Suspension advice on fast road car

[GT Two]

Hi,

My car is a 1970 911e dressed as a 1973RS. The suspension needs overhauling and I would appreciate any advice from owners that use their car for fast road and a few track days per year.

Struts

Im thinking Bilstein Race 1 inserts for the front and Race 1 shocks for the rear. Can anyone else recommend anything other than this setup?

Top mounts

Has anyone used Rennline with an early car? I have used them on a 964. Should I stay OEM?

Many thanks

Lee

[sladey]

That may be a little stiff. I think I went bilstein sport all round, and many argue to go one softer than that (can't remember what they are called)

Re rest of suspension components you can spend a happy few days trawling through the elephant racing website' Rebels racing one is quite good.

I've got elephant polybronze all-round but the regular greasing is a bit of a ball-ache - will replace with their spherically when I get round to it. I used to have their monoballs on my front suspension tops but eventually they failed (I drive the car every day - 10-12K a year) and I've gone with super-pro which were a lot cheaper and not much different.

[redrobin911]

Firsty don't do all your modifications at the same time tempting as it may be. You need to do one at a time to see what differences they make you car and if it starts to handle the way you want it to. I had a similar car to yours, raced it, hillclimbed it drove it.

I wouldn't go too hard on dampers - bilstein sport is what I think you'll want, also consider slightly bigger torsion bars front and rear - but do both front and rear at the same time, same with anti-roll bars go up slightly and put adjustable drop links so that you can tweak it for road and then trackday use.

I'd also fit a front strut brace to improve turn in.

The most important thing is getting the car corner weighted - this makes a massive difference - plently of refernces on this forum regarding this. And at the same time get the camber and castor set up - factory settings (for an RS) are pretty god out of the box but could be a little more agressive. Doing this alone will greatly improve roadholding.

Lastly - dont forget to put good tryes on it - I would stick to factory sizes and something a little more sticky.

All in all there are so many modifications and its easy to get carried away with so much (sometimes conflicting) info out there, do it bit ny bit until your happy.

[GT Two]

Thanks for the details, very helpful!

Ok I will go for the Sport dampers and probably elephant racing adjustable top mounts.

The car already has RSR torsion bars and Turret strengthening plates as well as a strut brace.

I will add turbo tie rods, new ARB drop links and superpro bushes.

Re Tyres, I have Toyo T1r. 205/55 and 225/50 and am struggling to find anything else in correct sizes. I had Michelin TB on a previous car that I loved but they do not make a 205.

I heard somebody say that r888 will be banned for road use? Can anyone confirm this?

Thanks!

[hot66]

before you buy your shocks, try and find out what diamter torsion bars youve got. It might be worth spending a bit of time reasearching what shock rates match the spring rates of your torsion bars.

Also, don't be swayed by the US trend of over stiffening the suspension .. they always seem to go OTT on torsion bar size etc etc

I'm running ER polybronze bushes , have been for maybe 7 years +. I find them to be great. A asquirt of grease every so often. We stipped them down recently and they were almost like new

[Lightweight_911]

Assuming your car is fitted with 7" & 8" wheels you may want to consider original tyre sizes - 185/70(F) & 215/60(R).

Avon CR6ZZ's are one of the best road-legal tyres available in those sizes.

[911hillclimber]

Just another slant for you that might not be popular.

My 911 is a 73T that has had a 2.2, a 2.4 and now has since 1998 a 3.2 in the back.
Road car used for hill climbs for 14 years with all 3 engines. The 3.2 is far heavier than the 2.2/2.4 hence adding that detail.

Much of this advice came from Bob Watson and a bit from Josh Sadler since 1991. I still have the car, retired from the hills now.

My car got

3 Litre turbo rear torsion bars, T front ones (standard)
Bilstien dampers custom valved by Bob, but = to Sports mentioned. Not too stiff. I feel the 911 chassis need to be compliant rather than Kart stiff.
Poly bushes all round, no rubber anywhere, but I then fitted rubber to the front wishbones and top mounts due to polybush squeeks. Never noticed any difference in the drive.
I had monoball top mounts made by Bob, but replaced by stock rubber, never noticed any difference except a lot less noisy.

Turbo track control arms.
RSR style strut brace when I fitted the monoball top mounts. Still in the car.
Aluminium rear arms with split spring plates. Your alignment man will thank you.
2.7 RS size rear antiroll bar, S through the body front bar.
A type calipers front with Carbone Loraine pads, stock rear with same pads.
Vented/drilled discs.

7" wide rims and for the best grip, Kumho V70 E marked tyres which are low profile but sure grip. Tyres are a very very big part of this list!

Good racing seat that fits you and sat low in the car.
Momo or similar smaller steering wheel
4 point harness for the track, road belt for the road.

