Julian Thompson

Jeez - ride quality! My Euro RS is bloooooody hard anyway on its SM Magnesium 17" wheels, so christ knows what it'll be like running 18" ones!

However, if you look at the pic I posted at the start of this thread very closely you will see that the black 964 running the 18" speedlines is driven by Mr Walter Rohrl himself.

If it's good enough for him on the track it's good enough for me

tonytaylor

was tongue in cheek, there are plenty of 964's with 18ins but Porsche did advise against. The turbo's and 3.8RS were homologated for 18ins wheels IIRC.
Picture in the other thread show Mr Rohrl driving with the spoiler down - perhaps he didn't want to drive too fast because of the 18ins wheels

ian c - u.k

i've even heard of the 3piece wheels being a no-no for racing !!!
coz the stress on the little bolts was removing laquer around them !!

porsche replaced the guys wheels 3-4 times when the car was new

ian c - u.k

tony ,
cant find the price on the rs mags , must be at the lock-up

Julian Thompson

Jasmine only have 3 wheels left now (2xfronts 1xrear) so unless you've got a Porsche ReliantSport rather than a RennSport you are stuffed

I'm looking into alternatives that will allow me to keep the mags at home safely and still get as good performance!

adewatson

I seem to remeber reading somewhere that the problem with fitting 18" wheels is to do with the rolling radius being outside the parameters of the ABS system.

As such the ABS can either cut in too early or too late (can't remember which) so it may be that this wheel size requires more than just bolt on and go.

I may be wrong but as I say it's a vague recollection.......................

Adrian

cobalt

I have made this comment several times about the refinishing of fan housings.

Magnesium is a very tricky material. It is highly susceptible to corrosion from the elements and if not correctly maintained will fail structurally.

Powder coating or painting will not work unless the wheels are properly treated prior to finishing. You need to etch the surface with a dow treatment either type I Chrome Pickle treatment or Type III Dichromate Treatment per AMS-M-3171. To really do the job properly you should apply a resin sealer such as Sermetel or Rockhard PT961 to a thicknesses of about .0005 to .0012 inches. After this you can coat the rim with paint or powder coat. This is the only way you will obtain reliable adhesion. There are many defense contract facilities that can do this for you, most likely at a minimum charge. They may even be able to paint the rims for you after applying the appropriate coatings.

Cupcar

Here are the service bulletins I found regarding 18 inch wheels on Porsche's that didn't have them stock:





The 964 Carrera Cup cars had 18" wheels but have lots of extra welding in the chassis at the rear.

The 965 Turbo 3.6 with them has a reinforced front wheel carrier.

I wonder what the issues are and if they have any meaning if the car is driven on the street only. I would at least inspect any track car regularly for signs of chassis failure if using 18" wheels.

Julian Thompson

Will my 964RS have these reinforcements too?

Cupcar

The 964 Carrera RS cars were seam welded, to double check your car go to pictures HERE of RS seam welds.

Julian Thompson

Thanks for that and can indeed confirm my car's welds on the strut towers look identical to those in the pix.

ian c - u.k

so do mine
1993 c2 cabrio !!!!!!!!!!!!!!!!!!!1

cobalt

Cupcar,

May I ask what document you posted the info from? I am interested in what it covers and is there a Part number so i may do a search for one.

Thanks

Cupcar

The pages were scanned from:

Technical Bulletins, January 1993-December 1993, Book J, Service Information, Porsche Cars North America part number PNA 000 082D

The bulletins within book cover all Porsche types.

Note the first bulletin warns against installing the 3.6 Turbo wheels on any other Porsche, but the part number listed for the painted 8" wide wheel is the same as that used on a late 964 Carrera Cup car in the front.

The second bulletin covers all Porsche cars.

cobalt

Thanks,