Monthly ArchiveDecember 2016

Installing a proper swaybar on a G-Body

“If you can raid the NASCAR parts bin, do it.”
– Dennis Grant

So, in my last entry, I barfed out my thoughts on sway bars for my car. Today’s entry is me actually acting on those thoughts. Today is a step-by-step on how I put a three piece swaybar on my 1987 Grand National.

Underside prior to removal of OE swaybar. Note the diagonal braces. They'll have to go.

Underside prior to removal of OE swaybar. Note the diagonal braces. They’ll have to go.

First, the underside as it was. Please pardon what appears to be an oily mess. The car has the factory undercoating on it, and while it currently doesn’t leak, all the previous leaks have turned the undercoating into what can only be described as black slime.

You can see in this picture the stock 32mm conventional swaybar, along with some add on chassis bracing. The diagonal jounce bars you see will be deleted to make room for the new bar.

Original rubber sway bar bushing

Original rubber sway bar bushing

In this picture, you can see the original sway bar chassis mount, and the 30 year old rubber bushing. The bar is supposed to be able to pivot in this mount as the suspension moves. It didn’t without considerable effort.

All the stuff I had to take off/

All the stuff I had to take off.

And here’s all the old stuff off the car. This is all you have to remove. The bar, mounts, endlinks, and that bracing if you have it.

What I’m installing is no less than a full-on NASCAR road race sway bar setup. Instead of a bent bar mounted in rubber mounts with a sandwiched bushing scheme at the ends, this bar is mounted in brass-raced pillow block bearings, with rod ends connecting the bar to the lower control arms. This setup will eliminate any bind from the crappy rubber bushings sticking and should sharpen steering response since the car will no longer have to wait for bushings to compress before the bar starts to work.

I used a 37.5″ torsion bar from Speedway Engineering. The bar is 1.25″ on the ends, but thickens to 1.5″. This meant the pillow blocks needed to be set a tad wider than the stock mount holes. I also needed to set the bar about an inch forward of the factory bar to clear the idler arm and pitman arms.

The original GM mounts were simply screwed into holes that had been drilled and threaded directly into the frame at the factory. This seems a bit sketch, but if the bar is set up correctly, the body mounts really should not see much load other than holding the assembly to the car. If it was good enough for GM, it was good enough for me. I mocked the bar and pillow blocks in place, and marked the rear mount hole locations.

Drilling new holes for the pillow blocks.

Drilling new holes for the pillow blocks. Don’t use this as a guide on yours, MEASURE!

I then drilled them and tapped them to 3/8-24, and mounted the pillow blocks.

Pillow Block on new rear mount.

You can see in the picture that the frame slopes upward away from the mount. A spacer had to be made. In my instance, a lug nut ground to the proper angle to sit flush on the frame while also providing a level mount for the pillow block worked perfectly.

The next step is the bar arms. I got my from Coleman Racing. They’re 49 spline and 17″ long, with a 30 degree bend in the vertical plane. However, to clear the frame and meet up with the end links, they needed to be bent 45 degrees outward. Since these bar arms are 0.75″ thick steel, that was a concern. I considered trying to heat them and bend them with a hand sledge, but that didn’t look like it was going to pan out well. Thus came the only really specialty service required for this install: a 50-ton press.

I got lucky, really. The good folks at RLC Fabrication had a few down minutes and were able to bend these arms for me. Much thanks to them.

New bar arms after bending.

New bar arms after bending.

Now, this being a non-standard install, it’s important to mock stuff up every single step of the way. Here is one of the bar arms on the end of the swaybar for the first time. It looks great, right?

First mock up

First mock up

Wrong. There were issues. First off, the bar arms would hit the steering box bolt heads on the driver side. Shifting the bar over to the driver side to clear the bolt heads rendered the passenger side nearly immobile as it hit the frame on the way up. When you get down to the finished pictures you will see that I flipped the bars side to side. It provided way more frame clearance that way.

Now, after getting the arms in place, I used a piece of baling wire jammed into the rod ends as a sort of variable length end link. I used this to set the end link length, and mark the arm bars for drilling. You want the end links as close to vertical as you can get them at ride height. Once I had an overall length, I cut some threaded rod to fit and assembled the end links. Don’t forget jam nuts!

Once you’ve marked the spot, drill the holes. With metal this thick and tough a drill press is mandatory. Use a lot of cutting oil or you’ll dull the bit. We drilled a small pilot hole, then stepped up to the 3/8″ we needed.

