911 Suspension: Different worlds

[Marko888]

Observed after a ton of reading and many conversations with various tuners, it is quite interesting the difference in theory between North American vs UK ideas on setup of a street going 911.

My 1987 Carrera at 2800# is admittedly a heavy 911. When asked for a sport touring setup, NA tuners typically recommend 21/28 or 22/29 torsion bars and custom valved shocks.

Totally contrasting these suggestions, is the famous rally car builder in the UK recommending 19/27 TB’s for a fast road car, with HD/Sport Bilsteins or super trick EXC-TC dampers. Of particular interest is the comment that stiff torsion bars in the front “ruin the car”.

I’ve never been to the UK. Perhaps this is just a reflection of the roads they have fun on being rougher with a slower rhythm.

Thoughts?

[Reiver]

I'd be interested in the weight of the 911 they were setting up for....was it 2800 lbs.?

I've lightened my euro 911 SC to 2300 lbs. wet. The '83 year T bars are excellent for that weight stock.
Actually, many who want a firmer set up get the bars you are mentioning but with the lightened 911 my stock bars are a free upgrade. I also went with stock rubber bushings all around. I would not want a firmer street set up.
I think lots of mods go to far in this respect with 99% road and 1% track time.

[Bill Verburg]

Originally Posted by Marko888

Observed after a ton of reading and many conversations with various tuners, it is quite interesting the difference in theory between North American vs UK ideas on setup of a street going 911.

My 1987 Carrera at 2800# is admittedly a heavy 911. When asked for a sport touring setup, NA tuners typically recommend 21/28 or 22/29 torsion bars and custom valved shocks.

Totally contrasting these suggestions, is the famous rally car builder in the UK recommending 19/27 TB’s for a fast road car, with HD/Sport Bilsteins or super trick EXC-TC dampers. Of particular interest is the comment that stiff torsion bars in the front “ruin the car”.

I’ve never been to the UK. Perhaps this is just a reflection of the roads they have fun on being rougher with a slower rhythm.

Thoughts?

Different philosophy

In the US bigger is often equated w/ better w/ little thought to consequences

for track use bigger balanced t-bars makes for a sharper quicker handling car, great for fast smooth tracks, but a consequence is less grip in marginal slick conditions

19/27 changes the balance of the car, it increases oversteer or reduces understeer a lot from stock. This can be good it that is what you want

The higher the ride frequency the more the car wants good aero which is something many track cars will have but will be usually lacking in street cars

For street use the main thing that I don't like about a stock 911 suspension is the relatively large amount of roll that the cars exhibits, this can be mostly tamed by using moderately bigger bars, at 2650# w/ 300hp motor I like 20/26 , the suspension is still supple and responsive but w/o the roll and grip levels aren't noticeably reduced when the road gets a little ugly


The ride frequencies here are for a 2650# car split ~420/720(My car)

[Marko888]

Another part of the different philosophy is in the dampers. The European approach appears to tend towards softer springs and firmer compression valving in the shocks vs the NA approach of firmer springs with lighter compression valving. ... then of course the additional variable of progressive vs digressive valving.

[Marko888]

Originally Posted by Reiver

I'd be interested in the weight of the 911 they were setting up for....was it 2800 lbs.?

I've lightened my euro 911 SC to 2300 lbs. wet. The '83 year T bars are excellent for that weight stock.
Actually, many who want a firmer set up get the bars you are mentioning but with the lightened 911 my stock bars are a free upgrade. I also went with stock rubber bushings all around. I would not want a firmer street set up.
I think lots of mods go to far in this respect with 99% road and 1% track time.

Yes, 2800#

[donbecker1234]

Any discussion of springs (torsion or coil) seems low value if the discussion doesn't include dampers (shocks / struts) as part of the discussion.

Also, both the front and rear bushings have significant amounts of stiction (resistance to turning) so excluding those from the discussion also leaves questions.

[3literpwr]

I have run 23/31 on the street / track day for years with adjustable dampers. I would like to go to 21/31 as I feel that 23/31 has too much understeer for my taste. On my rally car, i'm planning to run 19/27 as of now.

