GrantG

I was one of the voices that claimed 20" wheels would be necessary for this car, due to the optional 410mm PCCB brakes. However, I just saw that the 991 Cup uses the identical sized steel brakes as the street car (380mm front and rear) with 18" wheels, so I guess it will be possible to run 18" rubber, if you don't order PCCB's (assuming calipers have as much wheel clearance as the race calipers on the Cup). Forgive me if most of you already figured this out...

18 track rubber would be WAY cheaper than 20's...

http://www.porsche.com/usa/eventsand...ogyandconcept/

Two independent brake circuits for front and rear axle, adjustable by the driver via brake balance system
Front axle internally vented and slotted:

Aluminium six-piston racing callipers in monobloc design
Multipiece steel brake discs; internally vented and sloted, 380 mm diameter
Racing brake pads
Optimised ventilation routing

Rear axle internally vented and slotted:

Aluminium four-piston racing callipers in monobloc design
Multipiece steel brake discs; internally vented and sloted, 380 mm diameter
Racing brake pads
Optimised ventilation routing

Front axle:

Single-piece Porsche Design light-alloy rims with centre lock, 10.5J x 18
Michelin rain tyres; tyre size: 27/65-18

Rear axle:

Single-piece Porsche Design light-alloy rims with centre lock,
12J x 18
Michelin rain tyres; tyre size: 31/71-18

mike2727

I know with the 991 C2S it had something to do with the rear suspension why 18's won't work, 19's will though, so that would be the best size for the track

Mike

GrantG

Wonder if it's the optional PDCC on the C2S that made 18" fitment impossible? That option is not available on GT3, although RWS may bring a new issue...

18s are much cheaper than 19s with much better selection

911rox

I think the suspension arms and geometry will be the limiting factor, particularly the rear steer geometry, less so the brakes (except for PCCBs that is)... The Cup car is made with the expressed intent of running 18s... They would ensure its engineered to clear these wheels.

One would need to get their hands on a car to measure clearances but I think that 19s at best will be the new 18 on the new car..

shizzle

The reason why 18" wheels don't work on the 991 C2S is because of the lower control arms in the rear of the car. They sit extremely low, and barley clear a 19" barrel. And even then, depending on the type of barrel, some 19" won't clear. Hopefully the GT3 doesn't share the same geometry as the C2S for the lower control arm.

Petevb

There is a lot of variation from one wheel design to the next. If you're willing to put some effort into getting the right barrel you can get a lot more clearance than most think. I fit 17s over my PCCBs, where most believe at least 18s are needed. I agree the cups suggest it's possible.

GrantG

Since the new center locks appear to be very similar to the Cup ones, maybe the factory race wheels will fit? Fronts are probably too wide at 10.5" though...

FabianG

Here's an example on a 991 (attachment)

GrantG

Yeah, Way outside the rotor diameter - wonder if the GT3 will be the same?

mdrums

Saw a 991S with PCCB at 48hrs. He was running 19" BBS with Hoosier R6. Brakes totally filled the wheel and wheel was very close to a dogbone suspension part. Not sure it's just the brakes keeping the 991 from running 18". I'd like to know for sure too

Dr.Bill

Mike - if it were just the brakes an 18" wheel would fit. It's the suspension bits that get in the way from what I can see on mine. One of the first things I looked at. I imagine the GT3 will also have the same stupid brake calipers as the rest of the 991 line. The ones you have to remove to change brake pads.

mdrums

Ray yep that is what I was getting at...it's the suspension parts that might not allow a 18" wheel on the 991. 991 GT3 will have the brake caliper off the 918. They are mono block and to remove the pads the caliper has to come off. So either you use stock pads all the time or race pads and deal with the squeal on the street or maybe get caliper studs and remove calipers for each track day to swap pads.

10 GT3

The standard front brakes on the 991 GT3 appear to use the same 15" rotors as the 997 GT3, but with different calipers. There appears to be sufficient space to 19" wheels based on the caliper clearance. With PCCBs would be another issue though due to the larger diameter. Of course why would you get PCCBs if you are going to track it? Let's face it, due to the risk of damage when changing wheels, brakes and replacement cost from wearing out rotors; it is hard to justify the cost unless you are just looking for long life brakes on the street. Would have to measure is a 18" wheel is possible with the new calipers. With the 997 GT3; CCW, BBS and Forgeline all make 18" wheels that clear the stock brakes.

wurlie

Alas, they will go on a 4.0...
Best, w

MiamiHeat

@ Wurlie, where did you purchase that full polish BBS monobloc and what was the cost? I would like to buy these wheels in 5-hole configuration if possible.