Any thoughts on this Hotchkis K member brace?

[Kobie]

Just looking at this https://www.hotchkis.net/20052011-ford-mustang-k-member-brace.html
It looks like it mounts in a different place https://www.hotchkis.net/_uploaded_files/1416instructions5216file.pdf
than the Whiteline brace. http://www.whiteline.com.au/product_detail4.php?part_number=KSB726
I was just wondering if anyone has opinoins on it.

 

[Philostang]

I only have opinions, no direct experience and have seen no data on it.

Me: "Looks like a poorly designed part."

The purpose of the K-member braces out there (as well as Ford's OEM pieces) is to laterally brace the K-member. That's accomplished by some sort of laterally arranged rigid member. Thus, the left-to-right tubes you see for these. Hotchkis has this covered by the large plate at the top of their "X" (though I'd prefer to see a tube here rather than just a sheet of 1/8" steel that's been further compromised by cutting a logo into it). From the limited pics, it looks like there's a 90 deg bend here, so to my eyes you're talking about comparing a tubular brace to an angle-iron brace. I say tubular wins.

Then there's the rest of the brace, the "X" part. WTF is that supposed to accomplish? I think of these as resisting forces along the legs of the "X" and then wonder what sort of force that might be. Perhaps the strategy is to distribute loads from one side of the K-member to the other side as well as the trans tunnel. OK, I think I get that. It's still 1/8" sheet metal here, so all I see is flexing in these legs if there were real forces coming through them. I'd still prefer to see tube of some sort doing this job (think of a roll bars - would you like to see them made with flat sheet down bars while the builder is telling you, "oh yeah-yeah, I think those will hold").

Then there's "chassis flex" which I always associate with torsional rigidity. This is doing diddly for that. The X is in the wrong plane to resist torsional loads. So you're not going to get an appreciably more torsionally rigid chassis bolting this in place. Besides which, the S197 chassis is already plenty torsionally rigid for most folks who will ever own or even track these cars.

My $0.02

Best,
-j

 

[Roadracer350]

Poor design and it really wont do anything because its to thin. It is going to flex. Get the Whiteline unit and you wont look back.

 

[dontlifttoshift]

Those are two totally different parts for two different things.

The hotchkis brace replaces the factory brace and triangulates it towards the rear of the car. It bolts to pre existing threaded bungs in the tunnel and will stiffen up the k member at a point where it is weak.

The whiteline unit is a different animal all together and goes forward to the sway bar. I don't have a good picture of it but I would like to see one. It looks like it attaches at or near the front LCA pivot where the K member is pretty beefy already.

I sort of think they are both dead weight, especially if one still has the stock control arm bushings. But to make a one or the other comparison is tough as they both do different jobs. If I had to have one, I would go with the Hotckis piece.

 

[fdjizm]

I'm using the CHE brace that came with the torque limiters, although I removed the torque limiters.
beefy enough!

 

[Kobie]

I realized that it was a different part different mounting location than the Whiteline. I guess my first post could have been confusing. Hotchkis makes a complete suspension kit that seems pretty well thought out and engineered although the K brace seemed a bit of a head scratcher.

 

[Kobie]

I'm using the CHE brace that came with the torque limiters, although I removed the torque limiters.
beefy enough!

No why would you go a do a thing like removing the torque limiters? Isn't that the main selling point of that part?

 

[fdjizm]

At the time I didn't have them adjusted right and they kept rattling at idle like a baby rattle. I was told no not pre-load them and maybe I should have just a bit. I still have them, might throw them back on soon and adjust them correctly.

 

[Department Of Boost]

Looks cool, but I don’t see it doing much being that thin. It would have to be seriously beefy to add any stiffness in the plane that it is needed.

The most flex in the K-member is where it bolts to the “floor/torque boxes”. You can add bracing all over the place but until you tie the K-member where it meets the floor/torque boxes to the frame and rocker you are polishing a turd.

This is obviously overkill but we had some scrap that was the right size so we did them out of billet. They could be done with welded together tubing.

The K-member is tied to the rocker and the frame rail this way. The entire front end of the car got a LOT more precise after we put these on (908SSP has a set too).

 

[Philostang]

More pics sir.
My welder has been sitting in the corner cold for at least two days... =)

 

[Department Of Boost]

More pics sir.
My welder has been sitting in the corner cold for at least two days... =)

I don't have any more, I'm horrible about taking pics. I just sent 908SSP an email with a link. If he has some he will post them up.

 

[908ssp]

The best one I have on the car. Once they were on we used them as jacking points. Never took any off the car, sorry.

 

[Philostang]

Ok, had a chance to crawl under the car today and have a look see, so here's how I'm reading this now.

Perhaps the Hotchkis brace is attempting to do two things. (A) laterally reinforce the A-arm mounting points as almost all other K-member braces seem to attempt. (B) triangulate the K-member to the body. In short, (A) makes the "K" stronger and (B) makes its relationship to the chassis more secure.

