Seeing as their are very few threads sharing all of the differences between the GT2 and GT3 suspension in any detail, I thought that I would make a thread to share the information I have found about about the GT2/3 front suspension and the uprights. For a while I actually considered the upgrade along with the supporting suspension mods, but decided that the cost was not worth the gain for the level of driving I do. For others this may not be the case. If you have the parts needed below already and can find a good deal on GT2/3 uprights, this mod may be perfect. Their have been people here who have done the conversion to either the RS uprights or the GT2/3 uprights, but the information on the what is needed for the upgrade is scarce. The difference between the GT3 and GT3RS upright is the location of the lower control arm attachment point distance from the wheel bearing and also the weight. The GT3RS is hollow and also has two bolts to mount the shocks instead of one. Here is a good link with some good info: http://forums.rennlist.com/rennforum...prights-3.html


You cannot do the upright swap if you are AWD. To update to the GT2/3 uprights you will need a pretty healthy list of parts. Below is each area needing to be modded for upgrade to these uprights.


GT2/3 Street
Left Upright 996 341 157 91
Right Upright 996 341 158 91
GT3RS
Left Upright 996 341 157 92 (superseded to 997 341 157 93)
Right Upright 996 341 158 92 (superseded to 997 341 158 93)


Brakes
The stock 996TT brakes will not work due to the rotor offset. Chances are if you are doing uprights, you probably already updated the front brakes. If not you will need to. One option is to upgrade to the stock GT2 PCCB setup with rotors and calipers. You can run the steel rotors with the PCCB if you choose to avoid the future rotor cost. Many GT2/3 guys have been doing this anyways and steel rotors are available. The other option is to run the 997TT with the steel GT2/3 rotors. Both are compatible and the important thing to accomplish is the correct rotor offset.


Their may be other ways to mod the uprights or brakes to allow for use with stock 996TT brakes, but the above are the only ones I am aware of.


Shocks
As some already know, you cannot just bolt a stock GT2 or GT3 suspension into a 996TT upright. And you also cannot bolt a stock 996TT suspension into a GT2/3 upright. The differences are shock diameter at the mounting point and sway link attachment points. The link attachment points are an easy solution that I don't need to go into. The shock diameter is the main issue. The stock 996TT shock diameter is 55mm and the GT2/3 is 52mm.


The easiest option is stock GT2 or GT3 suspension. Both suspensions are the same, but with different spring rates. If you have an aftermarket suspension, you will need to verify shock diameters. The JIC and Moton suspensions are compatible with the GT2 and 996TT. They just supply a shock sleeve to fit the 996TT upright. You can just remove the sleeve to make these shocks work with the GT2/3 upright. I am not sure which other aftermarket setups are dual compatible, but verifying will be easy.


Upper strut mounts
The rear upper strut mounts are the same and do not have to be replaced, but it is a good time for a mono ball upgrade.


The stock 996TT and GT2/3 have different front upper strut mounts. The differences are the geometry and the spring to strut mount seating. The 996TT upper mounts are setup for the angle of the shocks where it meets the upright. It also has a bearing between the spring sea and the upper strut mount to allow for the spring to turn without binding on the strut mount seeing it is rubber and does not spin like the mono ball ones do. The mono ball setups like the stock GT2/3 incorporate bearings which means you can use the cone shaped upper spring cups without the need for any additional bearings. You can either use the stock gt2/3 upper mounts or you can use the aftermarket camber adjustable setups available. It is important that it is compatible for the GT2/3. You have to match the front upper mounts to the upright. It is all down to the geometry. I attached a simple diagram to show the geometry differences between the two setups.





And a few more shots of GT2 shocks for reference.



For those wanting to install GT2 or GT3 suspensions with stock uprights
An important thing to note is that if you are not using the GT2/3 upright and you are going to fit the GT2 or GT3 suspension you will need to keep turbo front upper strut mounts to maintain the correct geometry. You can upgrade to the monoball aftermarket setups as long as they for the turbo. But if you intend to use the stock turbo front upper strut mounts you will need to find a way to incorporate the stock bearing that goes between the strut mount and the rubber spring mount. Otherwise you will tear the rubber part of the mount as the shock and steering knuckle turns. It is possible to fit the GT2 upper mount, but the geometry will cause the shock shaft and bolt to hit the strut mount as the suspension moves. I advise against it unless you are using the correct upright.

The other thing you will need is the sleeve that adapts the 52mm GT2/3 front shock to fit the 55mm stock turbo upright. You will also need the GT2 sway links and the rest of the spring perch hardware. And make sure if you buy a use suspension make sure it comes with the sway link attachment points. The rear suspension is a direct swap.

I hope this helps. Please let me know if there is anything here needing to be corrected.

 

Great Write-up!

In regards to the brakes, I believe one can use the PCCB rotors from a Turbo, but would need to change the hat to a GT2/3 as it's wider

Also, when one is talking about uprights, are they referring to the wheel carrier?

I'm actually going to be doing a full GT2 suspension swap into my PCCB equipped Turbo in the next month or so.

 

Excellent write-up!

