Vetch

Can a 991.2 GT3 (and 3RS) step down to a 19" wheel for track use?

mdrums

Vetch

Ahh... that was a sort of hidden part of my question. I've not bought the car yet but wanted to know if I should avoid the PCCB's. I know my 997 couldn't drop from 19" (OEM) to 18" if I had PCCB's. Is it correct that you can't drop from 20's to 19's on the 991.2 if the car has PCCB's?

MileHigh911

You can, but are limited to which wheels, and the clearance is so tight that the inner barrels will likely get grooved by rocks/debris picked up

A/S

I have track experience with 19" and PCCB in the 999.1 Turbo S, 991.1 GT3 RS, 991.2 GT3RS.

Plain answer: Don't do it. It is no longer necessary.

19" on PCCB will scratch the calipers with all the common debris we have on track days, all 4 calipers will need to be re-painted as often as this scratches bother you. At the rear axle, a lower control arm bolt scratches the wheels when the car hits bumps or compresses during heavy turns.

19" on Steel brakes: caliper problem is largely reduced but not eliminated, especially in the back. The problem with the LCA bolt remains.

There is a 4mm smaller head bolt from the Panamera that can be installed in the rear LCA (where the LCA attaches to the wheel carrier). This bolt eliminates the rubbing between the bolt and the inner wheel drum.

Only the following wheels have been tested in 19" in 991 GT cars: Forgeline GE1R-CL, GA1RCL, All Finspeed, some HRE. I tested OZ 19" CL and their inner drum is too small, so they can't be used in the rear, but the front OZ is fine only for steel brakes.

For track use, don't get PCCB. Get Steel brakes, or even better use the PCCB money towards Surface Transform CCB rotors or the magnificent AP Racing kit.

My 991.2 GT3 RS calipers (all 4) have scratches already, ugly ones, normal.

Vetch

Thanks for the posts. Even if I bought a PCCB car, I would not plan to use those rotors on track. I'd switch to steel but it sounds like there's no point in switching to 19's regardless of PCCB or not.

krell

There's certainly no NEED to switch but people have to provide additional tire options, plus the unsprung weight reduction can have a positive effect on the car's handling.

Wheels take a pounding at the track and it's almost impossible to keep them from getting scratched and marred with all the brake pad and rubber material flying around. That would be a big motivating factor personally to get track wheels -- just to keep the OEMs in good condition.

80p

I have no personal experience with any of the 19's, just reposting:
HRE R101LW in 19, PCCB:
https://rennlist.com/forums/991-gt3-...l#post15508602

BBS RE 19 MTSP (IIRC), steel:
https://rennlist.com/forums/showpost...3&postcount=49

ipse dixit

Stick with PCCBs for track use. 20" wheels as well.

80p

I looked into specs of a few lightweight 19" vs 20" options for GT3 sizes, interestingly there's not much of a weight decrease going from a light 20" to 19". Fronts are 17 +/- 0.4 lb, Rears 20 +/- 0.3 lb regardless of size. You have to go to Mg or CF to get lighter. I'm guessing the design process when removing weight wasn't optimized for GT cars for 19"s

Was thinking there might be an improvement in rotational inertia, but even if you assume all the weight is at the rim, the improvement is less than 10%.

19"s do look rad, though.

CharlieBrown3121

This advice seem counter to the prevailing current of opinions on PCCB vs Steel for track use. I like that

I just picked up a 991.2 GT3 RS with PCCB (my first PCCB car). I was going to run one HPDE track event just to feel them and then switch to steels and like the OP, switch wheels. Assuming all the advantages published and discussed about PCCB over steel, it seems cost is the main reason people switch to steels. I'm curious about your rationale. I'm hoping you'll say something like, "if you plan to keep the car xx months./years, that PCCB last x times longer than steels so overall total cost of ownership is near the same.." Do tell

ipse dixit

People who say don't use PCCBs on track are basing it on the Gen II PCCBs (from the 997 generation).

The Gen III PCCBs on the 991 are much improved. Are they as durable as Porsche OEM irons? No, of course not. Are they as fragile and brittle as some make them out to be? Of course not.

Here's an anecdote. A friend who tracked his 991.1 GT3 had to replace his engine more times than he had his PCCB rotors. This was after about 6k track miles.

Vetch

So bottom line...
If I were buying a 991.2 GT3 or 991.1 GT3RS specifically for the track, does it matter much if it has PCCB or steel brakes (assuming I will switch PCCB's to steel anyhow)?

Smoking Rotors

You will get slightly better steering feel and handling (subject to opinion of course) with PCCB's at 10/10ths which can be somewhat offset by lighter wheel and tire packages. The downside is they are brittle and relatively easier to damage, so might not be great if you are planning to track much; changing tires, if you chip one badly enough, your day and thousands of dollars can be ruined.

Those who go with steel like the reliability; don't have to worry about damaging at the track and fast lap times come with consistency. the N/A engine is less complex than a turbo and can run all day long. Same theme with steels. Lap times are combination of stop, go, turn. You can pick up times in other less costly ways, like suspension, tires, ride height, weight diet, or just plain old practice...

PCCBs have a look and status component.

Vetch

Thanks for the input. Again this car would be track only, and even if I got a car with PCCB's I would immediately switch to iron due to the cost and fragile nature of the carbons. I just wanted to know if there a down side to going with a steel rotor car or a PCCB car if I'm going to switch to steel anyhow.