KirkF

I am putting a set of RUF Speedline Rims on my 89 964.

The factory Porsche tire sizes according to the book are:

205/55 ZR 16 6JX16H2 Front
225/50 ZR 16 8JX16H2 Rear

The RUF speedline rims are marked:
8JX17AH2 Front
10JX17AH2 Rear

Therefor I figure the correct tire sizes to fit these rims and maintain speedo accuracy would be:

225/45 ZR 17 Front
255/40 ZR 17 Rear

Does this seem correct? I know alot of people on here are running RUF rims, what tire sizes were chosen and why?

I am thinking of using Michelin Pilots. Any opinin on these?

Thanks Alot
Kirk

tonytaylor

Kirk

I have fitted RUF speedlines ( the ex Phil Raby ones if any ones interested)with Michelin pilot sport cups, 225 45 front, 255 40 rear
I have experienced some slight tyre rub on the fender lip on one side at the rear.( my car is lowered to RS spec with H+R coilovers)
I was lead to believe the offset on the RUF speedlines was different.
The Michelin cups are great on the track in the dry but poor on the road when cold and hopeless in the wet.

Adrian

Dear Kirk,
When you say 89 964 what do you mean. Is it a 1989 Carrera 4 or a 1990 Carrera 2 or 4.
These wheels are too wide for the 89 C4. They are actually too wide for any standsrd narrow body and wheel rub will occur. The RUF offsets help a little bit. I think the fronts are 41 mm and the rears 47 mm. Look at the wheels they will have them stamped there. Standard is 52.3 mm
You will have wheel rub front and rear. You might not feel it but I can assure you that I will be able to show you the rub and when you remove the wheels you will see the damage for yourself. Lock to lock will also be reduced. Yes I have heard all the "no problems" stories but I advise a quick check of the archives of rennlist first. I also advise you that these wider wheels will have an impact on the handling of the 964 as well as additional load on the power steering. The widest homologated wheels for a standard 964 on the front is 7JX17 and 8JX17 on the rear. The 964 RS had 7.5JX17 on the front.
Ciao,
Adrian
911C4

Bill Gregory

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica"><strong>The widest homologated wheels for a standard 964 on the front is 7JX17 and 8JX17 on the rear. The 964 RS had 7.5JX17 on the front. </strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">The 964-based Carrera Cup cars used 8x18, offset 52mm and 9.5x18 offset 47mm, in addition to 8x17 offset 52mm and 9.5x17 offset 68mm (with spacers) wheels.

While I can't comment on the RUF wheels, if you're careful with the wheel offsets, you can fit wheels larger than the stock delivered sizes. As Adrian suggested, scan the archives for others experiences. With careful choice of tires, and attention to Porsche changes made in 1992 for 17" rims, you can generally fit different combinations without putting yourself in imminent danger. Note 18" rims were not approved by Porsche for 964 street usage - Cup cars use the stronger Turbo hub.

KirkF

Tony / Adrian,

Thanx for the info.

The car is a 1989 C4.
It looks like I have the right tire size at least. The rims are marked
8JX17AH2-ET56.7
10JX17AH2-ET56.7

I have spacers for all 4 wheels.

adsc4s

I had 215/45/17's in my 90 C2 with the 17" wheels (C2 Cup wheels) and 225/40/18 with the Speedline 3.6 wheels.

As stated earlier, you can probably make anything fit with the correct offset which should be around 52mm front and 47 rear.

By the way, the Speedlines were 18x8 52mm and 18x10 61mm. I used 14mm spacers in the rear.

Adrian

Dear Kirk,
The 1989 C4 has less clearance in the front wheel well. Take care. I have some horrible pictures of major damage caused by tyre rub in the front of 89 C4.The inner wheel well design was changed for MY 1990.
I also bring to your attention that the installation of spacers is something that needs to be thought out. A 964 as with any Porsche is a finely tuned and set up sports car. The front track is actually slightly wider than rear track. Messing around with this can and will cause a change in handling and ultimately safety, your safety, your passengers safety and other road users safety.
I repeat, "The widest front wheel homologated for a road legal production run standard 964 from PAG was 7.5JX17. Carrera Cups and RWS 3.8s and RSRs are not standard production runs. In fact the Carrera Cups around started life as race cars anyway. VERY few around as well. The subject was not about 18 inch wheels and I have no idea why the comment was made. We are talking standard here not VERY limited edition 964s.
Ciao,
Adrian
911C4

tonytaylor

Although I have no rub at the front (1990MY C2) it is probably worth mentioning that my car has the turning circle of an oil tanker - I suspect the bumpstops have been altered.

mattinmatsuyama

I have just purchased a 92 964 here in Japan. Didn't see a picture of the car before i bought it, but it does look great, imho. I have 18 RUFs on it and I was wondering if some one could tell me how to tell if there have been spacers installed in it. I have the turning circle of a small tanker as well. Can anyone point out how to tell if they are original RUFs or knock offs?
Also could some one point out a picture for me on the net of a normal front suspension, I suspect theres a ?anti roll bar? . . . . not sure, also a picture of a normal fuse box. As some of my very 'ahem cough cough scientific 0-100 times seem a little too good to be true.
I have a manual coming to me in English as the manual i have is in Japanese. quite annoying.
After dreaming about these cars since i was 8, owning one has been all that I have thought it was and a whole lot more.
Just a beginner but eager to learn so sorry if these questions are a little naff
Thanks to replies in advance
Matthew

Mr. C4

Kirk,

That seems to be about right but with that rather high offset on the rears being 10" wide, I would be careful with the right rear oil line, while fronts should be OK. There are so many factors to take into the equation, even things like how much travel there is in your suspension and how stiff it is. If neccessary, rolling the wheelarches is a "piece of cake" if you don't mind altering the bodywork. Are you sure these wheels are not for a 993?

