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boxing rear control arms


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#1 tommy vercetti

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Posted A week ago

Hi guys,

lately i'm wotking on the handling, i'm intalling the prothane total kit and i'm very happy so far (installed both sways and the track bar, also welded a tube in the track bar itself in order to not let it twist).

rear control arms are next. i already pulled them down.

 

question is: would you box the rear CAs? or am i stiffening it too much?

i want to keep some good drivability because it's my DD.

yes i have a "nervous" driving style, but i don't want to push it too much.

i'm also thinking that oem CAs won't take the abuse, they might crack under too much stress. "something has to flex".

what do you think?

 

97 Y87 3.8 5 spd


Edited by tommy vercetti, A week ago.


#2 Injuneer

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Posted A week ago

Problem with your approach is you're adding unsprung weight, which has a negative impact on handling.  1/2 of the track bar (panhard rod) weight and 1/2 of the lower control arm weight is supported by the rear axle assembly.  You want to reduce unsprung weight. That's why lighter weight tubular replacements are available.  


1994 FIREBIRD FORMULA
FRED

 
381ci all-forged stroker (Callies Stealth, Oliver billet rods, BME 2618-T61 nitrous pistons) - 10.8:1 - CNC LT4 heads/intake - Comp Cams solid roller - MoTeC M48 Pro engine management - 8 LS1 coils - 58mm TB - 74#/HR injectors - 300-shot dry nitrous - TH400 - Gear Vendors 0.78:1 O/D - Strange 12-bolt - 4.11 Pro-Street gears - AS&M headers - true duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP / 800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117 MPH straight motor
 
https://www.firebird...9_698_32777.jpg

 


#3 tommy vercetti

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Posted A week ago

okok i get the point, 

keep in mind that i was thinking to box them just by welding 3 smaller patches in 3 different points for each arm, so that would have not much weight added.

 

i have a couple of tubular that i borrowed from a friend, i'll mesure the weight in order to see the difference though.



#4 tommy vercetti

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Posted 3 days ago

bought a cheap press, pulled out the first 2 bushings from the firs CA.

much easier with this tool, will link it later



#5 Injuneer

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Posted 2 days ago

Did you notice the stock rubber bushings had “hollows” above and below the through bolts on each end?  Those provide the flexibility required when the body rolls and the body end bolt and the rear axle end bolt are no longer parallel.  Replacing the bushings with solid , harder polyurethane material can cause suspension bind.  That will increase the twisting moment on the control arm.

 

The best solution is spherical rod ends on each end of a tubular control arm.  But rods ends can be harsh and noisy. A good alternative is to use the poly bushing on the body end and a spherical rod end on the axle end.  Allows the required rotation, but minimizes the transmission of noise to the body end.

 

http://www.ws6projec...56g895hr05d25n7

 

UMI has a proprietary “roto-joint” which is basically a softer, non-metallic substitute for a metallic spherical rod end.

 

http://www.ws6projec...-combination-2/
 

If your application is primarily drag racing, using lower control arm (LCA) relocation brackets are ver effective in eliminating axle “hop”:

 

http://www.ws6projec...56g895hr05d25n7

 

In General, an “adjustable “ LCA is not required.  Can be beneficial if you have to move the axle assembly forward or backward for tire clearance.  I like the Spohn components.  I've worked with Steve Spohn to provide dimensional input for his designs, he has used my Formula for prototype installs.  Extremely high build quality on everything he makes.


1994 FIREBIRD FORMULA
FRED

 
381ci all-forged stroker (Callies Stealth, Oliver billet rods, BME 2618-T61 nitrous pistons) - 10.8:1 - CNC LT4 heads/intake - Comp Cams solid roller - MoTeC M48 Pro engine management - 8 LS1 coils - 58mm TB - 74#/HR injectors - 300-shot dry nitrous - TH400 - Gear Vendors 0.78:1 O/D - Strange 12-bolt - 4.11 Pro-Street gears - AS&M headers - true duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP / 800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117 MPH straight motor
 
https://www.firebird...9_698_32777.jpg

 


#6 tommy vercetti

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Posted A day ago

Hi,

yup, i noticed the hollow parts into the stock rubber bushings.

that is exactly why i was asking about boxing or not.

 

 

using the poly bushing on the body end and a spherical rod end on the axle end was my original idea, but , for the moment is way too expensive. 

 

mine is just a "poor man" 3.8 which is my DD.

plan for my application is to have a fun and relialbe DD and no more.

 

thanks for the tips and the links though, super interesting. 






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