964Dawg

Newbie here. I have 1992 964 that I purchased a couple weeks ago. I had Eibach Springs installed, and I put on my 18in SSR GT3 wheels from my old Boxster. I added a Rennline Strut Brace and was told I should also look into a steering cross brace - because of the 18in wheels. I called Jim Ellis here in Atlanta and they can't find the part, and have never heard of such an item. I asked them to look at the Turbo as well, and after looking they told me there were no differences. Now, I read that when Porsche went to the 17in wheels in 1992 that the beefed up the suspension and it doesn't need this part, but I would prefer to be safe than sorry. Is anyone familiar with the part/part #? It may be called a steering cross brace.

By the way, I have been reading the archives and your posts and already found many interesting and helpful posts.

Thanks, in advance. I am hooked!

Bill Gregory

Good luck. I have one, uninstalled, and was unable to see how to install it without bending existing 964 metal lines or installing 993 power steering lines. It's listed below the 993 steering rack, part number is 993.347.131.02, runs around $30, and requires 2 bolts 999.218.103.09 which are 20 mm longer than stock. If you have an RSA or the manual steering gear, it's no problem to install the support.

964Dawg

Thanks - What's your opinion on the 18in vs the 17in. I own a set of 17in turbo twists, but the 18in look and ride so much better.

Bill Gregory

Depending on your definition of ride...if ride means general comfort, 17's should ride better than 18's, as they have longer sidewalls with more give. 18's, with a shorter sidewall, should provide a stiffer ride and better high performance handling. You probably already know that Porsche never approved 18's on the non-Turbo, non-RS 964's, although people do use them. If you wanted to be really safe using 18's, you'd install the RS/Turbo hubs, which would also require 993 or Big Red/Black brakes.

964Dawg

Exactly, I really just prefer the performance. I certainly am aware that Porsche never approved the 18in wheels, though it seems strange that they would cause that much additional stress. I can understand if they are heavier, but couldn't a 17in aftermarket wheel at 10ins wide be just as heavy, and wouldn't spacers put equally as much stress on the hub as a light weight three piece wheel?

By the way, if installed the bigger brakes woould I need to replace or update my brake booster, etc?

I really do appreciate your advice. Thanks!

Cupcar

Here is picture of steering strut that Bill learned the hard way would not fit on a 964 because the steering pressure lines get in the way. I'm embarrassed to say I led him down the path of buying the part!!

Works perfect on 964 with manual steering though.

Sorry Bill

Bill Gregory

You don't have to, however, some have found that the pedal has more play with larger brakes. Solution for a C2 is to install a 993 master cylinder, which requires custom adaptors for the brake lines. Haven't looked at replacing the vacuum cannister, however, I don't believe there's enough room for anything larger in diameter. Most install the larger calipers and rotors without replacing the master cylinder.

Christer

I have 964 RS brakes now, and get a little more pedal travel but other than that they feel very strong...

964Dawg

Thanks for the help guys. I would like to add the stress bar, but I have a 92 and it definitely has power assist. I do have a question though, and as I say this please know that I have all the respect in the world for Porsche and their engineers. I work for a division of Ford and went and spoke to some of our tech guys. They tell me that the main thing to be concerned about when changing to 18in wheels is offset and the centerline of the wheel. They told me that as long as the overall circumference of the wheel/tire was roughly the same and the offset was correct that they really should not add any adiditional stress. They said that most of the stress would be on the bearings (ie, good advice on upgrading to 993 hubs - question, are those bolt on or do you have to modify?) but that if the centerline of the wheel didn't change significantly, then the stress would be minimal. They also pointed out that spacers would create way more stress on the suspension and steering than just a 1in larger wheel. What do you think?

By the way, I think I'll use my 17in wheels for track days anyway, so the 18s are really just for everyday driving.

Matt

Bill Gregory

I'm not an engineer, however, I would have thought the shorter 18" sidewalls would cause greater stresses to be transferred to the hub/bearing area. Any hub upgrading would be to the 965 Turbo parts, which is what the Carrera RS also uses. The Smart Racing catalog says that the 993 Evo hub would work, too, however I have no experience with that combination.

Since the control arm and ball joint is the same for non-Turbo and Turbo 964's, the other parts needed would be the wheel carrier, and other support parts. That does give you the opportunity to use the Carrerra RS aluminum hub and aluminum ABS parts, to save some weight. Before commencing down that path, ensure the Turbo wheel carrier will fit in the non-Turbo strut (if that's what you have). Going to the Turbo parts will also require going to either 993 brakes or Big Reds/Blacks, as the brake caliper mounting is different than the non-Turbo mounting.

964Dawg

Thanks Greg...that makes sense.

It would be interesting to know if anyone has really ever had a problem running 18s.. Seems like if the hubs and bearings can withstand racing with 17in wheels and teh stress of spacers that daily driving with 18in would be no more stressful. I'll have to consider the upgrade as it may just be better to put knew tires on the 17in Turbo Twists and spend the money elsewhere.

Thanks

Don C

I bought a 993 C2 with 18" wheels last year and the PPI showed that it did not have the brace. The mechanic said that unless I planned on taking the car to the track, that I did not need the brace. I recently took my car in for the 45k service and I asked the same question to my new mechanic. He also said the brace was not necessary unless I was going to the track.