight will drop a bit from here.

Sway Bars - 22mm adjustable set-up seems most common. Any reason to deviate from this?

Shocks - Running with stock Bilsteins. Need to be revalved. Front left strut is also bent a bit causing camber to be about -2.2 degress while the other corners are closer to -1 or -1.5 (can't remember as I write this). Best shock set-up?

Limitations - Tire size. I am running 6mm spacers all around and have a tight fit (needed to clear 930 brakes). Not sure if I can go to 225 in front, would like to stay with existing tire sizes for this exercise.

Tell me how you would set-up my car.....

[Jim Smolka]

What are your track goals? PCA club racing?, or Street/DE car.

To tighten up the rear, one has to make the front a bit stiffer.

Check that the rear sway bar mount has not broken loose.

Good time for all around suspension upgrades. All depends on one's budget.

[don911]

With your tire sizes, it should push all day long. I'm running RA1s and had similar hot tire pressures. I bled my rears to 38 when the pressures hit 40.
I also have the 930 brakes. The 951 8s are the way to go if you want to keep fuchs. The 8s allow 225s without a problem. Especially if you can put in -2 or more camber.
With the bent strut, I'd think it'd be hard to figure out the handling issues. It might be weight jacked. A new strut and corner balance/alignment might do wonders for the handling.

[2.7RACER]

Jakermc,
I drive a '76 911 on the track with stiff tosion bars, bilstiens, hoosiers, etc. When the rear of my car is loose I soften the rear sway bar a bit or lower the rear pressure about 2 lbs. I then go back out and check the results. Or stiffen the front or add pressure to the front.
With the Hoosiers they like higher pressures (38 to 43) than most other tires I've used. I always run higher pressures in the rear.
Since your car has not been corner balanced, I would ask you if it does better with right turns or lefts. A significant error with corner balancing will make the the car turn better one direction and worse the other.
Fix the bent strut. Then get an alignment. Go over all the suspension bushings and replace as necessary. Get the car corner balanced or it will make you crazy.
When your are racing your suspension needs to be right.
Racing isn't cheap. To get good results your car must be right.
Good Luck and enjoy your Stuttgart toy.

[Noel]

Corner balancing that is significantly off will also cause the car to pull in one direction under hard braking. Then again a bad alignment will also do this. Unfortunatly, the car in its curernt condition makes a lousy platform to use as a benchmark for making expensive suspension setup upgrade decisions. I would strongly suggest getting the strut replaced and checking the corner weights to make sure it isn't off too much before you throw any additional parts at it. Adding additional parts will only complicate matters.
Good luck!

[jakermc]

Goals for now are primarily DE and member days at MotorSport Ranch. Club Racing is a thought, but not for a few years. I don't mind 'throwing parts at the problem' because I enjoy doing the work and learning about the car in the process. Sometimes I think that part is even more fun than driving.

Corner weights were taken when the car weighed 2740 pounds with me in the car (2573 without me), but no balancing was performed. At that time the corner weights with driver were Left=51.8% Right =48.2%. Front = 40.7% Rear = 59.3%. Since that time I have removed the AC system from the smuggler's box and replaced/relocated the battery with a lightweight Miata battery in its place. Also added the 930 brakes. So while I have not had a corner balancing done, I'm not in too bad a place as I currently sit. Left and right turns seem about equal despite the bent strut and a g force circle seems to confirm this. Camber settings were -2.1 front left, -1.0 right front, -1.0 rear left, -0.9 right rear.

Bushings are all in good shape. I replaced the front sway bushings last year and the rears are still looking good. I know I have to replace the strut but I want to complete any other suspension work at the same time as I do not want to pay for multiple corner balances and alignments.

Thanks for the ideas, keep them coming ....

[petevb]

The first thing you need to do is figure out what your existing problem is. Make no mistake- something needs to be broken or badly miss-adjusted to cause what you’re feeling. I’d put my money on the brackets that attach the front swaybar to the A-arm. I had one go out on me and the car behaved as you describe. Whatever the problem is shouldn’t be too hard to find... After you’ve fixed the problem(s) you might want to give it another shot at the track before deciding on the rest of the upgrade path- you shouldn’t need to correct the tail happiness with torsion bars, for instance.

After this is worked out, setup suggestions:
I’d go with 22/ 29mm torsion bars- you’ll hear lots of opinions on this, but they will likely all be in this ballpark. I’d take some play out of the suspension (get rid of the rubber bushings) at the same time.

I can’t recommend a good re-valve spec for the bilsteins. I tried smart racing’s GT-40 spec, but I was not too impressed- the shock dyno showed what I believe was far too much compression compared to rebound. I never did get the bilsteins right- I switched to JRZs. I do feel the bilsteins, correctly re-valved, should do well for you.

Swaybars- I like the smart racing bars a little better than my racers group bars, but either are very good.

Oh yea, and put a cage in your 100% track car...

This will put you in good shape if you figure out what your basic problem is.

[rdane]

This is an easy one.

1. replace the bent strut

2. align and corner balance (within 10lbs or less)

3. Get rid of the spacers. Cut the front calipers so they fit inside the Fuchs.

4. T bars? I am using Sanders 22/30s

5. Sway bars..why not late 80s Carrera?

6. Bilstein sports all around if it is a track car

I have a similar set up. Dump the 205s as Don says and run a 225 up front. (7s or 8s) My car is almost perfectly balanced now and when it isn't tire pressure can handle it.

