taguy16

I'm upgrading the rear suspension on my '89 Camaro to make it more adjustable and I want to weld, not bolt, rear spring adjusters (aka "weight jacks") to the spring perches on the rear axle housing tubes. Is it best to center these over the original mounts, or is it best to offset them one way or the other (there's about 1/4" leeway), and should I mount them perfectly square to the perches? One thing I'm dealing with is I bought some new tubular trailing arms for my car and they are 1/4" longer than the original stamped steel arms for some reason, so I don't know whether I should allow for that when positioning my adjusters on the spring perches or not. It looks like the rear springs make a lot of changes in the angle they make with the mounts as the rear end goes up and down. I'm assuming the rear springs have ability to give a little either way to allow for this without binding.

Thanks for any input.

taguy16

I forgot to mention I'm using standard 175# 5" X 11" barrel springs with this set-up to begin with.

QwkTrip

iTrader: (22)

There is no need to weld anything in place. Stock springs just sit on the spring perch and so can your weight jack. Look at the Ground Control Racing rear jacks for reference.

The stack of parts likely will lift your suspension about another inch. Normally weight jacks are used with shorter springs to give the adjustability wanted. I custom ordered my springs 2 inches taller than normal weight jacks, I can look up the specs if you want. I can baaaarely get them in by hand with some "bench pressing". The lowest mine will go is somewhere around 1.5" drop and will easily adjust to stock ride height.

taguy16

I have some 8" springs, but they are 225 lbs. which might be a tad stiff for the street. The OEM springs that came on this car must be really soft because they are 15" tall.

I'm dead set on welding these adjusters in place. I don't like the idea of everything just sitting in there loose and dependent on the weight of the car body to hold things in place: seems pretty flimsy to me.

QwkTrip

iTrader: (22)

225 lb/in is roughly twice as stiff as stock. Your spring typically would be paired with something around 1200 lb/in front.

Front and rear springs have to be paired for the front and rear suspension to follow bumps in a similar fashion. I think too high a rear spring rate might cause more oversteer because it reduces mechanical grip over bumps (tire can't follow the road as well with high spring rate).

LAFireboyd

iTrader: (3)

Good to hear someone else identify this. I didn't like it either and took them out.

The way the rear weight jack is made, it sits loosely in the axle's spring perch. In addition, the construction (spot) welds on the bottom of the weight jacks cause the weight jack to wobble in the axle's spring perch; that's what bugs me the most. Then the spring rests loosely on the weight jack. And if you use the factory spring isolators on top of the springs, then that's another independent piece of the puzzle that's just resting in place. I've never read of anyone complaining of a sloppy feel or failure related to any of this, or maybe they just weren't keen enough to think it might be caused by the rear weight jacks, but it sure seems like it wouldn't take much for all of it to collapse.

I took mine out and installed lowering springs with heater hose. Can't say I like that either, but it's solid. I've been trying to think of a way to make the weight jack solid in the spring perch, because I really need more drop, and I'd like to use them, and welding them seems like a good idea.

Front weight jacks are a much more solid and safe design than the rear. And the 1.5 x more weight in front than in the rear helps too. UMI's rear weight jack design is similar to the front and looks much more solid and stable than GC.

Yes, by design, the factory springs simply rest on the axle's spring perches, but those perches don't wobble on the axle. The axle moves, not much, but the perches don't wobble.

Firechicken82

I have the UMI front and rear. The rears are in the perch really snug. In fact I had to grind a little of the inside of the perch as well as some of the powder coat off get it to fit. I thought about welding them but they were so snug there wasn't a point.

taguy16

I still think welding the adjusters on is the way to go since I don't know for sure what this car has in store for it. Better safe than sorry.

As far as my original question goes, since no one really has offered up an answer I think what I'll do is set the car up with all the parts close to the position they're going to eventually be in and let the adjusters find the spot they like the best, then weld them on there. In retrospect 1/4" leeway in the position of them probably isn't really that big of a deal.

I wish these cars had longer trailing arms so the angle of the spring perches wouldn't change so much during suspension travel. Now I can understand why NASCAR stock cars have truck arm suspensions where the trailing arms go from the middle of the car back to the rear end.

//<86TA>\\

iTrader: (14)

I wouldn't move the axle side mount, if anything I'd change the control arms back to something tye correct length or verify that axle is at least where you need it to be and square with the chassis.

I wouldn't weld the adjusters on either.

taguy16

I got everything mocked up with the 8" springs (preloaded), and the adjusters seem to be at home centered over the original spring perch humps. Everything looks like it lines up fine. Hopefully tomorrow I can get them welded in place and the paint touched up so I can move on the the next challenge this project presents..