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Broken Prothane Front LCA Bushing

807
419
Failure of the front poly bushing is not uncommon. If you don’t want to occasionally replace the poly bushing, you need to install an aluminum and delrin bushing. FRPP and Global West are a good source. I suspect the FRPP bushing is actually a delalum bushing from Global West.
 
Will the OEM 2013 Boss EPAS rack work with Global West's Del-a-Lum bushings? Any worry about steering shake?
Or will the Ford Racing EPAS rack be required with these?
Car is used for Autocross on BFG Rival S tires, so not on R-comp.
 

Grant 302

basic and well known psychic
I wouldn't worry about EPAS nibble control issues unless you have an '11 or '12.

I did feel it 'freak out' on my '11 once on the street when all stock and pretty new, but luckily hasn't shown up since.
 

Norm Peterson

Corner Barstool Sitter
939
709
Exp. Type
HPDE
Exp. Level
5-10 Years
a few miles east of Philly
Been thinking about this one a bit, and I'm not convinced that the failure can be fully explained by braking thrust.

I'm seeing what looks like stress lines on the body side of the failure surface being at an angle, which tells me that the poly was also under some amount or torsional stress when it tore through. That it at least involved the stress intensification at the 90° junction is no surprise (the crack or tear probably originated there).

Perhaps the installed length of the poly was longer than the inner sleeve that runs through it, which would turn some of the applied fastener torque into poly compression instead of useful clamp load. That would put torsion in the shoulder just due to suspension movement due to relative motion across the shoulder with friction on both sides. This would be happening all of the time that the car is moving, not just under braking.

As a first cut, I wonder if this sort of failure could be postponed by trimming a little off the faces of the shoulders. Or more nearly eliminated by replacing part of the shoulder thicknesses with pairs of nylon/teflon/Delrin washers.


Norm
 
Last edited:
Mine split the other way. If you look at the bore it has grease grooves, they are square, not round, bad design. I wonder if the square or sharp corner is another design flaw. I think these bushings fail for a lot of people. Go with delrin.
 

captdistraction

GrumpyRacer
1,843
1,476
Phoenix, Az
I wouldn’t put too much thought into trying to fix these, everyone I know with one glaring exception (who doesn’t run them anymore) has gone through multiple sets. Sometimes failing as quickly as one session. For the cost and hassle, the Delrin and FPP offerings are far better and more reliable.


Sent from my iPhone using Tapatalk
 

Norm Peterson

Corner Barstool Sitter
939
709
Exp. Type
HPDE
Exp. Level
5-10 Years
a few miles east of Philly
Mine split the other way. If you look at the bore it has grease grooves, they are square, not round, bad design. I wonder if the square or sharp corner is another design flaw. I think these bushings fail for a lot of people. Go with delrin.
Any sharp corner is a potential crack or tear waiting to happen, when the accumulated fatigue effects exceed what the material can handle.


Norm
 

Norm Peterson

Corner Barstool Sitter
939
709
Exp. Type
HPDE
Exp. Level
5-10 Years
a few miles east of Philly
I wouldn’t put too much thought into trying to fix these, everyone I know with one glaring exception (who doesn’t run them anymore) has gone through multiple sets. Sometimes failing as quickly as one session. For the cost and hassle, the Delrin and FPP offerings are far better and more reliable.
This is one of those things I'd take a shot at just to see if I could improve it.


Norm
 

captdistraction

GrumpyRacer
1,843
1,476
Phoenix, Az
I certainly tried. The biggest design flaw is removing the shell that had a face, leaving just the outer sleeve to cut into the bushing. I even looked at welding a lip into the arm to try and reduce it, but ultimately moved on to 302S/R arms and bushings which were not only more reliable, but made a noticeable difference in response over the prothane bushings when they were fresh

The energy suspension bushing that keeps the oem bushing’s shell with lip doesn’t have the same issue. The bandaid I mentioned above about trying to shim the rear bushing with large washers to limit movement and provide support under braking and turn-in came from Jack Hidley at MM, they had some limited success there.


Sent from my iPhone using Tapatalk
 

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