Planet-9 Porsche Forum banner

1 - 20 of 49 Posts

·
Registered
Joined
·
346 Posts
Discussion Starter #1
Question regarding 718 rear brace install

I’m currently looking to install this on my 981. I haven’t pulled the trigger yet bc I’ve read that I would have to drill into my transmission plate or buy a 718 plate to complete the install. My question is, do you even have to bolt the brace into the plate? From what I can see, the plate isn’t very robust, so I’m having a hard time understanding why the brace would need to be secured to it in the first place.

Would love to reach some absolute clarity on this. TIA
 

·
Registered
Joined
·
80 Posts
Re: Question regarding 718 rear brace install

I’m currently looking to install this on my 981. I haven’t pulled the trigger yet bc I’ve read that I would have to drill into my transmission plate or buy a 718 plate to complete the install. My question is, do you even have to bolt the brace into the plate? From what I can see, the plate isn’t very robust, so I’m having a hard time understanding why the brace would need to be secured to it in the first place.

Would love to reach some absolute clarity on this. TIA
The thinking is that under load the brace will bow towards the rear, it should not take a tremendously robust plate to prevent it from bowing. It's bolted to the plate on the 718 so people want to bolt it on the 981. No you do not have to bolt it to the plate to have it provide stiffening. To provide the maximum capable bolting is needed.
 

·
Registered
Joined
·
727 Posts
Re: Question regarding 718 rear brace install

You can do whatever you want, but the whole purpose of this brace is to in fact bolt it to the bottom pan. It gives you four mounting points in a trapezoidal shape that helps to stiffen up the whole rear subframe and suspension. The amazing ride that we all enjoy in our Caymans starts because it has one of the most torsionally stiff steel chassis on the market. Our cars are almost as stiff as a carbon tub exotic vehicle. Bolting up this 781 brace properly helps to make our cars even more structurally sound, which improves the ride whether you are on the track or driving down the road. Porsche put four attachment points on this part for a reason. It is way better than anything else on the aftermarket.
 

·
Registered
Joined
·
346 Posts
Discussion Starter #4
Thanks for the responses! Are there any other 718 suspension changes that 981 owners can add?
 

·
Registered
Joined
·
1,966 Posts
+1 on all the other advice given here to drill the holes. On the other hand, Porsche originally did not put a brace there, so not doing the holes is still better than stock.

The holes are not hard to drill. Start with a small bit - feel for the center of the hole in the mounted brace and follow up with a thin step drill. The brace is steel and the pan is aluminum and it will self-center if your pilot hole was a bit off. Note you may need a washer to take up space between the pan and the brace, depending on the alignment of the brace and the pan (the 718 pan is dimpled upwards to accomplish this without washers), as cranking down the bolt without a washer could bend the pan slightly.

I just tonight received a new Suncoast brace kit that I ordered for a new (to me) 2014 Boxster base that should arrive middle of next week. As cold as it is and continues to be, it may be a while before I install it.

V6
 

·
Registered
Joined
·
346 Posts
Discussion Starter #6
+1 on all the other advice given here to drill the holes. On the other hand, Porsche originally did not put a brace there, so not doing the holes is still better than stock.

The holes are not hard to drill. Start with a small bit - feel for the center of the hole in the mounted brace and follow up with a thin step drill. The brace is steel and the pan is aluminum and it will self-center if your pilot hole was a bit off. Note you may need a washer to take up space between the pan and the brace, depending on the alignment of the brace and the pan (the 718 pan is dimpled upwards to accomplish this without washers), as cranking down the bolt without a washer could bend the pan slightly.

I just tonight received a new Suncoast brace kit that I ordered for a new (to me) 2014 Boxster base that should arrive middle of next week. As cold as it is and continues to be, it may be a while before I install it.

V6
so you first install the brace using its main mounting points, then you drill through the pan blind based on estimating the support holes using touch? Would it be easier to just mark the support holes with a sharpie and uninstall the pan to drill more accurately? Or will uninstalling the pan require an alignment when reinstalled?

I guess if if the support holes are close enough to the edge, a rough estimate using a pilot hole is doable.

Idk, I may just buy the 718 pan if no alignment is needed after swapping.
 

·
Registered
Joined
·
1,966 Posts
so you first install the brace using its main mounting points, then you drill through the pan blind based on estimating the support holes using touch? Would it be easier to just mark the support holes with a sharpie and uninstall the pan to drill more accurately? Or will uninstalling the pan require an alignment when reinstalled?

I guess if if the support holes are close enough to the edge, a rough estimate using a pilot hole is doable.