End link mocked into the arm. The spacers provide room for the rod end to articulate.

End link mocked into the arm. The spacers provide room for the rod end to articulate.

Here’s the end link on the bar arm. Note the spacers. Without them, you lose a lot of articulation range on the rod end.

Now, right at this point is the important part: Make sure you have clearance. Mock it up, and articulate the suspension to make sure nothing hits. If something makes contact while you’re driving around, you will at the very least break something. At the worse, you’ll crash the car. Do not screw around with this step. Don’t save time. Don’t shave corners. Make sure the suspension can cycle through its entire range of motion with the wheels at full steering lock in both directions. If there is any interference anywhere, fix it now.

Powdercoated the arms chrome. Blang Blang.

Powdercoated the arms chrome. Blang Blang.

This is the purty part. We powdercoated the bar arms chrome. I think they came out quite nice. Mirror finish. With a Craftsman powdercoating gun from Sears. How about them apples?

Finished product. Arms had to be flipped to provide extra clearance close to the frame.

Finished product. Arms had to be flipped to provide extra clearance close to the frame.

Here’s the driver side snugged in. In the picture, you can see the pillow blocks, the shaft collar used to keep the bar from sliding side to side, the bar arm, and the end link. This photo was taken with the suspension at full droop. Even at full droop with the wheel cranked over to full lock, there is plenty of clearance between the bar arm and the tie rod.

All Done!

All done!

So there you have it. Total install time was about six hours, not including travel time to the store and to get the bar arms bent. I think with all the parts and properly bent bar arms ready to go, I could do this install again in about two hours.

Driving impressions? I’ve only had it around the block, and there is really no way to to test it properly on the street. But what I did get is that the setup is very responsive. It’s also more comfortable. With the new setup, the sway bar is not involved until the car rolls. So hitting expansion joints on the highway? Way better than before. The old bar was definitely binding up. However, street impressions are for naught. The real proof will come a the first event of 2017. During 2016, I was routinely pulling 1 to 1.1 lateral G in the car. It would understeer and wash out quite a bit as the inside front tire came off the ground.

If this bar succeeds in keeping the tires planted, I expect a front end grip improvement that should be measurable. Keep an eye on this space for an update in the spring.

Here’s a photo album with additional photos:

https://goo.gl/photos/enNV6Aki1ppkbELW7

And now, the parts list. I got the actual sway bar, the bar arms, and the pillow blocks from Coleman Racing. Other parts as noted.

1x Speedway 1.25/1.5 Hollow torsion bar, 608-49-150
2x Coleman Racing Products Sway bar arm, steel, 30 degree, 21915
2x Sway bar pillow block bearing, 12328
2x aluminum shaft collar, 1.25″ inner diameter, Amazon.com
1x 12″ fully threaded 3/8-24 rod, McMaster-Carr
2x (for me, you might need 4) Rod end, 3/8-24 female shank, 3/8 ID, McMaster-Carr
4x Steel unthreaded spacer, 3/8 ID, 3/8 length, McMaster-Carr
1x Pack of 4 Grade 9 3/8-16×3 hex head bolt, McMaster-Carr
1x Pack of 10 3/8-16 nylock nuts, McMaster-Carr

There you have it. A big shout out to my Dad for the lift, heated garage, tools, time, and you know, raising me. Also RLC Fabrication for getting me out of a bind with the bar arms; and Coleman Racing Products.

 

On the topic of anti-sway bars

Anti-sway bars are the stuff of myth and legend. Especially for the General Motors Metric mid-size platform (the G-Body). You can search and read forums and old magazine articles until your eyes bleed, and you will come away with the distinct impression that nobody really knows how to deal with them. How do they work? how big do you need them to be? Is the bar from supplier X going to be enough? Will it be too much?

When it comes to swaybars on the GM G-body, the conventional wisdom (and the product offerings) seem to center around going slightly bigger. If you’re fortunate enough to have a G-Body that came with the F41 suspension package, you have a 32mm solid front bar, and a smaller rear bar attached to the lower control arms. The aftermarket supplies 34 and 36mm solid and hollow conventional (1 piece bent) bars, and that’s about it, except for Ridetech, which can sell you a NASCAR style torsion bar that’s 1.5″ (38mm) in diameter.

So what do you really need? My opinions – and these are my opinions, but I’ll explain them – follow.

