Flagg

Hi everyone,

I have been thinking on the tire sizes for my new AutoX tires and all of you who wrote back to my last post (thanks!) seemed to agree on the Victoracers. My standard front tire size is not available, but everyone seems to agree that to get the 225/45 ZR17 (versus my size of 205/50 ZR17) for a bit more rubber up front.

I had my car Lowered, with new Springs/Shocks and corner ballanced before my last autocross last year. This was a tight course and While under very heavy breaking and turning at the same time, at one or two spots, I had a tire rub the front inside fender. See Picture..........(I tried to do 3 small attachments to this message - am not sure if I did it right........)

I had my local Porsche shop that did the lowering checked it out after the event. They said that I had an awesome set up, and the rubbing was so minor and would never do any serious damage. They would not compromise the set up.

A friend that does serious autocrossing in my area said that ALL his lowered cars always rub when autocrossing..........so I forgot about it......and have actually been too busy to autocross since.......but before I make this tire choice, and get back to another autocross, I want to do the right thing.

I have never experience this rubbing on the street. I LOVE the way the car handles!

--------------------------

Questions:
The front tire everyone recommend is wider by about .8" or .4" per side. It has just every so slightly a smaller sidewall. If my tire calculations are correct.

1) Do you think this will drastically increase my rubbing situation? Or do you think I still have no problem?

2) Is your car lowered? Do they rub when autocrossing?

Thanks for all your opinions,

Flagg

Flagg

Another image...........

Flagg

A final image - so you can see the scale of the first 2 pictures...........

Adrian

Dear Flagg,
I do not agree with the comments that have been made to you. 225/45s should not be impacting the top of your wheel arch like this.
Maybe you are a tad too low. Maybe the front spring rates are too soft. Maybe the front strut valving is not quite stiff enough.
In the end it is your pocket that will suffer. The tyres will be damaged and have to be replaced. Your 964 will sustain damage every time you go out.
Personally I would demand the shop that did the lowering work fix the problem.
I had a colleague with a RS America with a similar problem. It was fixed by raising the front by 3 mm.
I do not accept this rubbing as inevevitable. Maybe if you were running 235 or 245s up front or 18 inch wheels but I consider 225/45 a standard style tyre.
My C4 (1989) is lowered to Carrera RS specs and is fitted with 225/45 tyres up front and I have no had any rubbing at all under any circumstances, track or road. Not that I track it often but I occassionally get the urge.
Ciao,
Adrian
964C4

Johnny G Pipe

My car (90MY) is lowered on eibachs and I just put 225's on the front. No rub at all with street driving, but after a few dozen mountain hairpins chasing a Mitsubishi Evo, significant rub.

No surprise, I guess. I'm going to try 5mm spacers.

joey bagadonuts

I autocross with 225's and experienced the same rubbing prior to replacing my suspension. My car was previously equipped with stock shocks and Eibach lowering springs which were replaced with RS coilovers. Since the max front spring rates (realized under load) for both coils are in the 250-300 lbs/in range and the rubbing has been eliminated, I believe the stiffer RS shock valving made the difference.

I'd suggest you take a good luck at the inside shoulders of your tires for any unusual wear. I'm inclined to agree with your mechanic, though, that this issue may be minor since there are very few instances outside of autocross where you are pushing the car with full lock. And even then, it only lasts for a few seconds during a handful of low speed autocross runs. If, however, the tread suggests a more serious issue, then I'd look into possible remedies.

0.02

Flagg

Johnny G,

I am sure you were able to hang right with that Evo..........post how the spacers work.

I assume that you would want to be careful that you don't get rubbing occuring on the outer fender well................

So who else has a lowered car with tires that rub?

Flagg

Flagg

My standard front tire size is not available, but everyone seems to agree that to get the 225/45 ZR17 (versus my size of 205/50 ZR17) for a bit more rubber up front.

I assume they will rub a tad more if I do nothing?

Flagg

Bill Gregory

Flagg,

225/45 and 205/50 are within a decimal point of the same diameter (around 25"). The difference between them is width, and not height. As pointed out earlier, 225/45 is used quite regularly on 964's. The combination of springs/shocks/height is what is allowing the rub on the top. The simple fix, as already mentioned, is raise the body height up a few mm's. Other fixes are more complicated involving springs/shocks.

garrett376

Flagg, I am with Adrian on this one - rubbing is not something to ignore. Just think if you popped your tire because it caught on one of those fastener screws and you're headed for a wall at high speed (or if you're doing wheel to wheel, you slide into someone on your side)... not good. From a less dangerous perspective, I've seen guys "bubble" their paint on the outside of the car from a tire that kept rubbing, heating up the metal!

Also like Adrian said, the location of the rubbing suggests your suspension is being overtaxed - I think the setup appears too soft as well. I had a similar problem on my 65 until I went with much greater spring rates - never happened again.

Bottom line - I would not leave it as is - you're assuming too much risk especially if you're going fast...

Flagg

Thanks for all your replies...........when I get new autocross tires, I am going to have my shop mount them and also raise the front of the car a bit and try to eliminate my rubbing. I could also look into increasing the stiffiness..........or a conbination. It sounds like the amount I have to have it lifted will be very minimal.......at it is something I should do.

Thanks, everyone, for all your advice. Also, for the advice on my last post about which new tires are best.

I wish I had found this Rennlist web page YEARS ago. It is so great to be able to get opinions, ideas, and hear about other people with this same type of car - All over the world.

Thanks again!

Flagg

JoeW

Flagg, when you're autoXing, or any other kind of driving, the only rubbing you want to happen to the tires happens on the pavement -- or so I'd feel.

Raising the car may be the cheapest way out (or not), but it may not be the best for your performance .... you haven't said which springs/shocks you have or how old they are -- this could make a big difference.

My RSA has 225/255s, is lowered significantly, has linear Eibach springs and RS shocks and a bit larger sways -- no rubbing.

I think I would ask a good Porsche mechanic who is also friendly to track and autoX what the best course of action is to cure this and still end up with the car driving the way you want it to.

My .02

Joe