Idk, I may just buy the 718 pan if no alignment is needed after swapping.
The Porsche 981 factory service manual says that a rear alignment is needed after pan removal/replacement.

Yes, mount the brace and torque the four bolts on the sway bar carrier (Note when off, it will help to put silicone grease in the sway bar bushings to help the car transfer weight from side to side in turns.)

The holes are near the outer edge of the pan. You can use a thumb and finger to feel the hole location in the brace and estimate the location to drill upwards from below. Use a small bit (0.040" or less) and if you were off, you will feel it and can drill again until you are close to center. Then use a narrow angle step drill and it will self-center as once the step drill hits the steel hole in the brace, it will move sideways in the aluminum and center. Also the hole in the brace is larger than the screw used. The screw is 10mm, but the hole in the brace is 13 to 14mm. I got a large washer for the top and bottom to ensure full clamping force.

Finally, check the clearance between the bottom of the brace and the pan and use washers as needed. There may be enough slop in the mounting to get the brace all the way down to the pan. On my Cayman, I had to put a washer on one side and not the other. If you have a gap between the two and tighten the nut and bolt, you can deform the pan and and possibly alter alignment.

Of interest, there is no pan connection on the GT4 brace. It appears that adding the L tail of the brace and holes in the pan was an improvement on the 718 series. On my Cayman, I have a BGB harness/roll bar that ties the top of the two rear shock towers together, so I have as much rear chassis support as feasible.

It isn't worth the time to remove/replace the pan and then do an alignment.

V6
 

·
Registered
Joined
·
346 Posts
Discussion Starter #8
Of interest, there is no pan connection on the GT4 brace. It appears that adding the L tail of the brace and holes in the pan was an improvement on the 718 series. On my Cayman, I have a BGB harness/roll bar that ties the top of the two rear shock towers together, so I have as much rear chassis support as feasible.

V6
hmmm interesting that they just introduced this on the 718 and not the gt4. I assume they were both being developed at around the same time.
 

·
Registered
Joined
·
346 Posts
Discussion Starter #10 (Edited)
Actually, looking at the rear undercarriage of both gt4 and 718, it appears that the gt4 brace is mounted in front of the sway bar, where the 718 is behind. I’m not sure if that is due to the lack of space on the 718 or an improvement. I may just buy the gt4 version.

see below:
 

Attachments

·
Registered
Joined
·
151 Posts
Actually, looking at the rear undercarriage of both gt4 and 718, it appears that the gt4 brace is mounted in front of the sway bar, where the 718 is behind. I’m not sure if that is due to the lack of space on the 718 or an improvement. I may just buy the gt4 version.

see below:

You might want to read Voyager6's thread before ordering the gt4 version....

Voyager

I recently purchased the GT4 brace by itself and very quickly realized that it would not work with my 2014 CS w/PDK
and also realized that the sway bar bushing carriers needed to be different and that longer carrier bolts would also be needed. Was at the dealership a few days ago and got under a 718Cayman w/PDK and took this photo showing what appears to be the same brace you have and also the 2 bolts you need to add to your car, hope it helps.
http://www.planet-9.com/981-cayman-and-boxster-modifications/107247-voyager6s-cayman-s-monster-car-mod-34.html
 

·
Registered
Joined
·
346 Posts
Discussion Starter #12 (Edited)
when he states “carriers”, is he talking about the stabilizer bar brackets? If so, they are the same part number as my base 6m cayman. As for the bolts being longer, I’m not sure how they would be any longer on the 718 than the gt4. Perhaps the 718 rear sway itself is just larger, and that’s why the brace no longer fits in the gt4 location.

Or maybe voyager thought the gt4 brace was to be mounted in the same location as the 718.....?

From the the pics and part numbers I’ve looked at, I still don’t understand why the gt4 brace wouldn’t fit.
 

·
PCA Nat'l DE Instructor
Joined
·
1,846 Posts
when he states “carriers”, is he talking about the stabilizer bar brackets? If so, they are the same part number as my base 6m cayman. As for the bolts being longer, I’m not sure how they would be any longer on the 718 than the gt4. Perhaps the 718 rear sway itself is just larger, and that’s why the brace no longer fits in the gt4 location.

Or maybe voyager thought the gt4 brace was to be mounted in the same location as the 718.....?

From the the pics and part numbers I’ve looked at, I still don’t understand why the gt4 brace wouldn’t fit.
Well then, I'd suggest you give it a try and share your findings with us.

