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996GT3RS vs 996GT3 suspension comparison

 
Old 01-21-2018, 10:47 PM
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powdrhound
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Default 996GT3RS vs 996GT3 suspension comparison

I have a brand new set of 996GT3RS suspension components on hand and took a few pictures and measurements to compare with the stock 996GT3/2/Cup components. The RS has different front and rear uprights along with rear side members. These components were the homologation parts for the 996RSR. As such the RS uprights use the Motorsport castings but have pickup points machined roughly 12mm higher than the Cup/RSR units. The Motorsport casting are hollow and substantially beefier than the standard GT3 units. They use 6 bolt bearing retainers both front and rear, compared to 4 bolt on the standard units. While the 997GT3 cars (including the 4.0RS) use a 6 bolt pattern in the front, they still only use a 4 bolt street upright in the rear which is totally different from the Motorsport units. The front subframe pictured is a 996RSR subframe. The RSR subframe is identical to the standard version except the LCA pickup point is raised 6mm. The RS does not use this subframe, it uses the standard subframe. Cheers...




Front upright (This is the 380mm brake version used on 997.1GT3 PCCB cars. The 996RS uses a version machined for 350 brakes, same as those used on 997.1GT3 with steel brakes)



Rear upright




RSR front subframe The LCA pickup point on the RSR subframe is 6mm higher. You can see how the upper part of the subframe is milled to allow for clearance.



Below is a picture of the comparison of the 996GT3RS upright compared to the standard units. The pick up points have been substantially lowered on the RS parts:

Front:
LCA: -60mm
Tie rod: -55mm

Rear:
LCA: -30mm
Toa arm: -30mm
Upper arms: -25mm

Front 996GT3RS v. 996GT3

Rear 996GT3RS v. 996GT3 (Note that the LCA pickup is correctly angled on the RS units unlike the stock units. The angle now matches that of the rear side member LCA pickup)

Last edited by powdrhound; 09-20-2018 at 02:06 AM.
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Old 01-21-2018, 11:25 PM
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993GT
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fantastic documentation John! thanks for sharing!

Originally Posted by powdrhound View Post
I have a brand new set of 996GT3RS suspension components on hand and took a few pictures and measurements to compare with the stock 996GT3/2/Cup components. The RS has different front and rear uprights along with rear side members. These components were the homologation parts for the 996RSR. As such the RS uprights use the Motorsport castings but have pickup points machined roughly 12mm higher than the Cup/RSR units. The Motorsport casting are hollow and substantially beefier than the standard GT3 units. They use 6 bolt bearing retainers both front and rear, compared to 4 bolt on the standard units. While the 997GT3 cars (including the 4.0RS) use a 6 bolt pattern in the front, they still only use a 4 bolt street upright in the rear which is totally different from the Motorsport units. The front subframe pictured is a 996RSR subframe. The RSR subframe is identical to the standard version except the LCA pickup point is raised 6mm. The RS does not use this subframe, it uses the standard subframe. I will mention that the rear RS side members are the same as the standard side members. I could not discern or measure any difference between the two as all the pickup points measure identical. The only difference I could see was more machining in the area of the LCA pick up to create more clearance. If someone wants to convert their car to RS spec, I would not waste your money on the rear side members. Hope this settles some of the mystery surrounding the RS components. Cheers...





Front upright (This is the 380mm brake version used on 997.1GT3 PCCB cars. The 996RS uses a version machined for 350 brakes, same as those used on 997.1GT3 with steel brakes)





Rear upright






RSR front subframe The LCA pickup point on the RSR subframe is 6mm higher. You can see how the upper part of the subframe is milled to allow for clearance.




Below is a picture of the comparison of the 996GT3RS upright compared to the standard units. The pick up points have been substantially lowered on the RS parts:

Front:
LCA: -60mm
Tie rod: -55mm

Rear:
LCA: -30mm
Toa arm: -30mm
Upper arms: -25mm

Front 996GT3RS v. 996GT3


Rear 996GT3RS v. 996GT3 (Note that the LCA pickup is correctly angled on the RS units unlike the stock units. The angle now matches that of the rear side member LCA pickup)
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Old 01-22-2018, 02:17 AM
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Originally Posted by 993GT View Post
fantastic documentation John! thanks for sharing!
thanks Rob. You’re welcome...
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Old 01-22-2018, 08:54 AM
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Johnny DB
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+1 Great job John. Thanks for your contributions to the community!
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Old 01-22-2018, 08:04 PM
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Great info. The bigger question though. at what ride heights do these really begin to become an advantage vs toe arms with bump steer correction. I do realize one is a band-aid and one is a proper solution but still curious on your take.
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Old 01-22-2018, 08:24 PM
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An archetypal post.
Thanks for sharing the photo's and information.

Cheers

Craig
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Old 01-23-2018, 05:23 AM
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pete95zhn
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If one wants lowered rear subframes, the RSR is the solution. OEMs may be hard to find, but one can always mill (12mm in my case) std parts to RSR style. This with solid bushings moves Carrera's/turbo's suspension arm pickup points about 21mm (IIRC, have to check from my archives) up (=lowers chassis 21mm down). On GT3 solid bushings are already used, so drop is less.


