ok this is the second time that this has happened to me. Different side this time, but here is the ringer. Both times it happened I had just put a tire back on. About 2 hours before I had a tire plugged. I took the tire off myself and took it to the tire shop then put the tire back on and like an hour later the leaf spring bolt broke. Same thing happened to me last year. Could there be any corralation. To change the tire I backed up onto 3 2x4's( the car is lowered) then jack it up with a floor jack using the crossmember in the center. Then put the tire back on. I am not using a torque wrench but am not using excessive force to tighten them either. I am guessing about 30- 40lbs. of force. What do you guys think, what is the deal? I would like to use stronger bolts this time, could anyone recomend where I could get some. I was thinking I could just have them hardened but would that make them brittle? I had a suggestion of using some kind of aircraft bolts. What do yall think? Please help me figure out why this is happening and where I can find stronger bolts, or point me in the right direction where I can maybe get some answers from GM

 

First, I don't believe it's a GM issue. You didn't mention how much you had lowered your car, but I'd guess it's significant since you went to longer bolts.

Second, you mention going to stronger bolts. I got 1" longer grade 8 bolts at Home Depot and used nylon insert type locknuts for the top.

Look to see if the bolts are binding against the leaf spring when under load. If they are, then you'll fatigue them and they'll eventually break. The fact that it happened after you had completely unloaded them (by jacking the car up) and then re-loaded them could just have been the thing to push them over the edge.

Also, if you're using the stock shocks, they could be bottoming out, putting more shock loads into the bolts.

One other thing to look at is where the bolts are breaking. That'll tell you where to look to see what's happening.

Hope this helps,
Mike

 

I lowered it as far as the car would go stock. No aftermarket bolts. They are (or at least the last one) broke at the bottom(the top the way it sits) by the nut. Thanks for the help so far!


[Modified by abraham, 5:11 PM 10/14/2002]

 

ttt. Need help. Please!

 

no one has a guess on how this might of happened? I want to figure out why this happened so I dont have to be paronoid every time I change a tire.

 

Hmm. Well, if I had to guess, I'd say that you have a common problem to those two particular bolts, and if you replace those bolts with some grade 8 bolts and don't get them in a bind, then you're probably OK.

Did the bolts break where the threads transition into the shank part of the bolt? I'm just wondering if sometime in the past they were damaged in some way and fatigued over time. It was probably the jacking (where the bolts are completely unloaded) and setting the car back down (which would re-load the bolts) that finally pushed them over the edge.

If you have some pictures of the broken bolts you could either post here or email to me that would help greatly.

Have a good one,
Mike

 

is it possible that when lowering back onto the ground on one tire and the 2x4's on the other tire that the tires are pushed in. Maybe when I lower and pull the car off the wood it might be a good idea to raise the car up just a bit so the tires go back into the correct posision. Does that make any sense?

 

I don't think that would make much difference. As soon as you drive the car one or two wheel diameters they'll unload to their normal positions. Also, the side loads that wheels see when you lower the car back to the ground are absorbed by the upper and lower control arms; the spring and the height adjustment bolt aren't really in that picture. They're mainly looking at vertical loads.

And, consider this. The first bolt that broke has been working fine for some time now, correct? If you were doing something wrong it would have failed again. I really think now that you've got the bolts replaced your problem should go away.

Hope this helps,
Mike

 

there is more to this than we are being told

 

Dont have a clue as to what this thread means. I explained everything in my opening statement. There is something going on that wasnt told and that would be the reason why the bolts broke, which I have no idea. All my suspisions and the events leading up to event are laid out in this thread. I understand people saying that it could have stressed the bolts when the car was not under load but why both times it happened to the side that I had the tire off. Owell hope it doesent happen again. I will find out next time I have a flat. I certainly have no idea why it is happening, that is what I hoped to find out here. I was hopeing c4-c5 specialist or some one in his league would chime in so I could get to the bottom of this but it looks like I wont.

 

I know nothing about lowering stresses etc...but wanted to say that in your thread you state that you are probably tightening your wheels to 30-40 lbs. ?? I am quite sure that is not enough as I have read over and over that 90-100 ft. lbs. is the correct torque. (hope you were talking about your lugs in that sentence!)

 

realy? That seems like an awful lot.

 

:yesnod: Yup, spec is 100 ft-lbs. Don't think this has anything to do with your spring problem, but please bolt those wheels on securely.