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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
 

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1994 Firebird Formula 381ci LT1 / TH400+GV O/D
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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.
 

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Discussion Starter · #3 ·
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.
 

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Discussion Starter · #4 ·
bought a cheap press, pulled out the first 2 bushings from the firs CA.

much easier with this tool, will link it later
 

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1994 Firebird Formula 381ci LT1 / TH400+GV O/D
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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.ws6project.com/user_stor/catalog/82-02-spohn-adjustable-lcas-w-spherical-poly-combo-2/?osCsid=03mhcdprac356g895hr05d25n7

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

http://www.ws6project.com/user_stor/catalog/82-02-fbody-umi-performance-lower-control-arms-poly-roto-joint-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.ws6project.com/user_stor/catalog/82-02-spohn-lca-relocation-brackets-2/?osCsid=03mhcdprac356g895hr05d25n7

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.
 

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Discussion Starter · #6 ·
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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Discussion Starter · #7 ·
Hi,

yesterday night i installed the control arms with prothane bushings.

stock CA, not boxed.

ride quality is exactly what i was looking for.

i put them on in a hurry, so i forgot to weight them.

will do it in the next days.
 
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