New steel wishbones - switch from alloy control arms

After almost thirty years these Porsche 944's have either worn out their ball joints or are needing new ones fairly soon. Worn balljoints are a real safety concern and a MOT / roadworthy failure.

Ordinarily, it's an expensive fix as the alloy Porsche wishbones (or control arms or A-arms as our american brethren call them) have an integrated balljoint - making them costly to replace. Choices are: hopefully good used ones; a DIY ball joint repair kit; refurbished ones; or new ones from Porsche.

Even refurbished alloy wishbones are about £200 plus the exchange of your old ones. Not  a cheap fix although well engineered. The balljoint repair kits are around £50 and are a feasible alternative if the wishbone cup is in good condition. I had considered this route as my alloy wishbones look in good enough condition but rumours of poor longevity made me seriously consider another option - retrofitting steel wishbones such as those found on the 924's.

I found a pair of German made Febi units at my local motor factors with ball joints for less than £20 a side. These are identical to the ones on the VW Golf/Rabbit mk1's ( a throw back to the underpinnings of the VW-Porsche collaboration on the 924) so they are very well priced and offer cheap, yet safe, balljoint replacements for years to come. FTW.

 

I've heard a lot of talk about how much lighter the alloy wishbones are than the steel ones. Being a curious sort I just had to weigh them and discovered that the steel one weighs 2.1kg and the alloy 1.97kg. That's only 130 grams difference in this case! Hardly worth a debate.

I decided to have mine powder coated to keep with my "eighties disco" theme going on under The Hoff! Here all all the coloured bits laid out ready for assembly:

Here's a side by side comparison of the wishbones. The dimensions are obviously the same but it's clear to see they're not identical.

So what else will you need to make the switch?

Well besides the steel wishbones the other two big differences are the rear mount and anti-roll bar attachment. You can see from the image above that the steel wishbone has a protruding cylinder like prong; and the alloy wishbone has a single recessed hole where the ARB drop link attaches - the steel control arm has two holes for a completely different style of mount as seen below:

Although these are available new, I purchased a used pair and had them powder coated black. 

Here's a comparison between the 924 and 944 outer anti-roll bar mounts:

At the other end of the wishbone is the castor mount attachment and rear wishbone bracket. The standard 944 and uprated 968 castor mounts are not compatible with the steel wishbones at all. The alloy wishbones use a strange adjustable bolt that fits between the control arm and the castor mount to make the adjustments to, well you know... it also holds the rear of the wishbone secure. Once again I purchased used ones and had them powder coated black - the 924 style (right) compared to the standard 944 rear bracket:

The 924 style has elongated slots for the chassis bolts so that they can provide the adjustment to the wishbone as opposed to the eccentric bolt used on the alloy A-arms.

The 924 style rear bracket has another benefit too - cheap VW Golf/Rabbit uprated poly bushes. I bought a set of Prothane Bugpack poly wishbone bushes for £18 from VW Heritage - a huge saving:

So to summarise to make the switch to steel wishbones you need:

1. a pair of VW Golf/Rabbit mk1 wishbones and balljoints;
2. a pair of 924 rear brackets;
3. a pair of 924 ARB outer mounts;
4. bushes to suit;
5. your existing wishbone mounting bolts/nuts.