Rear sway bar install and custom brackets - Honda Prelude Forum

racinghonda · 07-02-2006, 01:24 AM

I have had my adjustable Whiteline rear sway bar sitting in my garage for 4 months now. Finally have time to get it installed.

WARNING: I strongly recomend NOT installing this sway bar unless you have taken some steps to strenthen the sway bar chassis mounts or the chassis rail. The stock only mount (especially the left side) cannot cope with the stiffer Whiteline bar. Typically, on the left side the tension will rip a hole in the chassis rail.

This photo shows what happens . . . . (this is NOT my car)

There are 3 factors that contribute to this.

1) The chassis rail is only 2mm thick mild steel.
2) The left side mount is shorter than the right, so the bolts that hold it to the chassis are closer together which means the load is more concentrated.
3) The brackets are made from soft pressed mild steel. With a bigger bar, it tends to flex and bend. This causes what engineers call "bending moment", a sudden increase in force cause by the bracket acting as a lever, it just tears the captive nut out from the chassis rail.

I consulted a mechnical enginner (father in-law) and he drew up the system in CAD, worked out what needed to be done.

Pictured here is the stock left mount.

See how short the top part is? The sway bar applies force to the longer part and it causes the problem.

So what we did was to "fillet" the brace, basiscally make the L shape a triangle for strength and then add a plate between the mount and the chassis rail to spread out the force.

This is what the bracket looks likve after we had welded the plates to it.

We also braced the right side mount. The right side mount is about 50mm longer on the chassis side so we didn't have to extend it. But we did the fillet on it too.

The Whiteline sway bar is painted silver:

This is no good to me, because on the 4th gen the rear sway bar is visible from behind and its a dead giveaway that the car ain't stock (don't want to attract attention to the car).

So I got some Epoxy paint and gave it a spray.

Now I have to wait a few hours for the paint to dry.

To turn the left side mount from a 2 bolt setup to 3 bolt, I will remove one of the large chassis rail grommets and carefully get a M8 flanged nut in there.

It was time consuming, the modded brackets went in ok but there was a problem on the right side. The sway bar end would touch the brake line so I ended up having to make a new brake hose bracket and reroute the brake hose. Making sure it didn't touch anything when the wheel moved up and down.

racinghonda · 07-02-2006, 01:25 AM

Ok to the install!

Here is the right side sway bar mount in place. Looks a lot stronger and should not have any flex in it.

I used new high tensile bolts (M8 x 1.25) and torqued to 22NM (as per specs).

Now for the interesting part, getting the rear mount in! The install was easy enough. The two stock bolts went in without a hitch and torqued to 22NM. But the trick was to get a captive nut into the rail so that the 3rd bolt hole could be bolted up. With the mount in place I drilled a M8 hole.

Then I removed the chassis rail grommet from the rail. I bought a M8 flanged nut that has these "teeth" on the back of it, so that it can bite into the surface of the rail.

Then I got some solder wire and wrapped it around the nut.

Slowly feed the nut in through the grommet hole and align it with the modified mount's 3rd bolt hole.

With all 3 bolts in place.

Compare it to stock.

Pic of the rerouted brake hose.

The sway bar installed. Looks nice and OEM no? Just need some dirt and mud on it.

Another weekend spent under the car . . .

Big thanks to my father in law Karl for helping me out with the mounts and my understanding wife!

Test drive was great, noticably less body roll. The Tanabe coilovers already reduced the body roll a lot due to the 10/6 spring rate but the car is incredible to drive now. So flat in the corners and the better weight transfer has helped corner exit traction a lot.

TruNinja619 · 07-02-2006, 01:50 AM

great mod there... I was thinking about putting the 5th gen sway on the 4th gen... b/c I noticed there is a difference between the two.. but yea..

yield · 07-05-2006, 12:36 PM

Running stock endlinks? I'd be interested to hear how they hold up with that bar. I'm thinking about making some custom but I don't have the time for it right now, plus I can't even get the nut off them as of now

71dsp · 07-05-2006, 12:38 PM

We are thinking of doing a limited run of our prototype sway bars. You can see the first prototype here that was tested at NPM: http://www.preludeonline.com/showthread.php?t=208228

Cost won't be cheap, but one advantage to this setup is that the mounting scheme is supposed to take a lot of the tension off of the mounts by giving the sway bar some extra movement.

The stiffness of the bar can be adjusted in two ways; changing out the center tube, and changing the mounting points for the end links. There are 5 different center tubes available, and there will probably be 3 or 4 mounting positions on the arms for the end links. If you are interested, look for a GB posting soon (after I get a quote from the machine shop for the necessary parts). The kit would include the sway bar, mounting plates, rod ends, and end links.

We'll also be posting a GB on end links soon too.

racinghonda · 07-05-2006, 03:38 PM

Quote:

Originally Posted by yield

Running stock endlinks? I'd be interested to hear how they hold up with that bar. I'm thinking about making some custom but I don't have the time for it right now, plus I can't even get the nut off them as of now

Yeah, I'm running the stock end links. There are a few members on Preludeaustralia.com who have been running this Whiteline 24mm adjustable bar for years and the end links aren't an issue. The issue seems to be the tension on the left side L bracket tearing the captive nut from the chassis rail.

Hopefully I have addressed that with my 3 bolt modification.