Rear coilovers on supers
 

I have maxx struts on the front and wanted to install the rear coil over kit. Does anyone know who would have the best quality kit out there. i have found several kits but i haven't really found the actually coilover shocks. Just the adapter kit.

Loads of companies sell coil-overs, AVO, Spax, Protech, Bilstein etc etc, we are spoiled for choice in the UK! Just measure up to see what you need. Personally I will (and have before) be going for protechs...

I've gone for Spax on the rear in anticipation of adding a threaded sleeve for coil overs. However, I will be retaining the torsion bars as well using the coils just to up the overall spring rate. I would be very nervous about relying on the 12mm bolt at the top and the aluminium housing at the bottom to withstand the stress of providing the fixing for 500lb/in + springs. Remember that the bolts are in cantilever bending that creates a moment that is around 4 times that of a bolt suspended between two fixing points. I can't see any good reason unless of course you would require a full progressive spring rate instead of the linear one that was imparted by the torsion bar.

evilC

Whenever I see coilovers mounted that way it always makes me nervous too. If you can fab up a double-shear situation, I think it would be just fine, but that single-shear situation is a little scary to me too.

Jason

can we get a bunch of various coil setups in reference pics explaining the various differences / pros & cons? the gallery isnt that great at explaining the variences between each, just a thought

I posted some over here, it's in Dutch though
http://www.keversite.nl/forum/viewtopic.php?f=5&t=16351
(Achterkant = rear)

Is it for steel trailing arms or for 944 Alu trailing arms?

About the single shear:
It's a good point, but in the Käfercup they raced with the single-shear setup and it didn't break. And they did push their cars to the limit.

To a degree it doesn't matter if its the steel or alloy arm since the connection of concern is the top mount, which is the same for both. The top mount has a single 12mm bolt that is in single shear but also has a significant element of bending that is compounded if the top bush is rubber rather than a ball joint. The shear value of the bolt is well within the bolts capability but it is the cyclic bending that is problematic IMO. Because of this cyclic bending NEVER use a stainless bolt because it will prematurely fail.
the lower mount on a steel arm is actually much better than the alloy arm because the bolt is only in shear, which it can cope with very easily. The alloy arm however, uses a 14mm bolt again in cantilever, this time with a substantial lever arm as the threads are well buried in the housing.
Remember, both VW and Porsche designed these fixings only to take damper loads that are minimal compared to the loads imparted by a spring.

evilC

Sorry, I forgot to comment on the single shear in racing. Most/all Kafercup cars used the rear cup brace that in general connects to the top damper mount. This point is then triangulated back to the frame horns at their front and rear so that the damper mount now becomes a simple double shear point not the single shear/cantilever bolt arrangement thus doubling the shear capability and quadrupling the bending moment capability (although as previously said there is very little bending moment imparted by this set up.

evilC

Sorry, my post was inclomplete again, I ment single shear on the trailing arm, since the upper mount can be made into a double shear mount.
Anway, thanks for your answer!

Why does the bolt in the alloy arms work in cantilever (and why doesn't it with the stock arms?)
Is the damper under a different angle compared to the stock arm?

And only the topmount is of concern, since it's the one that gets a bending load?

The steel trailing arm can be fabricated with thin metal to create a two sided cup that supports the bottom bush of the damper. The alloy arm is a complete casting and to creat a double sided support would be difficult without adding fabricated bits. Since the loads are relatively small through the damper (only) mount having a single cantilever bolt is no great problem. I don't think the angle of the damper changes between steel and alloy trailing arm.

The bending load is in both bolts equally but the bottom bolt of the alloy arm is M14 and the top bolt is M12 a difference of 36% in bolt strength but the M14 is a longer bolt and therefore the bending moment is greater (PL/4).

evilC

the mo30, 951 ALLOY ARM, USES A COIL OVER SHOCK, WITH THE TORSION BARS

I completely agree and it's why I will stay with the torsion bar set-up.

hello 951 - m030 option
 

look

rear coil over = stock
m030 option
http://www.weissach.net/968_M030-Opt...ocksAndSprings

Yes, but what else did Porsche do besides just bolt that "shock" on there? What other modifications were made, in support, of the M030 option?

it tells you on that link

-fat bars
adjustable koni's

there isn't much else you could do is there?