Leaf Spring Installation Problem

[Eden72Vet]

I am trying to install the 8 inch bolts in my leaf spring to lower the rear ride height of the car (right now it is at about 32 inches high, with the new leaf spring I installed late last summer). I am having the same problem with the 8 inch bolts that I had installing the 6 inch bolts last summer, and I would appreciate any insight or experiences on the installation process.



To install the new leaf spring, I bolted the center of the leaf spring to the bottom of the car. Then I attached C clamps near the end of the leaf spring and jacked it up to put the bolt through the opening. However, the bolts don’t line up with the leaf spring holes. The only way I have been able to get the bolts into the hole in the leaf spring, is to attach a “come along” to the front tire and the leaf spring and pull the leaf spring into place. Which takes a lot of force to get it lined up. After I do get the bolt installed, the leaf spring is pulling it back towards the rear of the car, which does not look correct. Please let me know if anyone has had an experience like this.



Thanks,

Matt

 

[JohnZ]

That's the natural geometry of the Corvette rear suspension (the trailing arm swings in an arc in the side view); you have to jack up the trailing arm to normal ride height (with the spring also at normal ride height) in order to have the link bolt vertical through both holes.

 

[rgtrough]

Hey Matt, I just did mine 2 weeks ago and did not have any of the problems you described. Did you place jack stands under the frame in the rear, letting the rear of the car just hang? I was able to position the spring using a small floor jack using this method. peace Bud

 

[Eden72Vet]

I have tried both ways. When I orginally installed the 6 inch bolts, I had the rear end in the air with the jack stands under the frame. The thing was just a bear to get the bolts to line up. This time I also have it in the air by the frame, and I am having the same problem. I will try to jack the trailing arm up the next time I can get out to the garage.

Has anybody installed the 8 inch bolts? I have 1 side installed, and it looks like it could rub on the tire when I am moving.

Matt

 

[ruby76]

That's the natural geometry of the Corvette rear suspension (the trailing arm swings in an arc in the side view); you have to jack up the trailing arm to normal ride height (with the spring also at normal ride height) in order to have the link bolt vertical through both holes.

Heck, without the rear tires on, I simply "lifted" the swing arm/trailing arm to the right height to get the bolt to line up. dropped it in place (with washers/bushings etc) and voila!

 

[Eden72Vet]

I think the part that I was missing as I was trying to change these bolts, was jacking up the trailing arm. I have one side to do yet, so I am going to try this on Friday. Hopefully this will get me there.

Thanks for the help.
Matt

 

[Vettehead Mikey]

You should try also slacking off the 4 bolts that hold the spring to the diff cover. These should never be tightened until the full weight of the car is resting on the wheels.

 

[Eden72Vet]

You should try also slacking off the 4 bolts that hold the spring to the diff cover. These should never be tightened until the full weight of the car is resting on the wheels.

Thanks Mikey, I knew to loosen the bolts. However, I did not know that I should not tighten them until I had the car back on the ground.

 

[WayneLBurnham]

I'm with Ruby76 - but I put on the VBP dual mount...

....and I use larger diameter longer spring hanger bolts - either 7/16th or 1/2" diameter (instead of the usual 3/8ish".) But like Ruby76, I didn't have any alignment problems that I remember with the spring hanger bolts (and I always remember the negatives...)

How much off are we talking about? Fractions of an inch just enough to stop the bolt from going through or a lot worse, like the width of the spring?

I honestly don't remember how I planted it....it was over a year ago. I know the car frame was on blocks and the rear wheels were off. I did use a floor jack to raise each spring end to put on the bolts, IIRC, but there wasn't an alignment problem. I think I had a real problem in having to pull the sway bar because it is another VBP number without the articulated mounting deal and the top of the spring hanger bolt had to be in there before the little mounting flange dealy was on - again, that's IIRC. Likewise I seem to remember enlarging a hole to get this bigger diameter bolt through.

I don't remember when I tightened and torqued the bolts on the dual mounts or them to the center....but I think it was before even attempting to put the ends on the hangers.

 

[Bill75]

Bolt Replacement

Matt,

I've done mine a couple of times, with the car suspended on jackstands and the wheels off, the tailingarms hang to the position of the spring. I used a clamp on the leaf spring to prevent the jack from slipping, then positioned the jack to the side of the clamp and raised the end of the spring. Don't go too far or you'll start lifting the whole car off the jackstands. I do remember having to fool around with the bolt a little to get it to pass up thru the hole in the trailing arm because when the suspension is hanging, the bolt is not perfectly straight up and down. But it wasen't a big deal for me anyway. Like someone else said, once the tension from the spring is off the trailing arm, you can move it up and down by hand.

good luck with it
Bill

 

[JohnZ]

....and I use larger diameter longer spring hanger bolts - either 7/16th or 1/2" diameter (instead of the usual 3/8ish".)

The stock end spring hanger bolts are 9/16"-18; anything smaller is a lower-strength aftermarket replacement.

 

[WayneLBurnham]

That explains it....I couldn't believe such a tiny bolt

was really used there.....

That may have been the diameter I used too - I'd have to go measure, except I used NF and Grade 8 nylock nuts. I know I got a bunch of them in several lengths and used the very largest I could fit in through the spring end.