Sent from my XT1650 using Tapatalk
 
  • Like
Reactions: Chaidell

·
Registered
Joined
·
95 Posts
I had the GT4 brace (if we are talking about the same part it is cross member part #981 331 071 80 in the PET file) fitted to my 981 Cayman S PDK. It just requires an easily fabricated spacer to be fitted to clear the longer PDK box.

I subsequently had the GT4 rear sway bar part fitted with no issue.
 

·
Registered
Joined
·
151 Posts
I had the GT4 brace (if we are talking about the same part it is cross member part #981 331 071 80 in the PET file) fitted to my 981 Cayman S PDK. It just requires an easily fabricated spacer to be fitted to clear the longer PDK box.

I subsequently had the GT4 rear sway bar part fitted with no issue.
I don't believe that's the correct part (#981 331 071 80) being discussed... Perhaps you meant 981 331 275 80 for the GT4 brace?
 

·
Registered
Joined
·
346 Posts
Discussion Starter #16
I think we are close to cracking the code on this! I just ordered the gt4 brace (part #981 331 275 80), and I should receive it in 7-10 days.

My theory is that the gt4 brace will in fact fit all 6mt 981 vehicles with no further modifications, and thus, is a direct bolt on. That said, things get a little fuzzy with pdk cars. In the pic from snip’s link posted above, you can clearly see why the pdk 718s brace is in a different location from the 6mt gt4. It’s bc the pdk is mounted too low to accommodate the same gt4 mounting position, and is why Porsche moved it behind the sway bar to obtain the clearance needed. I also believe that both 718 6mt and pdk cars share this new mounting to minimize complexity in the factory. We know that the gt4 is exclusively 6mt, so I’m confident that the brace is in a better position when located in front of the sway bar, as it’s location on the stabilizer bar bracket is more secure. Which is why 718 brace needs extra reinforcement bolts into the pan.

The final question is whether the gt4 brace will fit 981 pdk cars, and it seems that 38cayman above states that it will fit but a spacer is needed.
 

·
Registered
Joined
·
95 Posts
Good that we have part numbers, sorry for adding confusion.

I had the cross member 981 331 071 80 fitted. It is far more substantial than the pressed steel stock part. When we put my car on a ramp with a GT4 on the adjacent ramp and looked at the differences, we concluded that the 981 331 275 80* part did not add much if anything beyond the cross member. I'll be interested if there is a noticeable difference on track.

* corrected original post quoting wrong part#
 

·
Registered
Joined
·
1,966 Posts
38Cayman,

I was surprised to hear the GT4 brace fit. It was an eye opener to know it fits on the forward side of the sway bar.

Chaidell,

The carriers are a special part number where the rear side has additional aluminum so that through holes will be even with the back of the sway bar bushing and the 718 brace fits flat. The longer four screws are needed due to the additional length plus the brace thickness. The screws Suncoast sent are actually too long, but work. It just takes a lot of extra ratcheting to get them snug.

In my thread, I didn't want to get Suncoast mad at me for posting part numbers, but they are in the photos that I took.

V6
 

·
Registered
Joined
·
346 Posts
Discussion Starter #19
38Cayman,

I was surprised to hear the GT4 brace fit. It was an eye opener to know it fits on the forward side of the sway bar.

Chaidell,

The carriers are a special part number where the rear side has additional aluminum so that through holes will be even with the back of the sway bar bushing and the 718 brace fits flat. The longer four screws are needed due to the additional length plus the brace thickness. The screws Suncoast sent are actually too long, but work. It just takes a lot of extra ratcheting to get them snug.

In my thread, I didn't want to get Suncoast mad at me for posting part numbers, but they are in the photos that I took.

V6
sorry for the confusion. You are correct, the 718 carriers and bolts are 100% different. However, the gt4 carriers/bolts are the same as all other 981 caymans/boxsters. This is why I’m thinking the gt4 brace should fit my 6mt cayman.
 

·
Registered
Joined
·
1,966 Posts
sorry for the confusion. You are correct, the 718 carriers and bolts are 100% different. However, the gt4 carriers/bolts are the same as all other 981 caymans/boxsters. This is why I’m thinking the gt4 brace should fit my 6mt cayman.
Hope it does. The GT4 has a totally different rear suspension than the 981/718. That is one reason the wheel offsets are different.

I looked up the individual 718 parts and the 718 brace was $133, the sway bar carrier halves were $7.16 each and the four longer screws were $0.66 each. Add that up and you are equal to the Suncoast kit price.

V6
 
1 - 20 of 49 Posts
Top