Fitting porsche rear suspension and brakes to a bay

[richbaker78]

After numerous individual requests Ive finally decided to spill the beans on the rear suspension conversion ive done. Below is a step by step guide. Enjoy

The following information is for reference only – I take no responsibility if you choose to do this work and the suspension falls off 10 miles down the road!!! Take and use this information at your own risk. If you cant weld properly then get someone that can to do the small amount of welding required – its not much but its important!! I have completed this conversion on my own 1970 bay and also a 71 bay. I would therefore suggest that this conversion described below would fit an early bay - 68-72. It should work on later bays but I know the spring plates differ.

Parts

The torsion tube from 944 series 2 (you dont need springplates or torsion bars)
complete trailing arms including handbrake set up from 944 S2 (£200-400) these are the wider alloy version with abs.
Bay springplates
Bay torsion bars
Shocks - beetle rears or any other short shocks.
Auto short driveshafts (or machine spacers for normal shafts - don’t buy/make these until everything else is finished and you can measure them. Auto shafts are 525mm.)
Some spacers etc (more details below)
The Porsche wheels you wish to use.

NOTE:The 944 s2 has different trainling arms to other 944 models. Although the 944s2 and 944 turbos came with the Brembo callipers - The turbos did not have the same trailing arms as the s2. S2 arms are unique to that model.


Getting started:

General Tips:

I RECOMMEND YOU DO STEPS 1-6 ONLY ONE SIDE AT A TIME SO YOU ALWAYS HAVE THE OTHER SIDE FOR REFERENCE.

Remove your engine and gearbox for easier access.

Mark the centreline of your existing hub onto your wheel arch - you dont need this mark but its a handy reference side to side.


1) Jack up the van remove the swing arm and mark the height of the existing bolt eye of the bracket on the adjacent tube. Cut the bay swing arm mount off the torsion tube.

2)Now you need to cut the porsche brackets from the tube. Its VERY important that you first weld some temporary metal across the bracket on both sides to keep the bracket together as one piece – if you don’t do this once removed from the tube you will have two separate pieces whch you will spend ages trying to align again. Some small 2mm thick straps will do the job (basically something that wont easily bend). Cut the tube away from the bracket carefully trying to save as much of the radius on the bracket as poss because then it makes a nice snugg fit to the bay torsion tube.

3) Now you have to bolt your wheel up to your trailing arm (with brake disc). Also now bolt the porsche bracket to the porsche arm.

4) Position the wheel in the position you want it to run in the wheel arch - this will be determined by the offset / wheel that you want to run. Position it as if the van is on the ground. Allow plenty of space around the tyre - remember the tyre will expand and also allow for suspension flexing and movement as you drive - i would say at least 5mm clearance is wise. Make sure the wheel looks straight in the arch too - take lots of measurements from good references and spend time doing this. Using an arrangements of props/jacks/ wood/ straps etc etc secure the wheel with the arm attached to the location you want it. (it might be worth making a rough cradle in wood/metal to hold the wheel up)





5) now you should be able to offer up the bracket which is attached to the swing arm mount and see where it falls on the torsion tube. Chances are you will have to move your wheel to achieve contact of the bracket with the tube - the bracket should be able to sit against the tube on both sides or at least within 1mm (depends on the accuracy of your cutting) once its flush and the wheel looks striaght and your happy that everything alligns - put some strong tack welds on the brackets (make them accesible in case you need to cut and redo). The bolt holes on the bracket should aproximatly level with the original VW ones that you marked on in step 1.

6) Now you should be able to remove the support from the wheel and the arm will swing on the bracket. you will notice that becasue the arm mounting is at an angle the wheel will now follow an arc when you look from the front or back (unlike your old van ones). Jack the wheel all the way up and down to the limits of your suspension and make sure that the wheel and suspension is not making contact with anything like the wheel arch etc. If you run extremely low its possible you may need to notch the rear chassis leg but you wont know this till everything else is done and the vans back on the floor....make sure you check back though!

7) If your not happy with the location of the wheel now is the time to change it - redo the above steps 4-6 until your happy.

