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Suspension bushing design between OEM rubber and solid spherical???

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51
20
Exp. Type
HPDE
Exp. Level
5-10 Years
New England
@ShifterX this is what I am using:


To be clear, there is more tire and road noise transmitted into the cabin due to all the mods I did. But there are absolutely no squeaks, rattles, or clunks. I don't think you would find much of an increase in road noise using these LCA in isolation. I don't want to give the wrong impression that it's a loud clattering track rat car. For comparison sake, my friend measured a similar sound level to my car in his new Porsche GT4. And that's where the similarities between our cars end!
Thanks for the info. I reached out to MM with interest in a few parts. Once I told them what I was doing (more street than track), they dissuaded me from going with rod end control arms. So I will probably just keep it simple and go with something like these.


It seemed to work on the boss race car.

My only question is regarding adjustability. My plan is to keep the oem upper. Do in need adjustability to deal with pinion angle issues after lowering?
 
My only question is regarding adjustability. My plan is to keep the oem upper. Do in need adjustability to deal with pinion angle issues after lowering?
The pinion angle is adjusted with the upper link. Think of it as the lower trailing arms locating the axle forward-back in the wheel well and the upper link tipping the axle, rotating around the lower trailing arm axle mounts. You wouldn't want to push your wheels out of center chasing pinion angle.
 
Thanks for the info. I reached out to MM with interest in a few parts. Once I told them what I was doing (more street than track), they dissuaded me from going with rod end control arms. So I will probably just keep it simple and go with something like these.


It seemed to work on the boss race car.

My only question is regarding adjustability. My plan is to keep the oem upper. Do in need adjustability to deal with pinion angle issues after lowering?
Another option not yet mentioned is the Kenny Brown Performance rear suspension set up that uses rod ends on lower and upper links. The KB Rear Grip kit also relocates the adjustable PHB for a lower roll center. SB is deleted.
I have used the KB rear kit on two of my S197’s. NVH was somewhat worse than stock but our cars aren’t exactly a couch potato preference. Interestingly, the two cars reacted differently to the heim joints; in the Boss axle whine was much more noticeable, in the ‘14 GT there is no noticeable difference (more sound insulation?).
 
29
25
Exp. Type
HPDE
Exp. Level
Under 3 Years
SE Virginia
If you're going to drive it on the street (besides to and from the track) I vote for OEM rubber.
A couple of my cars have NISMO bushings that are just rubber, but 4x harder than stock, and that's hard enough to make a crack in the pavement feel (and sound) like an impact.
I would assume polyurethane is even harder.
 
51
20
Exp. Type
HPDE
Exp. Level
5-10 Years
New England
The pinion angle is adjusted with the upper link. Think of it as the lower trailing arms locating the axle forward-back in the wheel well and the upper link tipping the axle, rotating around the lower trailing arm axle mounts. You wouldn't want to push your wheels out of center chasing pinion angle.
My understanding is there is no better way to add NVH then to replace the upper link with a spherical or poly arm. Doesn't the stock upper link work for the ford race cars? I also thought Billy Johnson recommended against a non rubber upper link for a street/track car.
 
51
20
Exp. Type
HPDE
Exp. Level
5-10 Years
New England
Another option not yet mentioned is the Kenny Brown Performance rear suspension set up that uses rod ends on lower and upper links. The KB Rear Grip kit also relocates the adjustable PHB for a lower roll center. SB is deleted.
I have used the KB rear kit on two of my S197’s. NVH was somewhat worse than stock but our cars aren’t exactly a couch potato preference. Interestingly, the two cars reacted differently to the heim joints; in the Boss axle whine was much more noticeable, in the ‘14 GT there is no noticeable difference (more sound insulation?).
Originally, I set out thinking of going this route. Either KB or MM or maybe Cortex. Using spherical lower and stock upper. After speaking to MM, he highly recommended staying away from rod ends for my use case. Interestingly he said the axle (bearings/diff) and especially the brakes generate the most noise from the factory and the rubber bushings dampen it 100%. Once you eliminate the rubber bushings, he found some cars just make more brake/axle noise than others. Its a bit of a crap shoot. I mean he could have sold me some arms and elected not to. I appreciated the candor.

However, NVH is super subjective. Sometimes its the type or pitch of the noise, not just the volume. Like you said, these cars are not exactly E-class quiet.
 
I have poly body-side and OEM rubber diff-side for the upper mount and it's significantly quieter than my heim-joints on the axle-side of my lower trailing arms for sure. If you replace the diff mount with something stiffer you'll definitely get NVH. The Roush upper link was calibrated length wise for a 1" drop in ride height, hence why it was so popular.

You can find upper links that are adjustable with softer bushings if it's still a concern.
 
Last edited:
Originally, I set out thinking of going this route. Either KB or MM or maybe Cortex. Using spherical lower and stock upper. After speaking to MM, he highly recommended staying away from rod ends for my use case. Interestingly he said the axle (bearings/diff) and especially the brakes generate the most noise from the factory and the rubber bushings dampen it 100%. Once you eliminate the rubber bushings, he found some cars just make more brake/axle noise than others. Its a bit of a crap shoot. I mean he could have sold me some arms and elected not to. I appreciated the candor.

