Ive been thinking about changing my back wheels for sum wider rims of a turbo, maybe the 9" wide 17" cup type, with a 275-35 tyre.
Can you get a wider tyre under the arch?
Will this make any difference to the cars performance?
Is it worth the cost for another inch or so of tyre?
The car is allready on 17"cup with a 255 tyre.

 

You should have bought my car....

I have 10 inch rears with 265 and they are shoe-horned in there and it took a little time to get it right - rubbing when standing still is one thing....avoiding rubbing when driving hard is another.

In short, it depends on your suspension (ride height, camber etc), wheel offsets and so on, and also individual cars differ as well for some reason.

I only did it because I needed more rubber on the ground...I wouldn't bother if I didn't unless I was a 'looks wh*re'

trial and error would seem to be the normal SOP....

 

Will it make a difference in performance (on the street)? Not really.
Is it worth the cost? Only if your existing tires are shot and you need new ones and want to spend the money for looks. (That said, I used to run Cup II wheels on my Turtle and I use them on my 993 because I like to looks).

Will it fit? As Christer says, it depends. Not all 275's are the same width, it depends on brand. The lower your car and the more camber you run, the more likely it will fit (although in general you can get a 275 to fit). I think the turbo rims have the wrong offset and what you want in the Cup II rim is the standard tire from a narrow bodied 993 (offset of 52 mm - wheel says ET52 on it). IIRC the turbo rears are 10" and have an ET68.

 

I saw a 911 in the paint shop. The rear tires rubbed the fender when the car went through a dips at speed. The steel was fine, but the heat blistered the paint. With the experts saying "it depends", I would proceed with caution.

 

I've got 18x10et47 and 265's in the rear of mine (I could get away with 275s but have no reason to)...I got completely lucky and bumbled into a set of wheels that fit almost perfectly. My car is pretty low, and with rolled fenders, a flat oil line, and negative camber, its tight, but manageable.

 

So its not worth the effort then?

It was only an idea, best leave it then

 

Well, thats up to you - for me, I'd say it was. The look from the rear of a NB 964, with 265s, is pretty menacing...I also went from 205s/225s on 16" wheels to 235s/265s and on the track, before and after, the difference is INSANE (i.e. amount of grip available)

 

I believe mine are 10.5s with 265

 

I'm running the same wheels as Christer ( 18s 10J with 265s 47 offset) on a NB C2. On a similar suspension set up as he has on that car the wheels were a shoehorn fit and worked fine on the street but on track they rubbed everywhere; swing arm, oil line, fender lip, inside. Ultimatly rubbing ended by using far stiffer coilovers, a 22mm spacer and streching the fender lip 20mm or so.

It was worth it for me on track I believe but whether it's worth living with something that you know is inferior in extremis without other modifications or going the whole hog and making the other changes depends on your own POV.

 

I want to keep to a 17"rim and i like the cup wheels.
I just want a bit wider rears, so it fills the archs.
And the 17" turbo cup wheels dont fit due to the offset, so does anyone make a wide (9") cup wheel with the correct offset for a narrow body c-2???

 

Design911 do an aftermarket cup1 in a 9" for 964's.

 

964 turbo's use a 9" Cup 1 rear that should fit on a narrow body(That's what I have been told, have not tried the set I have) See if you can find a set of them. Good luck.

 

I have a good friend that runs the C2 cup wheels. He has 9 inch rears with 275 tires and used either a 5 or 7mm rear spacer.
he runs this set up on his RSA.

I am currently running 9" 993 cup II wheels on the rear of my C2 with 21mm spacers.
only running 255s currently but have considered 275s, and yes they do fit.

 

I run a 275 on Cup I turbo rims 7&9" for AX events I can bolt them on as is with minor rubbing on the inside but nothing that will cause damage. I use a 15mm rear spacer and a 5 mm front spacer and it works nicely. It fills out the wheel well and performs well. Although for the track I run 18's and use an 8 and 9.5" wheel with 225/265 tire which I think is far better than the 17's

Please note: I run a 1.9 degrees of camber in the rear and I have longer studs on all 4 corners.


Here are some pictures to give you an idea.

 

What you really need are 11" wheels up front and 13" wheels in the back, then it looks good. Only a few "minor" tweaks needed to make them fit.