Suspension advice for R comps?

[gliding_serpent]

Hi Folks. The development of my street/track car, and me as a driver, combined with R-comps for HPDE use, has resulted in me needing a bit more suspension. Body roll is starting to hurt my times (and tires).

So this is what I have:
- 1984 Carrera (~280hp), 2300lbs
- 225/245x16 Pirelli P Zero Trofeo R tires
- Porsche 22mm front, 21mm rear sway bars (new rubber bushings winter 2014, fronts yet to be installed)
- Wevo reinforced rear sway bar mounts
- 30mm Rear and 23 mm Front Torsion Bars
- Turbo Tie Rods
- Lowered w/ Steering Rack Spacer to correct Steering Geometry (now highter post 450lbs weight loss (~400lbs lost under my ownership)
- Bilstein Sport Shocks
- Front Urethane Bushings (or so the PO says... who knows which ones... all I know is not sway bars. (?control arms)
- Front strut brace (cambermeister - I will cut the mount to avoid known failures with monoballs)

So my car came with all of this suspension stuff, and was corner balanced and lowered (quite a bit) for autocross (using RA1's) by a PO. I then dropped ~400 more lbs, and the ride height came up (a bit, not a bad thing in my mind). With R-comps and a solid passenger it rolls on right handers, but tire wear is acceptable. Without a passenger, on the same right handers, the tires are rolling slightly onto the sidewalls. (maybe partly due to me trying lower tire pressures). I assume the increased ride height, and corner balancing had at least something to do with that.

Anyway, in my mind, adjustable roll bars (Tarett/Elephant) or Smart Racing (can't find them online), seem like the next logical step...along with a corner balance. I understand that lowering it further would help with camber and roll, but I found the old ride height a bit troublesome.

So i have two goals:

1. I have yet to really educate myself on suspension updates on our cars, but now it the time, so I am all ears. I do know the controversy of the cambermeister strut brace, especially if I go monoball, so lets just skip that as I know what mod needs to be done to correct that. Adjustable sway bars seem like a no brainer, but I am wondering what else might best be done with it to make a decent compromise track (r-comp)/street car. I am thinking that an uprated sway bar without poly bushings kind of defeats the purpose. Would I need to re-index my torsion bars? I hesitate to change much there as I don't have much clearance between my outer fender edges and my tires... and they don't rub under hard cornering.

2. Corner Balance: I am up in the Altantic coast of Canada, and as far as I know, there are no pros that know my era of car enough to do anything other than "learn" on my car when doing a suspension/corner balance setup. I have been advised to take my car to the North-Eastern states for a setup (not so practical, but I could take the ferry to Portland/Boston I guess). Any suggestions? Or it this really something someone new to this like me can do with a little help?

Thanks for any contributions.

I am about to do a search on articles on the topic, and will share anything I find. The performance handbookis a good primer.

[Cajundaddy]

If it were my car I would connect with a pro shop who also runs at my local track and arrange a test and tune suspension day. Pay for their trackside support and careful evaluation of your car's characteristics. Swap seats with your setup guy and come up with a plan based on your findings and measurements.

Others might suggest stiffer sways.

[Elombard]

Wow with those T bars and that weight I am surprised. I wonder if this is why many serious trackers seem to end up eventually with modern coil over spring suspension and go away from the T bars. I guess you cant go wrong with adjustable sways, if they are not enough you can still use them on the next suspension. At your level of prep I would want to start eliminating bind with monoball, poly bronze type bushings and bearings but I dont think that will help with lean. I wonder if custom valved shocks would help some? Intuitively I don't think so but it will make for a nicer ride with those beefy T bars.

Are you sure the T bars are that size? Have you had them out and looked at the number stamped on them?

[gliding_serpent]

There is a suspension operation that I see booking time at our track... But they don't know our cars.

And I have not verified the t-bars. I am assuming the PO knew what he was talking about. Mind you, a lot in the sale did not pan out as described, and we are not on talking terms. Heck, how does ine verify bilstrain sport shocks? The rears are legit with stickers, but the fronts are green painted yellow... Although I do understand that the frint bilstein sports Are green.

Monoball and polybronze does seem like a good idea... Same for the sways.

