Recently discovered this...

http://www.ajr-performance.com/ultraracing-la4-293-front-lower-bar-4p-fiat-coupe-p-7365.html

What's your opinion?

greetings, Jochen

It's not new and I think only the front bar does any job really. The OMP would be better/lighter/cheaper.

The front lower bar makes a notable difference, but there's very little point in having a four-point brace like the one in your link - it will add very little additional stiffness over a two-point brace mounted on the forward ends of the wishbone mounts. There cannot be ANY movement between the front and rear points and there definitely can't be any movement between the two rear points. The only flexing that the subframe can suffer is a lenthening/shortening of the gap between the front wishbone mounts and possibly a distortion of the overal shape (eg the "legs" of the subframe both distort in the same direction to create a parallelogram)

To work properly, a four-point brace needs to include triangulation between the four points in order to prevent a twisting motion.

100% true. That brace is a waste of money. Stick four pencils together at each end and see how much they twist with a small force applied.

/\ +1

They also do the rear braces... again they probably dont offer anything in terms of rigidness...

http://www.ajr-performance.com/ultraraci...fffcbc9eaf003dc

Hubby and Kelvs Group Buy ones looked far better as well

Even triangulating between the points wouldn't solve the issue. What you want is a bar that picks up on both bolt points of the front wishbone bushes. Couple that with stronger bolts and revised captive nuts and you've got something that should be rock solid. I don't think any of the braces on offer for the coop are as effective as they could be.

The stuff in the links us purely cosmetic.

Partly true....

A simple, straight brace between the front wishbone mounts makes a noticeable difference to steering precision.

However, if the subframe "legs" are capable of moving closer together under acceleration, and further apart under braking, they MUST be capable of deflection in the same direction when cornering hard. IMHO, simply using the two front wishbone mounting points won't give enough stiffness - the front mounts would have to be triangulated to the rear wishbone mount on the opposite side of the subframe.

So - instead of I could have built something more like

However, the cost would have been close to double the amount I had to charge for the straight brace, which would have made it far less appealing.

Not knocking your brace, I quite like it. A simple and effective design. But I think the movement comes from the legs twisting in the same plane as the wishbones. Hence mounting across the two bolt positions on each side should help to limit that more than using one.

Not sure what you mean...

The subframe is like a squared 'U' shape, with the "legs" pointing forward and the wishbones mounted on the legs. The current braces simply close the 'U' into a square, thus preventing |__| from becoming \__/ or /__\. However, my brace design cannot prevent \__\ or /__/ - for this, triangulation is the only solution

THe other solution is what N technology did in the 156 ST which is a 3ish inch wide flat plat (slightly curved for the pipe) with 4 bolt pick up onto welded pickup on the inner flange of the subframe, effectively giving a triangulated set up - obvioulsy more work then using the wishbone bolts, I'd like to try a brace sometime.

That's were using the two front wishbones bush bolts on each side comes into play. That would eliminate /_/ as there would be a resistance to that movement (not to mention others). The trick is one bolt takes a load (for arguments sake a shear load going perfectly towards the front of the vehicle) and the second bolt will receive the exact opposite. As each bolt provides a resistance equal and opposite to the load you end up with one sturdier subframe.

I agree - it would be a bit sturdier than a single bolt design, BUT what would happen in the /__/ scenario is that the forces would try to bend the brace into a very gentle 'S' shape. The whole idea of a brace is to keep the forces working along the axis of the brace - the resistance to bending just isn't high enough to put the brace under any kind of bending stress

But that's where material choice comes into play. You choose something springy enough that it doesn't deform and then give it enough cross section it will meet the requirements.

I understand ideally you want the brace to be either a compression strut or a tie rod, but there's no reason it couldn't do as I described.

Back to what I was saying earlier about the legs twisting; I believe that's the start of the movement i.e. /_/ may be the net result but it is the flexing of the legs about an axis that falls in line with the centre of the wishbone bush that starts it. My idea of a two bolt design would help reduce that and hopefully not let it get as far ad /_/.

It's all academic as I'm not sure how rigid you could make the subframe before you transferred enough of the loading away from the legs and cause issue else where.

Only a triangulated set up with straight tie bars would deal with this issue - which may not be such a problem the proposed issue of /_/ is less likely to occur as during cornering the inside wheel will not be generating the same bending moment on the frame as the outside wheel thus the simple tie rod would help distribute the load across the front of the frame. I often wonder about extending the frame forward to the legs dropping down from the x-member (I think the coupe has them), virtually any modern car I have seen has a continuous frame to the front of the car - I guess a sign of the fiat's design age.

wish I could weld!

Sounds interesting as race technology always is pioneering new and (hopefully) eficient ways to solve existing problems... do you have a pic of what you describe ??
In your opinion, is it something that could be copied for street use ??
Jochen