However, NVH is super subjective. Sometimes its the type or pitch of the noise, not just the volume. Like you said, these cars are not exactly E-class quiet.
I agree NVH tolerance is personal, with engine, exhaust and other great sounds, who needs a radio or Sync?
KB upper link does retain the factory rubber bushing on the top of the diff, spherical joint at the body end. The Boss had unacceptable axle hop so eliminating that was one key element for me and it did with the rear grip kit. The increased noise was unmistakable gear whine from 70-80 ish MPH, it was loud. Oddly none of that gear whine or any other NVH noise increase is noticeable on the ‘14 GT (which also has a 3.73 Torsen).
 
51
20
Exp. Type
HPDE
Exp. Level
5-10 Years
New England
There is some to be gained by using different lower trailing arms, IMO there is nothing to be gained by changing out the center link, as long as it is in good shape.
@blacksheep-1 So if I leave the oem upper and go with something like the frpp lower poly arms, I am forgoing any pinion angle adjustability. Considering I am targeting 1-1.5” lowering in the rear, is this a problem?
 
51
20
Exp. Type
HPDE
Exp. Level
5-10 Years
New England
If you're going to drive it on the street (besides to and from the track) I vote for OEM rubber.
A couple of my cars have NISMO bushings that are just rubber, but 4x harder than stock, and that's hard enough to make a crack in the pavement feel (and sound) like an impact.
I would assume polyurethane is even harder.
Yep, Sort of looking at this from a refreshening standpoint as well. The frpp oem arms are probably not a bad option considering I am on 13 year old arms with 90k on them. I found 2 other rubber bushing options, which appear to be stock +. The Eibachs have adjustability and a rubber bushing design.


Then there are these from Roush. Maybe more bling since they seems to use ford oem bushings. But maybe that’s what’s good about them.


Anyone have experience with either? Will both work with a relocation bracket if necessary?

Appreciate the insight.
 
49
42
Exp. Type
HPDE
Exp. Level
Under 3 Years
South Carolina
At the suggestion of the late, great, corner bar stool-sitting Norm Peterson from the S197 forum, I installed these LCA's from Spohn Performance:


They have a poly bushing at the front (chassis) end and Spohn's proprietary Del-Rin spherical bushing at the axle end. Also welded on Spohn's relocation brackets. With other mods, including a Ford Performance handling package, the car corners on rails. I drive it to work every weekday (four miles round trip). There is more NVH than my wife can stand, but it doesn't bother me. And I don't recall a significant increase in NVH after installing the Spohn LCA's.
 
51
20
Exp. Type
HPDE
Exp. Level
5-10 Years
New England
Firing this thread back up just to avoid creating a new one. While I was under my car replacing the over axle tubes, I noticed the factory uca bushings were torn badly. So after going back through this thread and others I decided to replace the uca with…..

wait for it….

oem.

No crazy spherical or poly. I am a trusting ford on this one. So I ordered the factory gt500 pieces from our friends at south Florida ford.
Looks pretty straight forward, my only question is what is the best method for removing the axle side upper bushing? Also I a swapping out the whole bushing, so I need to remove the sleeve as well. Thanks
 
1,068
1,056
Exp. Type
HPDE
Exp. Level
5-10 Years
Lenoir City TN
There is a rather expensive Ford service tool that is used to press out the upper differential bushing. Some use a ball joint press to get it out.
 
There's a diagram so you know how to set up the tool to press it out. You can use a generic tool or make your own with threaded stock, round tube, washers, and a welder.
The OEM bushing does have an orientation noted in the manual, so make sure you press it in with that in mind.
 
51
20
Exp. Type
HPDE
Exp. Level
5-10 Years
New England
Great info from the shop manual. Answered my subsequent questions. However reading the manual prompted another question. Obviously all these rubber bushings need to be torqued at ride height. What about the arm to bracket bushing? It comes assembled to what I am assuming is factory ride height. Should it be released and retorqued at actual ride height?
 
All suspension bushings should be torqued-to-spec when the car's body weight is being supported by the springs. Some common methods include using a 4 post lift for access, putting the wheels on cribs and sliding underneath, or loading the axle on a 2 post lift by using jack stands/pole jacks (just make sure you don't lift it off the rear lift pads in a dangerous way).
 
51
20
Exp. Type
HPDE
Exp. Level
5-10 Years
New England
All suspension bushings should be torqued-to-spec when the car's body weight is being supported by the springs. Some common methods include using a 4 post lift for access, putting the wheels on cribs and sliding underneath, or loading the axle on a 2 post lift by using jack stands/pole jacks (just make sure you don't lift it off the rear lift pads in a dangerous way).
I can manage setting the car to ride height. My question was specific to why the ford piece comes assembled with no apparent instructions to retorque in the service manual. Is there something special about that particular bushing?
 
I can manage setting the car to ride height. My question was specific to why the ford piece comes assembled with no apparent instructions to retorque in the service manual. Is there something special about that particular bushing?
Perhaps it's tightened below spec to speed up the installer's process so all you have to do is throw it on and then do the final torque. Doesn't change the order of operations, though.
 
184
149
Exp. Type
W2W Racing
Exp. Level
3-5 Years
Columbia, TN
Funny this thread got resurrected, my upper control arm is making a clunk noise and feel. I talked with BMR a couple of weeks ago and was told to go with the spherical on the body side for better articulation and their poly on the rear housing side. I already have the J&M lower control arms with poly on body side and spherical on axle side and the NVH barely went up. Gonna be a few months before I get to this, but I will let you all know results when I do get this done.
 

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