[gliding_serpent]

Here is a potentially dumb question for those in the know... My fixed 22 sways... Is an adjustible 22 (say tarret/elephant)
- no firmer, just adjustable to softer
- as firm, adjustible to firmer still
- or the same, adjustible to softer or harder?

[Elombard]

If the aftermarket bar can be adjusted so the moment arm is shorter than stock, then yes. IIRC the stock arm length is pretty long compared to the aftermarket arms.

I would verify the T bar size to start.

[Trackrash]

Assuming you really have 23 and 30 torsions, your next step is tuning the alignment.
I am also assuming that your wheel size is correct for your tire sizes.

Have you measured tire temps? If your tires are rolling over, it is due to not enough camber, too low pressure or too narrow rim widths.

Adjustable sways will allow tuning your over or under steer.

[rfloz]

What size are your wheels and tires?

What are your camber settings? This is the main adjustment that affects tire wear.

Air pressure and temp should be near tire mfg recommendations with about 5 psi more in back.

My car setup sis imilar to yours except 22/29 T bars, -2.4 camber front, -2.6 rear and 100# more weight and re-valved Bils. I run 9/10 1/2 by 17" wheels and (currently) 235/265 R tires. Oversteer/understeer balance is pretty good. I had a lot of low speed understeer running 245/315 tires.

It's setup for auto-cross mainly, with some street and a little DE.

My tire wear is pretty even across the tread front and rear as are temps. It rolls some, but not really a problem.

Oops. I just saw your tire sizes. Still would like to know your wheel width.

[Quinlan]

As you know, there are several variables in play here - ride height, corner balance, camber and toe settings, bushings, sway and torsion bar diameters, etc.

Playing a guessing game with all these could add up to a lot of dollars really quick, especially with the exchange rate.

I would seriously consider taking it to Dan Jacobs in Connecticut. He runs a very successful race and performance shop. He knows 911's like the back of his hand and has experience with all of the torsion bar/sway bar settings as well as the bushing combos.

It will probably be cheaper than throwing darts in the dark by experimenting on your own.

[Elombard]

I agree ^ but having read other posts by Mr. Serpent he enjoys figuring this stuff out. I think with a little investigation, a few carefully chosen parts and some tweaking of the settings (alignment) he can make huge improvements. Then maybe after a few dozen track days he can take it to Mr. Jacobs to get those last 10ths :-) Plus I love buying shiny parts and installing them even if it is a bad investment :-)

[Quinlan]

I agree with you too - and I too love to get shiny new parts in the mail.

This is more like "do what I say, not what I do" type of advice!

[Bill Verburg]

Originally Posted by Quinlan

As you know, there are several variables in play here - ride height, corner balance, camber and toe settings, bushings, sway and torsion bar diameters, etc.

Playing a guessing game with all these could add up to a lot of dollars really quick, especially with the exchange rate.

I would seriously consider taking it to Dan Jacobs in Connecticut. He runs a very successful race and performance shop. He knows 911's like the back of his hand and has experience with all of the torsion bar/sway bar settings as well as the bushing combos.

It will probably be cheaper than throwing darts in the dark by experimenting on your own.

There is some great advice!!

It sound like most of the the things that need to be done are already there.

the last few things are to get the bushes optimized, probably w/ Elephant poly-bronze + adjustable sways.

The contact patch between the car and the road is critical I'd want 8 & 9.5 wheels, w/ 235-245 front and 255-265 rears as short a tire as you can find

then have the car set up, as low & balanced as is possible

[gliding_serpent]

Originally Posted by Cajundaddy

If it were my car I would connect with a pro shop who also runs at my local track and arrange a test and tune suspension day. Pay for their trackside support and careful evaluation of your car's characteristics. Swap seats with your setup guy and come up with a plan based on your findings and measurements.

Others might suggest stiffer sways.

I may do this if able. Local to us is the chief engineer to the Risi Ferarri race team, and he has a 69 911. He is going to try to find the time to help me out. He races locally so I may be able too hook up with him on a race day as they do allow lapping at set times on race days.

[gliding_serpent]

Originally Posted by rfloz

What size are your wheels and tires?

