Do I need suspension work?

[Jims5543]

I grabbed this pic from our local PCA website. Its a shot of my car.




I know I am hard on the gas in 2nd gear. I am looking at the front right tire compared to the left rear.

This is my dilemna, the car felt awesome, but maybe it can be better?

I really like how well it handled and my only problem was my front air dam scraping the ground in slolems and under heavy braking. Obviously this is a result of the soft suspension and all the body roll / movement.

I am thinking I might get a set of 16" rims and get some R-compounds on it then address the suspension, if it even needs addressing.

Opinions?

[Steve@Rennsport]

Jim:

If your 3.6-powered SC still has its stock suspension, I'd address that long before doing anything with wheels & tires,....

Adding R-compound tires just simply makes a bad situation worse.

Keep the "cart behind the horse" and do your suspension, correctly,..

[Jims5543]

I really liked how it felt though. I was quite suprised when I saw that pic that the car was lifting the front up under acceleration so much.

What would you suggest I do to the car, I am really unsure, larger torsion bars? Adjustaboe shocks? Sway bars?

[jorian]

What torsion bars are you running?

[tonythetarga]

definetly something wrong going on there. In a straight line the car should be reasonably level left to right, even under hard acceleration. You might have shock and/or t-bar issues. Does the car sit level when you're not in and it is static?

[450knotOffice]

That picture seems to be showing that you were on the gas at the end of a right turn and in the process of straightening it out (look at all of the curved skid marks behind his car and all of the rubber thrown to the outside of the "turn" just laying there). It also looks like just a little smidge of over-steer was happening there and you were correcting it slightly. So, of course the car would be leaned slightly to the driver's left and would have the front end up. To me, the car's attitude looks pretty good.

What's the car's status - suspension-wise - right now? Is it stock? Have all of the bushings ever been replaced? How old are the shocks and struts and which one's do you have?

[dd74]

I'd let someone else drive it for a few miles, preferably where there are some twists and turns, then assess. Based on what work needs to be done, I would start with a corner balance and alignment, then bushings, then shocks, then think about torsion bars and sway bars.

[Jims5543]

FYI - I was able to put in one of the top 5 times of the day on street tires with it. There were many fast cars there on R compounds.

Thats why I am feeling like it might not be broke?

I was pacing a Lotus Elise on R-compounds and about 1.5-2 seconds slower than a GT3 on R-compounds. With a Natl champ at the wheel.

That might just be a bad picture maybe I was in the middle of a slolem and transitioning?

I have a bunch of in car video and I also mounted the camera on the side of the car I'll get those vids up and we can have a look at them.


As far as all your suspension questions. As far as I know from what the PO has told me it is bone stock. The only thing that was replaced was the bushings, Tie rods and shocks are newer.

I am totally ignorant in this so treat me like a total NewB when your giving advise. I am trying to learn as much as possible but there is a lot to digest.

[Richard Burns]

You liked it. It aint broke. Why fix it?

[randywebb]

2 issues, & they are interrelated
1. you want it stiffer than bone stock for DE or Auto-X
2. you need to alter the F/R stiffness to compensate for the add'l wt. in the rear

Start by reading BA's Handbook -- suspension chapter.
Next, get accurate wt.s on each of the 4 tires.
Select bars from there.

YOu will surely need to replace all the old rubber bushings! SRP, WEVo & Elephant racing are the products to look at for your usage.

[Grady Clay]

Jim,

Your choices of “levels” of suspension almost totally depend on your use and are always a compromise.

The issues are sufficient suspension travel, appropriate spring rates, shock rates, anti-sway rates, ride height, suspension compliance, alignment, tires and more.

The 911 comes from Porsche with the engineers having found a good compromise for many competing (and some mutually exclusive) factors. The ride height needs to be high enough to clear road debris and curb cuts yet not too high to be an off-road vehicle. The spring rates need to be sufficient to normally prevent the suspension deflection from bottoming on the stops yet not so stiff as to adversely compromise the ride. The shock rates typically follow the spring rates to remain “over-damped.” The sway bars need to restrict lean in a corner without adversely changing the ride. The ride height needs to be set so the car doesn’t ever hit the ground. The suspension mounting needs to be sufficiently compliant to not transmit too much road noise. The alignment must promote acceptable handling and reasonable tire wear. The tires need to be suitable for many situations; rain, dry, performance, noise, longevity and more.

Of course a street 911 will go multi 100K miles with only shocks and a few other maintenance items.

As you can see, your 911 does pretty well on all fronts in stock form, even with the more powerful engine.

Yes, you can improve the performance for auto-X or track use. The typical change is to dramatically stiffen the spring rate. This requires slightly stiffer shocks. The stiffer springs limit the suspension travel. This allows the ride height to be set lower. Stiffer springs require larger anti-sway bars for the same effect. As everything gets tighter (smaller deflections), suspension compliance becomes an issue. Here you replace the rubber suspension mounts with metal bearings. The alignment can be set more appropriate for track use. Finally, you can use track (R) tires or slick race tires.