The one on there that failed left a nice deep gouge in the pavement! Nothing else was damaged (other than the spring end) and, at least, it prompted the swap to the upgrade at that time. (That was even MORE fun to load up on the wrecker than when the spindle on the same side cut in two when the inner bearing seized the year before and activated the special "wheel eject feature"! ):cry

 

[Eden72Vet]

I completed the change from the 6 inch bolts to the 8 inch bolts. The part that I was missing was jacking up the trailing arm, so that it was at normal ride height. That worked a lot better than the prior way I was trying to do it. Athough the longer bolts had a very minimal effect on the ride height. I think I have a spring that has too much pressure.

Matt

 

[Blitz]

Mono-Spring Installation

I've been watching this thread for the last few weeks.... planning my own upgrade. Well, it's finally done ! I installed VBP Performance Plus kit for my 81.

The link below details our installation:
http://www.majgadget.com/81vette/suspension/rear-leafspring1.htm


Hope this helps!

Blitz:blue:

 

[dirtypants]

outer spring bolts

a years after reply..in case anyone looks. Great forum guys !!! lots of very helpful comments: I hope I can add to the value here.
Replacement outer spring bolts for C3 C4 are available from all the usual suppliers..auto grade, no need to risk the hardware store bolts..(ever see what a car looks like when the rear suspension comes apart at speed !!) the bolts can be stock, for the C3 about 6 3/4 or the longer more adjustable 8 in., and with rubber stock or poly U bushings. the longer 8 inch do not have cotter pin holes so that the Nyloc nut can easily be adjusted up or down..up to raise rear ride height, down to lower. note that new springs take a hundred miles or so to settle to their ride height, as much as 2 in, ..so wait a bit before adjusting. There is room for an addtl washer under the top of the bolt, or simply cutting wheel cut off the lower bolt end once satisfied with where it is. You do not want the bolt or spring end to make contact with the inner tire..and the tire will bulge some in hard cornering or if getting a flat, and you don't want the bolt to contact the pavement in case of a flat-shredded tire. The C4 bolts are similar but a different set up length so 9 and 10 inch which is far too long for a C3. You will need to check camber after the spring settles , and after any ride height adjustment as you are changing the arc of the spring and this will change the camber. Speaking of camber there are a lot of specs out there as to what camber and alignment should be..read a lot and take your pic based on your tire, suspension changes you might have made, and how you drive..but the original GM specs are highly suspect as far as modern settings, tires etc go. You should want some negative camber and about .5 deg is about right, which should give you about an 1/8 of an inch gap at the top of the wheel (not tire) if you measure with a level and a straight edge that contacts the wheel full diameter at the wheel rim. Same goes for toe..you want a little toe in, ..pick a number you like after reading up. While the wheels are off..check bearing end play..it is .001 on C3, and check rotor runout and thickness all around. A vette with faulty alignment will handle poorly enough to notice, so if it drives like a dream then it is probably ok. Still a small change in the right direction can make a big difference. That is why Nascar drivers/crews make constant suspension changes thru a race to adjust for changing track conditions, temperature, handling thru the turn..turn in, center,and drive off. Getting it right for how you drive will make a big difference. Rear wheel bearings and perished trail arm bushings are issues and need to be good. Perished trail arm bushings or bad yoke joints can induce rear end "steering" as power is applied or released and can be very dangerous. At recent car shows I have seen some beautiful Corvettes: paint, interior...but a look underneath was "scary".
Nick..near Spokane
81 4 spd.

 

[dirtypants]

rear spring outer bolts

update..I installed 8 inch rear outer spring bolts..to bring rear ride out down, which was too high due to a new stiffer rear spring. About one inch lower can be gained: the key to making this easy is to block the frame up after jacking, then a jack under the spring outer end near the bolt, with a c clamp and wood inboard next to the jack..cushion both the jack tip and the c clamp at contact with the spring ESPECIALLY if a composite spring..any nick in the composite spring can cause a failure..and..jack the trailing arm just ahead of the rotor..by finagling in no describable way..a little up, a little down with each..you can find jack settings that will allow the bolt to be withdrawn and replaced..it takes a few different jack postions for various bolt alignment positions. I noticed that some cars and some kits have a metal cup at the top, inside the square frame section where the bolt head and upper cushion live. Ecklers kits have 4 such cups, Zip has only two..being the lower cups. Looks to me like having an upper cup..faced up to accept and retarin the upper cushion makes sense..could the aim sketch diagram be wrong? Anyway I put in both cups..makes sense to me along with poly cushions. These two things do eat up a little of the bolt length but that actually helps in not having to cut off low threads. I also notice some forum posts showing the washers incorrectly installed. the rounded washer edge faces the rubber cushion. Once you set your ride height and level it out side to side, all set..unless too much thread remains below..where the bolt could contact pavement or tire..in a flat or cornering..if so cut if off. As your spring settles or loses arch you will not need to go lower..only higher...and the bolts alone are not costly if you need to replace em,. The 8 inch should do it..any longer than that is too long relative to pavement and tire. Now to the alignment guru.