Torque tube mods?

[gridgway]

Has anyone modified a 911 torque tube to extend the trailing arm brackets for the shorter RSR/930 ones?

If so, how did they do it, what 'design' of modification?

Thanks
Graham

[911hillclimber]

I think there is a detail in the Bruce Anderson book, but I've seen details of this mod from Autofarm many years ago.
Big job and you have to cut the rear seat pans open to do the welding.
Brave move imho.
Www.zuffenhaus.us sell all you need to use the turbo rear arms which I think were the same as the rsr arms.
There is a thread on Pelican all about doing it.
A good welder is needed.

[Lightweight_911]

Speak to Chris Flavell - he has converted several cars to Turbo trailing arms & they have fabricated jigs to ensure the correct geometry during installation.

[911hillclimber]

Is it worth it on a road car, or just the benefit of the stronger turbo arms bearings etc?

[Lightweight_911]

.
Not worth the expense/hassle/benefits on a road car IMO ...

[fetuhoe]

The influence of the 'short arms and the bracket modification on a LWB car is quite subtle.

The SWB car has a 'co-axial' type of geometry which allows the trailing arm freedom to pivot throughout its entire arc.

The image below shows the alignment between the bracket and the centre of the torsion bar.



When the LWB car was introduced the geometry changed and this 'co-axiality' was lost as can be seen below



This misalignment can cause some issues at the limits and does mean that the arm tries to bind up at the ends of its travel and will increase the effective wheel rate at some point.

This will be more noticeable on a lowered car and if Monoballs are used could create a 'hard' limit.

If you fit an RSR/Turbo Arm which is similar in length to a SWB arm but has a different angle the 'co-axiality ' becomes the same as the SWB car but with the reduced Polar Moment of Inertia of the LWB Chassis

[911hillclimber]

New knew Porsche simply did that mounting mod for the LWB, seems a bit clumbsy, but for a road car all is ok. I presume this was the case from LWB intro to the end of the 3.2 cars?
A lot of effort for a road car, but if you have the interest and the parts, why not? (Graham)

[gridgway]

Thanks all for the info. Chris, for the uninitiated (me) what is coaxiality in this contest?
Graham

[fetuhoe]

I think that the real reason for the shorter arm is to increase the camber gain during cornering so that the RSR could be set up with less static camber due to the wide tyres and this is the main impact.

I would agree that the 'co-axial position of the spring plate and intersections is probably not quite the best description and I am not entirely sure if its impact but it is interesting.

It would be good to model the complete set up an see what happens.

The RSR spring plate and torsion bar covers were also quite different to the stock parts and used needle roller bearings as pivots.

[brembo]

Has anyone modified a 911 torque tube to extend the trailing arm brackets for the shorter RSR/930 ones?

If so, how did they do it, what 'design' of modification?

Thanks
Graham

Graham,
Have set ready to fit.If interested,let me know.

[Darren65]

Graham,
Have set ready to fit.If interested,let me know.

Dougie, are these the same arms as fitted to a 3.0RS and would you know if they have the same larger bearing as fitted to this car?

Cheers,

[brembo]

Graham,
Have set ready to fit.If interested,let me know.

Dougie, are these the same arms as fitted to a 3.0RS and would you know if they have the same larger bearing as fitted to this car?

Cheers,

Darren, the arms are from a mid 80's 930 turbo,don't know about bearings.
Also have rsr handbrake set up that could be used on them.

Sorry,meant to send this as a PM