Vapour Trails

Well after trying to tough it out with factory LCAs, I'm finally sick of the sloppy feel & response from the rear axle, especially with the added gearing (4.10s).

I'm aware that poly bushings can bind and was looking at an LCA with a poly end and a spherical end for better axle articulation.

I was having a conversation with a local shop owner and he said that bushing binding really isn't a that big of issue. It got me thinking that I could save some money by getting a poly-poly arm, and maybe save some NVH too.

So my question is, how bad is binding? Is it something that is likely to occur often while autoxing, road racing, or street use? Is there anybody with poly ends that wished they had a spherical bearing?

Thanks

Norm Peterson

Have you ever seen the tabulated roll bind measurements developed by the Maximum Motorsports folks for the Fox body? Although strictly speaking, the tests weren't replicating pure roll, the general relationships would apply. I think in terms of wheel rate, the various combinations tested ranged from around 5 or 6 lb/in up to something like 60. For reference, 60 lb/in is stiffer than the factory rear sta-bar was in those cars. I don't have those numbers on this computer, but I could probably track them down.

Yes, you will easily feel the difference even in normal street driving in some situations. Crossing drainage gutters at an angle, for example. Going from all OE rubber to most aftermarket poly LCA bushings in all four LCA locations is clearly noticeable via lots more lateral head-toss (more like upper-body-toss, actually). So too, is the difference if you then modify the poly itself to soften its roll moment stiffness. BTDT, different car.

It is possible to tune around it with different springs and shocks, sort of (with a softer rear sta-bar and/or softer rear springs). But that's more of a band-aid fix for competition classes that limit what you can legally modify back there. I think Sam went through this some time ago.


I'm going to guess that that shop owner does lots more business with drag racers and people who just throw any old parts combination at their car just because they heard about the various pieces someplace. In straight lines and under most daily driving conditions, most folks wouldn't particularly recognize bushing roll bind for what it is, or have any awareness concerning what it can result in at much harder levels of cornering intensity.


Norm

jahudso2

J&M makes an "extreme joint" lca which has a hybrid bind free bushing which supposedly does not introduce NVH. Moosestang is running them and he likes them so far.

Sleeper_08

I switched from Steeda poly/poly to UMI poly/rod this spring because I was also concerned about poly bind on the road course.

I can't say if it alone made a difference because at the same time I also switched the Steeda poly/poly panhard rod for a FAYS2 Watt's link.

I know Norm - I should only make one change at a time and then test but that means two trips to my brothers to use his garage and I'm getting too old for spending my time under cars changing suspension components.

As a result of the two changes the rear end feels more more predictable and stable when cornering at or near the limit at the track. For my car the limit is about 1 G on flat corners.

With all of the rod ends there is also a lot more clunking and banging!

Hopefully Sam will also respond.

Norm Peterson

Up around the limit, both of those mods generally represent steps in the right direction. I'd think that mostly, you don't know how much of the improvement to ascribe to each.


Norm

Rubrignitz

I agree with the feeling at limit. I've swapped all of my suspension components in and out several times (just because it's so damn EASY) and have noticed the difference at limit of rod-end, poly, and stock vs. aftermarket parts. The rod-ends definitely articulate better... at a cost.

Vapour Trails

The J&M extreme joint LCAs are the ones I was considering.

Thanks for the replies. Because I do drive the car hard at times and I live in an area with 3rd world quality roads, I think that poly on both ends would be less than ideal. I'm going to get the J&M units and hopefully they don't make the car too noisy to be enjoyable.

jahudso2

Please keep us updated on how you like them. I will probably end up buying some in the next couple of weeks if they work well for you.

RodeoFlyer

Here ar J&M's results regarding the binding of theirs vs. pure poly bushings -



The Testing:

We built a fixture which simulated a factory control arm mounting and tested how much force was needed to make the control arm articulate (twist) in those mounts and the results where astounding.

Poly-Ball Bushings:
5 degrees of total rotation = 26.1 foot/pounds of torque
7.5 degrees of total rotation = 35.8 foot/pounds of torque
10 degrees of total rotation = 41.7 foot/pounds of torque

Standard 2 piece setup using only 85 durometer bushings:

5 degrees of total rotation = 124.7 foot/pounds of torque
7.5 degrees of total rotation = 156.4 foot/pounds of torque
10 degrees of total rotation = not measurable with fixture. The 1/2" grade 8 bolt twisted in half at 9.2 degrees which was 210 foot/pounds of torque.


Having used them myself, they work, but only "kinda". The hard inner ball/shaft tears up the softer bushings. I believe they have a lifetime warranty on the bushings, but I don't care to change them every 6 months. YMMV

Vapour Trails

****....there always has to be a downside. Ok, so once again I am lost.

What would I rather have? Sloppy stockers, binding polys, loud and deteriorating rod ends.