The answer to which swaybar you need? “It depends.”  But I’ll go ahead and spit out one answer early: If you are not racing the car, the F41 front and rear bars are all you need.

The more I dig into the actual engineering on this car,  the more I’m impressed by GM. Some of the perceived deficiencies in the platform are really the result of cost cutting or compromises made in the name of comfort, not bad engineering. The frame is a good example. It’s a c-channel structure. People knock it for being floppy. It turns out, GM engineered the frame to work with the body as a system. If you replace the squishy rubber body bushings with a better bushing material, all that frame flex goes away and the car feels as solid as a new unibody model. There’s no need to add weight or cost by boxing the factory frame, or replacing the frame entirely with a costly aftermarket frame. Once you identify and address the compromise (soft body bushings) things work as designed, and the design isn’t bad.

The suspension on these cars is no different. The geometry was parts-bin engineering, a metric-converted version of the A-body from the late 1960s. The design goals were cost and comfort. The front suspension was built without a lot of caster. Why? Caster stresses the power steering system. They’d have had to add a power steering cooler to all these cars if they’d run the kind of caster modern cars run. And all these modern cars have power steering coolers on them now.

With the F41 package, GM definitely subscribed to the soft spring, stiff bar mentality. And it works beautifully. So I’ll say it:

Unless you’re racing the car on race compound tires, the F41 swaybars are exactly what the car needs. Any more front bar without changes to the front suspension will make it push, and any more rear bar will make the car’s snap oversteer problem even more snappy.

Now, what if you’re racing? Things get more difficult. To keep the car planted and all four tires on the ground in a turn, you need to understand the geometry in the front, your shocks, and your tires. Fix the geometry and the tires, and the car will start heaving further, and will eventually start picking the inside front tire up. When you get your car to this point, it’s time to step up in front bar size.

Buick Turning hard

Buick in a Turn, check the inside front tire

It is obvious from this picture that the car is going to require more anti-sway of some kind to keep the inside tire planted, and transfer load from the outside tire, which is getting overworked.

Doing this with springs won’t help. Controlling roll with the springs limits the suspension travel without providing any load transfer to the inside wheels. Doing this with springs also requires some serious shocks.

So, do it with the anti-sway bar.

Why? First, you keep your softer springs, which keeps your ride tolerable and keeps your costs down by allowing you to run with a less expensive over-the-counter shock package. Second, Newton’s Third Law of motion means that in roll, the compression on the outside of the car will twist the bar and push the inside tire down onto the pavement, increasing the grip on the inside tire. More grip is what we want, not necessarily less roll.

That gets us to “which bar?”

Here, too, I will provide my answer: “Not the one in the catalog you’re looking at.”

To do it right, you need to give up on a conventional single-piece bent bar like you’d get from Hotchkis. Their 34mm bar isn’t big enough. Also, conventional-style endlinks that use poly bushings won’t work. The additional rate destroys the bushing material and creates slop in the links, which makes your bar not work at all. Additionally, the conventional frame mount bushings have a lot of friction and also complicate making your bar work.

To do your swaybar correctly, you need a three-piece unit like they use on actual race cars. Ridetech came to this conclusion when they designed their Musclebar(tm), but their design was built to be an easy bolt-in, so they make some compromises. Namely they welded stuff where it could have been bolted.  I can only assume they did this for durability on a street application where people wouldn’t be checking the clamp fasteners often enough. They also only have two choices for the center bar, and my friends have found it to not be enough for autocross.

So hit up actual race car part suppliers. Speedway Engineering and Schroeder Steering offer splined torsion bars in a large number of sizes. Once you fab up the mounting and get your sway bar arms bent right and lined up, you can easily swap out the torsion bar. Instead of having to buy a whole swaybar from Ridetech for $600 each time, you just swap out the torsion bar for $150-$300.  The torsion bars also don’t take up much space, so you can just throw them in the trailer. If need to make an adjustment at the track that can’t be accomplished by moving the link mounts, you can just pull out a whole different bar and swap it in a few minutes.

My suggestion is to go bigg-ish, with a bar rate somewhere close to 500-600lb-in, then increase the size until the car starts to push in corners. Then back off a step.

But what about the rear? I’ve not seen an instance where a stiffer rear bar will help this platform. In fact, you need to allow the rear to articulate as much as possible. Stiffer rear anti-sway bars will actually cause the car to pick the inside rear tire up off the ground (solid axle!). You’ll lose traction coming out of the corner and it’ll tear up your differential having that inside wheel freewheeling.