Last edited by pete95zhn; 01-23-2018 at 07:48 AM. Reason: Clarification
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Old 01-23-2018, 07:19 AM
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According to the homologation document the RSR's rear subframe mounting points are only machined 10mm down at the face. The fixing holes are moved up: Upper arms 9mm up, LCA 8mm up, Toe link 10mm up.
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Old 01-23-2018, 10:52 AM
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Very interesting stuff - curious as to what the parts cost to make the 996 GT3 suspension into a 996 GT3 RS suspension.
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Old 01-23-2018, 11:33 AM
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Originally Posted by AudiOn19s View Post
Great info. The bigger question though. at what ride heights do these really begin to become an advantage vs toe arms with bump steer correction. I do realize one is a band-aid and one is a proper solution but still curious on your take.






Hey Andy. I believe bump steer is only one part of the equation here. The more important thing here in my opinion is the fact that that the LCAs attach significantly lower (-60mm front, -30mm rear) on the RS uprights. This allows the LCAs to have a slight amount of declination at static ride height as opposed to an inclination with the stock wheel carriers. Toe arms naturally attach lower by a corresponding amount to keep them parallel with the LCAs. The RS uprights will allow one to run ride height in the area of 90-100mm front and 110-120mm rear while maintaining correct geometry. I am running the 997RSR LCA which allow me to further fine tune the roll centers through the use of 3 different length trunnion pins which give another 8mm of height adjustment at the outer LCA monoball. Based on what we’ve calculated, I’m shooting for about a 5 degree declination on the front LCAs and a 0-2 degree inclination on the rear. That should provide a solid starting point.

With that said, I would caution against blindly using Cup/RSR components on our cars. While it may sound cool, you may actually be going backwards. The 996RSR runs a ride height of 80/100 using 27.8” tall rear tires. As such, the upright pick up points are another 12mm lower and the subframes are mover closer to the body to account for this. Keep in mind, the 996GT3 uses 25.2" tall rear tires and a higher ride height (I am running 26" rears). I think running the RSR subframes and rear side members would work in conjunction with the stock 996GT3 uprights as it would raise you roll centers by a moderate amount. I would not recommend using the RSR subframes in combination with the RS wheel carriers components, especially if you are running the RSR LCAs which allow you to raise the roll centers further on the outboard side. Might sound cool at the water cooler but that's about it. Just my $0.02.

There are a lot of variables that go into optimizing each set up. The most important thing is working with someone that is intimately familiar with setting up these cars. It's oftentimes hard to make things better, and easy to make them worse.

Last edited by powdrhound; 05-16-2018 at 10:19 PM.
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Old 01-23-2018, 09:53 PM
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Fantastic, thank you for sharing!
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Old 01-24-2018, 01:06 AM
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Originally Posted by powdrhound View Post


The most important thing is working with someone that is intimately familiar with setting up these cars. It's oftentimes hard to make things better, and easy to make them worse.
amen.
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Old 01-24-2018, 06:29 PM
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Very cool parts. Just so I understand the big picture: you're upgrading these parts to maintain correct suspension geomtery (specifically roll centers) to better accommodate larger wheels sizes and/or get a lower CofG (aka faster car)?
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Old 01-25-2018, 01:06 AM
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Originally Posted by mistermct View Post
Very cool parts. Just so I understand the big picture: you're upgrading these parts to maintain correct suspension geomtery (specifically roll centers) to better accommodate larger wheels sizes and/or get a lower CofG (aka faster car)?
It's not really an issue with larger wheel sizes. I'm running 18x10x13 currently with the stock uprights. The RS parts will actually make a little harder to fit the same sizes but it can be done. Yes, the geometry is greatly improved with the RS parts and they are much stronger. On top of that, the current uprights are no longer available from Porsche with none worldwide and no ETA on if and when they will be available. Neither are the RS front uprights (the 350 versions) actually. None worldwide. Luckily a couple of pair of the the 380 versions were available in Europe so I grabbed the whole set. Spares are becoming very hard to source for these cars and it's only getting worse. I'm not sure what the hell Porsche is thinking when it comes to spares for these older cars.
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Old 01-25-2018, 01:13 AM
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Originally Posted by powdrhound View Post
It's not really an issue with larger wheel sizes. I'm running 18x10x13 currently with the stock uprights. The RS parts will actually make a little harder to fit the same sizes but it can be done. Yes, the geometry is greatly improved with the RS parts and they are much stronger. On top of that, the current uprights are no longer available from Porsche with none worldwide and no ETA on if and when they will be available. Neither are the RS front uprights (the 350 versions) actually. None worldwide. Luckily a couple of pair of the the 380 versions were available in Europe so I grabbed the whole set. Spares are becoming very hard to source for these cars and it's only getting worse. I'm not sure what the hell Porsche is thinking when it comes to spares for these older cars.
are you end-of-lifing your current parts or just collecting spares?

I just realized my last post may not be clear but I was thinking OD wheel diameter per your 26 in comment. big wheels raise it up so you'd lower it back with coils and correct geo with RS parts.

I'd be pissed if I had to replace an upright and I couldn't source one.. I guess be careful is the motto!
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