Speedline for Porsche 993 CUP SUPERCUP Magnesium Centerlock Wheels. Quite Light.

First the money shot, or more accurately, money number.

IMG_20211017_133011 — You have read that right.

10 kilos. The weight of a 18″ Speedline wheel with magnesium center. in 1995. Impressive. You might remember in the old 964 days, a front Cup wheel by Speedline was 11.2 kg. Florian from 944 racing listed a weight of 11.54 kg for this same exact wheel and even thought i would never go against what he says, the man’s site -that he seemingly built as a side project before moving on to something else as per his LinkedIn profile – is an amazing source of knowledge used by Porsche enthusiasts even to this day, i have to say my scale didn’t say the same, thought it is very likely his was more accurate. Well, now, 11.5 kg or even 11.2 kg is pretty heavy for a wheel made exclusively for racing purposes. Something had to be done. But first some history. Porsche and Speedline collaboration’s was, like all good things that happened to the car industry, born on the track. A few well appointed google searches tend to indicate a first notable collaboration the Porsche 961 and 962 racecars, both using the 935 engine. The next step was collaboration for a mass market road going car. It wasn’t to be the 911, and the first 911 who would be fitted with Speedline wheels would be… RUF. I have told this story before and the good people at Donut Media did an even better job. Fast forward a few years and the 911 typ 964 CUP cars ended up, like the 965 turbo, wearing Speedline 3 piece wheels.

They were gorgeous and still are. But yeah, the weight… Pardon me for name dropping a past BringATrailer buyer, one Dan C. from New Jersey who told me that Cup Speedlines are great on a Cup car for authenticity purposes but for proper racing his friends and he went for BBS E88s and E28s, or even LMs, lighter and/or less fragile and also not worth the price of a new Toyota Camry… So something had to be done, and something was done with a strike of thunder, bringing what at the time was the N°1 weapon for lightweight wheels. One word : Magnesium.

A proper 100% magnesium must be dreadfully light. Mind you about 66.67% density of an aluminum wheel is not much. Of course most wheels are not « aluminum » wheels but aluminum alloy wheels so let us not compare oranges and apples. On average for a monobloc cast magnesium wheel compared to a monobloc cast alloy wheel the weight difference is 32% Speedline went the conservative Mg content choice and the final weight difference, when compared with 18 » Speedline Cup 964 wheels, was -10.7 % less in the front and -7.82% in the rear respectively. More info on those elusive Cup 1964 wheels here. An additional caveat : only the centers are magnesium not the barrels or lips which further reduces the potential weight savings. All in all safety first, unlike SM who chose a 7% aluminum 93% magnesium mix for its Cup 1 magnesium monobloc wheels. There was an interesting debate on BaT when such a set was auctioned. I am team #965 in case you are wondering.

Now, let’s revert to the person who performed the restoration, Komatsu san. He actually restored a set of Cup 1 Magnesium wheels a few years back, so maybe just maybe he is the right person for the job ? Here is his procedure for « high spec » magnesium wheels : First he sends the wheels to a magnesium specialist to properly remove the old paint and when done, sanding to prepare the surface. Centers are inspected for cracks. A chemical conversion treatment is applied to specifically prevent the corrosion of magnesium. Then magnesium primer, further sanding, Powder coat « Porsche Silver » is applied, it is the same as the OE Porsche color for silver wheels. Lastly, urethane clearcoat specific to magnesium is applied and final curing with low temp baking, so as to prevent paint « bubbles », typical for magnesium wheels as the paint adherence is much worse than for alloy wheels which tends to push the paint outwards, this combined with excessive heat creates bubbles.

The eagle eyed readers will notice that the hub mating area is painted. people familiar with Mg parts know that they cannot stay « naked » for any period of time. Once stripped of paint they need to be repainted immediately.

Of course all nuts have been replaced, as is the standard for torqued to spec items. Bolts were stripped of paint and residue and the heads were powder coated.

Regarding the « Speedline for Porsche » and specs acid etchings, Komatsu san uses the usual method used by high end wheel shops the world over – and that was first brought to my attention on a German Porsche message board a few years ago, using acid to etch those words onto the lips – Food for thought here, most so called Speedline experts judge paramount that those etchings are present on « Speedline for Porsche » wheels to prove provenance. However those same wheels are almost 30 years old now, so in order for them to be in showroom condition like the wheels pictured here are, they need to be refinished by a shop that by definition is not Speedline SpA; so that the only indication given when those etchings are present after refurbishment is the attention to details of the wheel shop that performed it, not the provenance. Komatsu san was thankfully able to reuse all barrels and lips, as the castings on each OE part will show :

This wraps up the article presenting those beautiful 993 SUPERCUP wheels and the restoration process associated. They will soon be listed for auction on Bring a Trailer. Having been raced on a 993 SUPERCUP car in Germany and drilled there they will accommodate all 993 cars be it center lock or regular 5×130 PCD. For those interested i will upload the full cost of the restoration on the listing page. Full specs : FRONT 8.5 x 18 ET 53 Porsche part number : 993.362.136.085 10 kilos Production date (centers) Feb 1994 REAR 10 x 18 ET 60 Porsche part number : 993.362.136.080 10.7 kilos Production date (centers) May 1995