DDK - Die Deutschen Klassiker

I'm in the process or replacing my rear suspension bushes. At least, that was the original plan. As always, this is turning into a 'whilst you're in there project'

My 70T has a 3.2SS engine and 915 gearbox, so it's heavier in the rear than stock. After inspecting my torsion bars, they are the original 1970 parts and showing signs of rust and scratches. I've read a few horror stories about the torsion bars breaking, so I thought I would replace them whilst the car is in bits.

Reading Bruce Anderson's Porsche 911 Performance Handbook, he says a common upgrade for the early cars (up to 77) is to install 26 or 27mm torsion bars. I do the odd track day and its not a daily driver, so I'm not too worried about stiffish suspension, but I do want to keep it drivable. Given my car is heavier than stock, I thought 27mm might be better, although I'm no expert.

any thoughts / recommendations? I like the idea of adjustable spring plates though. I think that will make my DIY install a lot easier.

Option 1 - directly from the ER website with free shipping: $1,420 (about £1,226)
Elephant Racing Spring Plate PolyBronze Bearings
Elephant Racing Rear QuickChange™ Hollow Torsion Bars 27mm
Elephant Racing QuickChange™ Spring Plate Kit
I don't need the quick change bits, but as ER don't seem to provide a standard adjustable spring plate, I could go with that as presumably they would fit the polybronze bearings.

Option 2 (£963) from Design 911: This comes with standard rubber bushes installed.
Elephant Racing Rear QuickChange™ Hollow Torsion Bars 27mm
Adjustable spring plate, Rear. Porsche 911 1969-86

Given the expense of this project, my front suspension steering wobble project will need to wait!

Many thanks
Paul

Clean up and protect what you have ... rebuild , and save lots of £ (would be my choice) .... 26mm is seriously stiffer than 23mm (spoken as engineer) ... assuming raw material is the same !

Here are my experiences, not advice.
I have a 73T which got a 3.2/alum 915 back in 1994, the car was a road/hillclimb car, driven there and back to hills and road trips.
On the advice of Bob Watson I installed a set of 3 litre Turbo rear bars (cant recall the diameter) and SC adjustable spring plates to aide set up.

Dampers were custom valved Bilsteins to Bob's specs front and rear, the front bars were stock 73T.
I also installed anti roll bars, 2.7 RS spec. and all rear bushes were what we would describe as Polybushes today inc alum banana arms and their bushes.

30 years later the car still has this combination except the rear dampers which are adjustable KONI set 50/50 in the damping range. The Bilstiens leaked about 6 years ago so were changed.
It rides just great, takes all the bumps like a good 911 does and I would not change it.

I stopped hillclimbing it (it was in the road going class) 15 years ago and I've covered at least 70k miles in my 33 years with the car.

These larger bars are quite expensive (mine were £20 then) but i trusted Bob's advice totally. The car was superb on the hill climbs driven hard as I dared, now i just have nice days out in the car.
A measure is the wife likes the ride etc so certainly not as harsh as my Boxster...

As to your bars.
They can fail due to stress corrosion, a crack might appear and corrosion sets in and thing race away and snap, it has gone.
You could clean the ends of the bar to bar steel and carefully look at the surface and if good simply clean, etch prime and paint leaving the splines bare. Grease lots on assembly.
Any second hand bars could suffer the same fate, so new is the only way to be free of the thought they may fail.

They are handed, so be sure you have a L and R stamped boldly on the ends of any second hand bars if you go that way.

Anyway, just my long time experience with a car spec much the same as yours, hope this helps you.
Graham.

the torsion bar update Graham has got was a popular one, which from memory are 26mm. Something Ive considered over the years but never got round to although I do have ER poly bronze bushes and custom valved bilsteins at the rear and up front have custom raised spindles and again modded bilstein inserts. All with stock torsion bars. If I'm honest, I still probabally would like a slightly stiffer rear spring on mine and have considered the same upgrade but in reality I'm very happy with the set up I've got . I dont track the car though.

