Stress cracks at sway bar mount points

[matl59]

So I installed Addco front and rear sway bars on my GT a few weeks back. I'm very pleased with the handling improvement and intallation went well.

After a few hundered miles I have run into a problem though.

On my way to work last week I heard a clicking coming from behind me. The rear sway bar had been in place for a few hundred miles at this point without any trouble but I figured maybe something moved and was making contact. Bolt to spring in the spring perch area or something to that effect... When I got home to jack it up and fully inspect the situation I found that the sway bar mounting point on the body had began to crack on the drivers side and it was the cracked edges of the floor pan that I was hearing clicking back and forth against each other.

I haven't been driving the car hard and they've only been on for a short time.

I can't imagine I'm the first to encounter this problem but I didn't see any mention of it in other posts. Anyone have any solutions to reinforcing this area? Should be space enough under the rear tray to add some support so the floor doesn't flex and crack...

[yellaopelgt]

Is the car structurally sound? ie rusty? The only reason I can see the floors buckleing and cracking is because of structural intergrety. The purpose of the sway bars is to prevent body roll....maybe you hit a few corners too hard??? The sheet metal at the attaching points is relatively thin so maybe a plate of 1/8" on either side of the floor pan would be in order if you dont have any other rust issues to address. Might just have been a Friday at the Opel factory when your car was built.......dunno...

[matl59]

Structurally the car is very good. It had some rust when I bought it but it was not structural and I've repaired those areas. They were nowhere near the sway bar mount locations...

Haven't driven very hard with the sway bars on either.

I'll try to get some pics of the damage tomorrow.

[RallyBob]

Sounds like somthing *might* be binding up then. I've seen swaybars crack control arms and chassis mounts before, but usually only after years of very hard driving or racing. Otherwise the culprit is often binding in the linkage arms, or bottoming on other components which can put insane stress into the mounts.

[matl59]

I didn't crawl under the car today to take any pictures, too many none Opel related things going on.

I'll take a good look at everything when I repair the cracks to try and make sure nothings binding up or bottoming. I thought I was careful when I installed them...and I can't really say the install looks any different then JimSky1959's pictures on the classicopels yahoo group.

[Gary]

Originally Posted by matl59 I didn't crawl under the car today to take any pictures, too many none Opel related things going on. I'll take a good look at everything when I repair the cracks to try and make sure nothings binding up or bottoming. I thought I was careful when I installed them...and I can't really say the install looks any different then JimSky1959's pictures on the classicopels yahoo group.

Were the jackstands under the differential when you tightened everything up? If the car was supported at the jack points, the rear end would be at full extension and that may have caused some stress at the mounting points when the car was lowered.

[matl59]

Were the jackstands under the differential when you tightened everything up? If the car was supported at the jack points, the rear end would be at full extension and that may have caused some stress at the mounting points when the car was lowered.

Jack stands were under the rear end when I tightened eveything so the suspension was properly loaded, not hanging.

[matl59]

better late then never...sorry not the best quality...

I circled the cracks in red in the last picture. The cracks are on the drivers side above the mount.

Any thoughts?

[jordan]

Bolting on 2 doubling plates covering the effected area is your best bet. 1/8-3/16" steel plate with 4 bolts though sandwiching the area should suffice. You should do this to both sides to prevent a load bias and it is also preventative action to the non-effected (for now) side.

[OriginalOpelGTOwner]

Any load bearing attachments to the floor pan always require large, thick, flanged metal reinforcements spot welded to the top side of the floor pan with the attaching nuts welded to the reinforcement and even than road load testing is required to make sure cracking does not migrate to another area. The Opel factory must of not installed the reinforcements when the sway bar was deleted. Would be nice to see photos of the factory installed reinforcements on European Opel GTs.

[matl59]

The original reinforcing plates are welded in. The cracks formed right along the spot welds holding the plate...

I'll take a couple more pictures from inside the car tomorrow when I remove the rear self and repair the cracks. I'll see what I can come up with for reinforcement since I know it will just do it again without anything...

[matl59]

All welded up and hopefully wont cause any further issues. There wasn't much to see from inside the car. The reinforcing plate appeared to be a little lifted from the floor pan on the side that failed so it could possibly have been this gap that weakened the area. The cracks formed along the three spot welds holding one edge of the plate.

I opted to just weld up the cracks and then on the inside the reinforcing plate is now welded across the top.

Maybe my floor pan had some stress cracks from the stamping process or maybe the spot welds holding the reinforcing plate inside were in bad location...

I'll keep an eye on it and if it proves to be a problem again then I'll come up with some additional bracing.