johnny

so does anybody know if the 997.2 19" wheels fit the 991 gt3.
997.2 stock sizes. i just want to use them as a winter wheel on the road.

Tom Tweed

No. Centerlocks are not compatible between 997 and 991.

991_GT3

Rotiform also makes 19" CL for 991 GT3

Leclerc

997 centerlocks apparently fit on a 991, but it is not recommended/allowed by Porsche.
Maybe the 991 centerlocks work with the 997 centerlock wheels on a 991?

JesseRohr

I've seen two local 997.2 cars with 991 20" CL now. So I assume they work.

MileHigh911

It has been mentioned before that they are not compatible. As I say that, we have seen some people trying it. Maybe for street use, one could accept the risks, but I would never do it myself, and I would never run one on the track with mismatched Cl wheels.

Tom Tweed

Does this mean they are "backwardly" compatible, but not vice versa? 991 ---> 997 is OK but not 997 ----> 991 ???

Like MileHigh911, I would never take the risk of trying it, either way, unless Porsche approved of the application by saying they are essentially the same wheels and can be exchanged at will. Invalidating the warranty is not an option for me.

YMMV,
TT

Maxi_z

I fitted some 997.2 gt3 rs oz ultraleggera wheels in 9x19 and 12x19.

The rear of the wheel hub look different from the oem wheels but I don t know if it s a difference on the oz wheels manufacture or because they are for the 997.

The oem 991 wheel inside hub got some kind of extra lip.

Apart from that we tried the wheels on the car and except the usual rear bolt that need to be reversed the centerlock fitted perfectly.

Would like to know if anyone got more details about the centerlock differences or pictures of the back of a 997 centerlock wheel.

I don t care about warranty and the wheels would be used on the track but would lik to make sure that they should mechanically fit well.

MileHigh911

I think the most difficult part to understand is what has actually changed in design. The 997 CL hub design turned into a service problem for Porsche. Supposedly, they said they changed it for the 991. Of course, they don't openly say How they changed it. But they do not approve the 997-991 swap. Now, the CL design primarily uses the studs to hold the wheel's vertical load, and the CL to lock in the wheel into the hub for lateral loads. One would be using the same nut, and the safety design of the locking mechanism is the same.

I personally wouldn't take it to the track, unless the wheel manufacturer would tell me it is ok. They are the ones that make the 991 wheel, and the 997 wheel. So it would be prudent to call Tire rack, or Oz wheels.

Maxi_z

The centerlock hub on the car and they way it work might be a little different but at the end what we would really want to know it s if there is any design change on the wheel itself because of that.

Or for aftermarket wheels it would be interesting to know if the manufacturer
changed how they shape the wheel at the hub if they make a rim for the 997 or for a 991.

I would say that if you take the same wheel model in aftermarket for 997 and 991 the hub is probably the same but not sure and of course it would be good to got some info or pictures.

James-GMG

There are plenty of 19" wheels out there for the 991 GT3:
-BBS
-HRE
-Forgeline

We have installed all three brands on GT3's as well as HRE's on the RS....some pics below....









One more pic, sorry for the poor quality as we have more in the shop I can send....



Well sell all 3 brands and can source just about anything for your GT3/RS....


Cheers,

Maxi_z

James GMG

I would think that 19" wheels are especially an interesting choice for those who use the car on the track and are not only interested in look but mainly in real performance on the track tyre choice weight etc.

I think that to attract more costumers on the forums on the use of aftermarket
19" instead of oem wheels or 20" you should let us know more technical info on the use of those wheels.

Most of the people already know the advantages and the look and quality improvements of most of the good brands of wheels on the forums.

What we would like to know is the real advantages of the 19" over 20" on the 991 gt3 and for the moment there is not much feedback from customers or tuners

that prepare cars for track use about that.

How is the steering feel with the different off set and larger tyres at front?

Is there usually a lap time difference and did you try the same setup with different off set or tyre width and what is the feedback in terms of steering feel and performance.

It was written on the forums that porsche recommend not to use different offset in the front that would make the front wider as it could cause less stability at higher speed and I understand why and think that can be corrected with different little things as geometry but what the ones who tried the modified offset think?



And the other question can we switch the wheels between 997 and 991 assuming the offset and size are ok?

Leclerc

Am I correct in understanding that you used a 991 CL?
Or did you use the 997 CL?

Fingers crossed for the former, as I'd like to try fitting 997 wheels with the 991 CL (on a 991)

Maxi_z

We tried and fit some oz ultraleggera from a 997.2 gt3 rs 3.8

The centerlock fitted without problems but will fit them again end of week after reversing the lower supension bolt and bending the brake line bracket.

I also wanted to know if there are not anything to look for that could make problems but at the moment we did not find any difference of course except that you really need to look at the size offset and that nothing touch.

Of course we tried the wheels using the centerlock parts of the 991 so the only different part is the wheel itself.

If you think about it all the centerlock system is still the one fitted on the car and the only contact parts are the holes on the wheel for the studs that should be the same size and spec and the center hub of the rim that should have the right size and shape to fit correctly.

The recommended torque is the same and the lock system still work so I don t think there should be anything else except rim size and offset of course but that is also something that you can custom spec on some wheels and that would anyway be something that would make the car react better or worst.

What is changed with the front wheel offset is the scrub radius and I think it can make the car react less good at higher speed if you don t change anything else.

That s probably the reason for porsche to not recommend different offset wheels.

Then you can compensate that different offset to some point probably by slightly changing the setup of the car as rake spring rates tyre sizes but especially camber and toe.

But it s of course too complicated for most customers and for them to explain and so if you change offset you have to understand that if the steering feel it s better or worst or if a lot of other little things should be done it s your own choice and it s probably not completely street legal or supported by the manufacturer.

Leclerc

I'd use them as winterwheels with snowtyres. so no (excessive) high speed driving. It would be a perfect solution for me.