TPerkin2000 wrote:
If you got one of the new QR boxes (after waiting 4 months) then the sizing doesnt match the IA. I originally ordered a 54 Qbox for my 54 IA10 and it was way too big (too tall above the top tube and too long to fit between the wheel and the seattube. I re-ordered a 48/50 and that actually fits well to where its flush to the top tube, but the mounting for it is completely flunky. There is a recessed channel with some really thin plastic where you attach the bolts into the rear seat tube posts and I checked them after a day with just secure torque and the plastic is warping/derforming. I wouldnt trust this out on the road for 10 minutes with snapping off, so unfortunately I think this box is a no go for this bike.
This sounds identical to the mounting system for the old one. I also have the 48/50 one on my size 51 IA, and it is snug but just clears the tire. My experience is that the box is very secure, despite seeing a little warping. I did roughly four miles of accidental off-roading on my bike (washed-out road covered in crumbling asphalt and dirt, whoops) - and the box was fine.