As you can see these changes are interdependent. They should be done in concert.

Every one of these changes trade off (compromise) details from the compromise that Porsche had to choose. Fortunately, most are not egregious to an enthusiastic owner who wants the performance gains. The car will ride noticeably stiffer. If you don’t stiffen the shock rates much, the 911 won’t ride too rough.

All that said, if you stiffen a Targa too much, the chassis flex starts to become an issue and the cure is a roll cage. The “slippery slope.”

Best,
Grady

[JeremyD]

well - mine was just upgraded with a rennline front strut with monballs, new bilsteins and elephant racing poly bronze - wow - can't wait to get to the track - steering is instant








On the track, I found myself waiting for the car to settle before turning in - especially on a tight autocross track - here's what your stock rubber is doing - courtesy of elephant racing

[dfink]

In my opinion as stated in the racing forum you should upgrade if you want to run auto-x. The difference can not even be described between stock and stiff. The roll shown in your picture is about what I now get on a full out hard corner. I feel 22-30 torsions and some good shocks and then hold on. If however you like going for long comfy rides you might want to tone down the stiffness a little. As you hinted the car and the driver make a world of difference.
We have an elise running locally that I generally alway beat on times and can smoke every mazda RX-8 I have raced. Except for one and that is driven by two very capable dirvers. The time difference on a 40 second course can be several seconds depending on the driver. As a comparison I used to run BS against a BMW M3 and we were pretty close on times. After my suspension upgrades and moving to FP I was about a second faster on a 35 second course. This was without any engine changes. The suspension changes also dropped around 10 seconds off my track time on a 2.2 mile course.
These are just my opions and observations. At national level driver could probably beat me on bicycle. I was about one second behind the National Champion in CSP on that same 35 second course.

[Drago]

Originally posted by Jim Cesiro
... larger torsion bars? Adjustaboe shocks? Sway bars?

Yes, maybe*, and yes.

* Non-adjustable Bilstein Sports or HD should be fine. If not just have your existing dampers revalved to match what ever size torsion bars you decide on. 21 or 22 in front and 27 to 29 in the rear seem to be popular choices.

[Jims5543]

Wow!! Lots of good info in here thanks everyone and I mean that.


Lets assume everyhthing is stock. If this was your car what would you do and in what order?

I am assuming the monoballs is a good place to start along with a strut brace.

What then?

Should I start with Torsion Bars and shocks or should I do struts too?

I was looking in the hosts store and struts with shocks run in the $500 range. Ouch!

[JeremyD]

As grady said - everything works in concert.

I am not sure I would go too stiff with a Targa -

I'd probably do the upgrade with new Bilstein HD's in the front and sports in the rear. Monoballs (I really like the rennline integrated strut and monoballs) check out elephant racing's site - you can dial in packages for street/track recommendations

[jorian]

If your going to do shocks/struts and torsions I would do them at the same time so you only have to do one alignment. Any original rubber will most likely be pretty tired. I did mine all at the same time and then sent it out for a align/corner balance. I love the results.

My motor is the stock 3.2 and I run 7 & 8 Fuchs.

[Bill Verburg]

Originally posted by Steve@Rennsport
Jim:

If your 3.6-powered SC still has its stock suspension, I'd address that long before doing anything with wheels & tires,....

Adding R-compound tires just simply makes a bad situation worse.

Keep the "cart behind the horse" and do your suspension, correctly,..

Agree 100%, stiffen it up both w/ springs and sways, eliminate stiction, eliminate deflection.

problem is, the targa chassis just isn't stiff enough to take full advantage.

[Nine9six]

Originally posted by Grady Clay
Jim,

Your choices of “levels” of suspension almost totally depend on your use and are always a compromise...

Best,
Grady

In addition to what our talented Mr. Clay stated, they also depend largely upon the depth of your wallet!

[Drago]

Originally posted by Jim Cesiro
Should I start with Torsion Bars and shocks or should I do struts too?

I was looking in the hosts store and struts with shocks run in the $500 range. Ouch!

Why would you replace perfectly good struts?

I'd start w/ torsions, then get your Bilsteins rebuilt/revalved to match the t-bars. Add a couple of larger adjustable sway bars (19-21mm) and your getting there. The next level is monoballs and replacing the rubber bushings w/ bearings (ER stuff). Be aware that going to bearings will affect the amount of road feedback/noise in the cabin and they'll also require quite a bit more maintenance than stock rubber bushings.

FWIW I'm doing the T-bars, sway bars, dampers and an ER triangulated strut brace. I'll see what condition the bushings are in once I open everything up...I'd rather avoid plastic bushings and I'd prefer new rubber but they're just not available unless you want to replace your front and rear control arm$.