As an aside, I'm sure I read the weights somewhere & the 3.2 wasnt as heavy as you expect and the difference between it and an early motor not vast , especially if running the same induction etc

Again, not advice but my experience; I have a 3.2 made into a wide body hot-rod. I used 20mm front and 26mm rear bars, both ER hollow. As mine is somewhat lightened from standard 3.2 I decided 20/26 was stiff enough and indeed it is a good balance between road and track. One thing I can report is you will save a surprising few KGs changing to hollow bars, they are WAY lighter!

Weights:
The 3.2 has an aluminium block, much else the same as a 2.4, the same goes for the box, so i would guess the 3.2 drive train maybe 15Kg heavier, so not much considering how heavy the pair are anyway!

I was looking to get better hill climb performance at the same time, this combination gave rise to the 3 litre turbo bar choice.

The car was a much nicer 'sports car' after the mods and a more 'track' oriented set up by Bob, so a few things changed at the same time.

I would imagine the early stock bars for a road car would be fine, but nicer if stiffer for a track adventure.
I feel the 911 chassis needs to be kept supple.

.

In terms of the comparative engine weights an mfi engine (complete but without oil) weighs 182 kg & a 3.2 Carrera engine weighs 219 kg.

I've had several early 911's - each of which was significantly modified - with uprated (original) engines/brakes suspension.

Regarding the torsion bars they included 19 (F)/26(R), 21(F)/27(R) & 21(F)/28(R).

The cars all had other modifications - lowered, increased negative camber, thicker anti-roll bars, etc but only the 21/28 combination proved to be too stiff for me (exacerbated by the fact that the car was significantly lightened).

Other factors can have an influence too - including tyres - the car with the 21/28 torsion bars was on Avon CR6ZZ tyres which have very stiff sidewalls.

.

that is a big weight difference!
I certainly felt that for a while just after the engine/box swap over, but soon adjusted.
Soon after the swap I tried a set of huge anti roll bars, the Weiltmiester (sp) type from a circuit car and the car was really not nice.

Always felt my 911 rode on the UK roads well.

Andy, is that the block or complete with all the extra gubbins. I was referring to say a 2.4 engine on carbs compared to a 3.2 on carbs and early style exhaust etc

I read this thread with interest, I have a standard 71 S and during the build went back to standard torsion bars, I havent driven it in anger yet so I will look to see how it works out.

I ended up with a pair of 22mm front swayaway bars that I am not using if anyone is looing for a stiffer alternative!

hot66 wrote: ↑Mon Jan 23, 2023 5:33 pm Andy, is that the block or complete with all the extra gubbins. I was referring to say a 2.4 engine on carbs compared to a 3.2 on carbs and early style exhaust etc

That figure is for a standard 3.2 Carrera engine James - don't know how much it would be retro-fitted with Webers/PMO's - Jon (Miller) would probably have an idea ...

.

Thanks for all your advice.......

Just for reference, my car has 79 3.0 engine, which is now a 3.2SS with twin plug ignition, 46MM PMOs, lightened flywheel, FG tinware, Turbo Thomas dual outlet stainless exhaust. I also have a fibreglass rear bumper, aluminium engine lid and 915 gearbox. I would imagine that its probably lighter than stock overall. I also have Avon CR6ZZ tyres.

In the interest of cost, my stock spring plates are now being refurbished, so I'll keep them for now. I'll go ahead with 26mm rear bars and polybronze bushes. I'll keep the stock anti roll bar, but refresh the bushings on that too. The front end will need to wait, but I'll go with 20mm there when I get round to it.

Paul

26MM bar and polybronze bushes arrived from Elephant racing. Even with the 20% VAT and import duty, it was still a lot cheaper than buying in the UK. ARB bar is back from being powder coated, so I'm just waiting for spring plates, covers and hardware to be returned from the platers and a few bushes that are on back order from Design911 before I put the rear end back together and move onto the front end.

Late to the thread, but by my reckoning 26mm bar is 27% stiffer than 23mm. Is that a lot? It's what I have done and it's noticeable, but works well in my view

Spring rate increases by the 4th power of the diameter.

So: ((+3 / 23) +1) ^4 = 163% or 63% increase