From the looks of it, Mitch & 908's billet aluminum ones are aimed at accomplishing (B), but take the strategy of reinforcing the joint at the point the K-member is bolted to the chassis. Fellas, correct me if I'm missing something, but it doesn't look like your piece is triangulating any other part of the "K" to the body, it's just beefing up the lock that the mounting point has on the chassis (by multiplying it's points of interface w/the body). Correct?

For the record, I'd still prefer to see a tubular version of the Hotchkis piece, even if they were trying to do what I now think they were up to.

Best,
-j

 

[Department Of Boost]

Perhaps the Hotchkis brace is attempting to do two things. (A) laterally reinforce the A-arm mounting points as almost all other K-member braces seem to attempt. (B) triangulate the K-member to the body. In short, (A) makes the "K" stronger and (B) makes its relationship to the chassis more secure.

Yes. But in reference to (A) my estimation is as long as you have at least the factory cross brace (started 2007 I think) I don't think you need to brace the K-member any more than that. Once triangulated with the factory part it is triangulated. Done and done.

As far as B goes I doubt the Hotchkis brace is doing much of anything because it does not address where most of the flex is and that is where the K-member bolts to the floor/torque boxes.

Fellas, correct me if I'm missing something, but it doesn't look like your piece is triangulating any other part of the "K" to the body, it's just beefing up the lock that the mounting point has on the chassis (by multiplying it's points of interface w/the body). Correct?

Correct.

For the record, I'd still prefer to see a tubular version of the Hotchkis piece, even if they were trying to do what I now think they were up to.

Me too.

 

[Sky Render]

Poor design and it really wont do anything because its to thin. It is going to flex. Get the Whiteline unit and you wont look back.

The Whiteline unit is only sold for on 2005-2010 cars. The 2011+ cars have a brace there from the factory.

You may be able to use an OEM one.

 

[Philostang]

As far as B goes I doubt the Hotchkis brace is doing much of anything because it does not address where most of the flex is and that is where the K-member bolts to the floor/torque boxes.

So, to clarify, are you suggesting that you suspect the flex is in the floor/torque box area of the body itself (think "flimsy" steel pan), in the leg of the K-member itself (think "leg extended too far" for its own good), or in the interface of the joint itself (think "Elmers when it should've been superglue")?

You can see that each of these ailments might be approachable in different ways, not all of which would work equally well for addressing more than one of the ails.

Just curious what you guys found.

BTW, Sky Render, nice catch on the OEM option.

Best,
-j

 

[dontlifttoshift]

I like those aluminum plates.

 

[Kobie]

I like finding parts that actually do what they say they will do and improve the car. Sometimes you can buy them and sometimes you have to make them. If those aluminum plates do work I'm sure more than a couple vendors here will come out with something for this application or maybe some creative forum member will fab up a few sets for sale? Hint...Hint...

 

[Department Of Boost]

So, to clarify, are you suggesting that you suspect the flex is in the floor/torque box area of the body itself (think "flimsy" steel pan)

This is it exactly. The “torque boxes” are horribly flexible. I’m not suggesting you do this because it will hurt the torque boxes but jack the car up from the center of the K-member under the motor, put jack stands under the K-member where it bolts to the torque boxes and release the jack. You can watch the K-member under the motor droop 23mm! (I’ve measured it) and watch the torque boxes compress. Jack it up like that and stock jack stands under the torque boxes a few times and it will permanently crush the torque boxes. Ask me how I know. I had been jacking it up like that for so long that I crushed both of my torque boxes about 1”! Bolting up the aluminum plates allowed me to “fix” the torque boxes because it pulled them back down into place.

in the leg of the K-member itself (think "leg extended too far" for its own good),

This may be able to be stiffer, but the way the loads in the front end work and the way in which they triangulated the K-member in a couple planes I think works pretty well. Assuming that where the K-member mounts is not moving (removes a triangulated section).

or in the interface of the joint itself (think "Elmers when it should've been superglue")?

Oh, it's bolted up good. Not an issue there. But when what you are bolted to moves it may as well be loose.

Just curious what you guys found.

Some people know I come from a Pro-Am motorcycle roadracing background. Where I come from you have “telepathic” front end feel. By comparison cars feel really, really numb to me. After doing the Whiteline A-arm bushings, upping the front spring rate (425lb), putting in caster/camber plates with no mushy rubber the car started feeling a lot better. After doing the aluminum plates I would describe it as getting towards the feel of a motorcycle. I get a LOT of feedback from the front contact patches now.

 

[Department Of Boost]

I like those aluminum plates.

I like finding parts that actually do what they say they will do and improve the car. Sometimes you can buy them and sometimes you have to make them. If those aluminum plates do work I'm sure more than a couple vendors here will come out with something for this application or maybe some creative forum member will fab up a few sets for sale? Hint...Hint...

We could do a group buy on these. The only hurdles are that the materials are pretty expensive (those are some decent sized chunks), which means the parts would be to. I would be surprised if they didn’t need to sell for $600-800. The other hurdle would be that to install them you need to put 8mm Riv-Nuts in the bottom of the car. Not a lot of people even have a Riv-Nut tool. It does beat welding though.