[Ian Comerford]

There is also the issue of the discrepancy between our roads here in the UK and yours. Smaller, narrower, in many cases twistier vs the opposite.

[Driven97]

You forgot the classic argument of "what's better to control roll, spring or swaybar?" That's a good one to get people to start calling each other names.

Remember, chassis setup is like a cooking recipe. Small changes don't necessarily make things better or worse, just different. What's important is that you get an end result you like. And, you can also totally c*ck it up with too much of something.

[GH85Carrera]

My 85 Carrera is 2741 pounds on the corner balance scales. Part of that is the 4 condenser AC system. Being able to drive my car in the hot summer months and even have my wife with me is worth every ounce of weight.

I have 21 MM front and 27 rear, with the Bilstien HD shocks. Once again, I think it is prefect combination for a car driven on the highway or at the occasional track event. Of course the requisite turbo tie rods, new ball joints and all new rubber suspension parts make for laser pointer accurate steering, and very neutral overall handling. I love it.

I see guys that go for the stripped down lightweight car with squeaky plastic suspension bushings and no AC or heater. I can't do that as I have driven my car in weather with 16 degree mornings and in Savannah, GA 135 degree heat index days.

There is no universal right or wrong for suspension on a 911. It all comes down to what the owner likes, and what he wants to use it for. My track days are 100% for me to have fun, and I don't care one wit if other cars are faster. I am riding in cool comfort on the trip home from the track in the same car. And I can drive my car in the rain on the highway and feel completly safe.

[ClickClickBoom]

Suspension tuning is as much art as it is science. The art part is preferences, Picasso vs Van Gough, the science is how to attach the bits and pieces together. There is a synergy between all the parts and how they are set up, it is truly a system, and making it yours means you will love it and someone else won’t.
With all the stuff I have done to my car, my wife can’t tell the difference in ride. California has some of the roughest roads that rival the AlCan highway. My car is comfortable enough for 900 mile days and tight enough for constant mountain carving. I can honestly say there isn’t a thing I would change:
The suspension upgrade!
My set up is the result of fairly lengthy conversations with Chuck at Elephant, Steve Weiner at Rennsport and Clint at Rebel, I wish I could claim to be the designer, but when consulting with the likes of these gents, I end up being a parts monkey.
I have said it before, as the years went by Porsche slowly started catering to the luxury crowd. As a result the cars started becoming more bloated and soft, at the expense of everything they originally were designed for., Sport Touring. I wanted a Sports Car, light, tight and fast around a corner, I have achieved my goal and for once didn’t go too far. With the reduced ratio steering rack, sways and suspension bits, I would like to think my car has shifted back towards the long hood era, whilst keeping the good stuff(3.2).

[djpateman]

Is all of this with or without sway bars? If with, then what specification? Would tire choice also be important?

[GH85Carrera]

Originally Posted by djpateman

Is all of this with or without sway bars? If with, then what specification? Would tire choice also be important?

On my 85 I did replace the anti-swaybar bushings, but the antisway bars are original.

And there is no other single easy to replace thing than tires that makes a huge difference.

Bottom line, first determine what are your goals. Do you want a track rat car that is painful on the street, or a cruiser that is ultimate comfortable, or a general all around car. Every component is a compromise between price, comfort and performance.

[Driven97]

Originally Posted by djpateman

Is all of this with or without sway bars? If with, then what specification? Would tire choice also be important?

Sway bars add roll stiffness without adding single axle bump stiffness (and, by extension, pitch stiffness) so the answer is - it depends on what you want.

Tires are super important to the overall performance. Very very generally, the stickier the tire, the stiffer the car setup will likely be to maximize the potential.

Again, holistic approach. Define what your needs really are, and create your package around it. There's not one answer.

[smokintr6]

Driving style, diver preference, driver skill, and surface type are the biggest factors in what performance setups work best for each application. Driver skill is probably the biggest attribute, and its hard to nail down because everyone thinks they are an expert. real expert drivers will be able to drive around the setup preferences of others. "good drivers" may need the setup to be a certain way to feel comfortable pushing the car.

