RSR coil overs for street driving

Anyone have comments on the practicality of driving the RSR set up (1974 coupe) on the street.
I like the idea of adjustable coilovers better than torsion bars.

Well, ordered the front struts and rear shocks. Any suggestions for spring rates. Any comments on progressive vs straight rate springs?
I figured about 300 lbs for the front and about 450 lbs for the rear. But I am concerned about the added wieght of the 3.2.
Thanks

[Roland Kunz]

Hello

They work very nice on race cars and race tracks.

Use in a not massive modified car is absolute bull****.
Will just hammer your car togehter and leave a wrack
after several 1000 mls.

So add the reinforcement braces and the full roll gage plus
reweld many seams and body joints and you will be prepared for it.

BTW the torsion bars are easier to adjust and more flexible the Coil overs.

Porsche first used the coil overs in addition to the tosion bars and on race cars the problem was that the needed stiffniss would have forced to much heavier torsionbars and producing them was more expensive then a ceap coil. A race setup needs some 10-15 differnt coils to search for the optimum.

Grüsse

[KTL]

I remember reading/hearing what Roland said. Being that the rear shock tower/firewall was not designed to support the action of the coil-over setup, you need to reinforce that area. Such as with a full roll cage or the like. Not a street car now.

[Roland Kunz]

Hello

Yes KTL is right, i was a bit short. ( many other posts where waiting plus i work delayed offline so I thought I would be the 3-5th in the row )

The bodyshell isn´t designed to carry the load on the strut towers as the strut towers are only things that hold the shocks in position.

To proof that just remove your rear shocks and st the car to the ground. If you like a real wild ride then just drive around the block ( Well if you overdoo that local wrecker will be the last resort for the car )

To avoid stressing the car you have to go for a very low spring rate with is much softer then the original torsion bar.

Anyhow if you combinate both systems you maybe find a good improvment but with so much parts involved it is very time consoming to optimize the car for a perfect handling

Grüsse

Roland
Thats what I thought would happen being the car is unibody.

That being said the car more than likely will end up as a track car.
My main concern is the rubber bushings on the rear suspension. Looks like a very good way to end up with some very nice toe changes under acceleration and braking.

I have the adjustable arms but I am not very satisfied with the way everything works. It would seem the better setup would be monoballs on the inner mount and some sort of bearing rod end setup with the torsion bars. Kinda like the ERP 935 setup, but using bearings for the arm to rotate on instead of rubber/delrin bushings. That's why I am looking at the coil over setup.

I am new to Porsche cars but I am not new to racing or turning wrenches. I have gone through the whole race car engine & suspension setup for drag racing.

I would rather overbuild something than have to keep going back and repairing/changing it.

Having not looked at a newer model What did Porsche do to reinforce the front end to use coil type struts?

Also, you had some good advice on the 2.7 to 3.2 conversion that has been very helpfull.

Thanks Chris


Dickdarm unannehmlichkeit ist gute!

[Yargk]

This is the stuff headaches are made of. I am currently in the same position of considering using an RSR set up in a street/track 930. I believe my car will be in the "massively modified" category Roland mentioned. I will have an engine creating more go power than the current GT2 and as much stop as big reds supply to a 2800-2900 pound car. I want a suspension to match so I would like to go beyond the 23, 31 barrier of torsion bars. I think the other aspects of the car demand it. Is there anything I can do to get the car to safely carry it's bulk on coil overs? I understand reinforcement, however it seems from what I heard so far that it's just not desined at all for a coil spring set up. However, the race cars use it so is it just that it can't be made strong enough for the bumps of street driving?

By the way, the "porschtanic" metaphor in the other thread was great Roland.

What I did with my 1963 Nova was to tie the front and rear together with a subframe. I replace the front end (it unbolts) with a 2x4 box frame using mustang 2 controll arms and coil overs. The upper coil over mount was tied into the roll cage.
The rear end was replaced with a 2 by frame and the rear coilovers where connected to there own crossmember which tied into the roll cage. That was good for 10.53 @125 mph at Bremerton raceway. The car ran 10.09 @130 at Firebird untill it whent belly up going through the 1st mph lights.

So it seems we are in the same boat. How do you reinforce the tub without turning it into a jungle jim.
It can't be that hard to make it suitable for muliple use.
Chris

[cds72911]

Hi all,

I'd guess that you'll have to have a full roll cage tied in to the strut mounting points. At that point the cage is the structure that prevents the car from flexing or distorting rather than the unibody.

It is my understanding that a car with a full cage is not suitable for street use (without a helmet) because of the danger of smashing body parts (particularly the skull) into the roll cage and doing serious bodily damage. I heard of one rally driver dying of complications after crashing his car during "daily driver" use.

I always used my full harness if I was on the street, but I felt exposed (particularly on transit stages).

Cheers.

ps. here is my old rally car (full cage tied in to suspension pickups):

[89911]

FWIW, OG racing is coming out with a new adjustable spring plate/torsion bar setup for 911's to allow a stiffer functional bar. It seems 31mm is the max size you can fit in the torsion bar tube. Their design with effectively shorten the torsion bar by engaging the splines on the shorter bars closer to the center of the car. I spoke to them the other day and the plan to have this out soon. Could be worth looking into if not overly expensive. Ditto with all the coilover comments. If you are planning to track your car, coilovers will bump you into the modified classes. You then will be running against drivers with more $$$$$ then brains at times.

[Roland Kunz]

Hello

Yes the 911 is a unibody construction but its a optimized to the purpose egeneering. Why add wight and complexity for a strut design not needed for the car ? The beauty from the design is use the torsion bars and all the benefits offered with them.
The lighter the car and the lower the heavy parts are in the car the more effektive the system will work.

However the car was designed in 1960 and when it hit the road the first steel radials where used on it and in the 70´s the tire technology went durther in big steps forcing to more rubber and heavier wheelcombinations showing the limits from the torsion bar setup.

Sure there is a point when the coil over has better performance then the torsion setup.

Most parts are aviable and you just can follow the path from the factory or other succesfull raced cars.

The coil overs came with the 934/935 in the mid 70´s since then many people find better solutions or other ways to gain similar.
Anyhow to make it work you have to recunstruct certain areas and many parts need massive construction and welding

The 964 has a complete other pan ( and much heavier shell ) and only the old skin and the 993 rear axle is very clever made ( but very nervous if you missaligne ) and nearly ready to race.
Yet the pre 91 964 showed some stress in race use and with the 92 MY porsche Redesigned the axles and the strut tower just in time for the RS. But still the 964 and the pre 95 993 are slight critical using to heavy ( big ) wheels and need RS reinforcements if you wan´t to track them serious.

A clever way to incoperate a full gace into a early chassis is done by RUF. Not sure how they named it. Came wit every CTR.

Grüsse

Roland
You are taking all the fun out of re-inventing the wheel.
Has anyone tried replacing the spring plate bushings with bearings? Seems it would cut down on the toe changes and allow the suspension free movement.
Just a thought.
Guten Tag
Chris

[Roland Kunz]

Hello

Those things are offerd from smartracing

The RSR coil over front axle is a complete other lower A-arm. They have no bushings just direkt rods with a earlink on the end.

Very rough for streetuse only usefull if you have earplugs and goat leather skinned hands.

Grüsse