Adrian

If you want this information I suggest you contact Sportec @ www.sportec.ch and make your requests of them. You might wish to seek out the TÜV documentation as well.
I do not speak for Sportec nor do I provide their company's technical testing data. If they wish to hand it out that's their perogative not mine.
Ciao,
Adrian.

Christer

Sure, I understand - and it is of course not my intention to be derogatory or inflammatory in any way - its just asking the question/thinking through the logic!

Adrian

None taken, but you do say in your text "If" the Sportec wheels are approved.
I said they were and if you purchase these wheels you will get a TÜV certificate for them. It's illegal in Switzerland to fit non-approved wheels.
I handed my C4 over to the Swiss Authorities in Zürich so they could test them themselves.
These wheels are NOT approved by PAG nor are they approved by the Swiss Porsche distributor AMAG.
I believe they are DOT approved in the USA and in various Asian nations including Japan.
However I stress that the certification data for the Sportec wheels MAY NOT be used to justify or validate any other wheels that people wish to fit.
Ciao,
Adrian.

Adrian

Marc,
I have learned the hard way. I do not endorse anyone anywhere anymore. It has nothing to do with being allowed it has everything to do with never being paid and being held responsible by people who like to blame others when things don't go their way.
However to answer your question you might what to try and find the firm ATS in Paris.
Sportec no longer manufacture 18 inch wheels. 19s, 20s and 22s only I believe. I have not checked their web site for a long time.
Ciao,
Adrian.

loot87

Adrian,
Where in your book is it stated or implied that 18" wheels are OK for turbos?
Thanks.

Adrian

Porsche made the 964 Turbo S and 964 Turbo 3.6S with 18 inch wheels.
In these areas it is not my intent to imply or to make statements about what you can and cannot do.
I provide the information and the data and hope that each owner/reader will make their own decisions baed on the laws that apply to their car, their insurance requirements and plain old common sense.
Ciao,
Adrian.

chancecasey

This is a great topic - I think everyone here would jump at replacing 16 inchers with an affordable 18" wheel, but of course nobody wants to break their car. (or the bank)

One thing that hasn't come up yet is the stiffness factor. With a larger wheel, the tire sidewalls are shorter, and as I'm sure many of you know the ride usually becomes noticeably harsher. I would think street driving (where there are bumps in the road) and the less flexion allowed by the lower profile tire are at least as stressful as the other factors mentioned so far.

Has anyone proposed a method of reinforcement so that, even though not officially supported, 18s or 19s would be feasible without risk of damage?

P.S. - I'm coming strictly from the "not break my car" angle, I'm not concerned about what "the authorities" have to say.

Adrian

Another thing is tramlining. With the reduction in tyre profile and the increase in tyre width (by the way this is a width issue not a diameter issue) tramlining or following the ruts in the road is increased. Of the many owners I have met over the past X number of years some reverted back to 17 inch wheels simply because of the comfort factor.
When I was test driving with Alois RUF this was the only concern he had with his RCT Evo conversions was the increase in tramlining using the 18 inch wheels.
I like my Porsche harsh, but many people don't. The lower tyre profile on a bumpy road does increase vibrational stress and you can feel and hear it.
I always recommend before making such an investment in wheels and tyres that owners test drive another similar set up 964 if they can find one.
I should also point out that my C4 with the 19 inch wheels has been all over Europe at very high speeds at time and nothing has broken yet.
Ciao,
Adrian.

PS: One thing for those that do not believe that the wider 18 inch wheels increase dramatically the stress on the car systems. Again it is the width not the diameter that is the problem. Research the original Audi RS4 18 inch wheel problems. They had a habit of collapsing under the stress and folding up into the wheel well under worse case scanrios. I know of at least 5 fold ups.
Sportec were contracted to fix this problem and they did, but Audi prematurely ceased production of the RS4 (just over 6,000) and went back to the drawing board.
Americans would not be familiar with this problem because the original RS4 was not exported to the USA. It was not pretty. The wheel camera shots taken at the Ring were scary to say the least.
Our cars being so old are way below the radar screen in these areas. Few care and even less bother to test.

Christer

I find I get increased tramlining when there are very deep grooves in the road - like for example in the 'slow' lane on a UK motorway where the trucks have worn it down that way.....I don't mind it too much as I am never in that lane anyway, but if all roads were like that then I would probably sell the car as I remember that my D90's also tramlined to a point in *that* particular situation....

Premier Motorsp

Adrian,

Can you be more specific as to what the point of failure is? It sounds like the front suspension only. The 964 control arm to ball joint interface is bolted with some smallish hardware that was upgraded on 993s. Also the strut to wheel carrier bolts are smaller than on 993s.

I would like to know if there is a potential problem with the wheel carrier itself and whether the design was changed at a specific time.

Chris Cervelli
Premier Motorsports

Adrian

Chris,
The primary area of concern are the wheel carriers, in particular the front of the C2.
The hardware and the carrier itself both suffered under the testing done by Porsche.
The suspension and wheel carriers were totally redesigned for the 993 so they cannot be compared.
An interesting point is that Porsche originally included the model year 1994 and 1995 993s in their ban on 18 inch wheels, but then rescinded the 993s and removed them from the list.
Of great importance is the understanding on how the 964 is to be set up. Corner balancing, the correct wheel alignment.
Whenever the design specs are exceeded potential problems are created.
What people do not recognise is that the 964 was designed in 1987/88 with 16 inch wheels within a certain range of wheel alignments and weight distribution, wheel loading and other calculated dynamic stresses. Adding components to the car which were not used in the original design calculations which cause an increase in both structural and dynamic stresses can and usually do produce unwanted results.
Body flex whilst cornering is another area which is ignored. The more body flex the more weight and stress that will be transferred to any particular wheel when maybe it shouldn't.
Basically if owners want to drive like a 964 Carrera Cup competitor from 1994 then they should purchase a Carrera Cup from 1994 or correctly rebuild your existing car to emulate the Carrera Cup using all the racing components of that era.
For normal road use then I doubt there will be many issues, but how many Porsche owners, especially Rennlisters and other enthusiasts can truly say they just use their cars normally?
Ciao,
Adrian.

ttAmerica RoadsterAWD

Adrian, got any pictures of your car with the Sportec's??

Jaime

Adrian

On my web site,
Ciao,
Adrian.

last toy

With all that good feedback said, it appears that maybe under certain stress situations, a problem could surface but the risk may be slight. However, it only takes one incident to wish preventative measures were taken. So if one was not ready to go back to 17 inch wheels, is there anything that can be changed on the suspension to minimze an unwanted failure. I'm about to lower my C4 suspension, so this would be a good time to consider any recommendations to change any suspension components that would further accomodate my 18 inch wheels.

Feehliks

Are you aware of what (i.e. which improvements) caused Porsche to rescind 96+ models from this ban?

Best regards,

Felix