8) Now mirror what you have just done on the other side. This sounds easy but its easy to make a mistake - make sure that the arms are positioned exactly in the same location, measure off of the torsion tube and do not use body panels as references. You may refer to your original marks from general notes at the start as an approximate reference but dont get to hung up unless they are miles out. The most important factor is measuring the brackets location from the centre of the torsion tube and making sure they are located on the same level on the torsion tube. Once this is done repeat step 6.

9) Now you should have your two arms hanging down on the brackets - remove the wheels and brake discs now for access.






10) Raise the arms to the height of the spring plates. You will see that the bay spring plates have 4 holes....the porsche arm has 3. With the arm raised to the same height as the spring plate - transfer the holes from the arm to the spring plate. You can do this using some m10/12 stud bolted through the hole and cut to the length to touch the spring plate - draw round the contact area. do this for all three points. you may find the arm fouls the spring plate...if it does trim it back the bare minimum required...you can tidy this in a minute.

11) Remove the spring plate (take care to note its spline position) and drill the holes marked (check and double check this as early bays have rare spring plates!). Cut the excess spring plate off and tidy it up. You will now need to make these holes into slots about 20-25mm long - this will allow some toe in/out adjustment in the final set up...do this now or come back to do later. clean up the spring plates on the inside as this will now be a mounting face. with this done refit the plate to the torsion bar.





12) In the three holes of the alloy arm there are some steel inserts (about 2mm thick) which are countersunk. If they haven’t already fallen out - remove them and clean out the countersunk holes. The diameter of these inserts will be the outer diameter of your steel spacers.

13) You should now be able to pass a piece of long stud through the three holes of the arm and into the corresponding holes in the plate. With these in alignment you need to measure the space that is left - i.e. from the back side of the spring plate to the face of the recess in the alloy arm from which you removed the steel insert. The two back holes are a few mm less than the front one. This will give you the length of the spacers you need. If you’ve located your arm brackets correctly both sides should be the same.

14) Machine some bar to the sizes that you have with a hole down the middle for the bolt to pass through. Machine shops shouldn’t charge more than £60 inc materials for this.

15) Obtain some high tensile (at least 8.8) bolts long enough to pass through the spring plate, spacers and alloy arm with at least 15mm to spare. They can be trimmed at a later date. Also use washers and nyloc nuts in the final instalation.

16) With your spacer back from the machine shop bolt the arm to the spring plate with the spacers in position - now you need to weld the three spacers together using 3mm steel to create a triangle - each spacer should be joined to the other. The purpose of this is to make a solid spacer which will not move under stress....so turn the welder up to full and lay down some good beads.




17) You now need to remove the spacer you have just made and transfer the holes onto a 3mm or more thick plate. you need to make a large V shaped washer which will fit on the back (gearbox side) of the alloy arm - this will add strength to the area where the bolts mount through. With this all done - refit the spacer and bolt the whole lot together.







18) You can now final weld the brackets to the torsion tube. Again good quality welding needs to be done here. Remove the metal straps you have on the brackets if you haven’t already.
17) if you wish you can now put the van on the floor and see how things sit. if your happy....then continue to finish the job.

18) shocks: you will need to make some shock mounts - these will have to use shorter shocks due to the fuel tank. This bit is up to you really - towers can easily be made from box section or you can modify the originals. again just make sure that both sides match.




19) Refit the gearbox - the t25 short autoshafts (525mm) if your using them should fit both ends with standard CVs. alternatively you can machine some spacers to fill the gap - if you do this put them on the gearbox end.

20) Handbrake: i have used a 944 handbrake lever - this isnt neccesary. The 944 handbrake cables that run across the arms can be retained in either case. However if you use a 944 lever as I have you will need a custom cable from speedy cables. i made a template one up and they made me a proper one. The Porsche cables join into one near the gearbox so you only pull one cable unlike on the van when you pull 2. So you need to convert your van handbrake to pull this single cable. This is best done using a late bay handbrake lever as it has a single pull point (just bin the splitter set up) these fit into early bays as well. again a custom cable will be required although there are ways of joining cables cheaply that ill let you find out (i wouldn’t bother tbh)

21) Brake pipes: make up some new brake pipes and plumb in accordingly.



22) Congratulations you have completed the rear suspension conversion!!! Now you need some front brakes to match….info will follow soon.


[/img]