I'd like to buy a 1 gallon Rotopax water can to mount on my PMR rack. Has anyone suffered a broken subframe because of a Rotopax plus some gear on top?

I normall carry a gallon of water with me in my drybag on the rack, but I position them (two containers) closer to the front of the bike. I'd like to use a smaller drybag and thinking the rotopax would help free up some room, but the water would be more spread out over the rack...more towards the rear of the bike. I'm worried some harder off-roading might cause a problem.

 

I forget what the rack weight spec is, but I'm guessing it is at least around 10 lb or more. The Rotopax with water shouldn't exceed that.

 

one gallon of water is 7.5 lbs or so.
the answer is yes, your subframe will break, just depends on how much wt you put on it and how many times and how hard you take a hit.

 

PMR racks thinks they'll hold up, but obviously no guarantee. They have their rack drilled for the Rotopax mount and the 1 gallon container, but recommend against the 1.75 gallon container. But with enough rough riding, something will break. Others here can tell you their experience.

Anything, if pounded hard enough, will break. If carrying a gallon pack of gas/water on the back I wouldn't recommend doing your best imitation of Justin Barcia.

 

Ha! Imitation of an imitation of Justin would be about right

I've been looking over the subframe strengthening posts around the web. I recall seeing one before about someone putting some metal piping inside the subframe tubing to give it more strength. Can't find it now. Does anyone remember that?

Would that alone be sufficient or is welding some kind of crossbar brace essential?

 

Here are two of the mods I made to my KLX250 to ready it for our recent trip to Colorado. The left side needed only an extra tubular brace to extend the truss of the subframe.

The right side is more vulnerable, in my opinion. A stock bike's subframe is reinforced by the stock muffler. The muffler has three mounting bolts that span the weakest part of the right side subframe. Most of us, including me, are running aftermarket exhausts, which mount with only one bolt, which contributes nothing to the frame strength.

I fabricated an aluminum plate to simulate the effect of the original muffler, and went ahead and inserted a 10-inch piece of tubing into the right top member of the subframe. There's a slight bend in the subframe at this point so you need to prebend the reinforcing tube before driving in. You only get one shot. It would be very difficult to remove the tube.

We rode over 500 miles of rough Colorado trails with multiple crashes and I had no trouble with my subframe. It supported a luggage rack holding a pelican case, 2 tool tubes, a large duffle and 2 saddle bags, all weighing about 50 pounds.

 

This is perfect! Thank you for the pictures and details.

On the right side I got the Japanese-made black brace. It doesn't look quite as long as yours though.

Regarding the reinforcing tubing inside the frame. This will probably sound incredibly stupid. With the pre-bend, how can the tube make it all the way down the straight portion of the frame when it has a bend in it?

 

Not stupid at all. As you drive it inside the subframe tube it will straighten out, but will retain some residual stress that will help it conform to the slight bend in the subframe when it reaches it's proper position. Or, forget about the pre-bend and drive in a straight tube. It will impart a certain amount of stress into the bend of the subframe, though, but may not matter. Thin wall 1/2 inch metal conduit is close to the right size.

Yes my right side brace is a little longer for extra strength. I also had to weld a tab further back on the subframe to accommodate the larger brace.

 

Did you find a thread by Redpillar? He beefed up his subframe too and worth a look.

 

I think the internal tube was used when the break was in a straight portion of the frame.