Once again one thing about turbo's ( either 996's 330 mm or 997's 350 mm) brake discs with GT2/3 wheel carriers. Fully compatible with 1.5 mm spacer between the wheel hub and brake disc.
Calipers are the same than GT2/3's...colour may be different.

Also Cayenne turbo's 350 mm disc is a bolt-on without any spacer. Very affordable, not drilled but slotted, slightly heavier.

 

The uprights and wheels carriers are one in the same. The calipers are same as the gt2/3 calipers. Didn't know the rotor discs could be exchanged between hats though. But good info.

 

awesome writeup. although i dont intend on doing anything near this drastic, its always great to see the wealth of knowledge sharing that some people put forth. kudos to you, and im sure this will help answer alot of questions for people!

 

why is the turbo suspension leaned like that compared to the GT2/3? What was the point and why did Porsche decide to do something different? Is it only to let some space for the front axles?

 

It is to allow space for the front axles. Otherwise the bottom of the shock would hit the cv joint and shaft.

 

I know that a 997tt caliper and a gt2/3/tt pccb caliper are all bolt on compatible, but I have read that their are piston size differences between the pccb calipers and the 997tt.

On the cayenne rotors, are you sure they are slotted? I thought they were solid and vented only? Good to know they bolt up though. Pelican also has steel gt2/3 rotors to go on the pccb cars. And I believe they are the same price as the 997tt rotors unless you with a light weight floating setup.

 

Fronts are the same, but rears different.

I thought so too, but just saw this: https://www.6speedonline.com/forums/...ors-996tt.html

 

Those are not OEM, they are aftermarket. That is why they are slotted.

 

Great write up! I changed over to the gt2/3 because of the way the strut is angled. Your illustration show it perfectly. I just do not get how the strut can dive back and still work the same? Its almost like it is doing its job after the fact. Also the angle has to make a mess of the valving and spring rates. I also have a set of the 996 rsr uprights but would not be able to use my pccbs on them so i did not use them. The placement of the wheel bearing is about 1'' higher then the gt2/3 or even turbo wheel carrier. Just like the drop spindles of yesteryear. The geometry will be right but the car will be 1'' lower. less bump steer.

 

Niceinfo

 

FYI from another forum member.

"Q: Are 997 GT3 cup calipers compatible with 996 turbo uprights? These are normally paired with 380mm rotors. Do they work with the 350mm 997tt rotors?

A: They are not directly compatible. The 996tt uprights are a 142mm bolt spacing (as are the 997TT and GT3 iron-disc cars). The 997 GT3 cup calipers are 225mm spacing. This is true of the following:

997TT PCCB
997GT3 and RS PCCB
997GT3 Cup
997GT2 and RS PCCB

The calipers from these cars with 225mm mount spacing are only for use with 380mm discs. On both GT3 variants using these calipers, there are specific uprights used that have been built to directly mount them. However, on the 997TT, there are adapter brackets to bolt them to the standard 142mm spacing uprights. Another interesting bit is that the calipers on both GT3 versions have smaller piston sizes than the 997TT PCCB calipers* to provide a firmer pedal and also serve to shift the brake balance slightly rearward.

You can use the adapter bracket from the 997TT PCCB to mount them on the car (=996 turbo), but there is no factory Porsche disc option that will work with that other than the 997TT PCCB disc. The GT3 Cup disc offset is not correct. To use the GT3 Cup disc, you would need a custom adapter bracket.

Brembo has a 2-piece floating iron-disc replacement for the 997TT PCCB disc that has the correct dimensions, however. The part number for this is 102.9008A

All above I picked from another discussion about different brakes' interchangeability. BTW, part number for that adapter bracket is 997 351 505 02 ( x2 ). Needs also 4x M12x1.5 bolts, 999 073 313 09.

Once again one thing about turbo's (either 996's 330 mm or 997's 350 mm) brake discs with 996 GT2/3 wheel carriers. Fully compatible with 1.5 mm spacer between the wheel hub and brake disc. That's how I run them...
Calipers are the same than GT2/3's...colour may be different.

Also Cayenne turbo's 350 mm disc is a bolt-on without any spacer. Very affordable, not drilled but slotted ( aftermarket ones, OEMs are smooth), slightly heavier.

*I checked this from the PET:

Fronts:
996 turbo & GT3 -'02 36-44mm
996 turbo PCCB & GT2 & GT3 '04- 28-32-38mm

997 GT3 -'08 & turbo 28-32-38mm
997 GT3 '10- & GT2 & GT2RS 28-30-32mm
997 GT3 PCCB 28-30-32mm
997 turbo PCCB 28-32-36mm

Rears:
996 GT2/3 & turbo 28-30mm
997 GT2/3 & turbo 2x 34mm

NOTE: I've recently found out that there's mistakes in the PET, so do not take these granted."

 

Thanks for posting all the technical info on GT2/3 suspension uprights!

Would you know what is required to install GT3RS PCCB's (rotors/calipers) onto a 997.1 Turbo?

Are you aware of any adapter to get these callipers installed onto Turbo uprights?

 

That's not what will be installed though, the rotors, calipers, etc are all from a GT3 RS & I'm checking if it's possible to install them on 997.1 Turbo