Commuting - Topeak Beam Rack compatability

The Topeak Beam rack system is an alphabet soup nightmare.
1. The RX rack is a lightweight road bike beam rack with the MTX rack is more beefy and support 20 vs 15 lbs.
2. RX BAGS will fit on MTX rack tracks but somehow for safety Topeak has not made MTX bags compatible with RX racks. (they figure the bags are bigger and you will overload the rack)

3. My question: Does anyone know HOW they keep the MTX bags from fitting on the RX rack, and is their compatability restriction beatable by some sort of way? The track is obvioulsly the same since the RX bags fit on the MTX rack track.....anyone??????

The MTX bags are much longer than the RX bags.

I think there are some nubs on the MTX bags that are not on the RX bags that force them to be used on the MTX racks only. If you wanted to, I think you could file them off.

I made this mistake. I have an RX rack and an MTX bag (or visa versa - still not sure). The rails/tracks are different widths apart so I have to use the Velcro straps to fasten the bag to the rack instead of using the quick release on the bag.. It works, just not as quick and easy.

I'm not sure how the track it rides on can be a different width if RX bags fit on MTX racks?!

Does anyone else have any experience with these "nubs"?
I don't think the length should be an issue...

The MTX has a thicker bar so it will not slide into the RX track. The RX will slide into the MTX but it will not rest on the bottom of the beam rack. There are no nubs and it you were to file, you would be filing the entire length of the track that is on your bag or basket. You can get a replacement "fixer 6" for the quick track system but that too is only for the MTX.

I have a Topeak Explorer rack and use a Topeak MTX rear basket to pick up groceries and to hold schtuff when running various errands around the neighborhood. They work great together!

Unless you have rear suspension go with the Explorer rack. In most instance its will sit the load lower improving handling. I have done some light trails on mine and other then the track on the bag rattling on the bumps I really don't notice the weight. I have heard others complain that the beam racks you can feel that weight swinging around especcialy the ones that come straight off the seat tube.

Its also less expensive and will not need the pannier add on brackets most of the beam racks require if you want to use pannier bags. The MTX bags are about 3 inches longer and while that doesn't sound like much, it is. I was worried my EXP was going to be too big and I find it is just the right size for commuting. I can get my lunch, cell, eyeglasses case, head light, lock and cable and monster key ring for my office in there with a small towel and a dry shirt all of that fits in the main compartment other then the light and lock stuff. Those are in the Pannier pouches when closed so they still have storage use without the panniers being deployed. The panniers let me handle the "will you pick "X" up on the way home" calls from the wife.

I want to get the basket at some point for bigger grocery runs and I would be hesitant to put 20lb out on one of the beams.

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