Race Skids now offer Butt Brace

[bradnic]

In for a group buy

[iBazooka]

Any pictures of it mounted on cars? Curious to ground clearance with lowering springs & 15's

[ejnight]

I'd be interested in that!

5 buyers and I can do $250 shipped

[exhaust]

Would a group buy get price down a bit?

I'd be interested in that!

[ejnight]

Would a group buy get price down a bit?

Pm sent

[Julien]

Would a group buy get price down a bit?

[ejnight]

all orders shipped

[ejnight]

I have an xbrace up front and was looking tody, I doubt it could be any lower that that is.

I may be checking this out in a few weeks. I'm s52 swapped and would love to tighten up the rear end a bit.

In stock and ready to ship

[Mwishlist]

I have an xbrace up front and was looking tody, I doubt it could be any lower that that is.

I may be checking this out in a few weeks. I'm s52 swapped and would love to tighten up the rear end a bit.

[ejnight]

Would love to get a few pictures from the back level, to see how low it hangs. I'd love to get one, I'm on ground control and not too low in the back; but I am pretty worried that if I hit something I'm going to rip the whole rear end out of the car.

My vert was lowered about 2in and I did hit coming out of a drive way now and then but I never had anything come off the car.

[Mwishlist]

Would love to get a few pictures from the back level, to see how low it hangs. I'd love to get one, I'm on ground control and not too low in the back; but I am pretty worried that if I hit something I'm going to rip the whole rear end out of the car.

[ejnight]

This style of brace has been used on the Z3 for 10 plus year without any problem.

[validius]

:EDIT: I totally forgot about the parts 4-6 when i wrote this. The Butt Brace has my approval.

So you're thinking the force is more lateral than torsional ?

Allow me to propose a model.



Here we see the car from the top down. The simplest form of twisting would be the FL and RR corners to stay fixed with the FR and RL corners to move down equally, creating a sort of diagonal taco.



This view is meant to be looking at the car from the rear. The boxes are the rear subframe bushing insert pieces that bolt to the car. In the first view, the car is not twisted. In the second, the car has twisted slightly. The distance between the ends of them is slightly smaller. The brace would act on the ends of these to fight any such displacement.



My fear with long term use of this would be that excessive stress would be placed on the mounting points of the rear sub-frame bushings. Yes, these are particularly strong points but as can be easily seem with the math, the forces on them will be quite high. There is also a twisting moment whose math i didn't write out created by the combination of the bolt force (red) and reaction from the body (blue). It's magnitude would be:

T = Fbrace * X

This may not seem like much because X is rather small but remember, whatever the Fbrace is, it is enough to meaningfully impact the flex of your chassis!

:EDIT: I totally forgot that there is that extra bracket that ties the bottom of the rear sub-frame bushing to the pinch weld. This would be inline with the force vector Fbrace and would handle the reaction forces. I'll definitely be picking one of these up sometime.

I understand that the R&D and tooling are nontrivial to develop and bring to production something like this. That said, the price is a bit steep. I have the Race Skids front brace though and i love it.

[jeffnhiscars]

Forcing the portion of the rear end to move as a parallelogram where the top is the chassis, the sides are the subframe bushings and the bottom is the butt brace could be meaningfully stronger than the open 'C' that exists without.

It is counter intuitive that such deflection exists. I would question the benefit of this bar strongly if i hadn't also heard positive reviews from people who had put even mild polly rear subframe bushings in. Doing this would allow the rear subframe to act as more of a stressed member under similar conditions as the butt brace would be a benefit.

It makes me worry about the load on the subframe bolts & mounting points. To make a meaningful difference in chassis flex i imagine there would be considerable force in directions not necessarily intended by the chassis engineers.

So you're thinking the force is more lateral than torsional ?

[validius]

It's not that much more considering the extra heft the Strong Strut appears to have. I can see where a tubular brace will keep the anchor points (subframe bolts) from spreading but don't see how it would limit twisting.

Forcing the portion of the rear end to move as a parallelogram where the top is the chassis, the sides are the subframe bushings and the bottom is the butt brace could be meaningfully stronger than the open 'C' that exists without.

It is counter intuitive that such deflection exists. I would question the benefit of this bar strongly if i hadn't also heard positive reviews from people who had put even mild polly rear subframe bushings in. Doing this would allow the rear subframe to act as more of a stressed member under similar conditions as the butt brace would be a benefit.

It makes me worry about the load on the subframe bolts & mounting points. To make a meaningful difference in chassis flex i imagine there would be considerable force in directions not necessarily intended by the chassis engineers.