I just replaced the rear shocks on my truck and I noticed that the crossmember that the shocks bolt to was loose on one side. The crossmember is riveted?? to the frame and it seems that the rivets are loose. Is there any way to tighten them?

I was thinking that the best fix might be to grind them off and replace them with bolts. Anyone else have this problem or have a fix or a way to tighten the original rivets?

Thanks!

 

I've always heard loose rivets should be replaced with new ones, never try to "tighten" old ones. Bolts won't work good either, they will move and enlarge the holes. When a rivet is set besides pulling the two pieces together the rivet expands and becomes tight against the sides of the holes allowing little movement, a bolt doesn't do that.
I would go ask what's involved at a good body shop, it might be better to let them do the work.

 

I would remove old rivets and put grade 8 bolts.They use rivets because $$$$$$,I have replaced rivets in the past with bolts,it did past a structal (spelling) safety.Just my .02

 

Very bad advice. There's a reason airplanes are put together with rivets rather than bolts and it isn't because they're cheaper. It's because they usually stay tight.
Another common misconception is that grade 8 bolts are stronger. Grade 8 will shear easier when exposed to sideways forces than a softer bolt that will bend. Grade 8 is stronger when the force is along the length of the bolt.

 

Well thanks Bill.I learnt something new today

 

I would drill them out and replace them with grade 8 bolts but use flat washers on the bolt and nut sides. You will be ok, Have used bolts on frame rails many times no problem.

 

Mark’s Standard Handbook for Mechanical Engineers lists Grade 5 fasteners as 120 ksi fasteners. This means the tensile strength is 120,000 lbs per square inch. It also lists Grade 8’s as 150 ksi fasteners meaning the tensile strength is 150,000 lbs per square inch. Also, the ultimate shear strength of a fastener is typically about 60% of its ultimate tension strength. So given a certain diameter (cross-sectional area) and strength rating, someone can figure out how much load that fastener can carry in both tension and shear.

Limitations of Rivets

Lower tensile strength than most bolts
Lower fatique strength than most bolts
High tensile loads can cause loosening in the clinch
Rivets are generally neither water or air tight
Disassembly of Rivets is moderately difficult (usually requiring drilling and cutting)

 

Thanks for the information everyone. I think I will try the bolts and just check them every once in a while (this seems like the easiest fix to try first). If they don't seem to be holding I will go the rivet route. This will be sort of an experiment to test the theories given above and see who is right.

It's great to ask a simple question and learn something at the same time.

 

You could always weld the crossmember to the frame rails, too. The bolts would be an easier fix (and easily reversed), though.

 

I thought about welding but I don't weld myself. What kind of welding would you use? I have read in other posts that you are not supposed to weld the frame so I did not consider that option. I have a friend that has a "stick" arc-welder, nothing fancy. Would this type of welder be OK?

 

Well, I had a '79 GMC 1/2 ton that had the rivets work loose on the front crossmember, and my dad and I welded it with a stick welder and 6011 rods. It never came back loose!
You may be right about not welding on the newer frames... no tellin what they're using for steel on those. I'd check with a good body shop that deals with frame repair before doing anything.

 

Bolts are permissible, several manufacturers allow for the use of bolts during frame replacement and repair. The rivits the manufacturers use are not readily available to body shops. As far as wear on your frame, the manufacturers also give most frames 3-4 mm of latitude for being withing specs....I have NEVER used rivits on a frame during a repair process.

 

I would go to the specialize hardware dealer and get the flanged frame bolts that are made as a replacement just for that type of job, done it many of times on crossmembers on class 8 trucks .

 

On a larger vehicle you pay more for a bolted frame.

 

If you do replace the rivets with bolts, drill the hole as small as possible and if possible drill them so that you have to force the bolts thru the hole with a hammer. In a case like this NEVER make the holes any larger than they need to be.