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Old May 26th 2015, 15:15
spannermanager spannermanager is offline
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Join Date: Nov 2005
Location: London and kent.
Posts: 185

Hi Graham, well I've never actually modified the Porsche ally a arms, but yes, it must be doable, firstly, from the pics above, it looks as if the lower fixing offers more ground clearance then the steel arms, VW or Porsche being the same in dimensions, it's always clearance to the spring from the outboard end drive shaft/cv over the range of travel that is tight, I would use 2 1/4" spring units, but as to a brand name? Well there are many top quality products out there, Koni are right up there for quality if the budget is high end, cheaper quality? Spax or protech are both very helpful, I would only say stick to a simple adjuster spec, 4 way adjusters are just overkill for all but race teams, 2 way are plenty enough, bilstein don't adjust and will work brill straight out the box, the engineers did the work, your application is a little different tho!!
Have a look at the Japanese blue bomber, moving the lower damper mount to the top of the a arm is a smart move, the higher compression loads are easily supported, something similar would be doable in alloy, and the top mountings are cage mounted, I don't like the opposing fixing bolt axis they've used but it must work for them. NVH may be a problem to consider, even with rubber bushings, solid spherical eyes will be a mare on the road, we have it easy for track only, but I'm now deaf as a post from it all lol..
Watch for wheel/tyre clearance over the full travel, there's a fair old swing on the dampers, damper length? Probably best measured once it's all been mocked up, upper/lower bump stops can be built into the units if needed, a lot depends on the mechanical/existing droop and bump stops, if any, provided by whatever type of spring plate and trailing arm fixings you use?
The downer to modifying stuff away from the brilliant original conception, is that it becomes a major mechanical exercise to do what was originally easy, a rear shock Change now takes me an hour at least, colour code the bolts/ nuts for shock or roll cage members if they are different specs.
You will need a fair old spring rate for stock location dampers with no torsion bars, less spring rate if they are moved outboard towards the wheel, considerably less in fact, less leverage acting on the spring/damper units.
Wally will shoot me in the head now, he's done OK with Billy's in the stock location, not sure if he uses torsions or not, but they do take the load off the shock bolts.
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