So I "finally" cracked the subframe cross-plate. It cracked around both mounting bolts. (See picture) I figured it might happen and should have gotten around to strengthening that part, but oh well. I'll chalk the timing up to a coincidence, but it happened two rides after I swapped my broken PMR rack for their new enduro version. (Btw, they're great to deal with. Replaced the broken rack free of charge)

Anyway, trying to think how I should handle this. I know little about welding, so maybe this will sound stupid, but for the time being could I just have the cracks welded until I figure out a permanent solution?

Ultimately though, I'm thinking I'll need to have something fabricated like this guy did:



The way mine cracked though, I'll prob need to go thicker on the new metal, what do you think?

 

If you have a rack and plan on using it for anything heavy. And/or hitting very bumpy trails at speed (pretty normal for a dirt bike)..... You should just bite the bullet and reinforce the rear subframe. I fabricated several parts and although I can weld, I took it to a professional for the final welding.

 

The rest of it I have strengthened (tubing inside the tubes and braces on either side). Just didn't get around to that cross brace piece. From the looks of it, must have happened when the rack flexed downwards.

 

You might be able to make a couple of 'doublers' that would help spread the load transmitted through those mounts and reduce the cracking. Basically, they're just custom shaped washers that you tack into place around the boss.

 

That's a good idea. Thanks

Expanding on that, do you think a single plate that extends from hole to hole would work better to spread the load? Something like this:

 

Finally got this fixed. Forgot I have a buddy who works at a yacht custom parts maker. They have every kind of welder known to man there...and the people to use them.

His boss thought it best to cut the old one off and weld on a new fabricated piece. In his opinion he thought it not a good idea to weld it directly to the tubes. They only work with stainless steel, so that was the only option. The original was 2mm thick, the new one is 5mm.

I can't see it cracking in the same manner as before. Now just have to hope it won't crack around the new weld or at the tubes.

What I'm planning to do next is spread the load by drilling from the back of the rack to the second cross beam at the very back of the subframe. I'm thinking this third attachment point will spread things out enough to not cause a problem in the future. Though that back crossbeam is also only 2mm...