Originally Posted by
shauramo
Thanks! I took the "lower load capacity due to QR use" as given from qr adapter description by manufacturer (not sure if was for tubus). I personally thought that the QR wouldn't be the problem, if there were no braze or p-clip type clamps, but the seatpost collar use.
Just to be clear, while the QR as an attachment point might be incredibly strong, that doesn't mean that a particular manufacturer's QR rack is as strong as the eyelet design. Many QR racks use a pretty long lever arm to move the rack back for heel clearance, and that might be an issue for heavier loads.
So while I would trust the dropout mounting point, I would be inclined to take the advice of the rack company about their product's capacity.
I have also seen QR mounts that didn't look like they were providing enough overlap with the QR head, possibly causing the QR to bend as it is tightened down (Axiom Streamliner). Unlike a bolt, the head of the QR is mostly hollow and really just engages along the edge. If that's what's happening it is bad news.
And if you are going to use P-clamps, don't use electrical or any other adhesive tape under them. The adhesive tends to act as a lube under clamping pressure and makes the clamp creep. Thin, rubbery plastic is ideal.