[Noel]

Another thing I noted was the camber, the generally rule is to have about 1/2 degree more negative camber in the rear than in the front. Also, what is your rear toe? It should be toed in slightly for best stability.
I also agree with RDANE except for the Sport Bilsteins. Since you already have Bilsteins, simply send them back to the factory and they will rebuild them and custom revalve them to match your torsion bars for $65-75 per shock. Not only is this cheaper but you get a custom shock too. They tune them to have less compression then the HD (Non-Sport) and more rebound than the Sport. You won't believe the difference. I love my setup and it had everything to do with the shocks.

[jakermc]

I am confused about the suggestion to increase my front tire size to 225. If I am trying to increase understeer/decrease oversteer wouldn't increasing front tire size have the complete opposite effect of what I am trying to accomplish?

T-bars - I had thought of 23/31, but would 23/30 make more sense given the current tendencies of the car.

Sway bars - Would putting a 22mm front sway bar in from a late model Carrera and an aftermarket adjustable 22mm bar in the rear make sense. My thought is the front would be cost effective and the rear would allow me to adjust and tweak. The idea is to use a softer setting in the rear to reduce oversteer, correct? And adjustable bar in the rear would allow me to dial this in. Any need for adjustable bars both front and rear?

Strut will be replaced and shocks will be re-valved, that is a given. Corner balance will be done at that time as well, but I'd like to install any other hardware I would need before this step. I know each part is just a cog in a larger suspension system, thats what makes the choices so difficult.

[89911]

If your car is primarily a track car, the answer is do everything . A Stock 911 is too soft, too high, has too much body roll in my opinion. I've used my car for 5 years on the track, going from bone stock to replacing every single suspension component (next to coil overs) there is. Again, this is for track use. Now I have a car that is a point and shoot vehicle. I don't need to worry about the car "settling" before the next turn or the weight balance being off and upsetting the car through a series of turns. There are compromises indeed, but not on the track. I just drove a stock 3.2 the Carrera the other day and I had to jump out and make sure the "Carrera" emblem was on this vehicle. Sure they came out to the factory a good car, but you can turn them into a great car with some well chosed upgrades.

[rdane]

You have a lot going on. What you think is causing your problems isn't.
Here is a good place to start making comparisons:
http://rogerkrausracing.com/overundr.html

Nothing special about your 911. It will react the same as all the others if you set it up correctly. No reason to reinvent the wheel here. It has been done many, many times before.

Easy oversteer corrections?
Suspension may be too soft.
Shocks may be too soft.
Lower vehicle.

You can't tell what your car should be doing or will do, until you replace the strut and get it aligned and c/b'ed. You might find that is the smart money in your case instead of looking farther at the moment. Or look at a good example of what you want to duplicate and just copy what has been done. Lots of good examples on this board.

Having done it all, I'd do less first and then think about changing other things.

Easy thing would be to get your track narrowed back to original OEM spec by loosing the spacers. They aren't needed at all in back with 930 brakes and widen the track which is part of the oversteer.

A 225 will eliminate some of the understeer that comes with a 205. Keep the 205s and you'll under steer which makes the car easy to learn to drive. 205/245s are a good set up. Almost everyone has used it. Most of us think the 225/245 is better on a well sorted car.

Shocks, (and the revalue is a great idea) bigger T bars and sways bars will mellow your car out a good bit. Keep the 205s and you'll under steer which makes the car easy to learn to drive.

23/30s are generally considered too big and a poor balance 21/29-30s or 22/29-30s or 23/31s are typical set ups.

What are you using for a wing and front air damn? It is a total package, not just one thing. More importantly it has been done now for 30 years

Again look here:
http://rogerkrausracing.com/overundr.html

[jakermc]

Stock factory bumper with lip spoiler. Rear fiberglass ducktail. I typically drive on slower, techincal tracks such as MotorSport Ranch. Where are you tracking yours?

The spacers were required all around with the OZ Racing wheels I have on the car. I could have grinded the calipers down further, but wanted to try spacers before shaving off all of the fins. Adding the 6mm spacers did not change the handling characteristics of the car, nor should it, as all four corners have the same spacers so the relative track front to back stayed the same.

Despite the fact that I did not corner balance the car, I am not far from ideal conditions right now. Look at the numbers I posted. The left/right balance was off by about 90 pounds before I removed a 50 or 60 pound battery from the left and put a 25 pound battery into the smugglers box on the right. Front/rear weight was 40/60. I don't expect miracles to occur when the car is rebalanced as the improvement should only be about 10-15 pounds between the left and right side.

[Wil Ferch]

We've gone way too far before we exploited some basics:
- what are your toe settings...front and rear?
- get the RF and LF camber to be about the same. I saw an incredible improvement on a squirrelly feeling car when I got the camber closer to being the same.

I also think you're misunderstanding corner balance. Most do. Before and after a corner balance...you will see "no change" for the weight of *any two* adjacent wheels. Meaning...total front weight, total rear weight, total right side weight or total left weight....will be unaffected. Surprised? Check archives and search under my name, Chuck Mooreland, "corner balance", etc....

---Wil

[rdane]

Here are some typical weights from a professional corner balance on my car. Most cars are even better, under 10# left to right.

unloaded
483 lf 476 rf
776 lr 772rr
38% to 62%

mild performance set up:
front: camber -1.
toe 1.
rear: camber -1.75 rear
toe 1.3

loaded @ 200# in the drivers seat
559 lf 502 rf
849 lr 800rr

As you can see moving weight around the car isn't as simple as you might think.

Adding track does change things. You have added .50" to the front and back. The typical 911 SC with a street setup with 7 and 9s is going to understeer not oversteer. Sorry just figured you were using 16" Fuchs.

"Entering turns I need to stay on the throttle nearly 100% to keep the back end from swinging around."

Lot of very good drivers here too. I don't count myself as one of them. But this tells me things are not right.