What are your camber settings? This is the main adjustment that affects tire wear.

Air pressure and temp should be near tire mfg recommendations with about 5 psi more in back.

My car setup sis imilar to yours except 22/29 T bars, -2.4 camber front, -2.6 rear and 100# more weight and re-valved Bils. I run 9/10 1/2 by 17" wheels and (currently) 235/265 R tires. Oversteer/understeer balance is pretty good. I had a lot of low speed understeer running 245/315 tires.

It's setup for auto-cross mainly, with some street and a little DE.

My tire wear is pretty even across the tread front and rear as are temps. It rolls some, but not really a problem.

Oops. I just saw your tire sizes. Still would like to know your wheel width.

Wheels are 7 and 8's BBS RS.

I don;t know my camber as my car now sits a bit higher with weight loss. I will do alignment with corner balancing (thus this thread).

Air temps are my main issue I think. My first day out I ran 28/36 (stock, nitrogen), marked my tires and I was a bit over-inflated based on roll-over, and then lowered pressures to 27/34 and it was about perfect. The tires were a bit squirmy with stock pressures, only slightly so with things slightly lowered. Track was no more then 15oC however. And it was damp, so the tires were not getting super hot.

Day two got up to about 20oC, and was dry (still not warm on southern standards). I pushed my pressures down to 26/32, and was getting rollover on front and back drivers side (lots of right handers on our track, one off camber). I edged them up again to 27/33 and still had a bit of issue.

But my car still is rolling too much (day 1 below). So in addition to addressing camber, I want to cut down on roll, thus the roll bar upgrade .


Of interest, with a stock 3.2 being 2750lbs, and mine 2300lbs, if you calculate the ratios, I should be running 24/30 pressures based on the weight of my car. However, where my error of logic arrives, is that is for a straight line. The cornering forces in effect make my car far heavier in the turns, thus the need for stock, or near stock pressures in the corners. This is my lesson learned for the night. Expecting my car to operate at the lower pressures was poor logic, and I paid for it with (mild) rollover on the sidewalls.

[gliding_serpent]

Originally Posted by Quinlan

As you know, there are several variables in play here - ride height, corner balance, camber and toe settings, bushings, sway and torsion bar diameters, etc.

Playing a guessing game with all these could add up to a lot of dollars really quick, especially with the exchange rate.

I would seriously consider taking it to Dan Jacobs in Connecticut. He runs a very successful race and performance shop. He knows 911's like the back of his hand and has experience with all of the torsion bar/sway bar settings as well as the bushing combos.

It will probably be cheaper than throwing darts in the dark by experimenting on your own.

Many variables. Only when my lap times started hitting within half a second of one another consistently did I even allow myself to worry about suspension (as my car came with a basic, but sorted setup until I dropped 450lbs last winter).

Originally Posted by Elombard

I agree ^ but having read other posts by Mr. Serpent he enjoys figuring this stuff out. I think with a little investigation, a few carefully chosen parts and some tweaking of the settings (alignment) he can make huge improvements. Then maybe after a few dozen track days he can take it to Mr. Jacobs to get those last 10ths :-) Plus I love buying shiny parts and installing them even if it is a bad investment :-)

Yup, you are right, I would rather pay a bit more, take a bit longer, make a few mistakes, and learn, than to pay for someone to fix my problems for me. But maybe I should bounce things off of him and see if he has thoughts on directions.

Originally Posted by Bill Verburg

There is some great advice!!

It sound like most of the the things that need to be done are already there.

the last few things are to get the bushes optimized, probably w/ Elephant poly-bronze + adjustable sways.

The contact patch between the car and the road is critical I'd want 8 & 9.5 wheels, w/ 235-245 front and 255-265 rears as short a tire as you can find

then have the car set up, as low & balanced as is possible

I was thinking poly-bronze and adjustable sways was the next step also! A friend who whent with a tricked out track suspension warned me of the slippery slope of monoball and all that jazz (he said you change it all or not at all).

