Aluminum Suspension Weight Savings

For those interested in what changing out to a Spec B aluminum suspension setup saves in weight, see below. I don't expect it to be much and don't expect much improvement, but I got the parts cheap and needed new bushings anyway.

 

Front A-arms - Approx 3 lbs savings per arm

Rear trailing arm - Approx 6.5 lbs per arm

Rear lateral links - Approx 1.5 lbs savings per link

 

Total savings of approximately 22 lbs.

 

Still think it's worth it?

I measured less difference in the LCA, but the others look similar.

 

Okay, here it goes:

 

20202AG160 - Front RH Control Arm - Bought from Legacy_Otaku, used with AVO bushings ($237.50)

20202AG170 - Front LH Control Arm - Bought from Legacy_Otaku, used with AVO bushings ($237.50)

20252AG021 - Rear RH Trailing Arm - Bought from K.O.P. ($296.17)

20252AG031 - Rear LH Trailing Arm - Bought from K.O.P. ($287.55)

For reference:

 

20250AG030 - Rear RH Upper Lateral Link - Bought from K.O.P. ($57.75)

20250AG040 - Rear LH Upper Lateral Link - Bought from K.O.P. ($57.75)

4BoxParts Adjustable "Forward" Lateral Links - ($175)

 

Differences:

Front Control Arms:

Steel 7.5lbs - Stamped and Welded Construction

Aluminum 6.5lbs - Cast/Forged Construction

 

Rear Trailing Arms:

Steel 17.8lbs - Cast Construction

Aluminum 11.2lbs - Cast/Forged Construction

 

Upper Lateral Links:

Steel 4.9lbs - Cast Construction

Aluminum 3.3lbs - Cast Construction

 

Rear "Forward" Links:

Not yet measured.

I've done this and you can certainly tell it's different.

Don't control arms count as unsprung weight which would make a significant difference in handling? Same effect as lighter wheels, less weight moving up and down so responsiveness increases, only thing is right quality might suffer a bit.

The aluminum control arms are the Spec.B's magic mojo. They are what allow it to be a luxurious, high performance rally machine that can hit 1.8g's on the skidpad and click off a 3.2 sec 0-60 in the rain.

 

Don't doubt the mojo.

Don't control arms count as unsprung weight which would make a significant difference in handling? Same effect as lighter wheels, less weight moving up and down so responsiveness increases, only thing is right quality might suffer a bit.

 

Their mass is not entirely sprung or unsprung since they are attached to the chassis. Use 1/2 for approximation sake.

 

I agree with fahr - they make a noticeable improvement (more nimble and more comfortable), although I would argue if they are worth it at retail price. If you can get a clean used set for a good price then it becomes easier to justify.

I'm curious now how it will feel. I'm wondering if the bushings I'm replacing will make the biggest difference.

It's going to be a while though. This car has been in salt for half its life and I am having to replace knuckles from rusted bolts and I might as well replace the bearings, tie rod ends, and balljoints while I'm in there.

I had installed Powerflex bushings into my old steel arms before coming across the alloy ones used. I didn't like the Powerflex bushings so I installed GrpN bushings into the alloy which are a little more compliant. For sure the ride quality got better but I can't say if that is the weight difference or the bushings. What I can tell you is that I had to back the damping on my Konis off a little to compensate for the decreased weight.

I only did the rear lateral link in aluminum. Everything else was done with bushings/camber/coilovers. I was doing 1.5g turns on the track (on slicks), so I didn't see the benefit of another $1000 for a couple pounds of weight savings.