The best alignment you can get from somebody who knows these early cars.
Corner weighting has a dramatic effect on the handling towards the limit and you will notice things on the twisty Welsh roads too!

Set the front height such that the track control arms are level static on level ground/bench
Raise the rear such that with a spirit level on the sill of the shell there is a 1 degree 'nose-down' stance.
Caster/camber/toe are all where you need to talk to a real expert in these cars. Centre Gravity come to mind.

By car was NEVER as good as when Bob Watson did the whole alignment on the car using string, Dunlop camber castor gauge and Dunlop tracking frames.
Oh, and he actually new what he was doing.

Hope this is of help.

[smallspeed]

I'm reading this with a general engineering interest and a hunger for learning about anything car related. I have nothing 911 specific to add, but the following points stood out to me, and I feel are worth highlighting based on my experience elsewhere

Carbone Loraine pads

I've put about 10k miles on my CL pads (I have RC6 compound, although 5 or 5+ are prob better suited for road/track use) and I'm convinced there's witch craft at play.. They have great bite from cold, produce eye-popping deceleration when warmed up, but some how don't wear that badly AND don't wear out the discs either. I'm still trying to understand how they've achieved all of those things, because normally the most desirable characteristics are traded off against one another. Best pads I've used hands down (history includes several different sets of Ferrodo, Pagid, Mintex and Hawke pads)

Kumho V70 E marked tyres

I've run these on my e36 as they're the control tyre for several championships and they're awesome! Not stupidly expensive like some of the other "track-day" tyres either. If you need a one-tyre solution this is a great option! R888's last no time at all on my car (aggressive camber/toe) and Dunlop direzza's are too rich for my blood but if you can justify them though, they're worth considering also

Corner weighting has a dramatic effect on the handling towards the limit

Make sure corner weighting is done with the correct weight in the car (fluids, driver weight, etc) - I've heard of 3 cars THIS YEAR which people spent a lot of money having set-up without any weight in them

Set the front height such that the track control arms are level static on level ground/bench

This is really important - I'd even say set to this height and then raise the car by 1/2 the expected compression due to cornering roll. It might not look stanced, but it will help you out a lot. Big mistake I see all the time on BMW's is cars lowered to the point the front control arms are horizontal or even pointing upward - as the car rolls in a corner you get a very rapid "bleeding off" of camber from negative to positive, compounding the reduction of grip you get as you push-on.. Not sure if its possible on 911's, but if you want to go really low, add some bump steer and roll centre correction to off-set this and get you back to a geometry where you're maintaining your negative camber for longer
The right alignment people will know what the compression / camber curve looks like for your car and set-up accordingly

My car was NEVER as good as when Bob Watson did the whole alignment on the car using string, Dunlop camber castor gauge and Dunlop tracking frames

3 golden rules of alignment..

Knowledge is king - go for someone who knows what they're doing
Never underestimate the power of string - LASER's are just showboating
Hub stands are worth every penny

Even the F1 boys use string

[Steve Warson]

Also, don't be swayed by the US trend of over stiffening the suspension .. they always seem to go OTT on torsion bar size etc etc

Set the front height such that the track control arms are level static on level ground/bench

This is really important - I'd even say set to this height and then raise the car by 1/2 the expected compression due to cornering roll. It might not look stanced, but it will help you out a lot.

That! No matter what the stance-monkeys say or simracers think they learned on their playstation, believe the above!

[Uk911]

Hi Lee,
Just my two pennerth, but please remember my car is still a work in progress and at time now hasn't turned a wheel, but re suspension I rang Tuthill porsche and spoke to Paul Green, told him what the car was to be used for , approx weight, driving style and a few other questions he asked me and he supplied the Bilsteins with the correct bump and rebound for my use and they were no more expensive than anywhere else, and he even give me torsion bar and anti roll bar size advice too
Regards
Mark

72' Marmite Panzer..

[GT Two]

This thread has been massively helpful to me, thank you very much.

One of the main themes is do not over do it with a too firm setup. I need to find out what size my torsion bars are as the only information I can find is that they are 'RSR'

The car was used for hill climbs by Josh Saddler and Rod Carmen so I will dial it back a bit for general road use and the odd track day.

Thanks again!

[911hillclimber]

You could do far worse and simply ask Sadler to do the lot.

Ref the brake pads, I fitted these after trying 5 different types over ther years and it is uncanny how good they are yet little brake dust ( and what there is does not stick to the wheels) and the discs look good as new.
They have done 3000 miles now.
The biggest drawback to them is they are noisy, squeal a bit under light braking and groan when working hard, but do they ever work!
They are not cheap!