Adrian, everybody on this board including myself appreciate all you knowledge and willingness to share but why all this condenscending tone lately?
In Bill's post, I guess he just wanted to share his knowledge regarding 18" wheels, in case it was to come up under this thread. I don't see anything wrong in doing that, threads very often go off topic but who cares.

Ciao,

Johannes E.

tonytaylor

My wheels are marked

8Jx17AH2 ET56.7
9Jx17AH2 ET44

Adrian

Dear Johannes,
The subject was installing 17 inch RUF speedline wheels to a 1989 C4. Not 18 inch wheels on special versions converted from race cars. Only one person who owns a 1989 C4 answered.
If you do not like my tone when I try to get the thread back on track and answer the specific persons question then sorry for you.
I get heaps of private emails from posters on this forum who complain about people changing the thread and the flow of additional and often useless information (as far as they are concerned) ends up confusing them. You might not see any harm on changing the direction of a thread but a lot of people who want their questions answered do. I have no problem if you want to discuss 18 inch wheels again and again and again. Why not start a new topic.
I would love to get some of the real suspension experts to a tech session so many of you can start to learn about this subject properly. Might cause your hair to go grey. Caused mine to fall out. As an example I will never endorse the installation of 18 inch wheels on a standard 964. If anyone finds this a "bad tone" so be it.
Ciao,
Adrian
911C4

Jim Michaels

Adrian:

I think a tech session with some of the real suspension experts contributing right here on rennlist is a great idea. I'm certainly ready for a proper education; my hair is already grey. Suspension topics (including springs, shocks, swaybars, wheels, tires, spacers, etc.) certainly account for many of the FAQs here.

KirkF

Thanx everybody for the input!

I will indeed be very careful to check the front wheel clearance, and make sure I am well clear of the oil lines at the rear.
I'll be sure to let everyone know how it turns out.

Kirk
'89 911 C4
'84 944

Adrian

Dear Jim,
Suspension and related issues is the most subjective of all issues related to any automobile. I have even been condemned for reminding people that there is a design and a set of specs which are applicable to the 964 and stretching them too far can lead to some seriously negative problems.
I have files filled with photos and descriptions of damaged Porsches of many kinds (not just 964s)caused by straying too far from the Porsche design specs.
I will share a little story. This happened to me in 1998. I was looking for a set of 16 inch 993 wheels for my C4. My knowledge of these issues at that time was somewhat lacking. I was contacted by a fellow who said he had these wheels on his C2 and he did not have any problems with fitment and certainly no wheel rub. I believed him. I purchased the wheels, shipped them to from the USA, installed nice new tyres on them and installed them. Standing back the C4 looked great. I went for a nice drive. I heard funny noises coming from the rear end. The rest was history, I damn near ripped out my oil line and I still carry the scars of the damage in my rear wheel arches and oil line. I learned my lesson the hard way. Many people state "I did this and had no problems". Some people genuinely did not. Some people are only telling half the truth and some are simply not telling the truth. It is always buyer or reader beware.
Recently I was helping a person out. He wanted to know what the standard front tyre size was for the 964. 225/55ZR16 was the answer. He installed this tyre and promptly wrote back to me saying he had installed this tyre and damaged his 964 front end. Quite nasty actually. I was shocked, how could this happen. Especially since I gavwe him the data. It took a while but we worked it out. I asked many many questions and finally we established that the pervious owner had installed 14 mm spacers on the fronts and 25 mm on the rear to fill out the wheel arches using standard offset wheels. The PO selected front tyre profile to avoid impact damage at the front. So here was a case of an unauthorised modification being carried out on a 964 just for looks. The new owner was not informed, he did not know, asked a question, installed the standard tyre and damaged his 964. This s not an isolated case. In fact it is the third this month I have dealt with just related to spacers.
The number of unauthorised and sometimes downright dangerous modifications carried out to install parts that were not designed for a 964 or for a different version of 964 which is not compatible is scary.
I intend to write up some technical reviews on some of these issues. A lot of this is covered in my book and I hope this is all speeding up now so I might not need to write these reviews.
Remember always. Porsche have specs. The 964 is an approved design. Porsche issue supplemental information to support retrofits of mods and new equipment. If you exceed these limits you are entering a grey area. My job as I see it is to at least inform people that they may be exceeding limits. The final choice is personal but nobody can come back and say they were not told.
Ciao,
Adrian
911C4