How much bondo

[71bigblock]

is too much Bondo?  As in, how thick can it get before it will crack, or what determines if it cracks?  I dont want to be bondo happy.  I'm guessing that I wont need it thicker than an 1/8 I hope.  Maybe 3/16, but definitely not as thick as a 1/4". 

Thanks.   

[72bluNblu]

Depends on a lot of things, mostly on a good solid application. If it doesn't adhere well it doesn't matter how thick it is, it will cause problems. You want the area to be as absolutely clean as possible, and completely free from all rust and moisture. It should have a rough finish on it, but don't go crazy, 40-60 grit paper is plenty, and you don't need to "grind" it with that, just "surface" it. But if you're using more than 1/8" you should be doing more hammer or fitting work. And if it looks like it will need that much, it will probably need more.

[somedaysoon]

 
 got pics of the area. Pete

[71bigblock]

I sure do.  Its the bed end, goes on my truck. 

[elitecustombody]

I agree with 72blu, you'll be fine even if it's thicker in some spots than 1/4, but I'd hammer & dolly to get the surface as smooth as possible before filler, just don't buy cheap $9.99 bondo from auto parts store, spend $30-50 a galon for the good stuff  like Rage Gold or Extreme from Evercoat,it goes on like butter and sands very easy,feathers like nothing else and if mixed and applied right,you should have little to no pin holes, good luck with your project, BTW, love that blue  

[ksierens]

Especially on the top of the fender.  With the sun beating on it it will probably cause some shrinkage and it will show up later.

[71bigblock]

Cool, thanks guys.  Actually, there is minimal bondo on the fenders, just a bit down by the dogleg, nowhere else.  None on the doors, I spent $$ to get nice ones.  A little on the roof, and there will be very little on the bed. 

That bottom bed end corner will be clean and rust free, so it will stick fine.  Thanks guys.   

[ksierens]

Looks great!

[RedMan]

Depends on a lot of things, mostly on a good solid application. If it doesn't adhere well it doesn't matter how thick it is, it will cause problems. You want the area to be as absolutely clean as possible, and completely free from all rust and moisture. It should have a rough finish on it, but don't go crazy, 40-60 grit paper is plenty, and you don't need to "grind" it with that, just "surface" it. But if you're using more than 1/8" you should be doing more hammer or fitting work. And if it looks like it will need that much, it will probably need more.

I concur