Ref Corner weighting.
If the alignment man does not ask you what tyre pressures you use, or do you want to drive fast on your own (hill climb) or track day with a mate, or is the tank 1/2 full he is a waste of time, and move on.
Bob asked all this and my weight and ballasted the drivers seat AND footwell before he started.

Simple equipment and a top bloke who actually knows what works and why.

Bit rare nowadays, especially now....

[smallspeed]

Yeah I heard the rc5 compound was noisy and so moved to rc6 which are a bit worse bite when cold but better hot and no squealing.. Heavy-ish car (1050kg unladen) so a good choice. By all accounts the newer rc5+ compound fixes all your issues
Price wise they were 200 per axle I think for my car so about 25-50 cheaper than the pagid ones they replaced..

[911hillclimber]

I paid the same 4 years ago!
Never tried Pagid, about the only make I haven't tried.
Can't remember which grade I have, but were supposed to be noise-free...

[NurLinks]

To confuse you a little more, some thoughts from personal experience. If you just want to have another example, please skip my ramblings and go straight to the end.

Some general stuff:
-Don't rely on descriptive advice from 'specialists': 'RSR' or 'RS' doesn't say anything about the specs or performance of dampers, bars, ARB's, etc... These descriptions are marketing tools and nothing else. If someone sells you an RSR spec engine would that mean anything to you without a BHP and Torque graph?
-Be careful when buying of the shelf stuff. It's your car and is specific in terms of weight, tyres, engine power, intended use, etc... What works on one car won't necessarily work for others. Of course this doesn't mean you can't learn from others but factor in differences between your car and the cars of others who give you advice.
-If you spend (a lot of) money on dampers, make sure that you buy from someone with the facilities to test and adjust settings. First of all some brands have considerable variations even between freshly unpacked dampers of identical specs. Have them tested. Secondly almost every damper can be revalved to you taste by a professional (even most non adjustable dampers like Bilsteins can be revalved to your tastes and needs). Anyone who tells you differently doesn't know his stuff. Adjustable dampers sound nice, but they only work if their basic characteristics are correct and if they have a workable adjustment range. If you have dampers with '45 clicks' of adjustment and only 8 of them make a meaningful difference they are of limited use. Again: 'Bilstein 1' or KW Variant 1, 2, 3 or 876 means very little to me. It's descriptive marketing bullsh*t, have someone show you a graph of the damper and ask for an explanation why it will work on your car.
-Contrary to what others said, I prefer to change the suspension as a package. In my experience components usually do not work to their best when fitted separately. E.g. stiffer bars with soft dampers will drive horrible. Some things you can upgrade, but the initial package should already work correctly as a system. Don't forget that you will have to align and cornerweight after almost every change, so getting it right in one go also saves a lot of time and money.
-I agree with some others who say that the basics are essential for the suspension to work: cornerweights (done correctly of course as said above), elimination of friction and play in all parts, bumpsteer correction, alignment (indeed, a string works perfectly), tire pressures. All these things can make a massive difference to the feel and performance of a car. A car with GBP 5000 spent on parts but with bumpsteer and poor alignment will drive like a turd.

More 911 specific:
-If you want to track your car and drive it on the road as well, you will always make a compromise. However, you can compensate a lot by adding some adjustment options. Adjustable dampers and ARB's can greatly affect performance (if you have chosen well on torsion bars) and can help you to have a more road or track biased setup depending on your mood or the day.The same goes for an extra set of wheel with track focused tyres. I think it's great to be able to make the car softer on a wet trackday, have more traction and wet weather grip. With some practice you can change damper settings and roll bars within 20 minutes.
-As said by others, split spring plates are great for speeding up the alignment process
-An adjustable bumpsteer kit is necessary of you lower your car significantly
-Struts with (19mm) raised spindles are great if you want to have a lower car without messed up geometry

My specs on the RSR look-alike:

Weight: 960 kg
Tyres: Michelin TB5 (for dry/damp/hot track use) TB15 (damp/wet/cold track use and road use) in dimensions 18/60 and 23/62
Wheels: 7*15 and 9*15
Bushings: uniball topmounts, uniball rear suspension arms links, polybronze bushings for spring plates and front suspension arms
Anti roll bars: 19 front, 22 rear (Ben Coles, both 5 position adjustable)
Torsion bars: 21 front, 28 rear (Elephant) with adjustable drop links (to eliminate pre-tension)
Struts bodies: Bilstein with 19mm raised spindles
Dampers: Ohlins (one way) adjustable dampers with custom settings
Weld on bumpsteer kit (Elephant)
Split spring plates (Elephant)
Turbo steering arms (Elephant)
3.3 Turbo brake calipers with Performance Friction PFB 08 brake pads and driver adjustable balance
Front strutbar (weld in)
Reinforced inner wings