This may or may not be seen as advanced. Someone who knows more than I will make that distinction.

I have been reading the handful of articles I could find on NHRA and IHRA 'stock' class racers using the 4th-gen plaform (and articles of others in the class).

This suspension factor called 'stiction' came up and has me thinking.

For those that don't know, that term refers to the amount of force needed to move the assembled chassis (without spring or shock) through it's cycle of movement. It's typically measured in in/lbs or ft/lbs.

Any real measurable force will hinder the effectiveness of your shock and spring combination and ultimately, the car's ability to move how you want it too repeatedly.

Since the stocker guys have very stringent regulations concerning the use of aftermarket parts (or more specifically...the prohibition of their use) I'd though I could use this information to get my street/strip, low-budget 4th gen some improvement.

I know, for a fact, that if I unbolt one of my rear control arms from the LCA relocation bracket and pull the axle away, the arm will stay in what ever position I unbolted it in. Thinking of this using the new (to me) concept of 'stiction', that sucks. Combine that with sway bar mounts, the other LCA, the other connection to the axle, etc..... You might get a high number if you could build a fixture that could measure this accurately. Knowing the number isn't that important to me. Getting things moving more freely is.

What I want to know, is how can I reduce this stiction or binding of my chassis compoments without compromising the driveability...? I even read that temperature changes can have a drastic affect on this as well. Simply leaving the fasteners loose is not the correct option and will leave you with an unsafe and unpredictable car.

In the articles I read, they spoke of having a custom bearing made for the horizontal bushing on the front lower control arm. This isn't an option for me as $$$ are an issue, but the solution sounded like it worked well. They also spoke of 'clearancing' the bushings so that they weren't loose, but also weren't tight.

On one car, the torque to move ONE SIDE of the front suspension was ~55ft/lbs (without spring or shock). After working the bushings and installing the custom bearing in the lower, it dropped to ~5ft/lbs...!!! That's loose, but they claimed it had no slop and was still quite driveable.

What is the best way to go about making some of these modifications (safely) to help the suspension lose that 'stiction' and let the springs/shocks do their work more effectively...?

thanks....

 

easy.. spherical bearings. thats what most of us use

www.bmrfabrication.com

 

Jordan,
I looked there and did not see the spherical bearings for factory control arms.... Do you have the specific item number or something like that for me to seek..?

 

I'm looking very seriously into the use of spherical rod ends for the rear control arms in my Impy, as the upper arms are not perpendicular to the axle, and therefore require more than a simply pin joint to allow proper articulation. The soft stock bushings allow this by being rather soft, but this doesn't help when trying to locate the axle (either fore/aft or laterally, as there's no Panhard bar) or when trying to avoid axle hop. Stiffer poly bushings help to locate the axle properly, but unless they're a sophisticated multi-durameter part (similar to what Ford uses on their IRS systems), they start to lock up the suspension.

So far, it looks like a high-end 5/8" rod end will work for the LCAs, and for the front of the UCAs. The rear of the UCA attaches to an ear on the axle housing, so I'd either have to bolt on a rod end using a fastener in single shear (not good!), or using one of those internal spherical bearings that Aurora offers. Right now, option 2 looks to be the superior technical solution, but will require some work.

Doing this should go a long ways towards eliminating stiction and compliance. I have my doubts about the longevity of such parts on the street, and they're not cheap. I think that they also might transmit a lot of noise into the cabin. But, there's only one way to find out, right?

For the front end of a B-body, it looks like a simple delrin/aluminum bushing (like a Del-a-lum part) will work just fine, as the control arms only require a simple pin joint.

 

The del-a-lum stuff is pretty nice, not sure if they make one that goes into factory arms.

When I said spherical bearing, I meant use a real control arm instead of stock stuff.

hell, if you really want you could hack off the neds of a stock LCA, box it back up, weld a nut on there and thread the spherical ends in..

 

What worked on my old malibu...

