Bushings, what did Porsche use?

[safe]

On race cars, like the RS, RSR, IROC, Turbo Carrera, 917 etc, that is.

On the 911s did they use the stock rubber or did they install something stiffer?

[wildcat077]

Magnus,

I'm currently reading an interesting book on the Porsche history from day one including racing and Porsche did have to build so many "street legal"race cars to homologate them for different classes of racing and i believe they used stock OEM bushings and mounts as they were excellent as delivered from the factory ... How many other cars do you know of that have suspension and motor and transmission bushings that last 20+ years !!!

Of course they did have many "limited" build cars that were pretty exotic including a 2.1 liter turbo 911 which developped 500+ hp ...

Cheers !
Phil

[Flieger]

They used hard plastic Delrin for the RSR and later moved to Heim joints and monoballs.

Prototypes like 910, 907, 908, 917 used Heim joints.

[safe]

Originally Posted by wildcat077

Magnus,

I'm currently reading an interesting book on the Porsche history from day one including racing and Porsche did have to build so many "street legal"race cars to homologate them for different classes of racing and i believe they used stock OEM bushings and mounts as they were excellent as delivered from the factory ... How many other cars do you know of that have suspension and motor and transmission bushings that last 20+ years !!!

Of course they did have many "limited" build cars that were pretty exotic including a 2.1 liter turbo 911 which developped 500+ hp ...

Cheers !
Phil

Which book?
I have a few but I can't recall reading about bushings anywhere.

[safe]

Originally Posted by Flieger

They used hard plastic Delrin for the RSR and later moved to Heim joints and monoballs.

Prototypes like 910, 907, 908, 917 used Heim joints.

That was what I thought.

I had a internet-conversation with a guy, that seems knowledgeable in vehicle dynamics, who claims that Porsche took great care designing the rear suspension with the right amount och toe change for throttle, brake, etc. Hence that solid bushings would only destroy the handling and of cause the comfort.
I'm not sold on his arguments yet...

[Bill Verburg]

Originally Posted by safe

On race cars, like the RS, RSR, IROC, Turbo Carrera, 917 etc, that is.

On the 911s did they use the stock rubber or did they install something stiffer?

917 - uniball/heim
2.7RS - stock rubber
2.8 & 3.0 RSR, IROC - needle bearing
2.14Liter turbo Carrera - uniball

It's all in Frere '911 Story' & 'The Racing Porsches'

[safe]

Originally Posted by Bill Verburg

917 - uniball/heim
2.7RS - stock rubber
2.8 & 3.0 RSR, IROC - needle bearing
2.14Liter turbo Carrera - uniball

It's all in Frere '911 Story' & 'The Racing Porsches'

I have both books, better do my homework and read them again.

Thanks!

[stlrj]

Originally Posted by safe

That was what I thought.

I had a internet-conversation with a guy, that seems knowledgeable in vehicle dynamics, who claims that Porsche took great care designing the rear suspension with the right amount och toe change for throttle, brake, etc. Hence that solid bushings would only destroy the handling and of cause the comfort.
I'm not sold on his arguments yet...

Makes perfect sense since they (Porsche) must have known of the inherent compliance of their bushings, the suspension dynamics must have been carefully calculated with that in mind.

Another reason to keep my old rubber bushings! Comfortable, quiet and still handling like she's on rails, why would I fix that?

Cheers,

Joe

[wildcat077]

Magnus,

I saw a reference to "racing" hardware in the Porsche Chronicle book i'm currently reading.I purchased a ****load of Porsche books from Peter S on Pelican and i have yet to read them all but they certainly are a great reference to P cars past and present !
Still have a bunch of racing years books to read up on ...

Cheers !
Phil

[Flieger]

Originally Posted by Bill Verburg

917 - uniball/heim
2.7RS - stock rubber
2.8 & 3.0 RSR, IROC - needle bearing
2.14Liter turbo Carrera - uniball

It's all in Frere '911 Story' & 'The Racing Porsches'

I agree with Bill. I got the Delrin to Heim joint (935) and needle bearing (RSR) from Norbert Singer's 24:16

[Flieger]

Originally Posted by safe

That was what I thought.

I had a internet-conversation with a guy, that seems knowledgeable in vehicle dynamics, who claims that Porsche took great care designing the rear suspension with the right amount och toe change for throttle, brake, etc. Hence that solid bushings would only destroy the handling and of cause the comfort.
I'm not sold on his arguments yet...

He is referring to the "Weissach axle" used first on the 928 and later adapted to the 964. The 993 used a multi-link setup rather than trailing arms, but they continued (to this day) to try to get rear toe-in under braking. It is also sometimes called passive rear-wheel steering I believe.

Basically the Weissach axle uses tuned bushings in specific places in the semi-trailing arm to be stiff in some directions and compliant in a certain direction. This means that a braking force causes the wheel to toe-in, adding stability.

The Weissach axle was never used on a normal "911"- 1964->1989, so you do not need to worry about messing up the handling.

On race cars, they go with metal bearings since they deflect less and have more controllable friction than plastic bushings. They just let the racing driver deal with a looser rear end.

[safe]

Originally Posted by Flieger

He is referring to the "Weissach axle" used first on the 928 and later adapted to the 964. The 993 used a multi-link setup rather than trailing arms, but they continued (to this day) to try to get rear toe-in under braking. It is also sometimes called passive rear-wheel steering I believe.


On race cars, they go with metal bearings since they deflect less and have more controllable friction than plastic bushings. They just let the racing driver deal with a looser rear end.

Well, no, he meant the traditional 911 rear suspension, but probably from a street car view.

I learned the other day that the 928 rear axle is very similar to the current 997 rear axle and that you could relatively easy adopt a 997 rear suspension for a 928.

On the current 997 CUP cars do they remove the compliant bushings for solid stuff and skip the passive steering?

[Flieger]

Right, he was mistaken about the bushings being designed to add toe-in on the 911s. The semi-trailing arm geometry does add toe-in but not because of the bushings. The deflection of the spring plate bushing would add toe-out if there was a metal bearing in the trailing arm. Racecars used hard bushings in both spots. The rubber bushings were not designed to have stiff and soft modes of operation, until the 928.

Since the 993, the multi-link suspensions use a toe-control link that changes the toe for passive rear wheel steering in accordance with wheel bump/rebound travel (up/down). This means that they do not need "tuned" bushings, though they still use traditional, more isometric, rubber bushings (slightly stiffer for RS models).

[Flieger]

964 is a bit of a hybrid. It still looks like a 911 and uses a variation of the semi-trailing arm suspension, so if he is right in a way since 964 used tuned bushings.

Anyway, if you replace the tuned bushings with harder ones the rear will be slightly less stable under braking, but that can be a good thing for an autocross car with a competant driver, so I would not say it would "mess it up".