I have heard this reference to welding weakening the frame quite a few times ( usually when someone looks at my old 250X frame that has the 350X in it and set up for MX)I could see a problem if the frame was hardened like 2Tall refers too. All these 4130 chromalloy aftermarket frames might make you think that frames are hardened because that's one of the main reasons to use chromalloy - it takes hardening well. But hardening would be counterproductive if torsional strength and tensile strength is what you want (which is the more likely reason to use chromalloy a very tough and strong metal), in fact hardening can promote cracking due to lower torsional flex. Hardening is usually used to resist friction, abrasive wear, or direct impact. Welding on hardened surfaces will reduce the hardness not necessarily the strength. Like stated above: never reweld an old weld. If you are going to weld, always (if there is enough metal) grind down to "virgin" steel and weld from there. "Sub arc" would be good if available to resist heat distortion. Gussets are important if the cracking is due to additional stresses in that area caused by jumpimg or other competiton phenom. Usually a fatigue type crack happens in an area subject to distortion over time. Making this stronger makes sense. Actually if you could do it right, bolting the entire frame together would be the ideal solution, as the bolts allow more distortion with less damage. Tightening them regularily might pose a problem.

 

Anyone seen an old livestock trailer? I challenge you to find one over 10 years old that has been USED that doesn't have any cracks or welds. IF done RIGHT, the welds won't weaken anything. I have to argue with the logig of NOT welding it. How can a solid peice of steel, even if slightly weakened, be weaker than a weld that is cracked/broken? To me a 100% weld holding at 90% strength is better than a 100% strength weld that is 75% broken. Yes, grind away some of the old weld. Add a gusset if necessary. But beware of one thing. The frame is designed to have a little 'flex' to it. If you brace it to the point that it can't flex at all, it might crack somewhere else, usually at the point where the part that can flex meets the part that can't.
As long as the welder knows what he/she is doing, I wouldn't be afraid to have it welded. Heck, I would do it myself if my ride had a cracked frame. I would recommend a Mig or Tig welder.(filler alloy is important, too) Less distortion than using a stick welder or a torch. I don't believe the manufacturer hardens anything AFTER welding, so you shouldn't either (if they would heat-treat the frame after welding, it would warp).

 

prs311
Welders often weld on top of another weld (building the weld) this is common practice. Often when arc welding a person welds a route pass then begins filling with a rod such as 7018. GrizzMeister make sure you can find someone who knows what they are doing.

 

Thanx for all your help