RLCA Help: Spherical Bearing vs. Poly Bushing

[TeeLew]

Stiffening up the differential bushings sounds like a mod you'd do for drag racing where clutch engagements would normally be much harsher than in HPDE, time trialing, or autocross (drag-race-start Pro-Solo perhaps excepted).

The hub carriers are isolated from the pumpkin by pairs of universal joints so I'm not seeing a lot of crosstalk between pumpkin deflections and suspension reactions like there is with the S197's stick axle where the suspension is what locates the pumpkin.


Norm

To be completely honest, I can't give you a good opinion on the matter of the diff bushings, because I didn't run the stock stuff very long and never in anger. The rear sub-frame bushings made a significant difference on the responsiveness of the rear of the car. That was very apparent. The diff bushings were a pre-emptive measure to address wheel-hop. In my experience, any time you're traction limited it's possible to set up the grip-slip-grip-slip condition which causes the final drive housing to bounce around cause problems.

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[TeeLew]

I'm leaning towards the BK-055 bearing vs the Superpro bushing.

I went with the SuperPro bushing because of 2 things.

1. They might require greasing from time to time, but they won't require yearly replacement. Sphericals driven on the street will need regular maintenance.

2. I'm concerned about the impact loadings of a spherical going to the chassis. The peak loads go up considerably with a spherical and can lead to cracks in the chassis mounts over time. Even thought the bushing is quite stiff, it has enough deflection to absorb a lot of the higher frequency inputs.

3. I feel like this gives most of the performance advantage without reducing the comfort of the car on the street.

If you have different requirements/opinions, you may very well choose a different option.

 

[Norm Peterson]

3. I feel like this gives most of the performance advantage without reducing the comfort of the car on the street.

I tend to agree with this. The first "x" amount of bushing stiffness increase over that of the OE rubber is going to give you the most performance benefit for the lowest costs in terms of things like NVH and resistance induced by off-axis rotation (aka "bind"). Bearings represent a maximum amount of added stiffness, which completely eliminates all impact-softening compliance in exchange for zero "bind".

I can't tell from the available pictures how much the axis of the Superpro bushing "misses" the center of the rear LCA's other pivot, but that'd be your indication of how much the off-axis rotation effects amount to. At least with the Superpro bushings there is some length beyond where the outer diameter is captive inside the arm itself (IOW, the joint doesn't instantly go all bound up the instant the suspension moves and the arm starts to rotate as seen in rear-ish view).


Norm

 

[SlowStangGT]

Hey all, I was curious about the lifespan and durability of the spherical bearing.

I got the FRPP knuckle bearing installed this weekend (what a huge PITA that was), and wanted to be sure of my decision to go poly vs spherical before I tackle the RLCA.

I bought the BK055, but am hesitant to install it after reading some stories about "clunking" on this forum. While NVH is definitely a concern, it isn't as big of a concern as a bearing that will fail in 20k or 30k miles. I see some of you definitely hear some noise; I'm not sure if that's an indication of failure or just the fact of life living with the bearing...

SuperPro definitely interests me, since the only maintenance there seems to be is that they need to be greased occasionally. However, as several members pointed out, any off-axis rotation is going to result in a far-stiffer bind (if you can even call it that) than the stock rubber bushing.

Supporting mods will be the BMR poly vertical links, the BMR CB005, and the FRPP Knuckle-To-Toe-Link bearing, paired with the BMR SP083 handling springs, FRPP Track Shocks, and J&M Shock Mount. Listing here in case any of the supporting mods will interfere with the performance of the SuperPro RLCA poly bushing

 

[NGOT8R]

The spherical bearing is definitely a PITA to install, but I‘m happy with mine. I just turned 3K miles on my car, so I don‘t have any data on the lifespan of the bearing yet.

 

[Radiation Joe]

I just completed my third 300 mile, high speed, rough road trip with the RLCA bearings installed. The rear suspension is now quiet. I just wish I had installed the knuckle toe bearing at the same time. With the exception of toe issues when going through large suspension travel or sharp bumps, this car is dialed in.
Sharp impacts are definitely louder now but within my tolerance band. I realized this morning that the increased impact noise reminded me of my old RS-6 when it would go over frost heaves. Good company to be in.

 

[Bluemustang]

Having driven in @SAY WHAT 's car that has the Superpro RLCA bushings installed, I can say pretty confidently that this is the place to be for most of us. I plan to remove my bearings at some point and install these. He has almost as many suspension mods as me and our cars are pretty much identical under there except for the springs (which I also once had). His car drives like a great OEM sports suspension. There's no reason to have bearings in there vs. these unless it is a track only car and you're very serious. Either option is better than the crap OEM bushing though.

 

[SlowStangGT]

Pulled the trigger

@SAY WHAT @TeeLew Any tips on the install? Not sure how exactly I'd want to press the bushing in. Seems like it would be a bad idea to press it on the polyurethane part itself, perhaps I'd want to find something that would press on the outer metal sleeves?

 

[krishelnino]

I pulled the trigger as well. $90 shipped! I have to hunt for a 2nd set of RLCAs now to minimize down time.

 

[NGOT8R]

@SlowStangGT, here is the Steeda press tool that came with my spherical bearing. I had my buddy turn it down in his lathe (created a lip on it), to make it fit perfectly into the sleeve. Maybe you could make one from aluminum to suit your needs as well.

 

[TeeLew]

I had a machine shop press and install the bushings. I don't have that type of equipment. If I had to have done it myself, I would have had to burn the rubber bush out & then hacksaw the sleeve...or pay a guy with the right tools a could hundred bucks. I took the latter path.

 

[SlowStangGT]

I have a ball-joint vise I plan on using, with all the fun adapters it came with. I'll probably see what adapters I can use to push them in at the metal sleeves so it doesn't put all the force on the poly that sticks out over the edges of the sleeves. Steeda tool would be nice to use though!

Also pulled the trigger on the front bushings as well, I'd most likely want to install those instead of the Steeda bearing I got. Probably will end up posting those two items on here for sale soon

 

[NGOT8R]

To install just the polyurethane bushings, you can press the rubber out of the factory sleeve and then burn the residual rubber out, using an arbor. This is what I did with my 12 ton shop press. I only ran into trouble when I went to press the sleeve out. My brand new 12 ton press was no match for the sleeve and bent the press ram, rendering my press useless. It was at that point that I had to take it to my buddy’s shop (as seen in the pic), where he used his large 20+ ton press, which was still a bit of a struggle to press the sleeves out, but eventually got the job done.

 

[SAY WHAT]

I had a shop put my Super pros in. I was also doing other mods at the time, so I had a shop do them all at once.

 

[SlowStangGT]

Welp, funny enough, the *easiest* part of the RLCA was removing the bushing. It was a real PITA to remove the entire control arm from the car, having to drop the exhaust and remove all the shocks and springs.

I used the Astro Pneumatic Goliath C Frame with an impact wrench to press the bushing out in about 20 seconds

The problem I'm currently having is difficulty pressing in the bushing. I have a ball joint receiving tube with a diameter 0.1mm too small for the bushing, and is digging into the polyurethane part slightly. I'm currently trying to figure out how to get it in, but worst case I'll probably resort to finding a shop to press it in. Or maybe just going the BK055 bearing route for now, as the press adapter fits those just fine.

Ahh decisions

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