DAG 2.2 uses the thumb screw to lock the pin into a fixed position in the bracket so you know the length it protrudes is consistent (the L-R of the bike or the inboard/outboard amount). The bracket itself is free to move up and down the box steel beam (ie closer to and further away from the axis of the bolt that fixes the gauge to the mech hanger). The idea is that for the entire measuring and aligning process you never loosen the thumb screw, so the pin always holds the exact same measurement - you're just moving the whole bracket up and down along the main beam to get it out of the way and then into an appropriate measuring position again.wheelsONfire wrote: ↑Fri Jun 09, 2023 7:30 pmOki, i got one of these copies (i guess). It looks identical to Park tools DAG 2.2.
If the tolerance is as good or not would be impossible to say. Using the alignment pin at 9, 12, 3 and 6, is pretty difficult to get the pin "exactly" at same distance at all 4 points. The longer the extension arm plus the fact that the arm is locked at the bolt (that goes in to the ears thread) and further next locking is the pin itself.
I have no idea how a more expensive tool would be better without actually testing one.
I used the valve (body) as a reference point instead of rim. I have noted that my hanger bends very easily after it have been bent at 2 occasions.
So you're supposed to lock the pin relative to the bracket to take an arbitrary first measurement - usually 6 o'clock and right at the base of the valve stem for me (but it really doesn't matter where you start or what point on the wheel you measure to as long as you keep the same point throughout). Then you slide the bracket-with-pin up towards the hanger so it's pointing at an empty space between spokes (say, ~5cm above the valve stem). Then rotate the wheel and gauge together to move both into the 9 o'clock position. Then slide the bracket-with-pin back out along the beam til it aligns with the base of the valve stem again and see if it makes contact, binds hard, or leaves a gap. Repeat for 12 o'clock.
3 o'clock is harder because in order to get into the rear triangle you have to remove the gauge from the mech hanger entirely and then re-install it (or loosen the thumb screw, move the pin, and lose your initial measurement). I usually don't bother with 3 o'clock and cheat that check a bit by making it more like 4:30 and/or 2 o'clock (just below the chainstay / just above the seat stay). I'm pretty sure this is what the updated DAG-3 solves - it adds a swivel to the pin-bracket so you can just swing the pin out of the way, making it parallel to the main beam, rotate the whole tool into place in the rear triangle, then swivel the pin bracket back to the 90 degree position without losing your measurement reference or unscrewing the gauge from the hanger. Also saves the hassle of constantly sliding the bracket up and down the beam to get it out of the way of the rim as you rotate. It's a very expensive tool though, so for those of us home mechanics that already have 2.2 it's probably not worth upgrading.
I'd guess even a knockoff will have all the main functionality of the 2.2. Hope that description helps - if not there's probably a youtube video somewhere that shows the process much clearer in far fewer words.
Or are you saying that on yours the thumb screw that locks the pin in place ALSO locks the bracket in a fixed position on the beam? I can see how that would make it cheaper to manufacture, but it would also make the tool kind of useless.