Source up bolts that have a shank the same length as teh spread across the axle bracket..You will be tightning them up against the shoulder to hold them.Trim away very little at a time of the stock rubber bushings till you can tighten the bolts and the arms flop around if you blow breath on them..ARP will have the stainless steel hardware that you require for this.In essence you want the shoulder of the bolt to stop the nut just at the same time it snugs against the suspension bracket.In the f body case its the lcas..Furthermore than that would require a custom torque arm bracket at the trans with a monoball.The stock rubber bushings will flex enough to work well and keep the car tight feeling.

Up front you can do the same with teh suspension as well..Hope this helps you out..That setup helped me run an 11.88 with a completely stock internally (no rocker covers off)LT1 and stock 4l60E with 4.10 gears and sticky tires..

 

Please don't take this the wrong way, but this is a very, very unsafe use of fasteners. You're providing absolutely no preload/stretch of the bolt, which leaves it vunerable to fatigue failures. Additionally, when you crank a nut down on the end of the threads, you're stressing the fastener at the absolute weakest spot. The likelihood of twisting off the fastener or starting a crack is very high.

A better solution would be to find a bushing with an inner, uh, tube-y thing (is there a name for the inner metal sleeve?) that allows you to torque down the bolt without compressing the compliant part of the bushing. This will accomplish your goal of reducing friction while using the bolt in the proper manner.

 

http://www.smithperformance.com/

These guys might have some parts you are looking for if you are looking at stock style racing.

Not sure what class you are wanting to race as to mods you can do but there is lots of places out there to help you out.

http://billingsleyracing.biz/
http://www.paracing.net/
And many others i am sure.

Steven

 

Just curious how this got to Advanced Tech, when it would seem to be a natural for the "Drag Racing" board?

Advanced Tech seems to be becoming a catch-all for everything and anything. I'm really not sure what to move and what to leave any more.

 

A shoulder bolt would be a better solution IMO. http://www.mcmaster.com

Global West used to sell spherical bearings for stock LCAs, but were cost prohibitive -- one pair cost more than most aftermarket LCAs that had spherical rod ends.

I think you may be looking at this too hard. With our cars being as heavy as they are, having some stiction isn't going to really effect that much IMO. Personally, I would lube up the bushings with a silicone-based grease and leave it at that.

Since this is about maximizing the performance of suspension, this thread probably belongs in the Auto-X/RR forum.

 

I still maintain that the board has issues with the way its categories are organized. As this issue covers any gen of car and both drag and autoX/road-course racing, it seems like a natural for the "Suspension" category. Except, uh, there isn't one.

With regards to what Curt said, I think it is a real issue. If you've got bushing soft enough to allow multi-axis movement, then they're too soft to properly constrain the suspension. If you simply make the bushings rock-hard (like a typical poly setup), then you're forcing the bushing to act as a pin joint, and that's often bad for a rear control arm. I guess what I'm saying is that it goes beyond a simple issue of stiction.

 

Jordan, what I am saying is the stock class guys have found ways to do it without the $500 tubular control arms (mostly because they can't use them). This is the approach I am looking at.

 

Fred,
sorry for posting it here.....I did note in my initial post of this thread that I wasn't sure this is where it should go and you all should decide that.

I agree there should be a suspension area that specifically deals with the advanced nut&bolts and theory involving suspensions/chassis.

I suppose the best thing I can do it look at each joint individually and see what I can do. Greasing things up, taking a little extra material off that extends beyond the bushing core (no, not taking it flush), and maybe look at adding shanked bolts in a few places. It's low-buck and probably won't help a whole lot, but as we all know.....every little bit helps. Thanks folks.

When some of you all get a chance, teach me how to wheel and deal to get good parts cheap and how to allot extra funds to the car and not all of it to the home's general fund.......

 

The initial post deals specifically with NHRA/IHRA drag racing.... so I don't see this crossing over a lot of territory. It is relatively specific to drag racing, and 3rd and 4th Gens - not every gen. And I don't recall "suspension" being covered in the Advanced Tech guidelines either.

I guess I get confused when one member "reports" several posts a day as being on the wrong forum, then pitches in vigorously to something that to me is misplaced.

 

On the Smith Performance webpage, they have the kind of bearings that go in the stock LCA. They are $200 though. If you were going to spend that much money then get a set of BMR LCA with rod ends.