They are cup shocks. They will work on the rears with the correct supporting mods. It has been done before on 996 street cars. And the shocks are adjustable to accommodate 1000rear/900front. Trust me, I don't have a pile of parts without a plan.

 

No worries. Anything can be made to work. I was just wondering how effective running a shock that is almost two inches shorter with very limited travel compared to a street GT3 shock is going to be on a heavy street car with soft spring rates. Glad you have a plan. Good luck with the project...

 

It has been done on 996 C2s and GT3s with great results but not turbos. The shock length problem is easy to resolve. The shock travel in itself is not an issue unless you just bolt the shocks on without correcting for the length issue. Because if this is not corrected for them the shocks will be over extended when the perches are adjust to correct ride height. These differences in shock length is because of differences between the cup rear spindles and rear subframe and that on the street cars. I have solid subframe bushings going in and a 20mm spacer going between the upper mount and the body to counter this.

 

pics are up on the gt3 parts i linked you to

 

Plus 640 mm diam front and 680 mm rear tires, while the rake is still about the same 20mm than in street cars. Ie rear wheels are really deep inside wheel wells. If you're not going to run similar set of tires, you need to use 40-50 mm spacer. Again, don't ask how I know...

Here's a pic of my "new" ones, they will be anodized black next week. "New" because they were just round ones before some weight reduction. Lost 60% of their weight. 50mm thick.

 

Exactly. I doubt a 20mm spacer will cut it. That's why I said a shock length difference of about 2" (50mm) in my earlier post taking into account 26.8" (680mm) rear cup tires. The cup chassis has a lot more room in the wheel wells than the TT and wheel compression is very limited with 1480ish springs. No way could you run 680s on the TT.. I've found a 26.4" rear tire is about the max on the TT/GT2 chassis when run at a 120mm ride height without rubbing even with 1500# springs.

 

Nice find - but $3200 for the 4 uprights is anything but a steal...
2010> 7GT2/3 uprights can just about be had at that price. At least over here.

 

What outer diameter tires are you running front and rear?

 

Also, I spoke with a Cup/RSR team engineer that told me that the taller tires in the rear on the 996 cup was that way because it was to put relatively more of suspension dampening work into the tires versus shocks and springs. Interesting concept IMHO.

 

The factory cup car rears are 305/35/18 which is 26.3" versus factory 996 turbo of 25.1" depending on which tire you are running. That adds .7" inch to the actually height. I have successfully run 26.0" on the rears of my car. Also, the GT3 cup ride heights all seem to range from tucked deep into the fenders to extremely low street settings. So, if the shock is too short to run a street able ride height without the shocks constantly over-extending, then I am to deduce that the cup car guys must also be very limited(no more than .5" adjustment to ride height) with ride height adjustments? So that being said, what would you call minimum safe ride height on the street? Keep in mind that Cups measure from a subframe point that is not apples to apples with a turbo due to subframe differences.

Again, not trying to argue my point. Just hoping to share and pool as much knowledge on the topic as available.

 

Factory Cups do NOT run 305/35/18s.

Factory 996Cups run OEM N1 spec Michelin slicks size 24/64 18 and 27/68 18 on 18x9x11 wheels. Fronts tires are 25.2" and rear tires are 26.7" in diameter (there is also OEM approved Pirelli slick with the same diameter dimensions). Midway through the production run, the rear tub was modified on the Cups to give the tires more clearance.

Regarding 996 Cup ride height variance you may have seen, per the Porsche Cup maintenance manual, there is none. Ride height is clearly spelled out as 86mm front and 107mm rear. Fine tuning is allowed to bring corner weights within specifications. Other than that, Porsche does not give you leeway. This is clearly done to make sure the shocks are operating within their design specification. For example, if you raise the ride height up, you will severely limit the already minute amount of droop built into the shocks.

The popular 996TT/GT2 rear tire diameter is 25.5" which is 1.2" (31mm) shorter than the Cup tire. This translates to 15mm shorter radius. If you were to bolt a 996TT sized rear tire on the Cup car, you would get a rear ride height of 92mm (107-15). Taking into account the TT rubber subframe bushings thickness difference (7mm) compared to the solid GT3 cup bushing, you end up with a rear ride height of 85mm when translated to 996TT numbers.

Compare this 85mm ride height number to the factory ride height of 163mm for a stock 996TT or 135mm for a GT2 and you begin to see the light. Even when comparing the Cup with the GT2 (both solid subframe bushings), you are looking at a difference of 50mm in ride hight. As a result, if you are shooting for GT2 ride height on your car, you will need a 50mm spacer on the rear Cup shock.

So I wanna use a 0.9" taller 305/35/18 (26.4" NT01) tire you say? Well, to preserve GT2 ride height of 135mm you will need to lower rear spring perches 11mm down to 124mm at the rear measuring point of the subframe. If you do this, then you will need a 40mm spacer on the shocks. This is about as low as you will be able to go with the relatively soft 1000# springs you are wanting to run as the larger tire diameter will rub the fender liner under hard compression. Remember, a 3500# TT will have a lot more compression of the shock with 1000# springs than a 2600# Cup car will with 1484# springs.

As far as minimum safe ride height on the street? Depends on your comfort level and type of streets. I am at 98/124 with 25.7" and 26.4" tires in 1400/1500# springs. I do not rub anywhere but my suspension is very stiff and I have GT2 fender liners along with all Cup/RSR fully adjustable suspension components to maximize clearance and minimize movement. This is a picture of the ride height to give you an idea. I would not call it street friendly...

Hope this helps...

[url=https://flic.kr/p/nTLbX7]

 

I was off in tire sizing. According to this they call for 304/660-18 which should be 25.93. What am I missing?

 

Nobody runs that size. PCA mandated rear tire size is a 680. The Michelin N1 Cup rear measures 26.7" and the Pirelli 305/680 Cup measures 26.9".

 

Slightly off topic but I was wanting to run the new nt05r in 315/40-18 which is 28.4 tall will I have issues? Need more sidewall for launches at the track

 

Seeing their is not a apples to apples ride height measurement reference point between the turbo and cup due to subframe variances, does anybody have a wheel well measurement from a cup for comparison?