tx_stingray

anyone have any experience or knowledge of a c3 IRS with a true coil over rear end?

i'm sure there are some kits out there, or at least a couple have experimented with one.

i've been in the process over the last few years of modifying the IRS in my project, and would like to compare my ideas with what has been done or what's in the works.

norvalwilhelm

I have true coil overs on the rear but didn't buy a kit. I bought Pro shocks and 250 pound 12 x 2 1/2 inch springs and made everything else.
You can not just weld on the bottom of the trailing arm, it puts the welds in shear and the metal is too thin.
It took me 7 attempts before I was totally happy with how the rears fit. YOu only have about 4 inches between the battery box and the trailing arm so it is a tight fit with the od of the coil springs about 3 1/2 inches.
You only need 5 inch travel shocks to give 7 inches of rear travel.
Double click to really enlarge




[Modified by norvalwilhelm, 12:38 PM 5/8/2004]

battsup

would it be possible to make some sort of ghetto coilover setup for the rear by just welding a bracket onto the trailing arm and one onto the crossmember up top and then just remove the spring?

norvalwilhelm

I just did weld a bracket to the swing arm and while the stock upper shock mount could work I made a much beefier one, cut the old mount off, reinforced the frame and welded the new upper mount in about the same spot.
For the trailing arms I just don't like the idea of welding on the underside. I puts the weld in shear. You also can not weld anything too big on the inside of the swing arm because of extremely limited space.
I have seen kits where they just weld a angle on the underside and I believe partly on the outer side of the trailing arm.
On monday I have links at work and could carry on this post from there.

norvalwilhelm

<font color=red>just trying something different<font size=H1>

battsup

sure i would appreciate you continuing this post. I always dismissed the coilover idea because i thought it was too difficult for the rear. But no that i think about it you can just get some L brackets made out of 1/4 inch steel and bolt them into the trailing arms right? I haven't given much thought to the top but im sure you could retrofit something from another car.

tx_stingray

that's a good set-up--- how does it handle? any noticable difference?

i designed a bracket (in the process of making it now) that will eliminate the upper rear crossmember completely and double as an upper link rod mounting point. then i can cut out those 2 mounting pads (the welds are cracked anyway) and that will make much more room for a set of coil overs mounted towards the rear more. i plan on making a set of lower mounting brackets for the coil overs that will attach to the upper rear portion of the trailing arms (offset type arms) where the anti-roll bar normally mounts and then i'll just have to mount the top ends-- probably straight to the cage.

my vette isn't going to be a daily driver anymore, building it up for just race. once i finish welding the frame up and reinforcing it in certain areas and drop the body back down, i'll install a 12 point cage. my goal is to eliminate as much weight as possible, and so far i've managed to remove approx 500 lbs.

what are the part numbers of the coil overs you are using norval? thanks for the pics.

GrandSportC3

:cool: :cool: setup!! :thumbs:

lostpatrolman

What is the advantage of coilovers over the dual mount vbp spring?

LiveandLetDrive

Norval, how long until the Vette leaves the garage again? How's the weather looking up your way? And as long as I'm asking a million questions, how's Strider?

-Chris

norvalwilhelm

I had the car out this weekend for about 10 miles then it started raining again. I constantly pull things apart, I had both 3 of the 4 coilover out this weekend for adjustments, I am forever pulling them off, it only takes me about 5 minutes to pull a wheel and remove the shock/spring combination for checking the suspension .
For somoeone who likes working on their car coilovers makes it easy to pull the suspension.
I had my upper A arms out 4 time last week alone. Whenever something doesn't seem right to me I pull it , go through it and make it right. The coilovers makes spring/height adjustments so easy.
As for bolting mounts to the swing arms NO. They must be welded. You have at least 1000 pounds static load on each shock/spring and bolting is not good enough. The swing arm material is not thick enough for just bolting.
It must be welded and all corners must be put in tension, not shear.