The wheel thing is kind of non-negotiable at the time, as I have used my wheels only twice, and the tires are brand new, so my 7/8 bbs RS will have to do... at least for this year. And with my narrow body, I have a hard time thinking bigger will fit. Getting proper sized offset to allow those sizes on a narrow body would be big $$$ right now unless I find a used gem. Maybe another season. I need "room to grow" anyway. A real slippery slope, as larger tires and wheels would increase grip, and stress further, possibly forcing me to go even more aggressive on most of my suspension, further compromising my street liveability for the sake of lap times on what is, lets face it, hobby-style lapping of the track (Even if I do approach it in a very scientific and competitive manner). The good old slippery slope. I need to draw a delicate line in the sand and try not to cross it as some days I drive my car to work for fun and some of our b roads are less than perfect.

[Elombard]

The thing for me is I just cant enjoy track days when a car is rolling too much and I think the handling can be improved. I know I can learn stuff as is but its too frustrating. Got to try and fix it!

[gliding_serpent]

interesting comment from Steve Weiner on sway bars... (his site has a good suspension primer)

"Using the swaybars as part of the overall suspension system is necessary for chassis balance. There are several opinions on this, but we feel that the vehicles’ springs should carry the majority of the desired roll stiffness, not the anti-roll bars. These should be used as tuning tools to adjust the understeer/oversteer balance of the car, not as primary roll stiffness components."

confirms an earlier suggestion to verify my torsion bars (plan is to verify easier to id fronts... because if they are as stated, rears probably ok also)

[gliding_serpent]

Originally Posted by Elombard

The thing for me is I just cant enjoy track days when a car is rolling too much and I think the handling can be improved. I know I can learn stuff as is but its too frustrating. Got to try and fix it!

For me, I want to push the limits. I develop, reach a limit, then adjust the car to push harder. My goal is to find a setup that works with decent width r comps on the track, while keeping some road manners. There will always be a compromise as I am not willing to go "race car." That is why adjustable sway bars are a no brainer for me. Cake and eat it too kind of thing.

Thoughts on the tarret rsr vs standard bars? I like the low key color and notch adjustment of the rsr bars.

[TT Oversteer]

My 77 911S is running 21/28 torsion bars with custom-valved bilsteins and stock front swaybar with a tarrett adjustable rear bar. Urethane bushings in front and polybronze and monoballs in the rear. Tires are RA-1's 205/225-16 on 7's & 8's. It weighs in at about 2400# with a modded 3.2

Based on your photo my car doesn't lean anywhere near as much as yours....Which makes me question your torsion bar sizes.

I'm just a hobbyist and not a racer or pro mechanic but from what I've seen at the track with my car and other 911's, in my opinion, there are things that make large differences and many that are minor in effect.

In order of importance:

1) tires: correct size, pressure, compound

2) alignment and corner balance

3) ride height

4) swaybars: (adjustable) balanced f/r

5) shocks/struts

6) stiffer T bars

The other stuff: bushings, monoballs, strut/shock tower braces, lowered spindles, etc are what I would put into the category of incremental gains and barely noticeable to the average weekend track day warrior.

IMHO, based on what you have described, I'd start with lowering the car as low as you can tolerate on the street and get a professional aggressive alignment and corner balance. Then a set of r comp tires. Your car should handle great with those things alone. When you lower the car you can verify the T bar size as you will have it mostly apart and will need to realign everything anyway.

If you're still not happy then maybe up the T bar size (if not as suspected 23/30, which should be plenty) and send the bilsteins to the factory for custom valving based on your T bar size and vehicle weight. Then adjustable sways.

I would only add bushings and monoballs, etc if you have money to burn and just like the "cool factor".

As a point of reference, one of the faster guys at the track in a 3.2 carrera is running STOCK T bars, sways & shocks with rubber bushings. His car is very low with an aggressive alignment and yoko r comps on 7/9x16's. THATS IT! I've ridden in his car and its PLANTED with little to no body roll.

You seem like a very analytical guy and I've enjoyed reading your posts and following your project. Looking forward to your findings..... Have fun

[TT Oversteer]

Forgot to add the Tarret swaybar is a nice and easily adjustable piece but the plastic bushings make it rattle noticeably which can be annoying for a street car. There's a reason your car came from the factory with rubber suspension bushings. Race cars are noisy and harsh. Weigh the compromise carefully.....