[icarp]

Marko, I have a somewhat different driving philosophy. I have been teaching driving and racing for 45 years . I just had a driving day at Thunderbolt race track in Millville NJ. I run my 73 rs clone
( actual 80 sc ) 2300# 3ltr with 205/60/15 and 225/60/15 mini van tires . The car is fantastic fun .
I get to drift it where ever or whenever I want . I am running the stock SC suspension . I was able to keep up with spec E 911's in most of the turns , they have R compound tires . I am a real fan of softer springs and smooth driving , my shocks are Bilstiens front and rear . The ride height, @ fender lip, is also 24.8 " up front and 24.5" in the rear. The toughest turn was the octopus 270* and I had more body roll than the other cars , but so what , that is called mechanical grip. I would loose maybe .2 sec per lap in that one turn . My driving style would let me catch up in the other turns . Also I drove the car from my home in New Mexico to the east coast and back. 6,000 mile round trip. Same tires the whole way and no visible wear , UTOG of 600. Very smooth tires at 80- 140 mph, 33 psi hot
Just my thoughts
Ian

[Jonny042]

Sounds like a great trip, Ian!!! We are due for a catch-up.

Similar to Ian I have a 2250-ish pounds backdate running the 18.8mm front/25mm rear SC setup and at that weight can't imagine wanting more spring. Also running Pirelli CN36's which aren't the stickiest tires ever so the package as a whole is balanced and fun and low stress.

On my 2300lb AutoX car with far bigger and stickier tires (RE71R), I have 21/28 torsion bars and bigger sway bars from Eibach. Also a balanced package but certainly a lot stiffer.

I think a lot of people overdo it with front bars, but then don't notice because they are running on the bumpstops anyway. Check your travel, you might be surprised at how little you have left (if any!!).

[Marko888]

Learning more about this. Ride height. UK setup not as low as NA. Makes sense in that firmer setup with less travel... vs softer setup and more usable suspension travel.

[Bill Verburg]

Originally Posted by Marko888

Learning more about this. Ride height. UK setup not as low as NA. Makes sense in that firmer setup with less travel... vs softer setup and more usable suspension travel.

the wheel/tire setup used also affects this, narrower & taller will be less degraded by roll and travel induced geometry changes, wider/shorter more so

shocks were mentioned earlier while rate requirements will vary by the various weight, speed and environment needs all can benefit from a good digressive valve stack that allows the tire to stay in better contact when presented w/ normal small roads issues control the bigger issues and yet not go harsh like a progressive or linear stack will, If you ever get to do back to back sessions w/ a linear vs digressive setup you will be absolutely amazed

[David Inc.]

Originally Posted by icarp

Marko, I have a somewhat different driving philosophy. I have been teaching driving and racing for 45 years . I just had a driving day at Thunderbolt race track in Millville NJ. I run my 73 rs clone
( actual 80 sc ) 2300# 3ltr with 205/60/15 and 225/60/15 mini van tires . The car is fantastic fun .
I get to drift it where ever or whenever I want . I am running the stock SC suspension . I was able to keep up with spec E 911's in most of the turns , they have R compound tires . I am a real fan of softer springs and smooth driving , my shocks are Bilstiens front and rear . The ride height, @ fender lip, is also 24.8 " up front and 24.5" in the rear. The toughest turn was the octopus 270* and I had more body roll than the other cars , but so what , that is called mechanical grip. I would loose maybe .2 sec per lap in that one turn . My driving style would let me catch up in the other turns . Also I drove the car from my home in New Mexico to the east coast and back. 6,000 mile round trip. Same tires the whole way and no visible wear , UTOG of 600. Very smooth tires at 80- 140 mph, 33 psi hot
Just my thoughts
Ian

I didn't mind body roll in itself when I had softer springs in my stock weight SC, but I got tired of replacing tires that had full tread in the middle and no tread at the shoulders. Even with 1.5-2 degrees negative camber these cars have way too much body roll to properly plant modern tires.

I don't care for how thicker sway bars will affect handling so I went with stiffer springs. Sometimes it's a little much but it's not a daily driver anyway.