Comments about Park Tool DAG-2:

Had a bike mishap, crashed and bent up my derailleur. Could not shift in every gear smoothly afterwards. Derailleur didn't look bent? Got this tool and it worked great. Simple to use and did not take long to correct problem. Now I am able to shift fine, like a new bike! This is a must tool for the tool box!!!!

Comments about Park Tool DAG-2:

This thing will pay for itself the first time you use it. If you ding your derailleur off a rock, tree, curb, competing rider, small farm animal, etc.., this thing will straighten out your hanger and get you shifting again. Simple to use and is pretty much idiot proof.

Comments about Park Tool DAG-2:

I use this on every bike that I work on, whether I think it has a bent hanger or not. In most cases, there is some mis-alignment, and starting out by using this tool, you can head off a good deal of headaches later.

The operation of the tool is very simple...remove derailleur, replace wheel (and of course, clamp it in the dropouts) and screw in the gauge. As long as you check your work on 3 spots (I prefer the top, bottom, and left, since they are the easiest to reach on most bikes) you are almost guaranteed an aligned hanger.

My only gripe with the tool is that as a function of it's design, it needs to be able to rotate. The axle that the tool is designed around, however, has a good amount of play in it. While this does not make it impossible to use the tool, it makes it more difficult than it has to be.

Bottom line, if you maintain your own bikes, or work on others, this is a tool you have to have, and the one made by park works well enough that the price should be no obstacle.

Comments about Park Tool DAG-2:

As with Park tools in general, the DAG-2 does what it is designed to do quite well: allow the user to align a bent derailleur hanger. In order to do a proper job one is supposed to bend the hanger on the vertical and horizontal axes. It's probably not necessary to use those specific axes as long as the ones you do use are perpendicular to one another, but you have to eyeball the bar's position; there is no bubble level or angular measurement integrated into the tool, and using a separate protractor or level would be something of a pita given that you are trying to hold the bar motionless while adjusting the gauge rod measuring distance to the wheel. I found the process reasonably easy, but I do wonder, considering the precision of some modern derailleurs, if this system is accurate enough to yield good results with them. I used it for a bike with non-index shifting.
The bar gives enough leverage that it's easy to over-bend. The instructions take this into account when describing the alignment process, but, depending on how the bike is mounted on a stand, it can also make it easy to move the entire bike, requiring the user to find a clumsy handhold on the frame and try to do a precise one-handed bend. This is not a major criticism, just a practical problem to bear in mind when using the tool.
Bear in mind that you are bending, and therefore fatiguing, a bit of steel welded onto the frame. This does weaken it and make it easier to bend back out of shape. Enough of this and it will break off or become too weak, requiring a frame builder to replace the dropout.
All in all, this is a good tool which I think an integrated bubble level or protractor would improve.

Comments about Park Tool DAG-2:

If you haven't had your derailleur hanger checked you will never know how good your drive train should be!

Comments about Park Tool DAG-2:

I work on my friends and neighbors bikes, buy and sell a few too. I've 'straightened' a couple of hangers by eye, and gotten them closer to straight. After buying myself a newer high-end cx bike that looked to have a bent derailluer hanger, I finally decided to step up and get the right tool for the job, and bought the DAG-2. I've used it on about a dozen bikes since I got it 2 weeks ago, only 2 of those did not need hanger straightening. My neighbors 1 week old carbon fiber road bike ($1200 on sale) needed straightening, as did my friends high end East Coast cf road race bike -I think it's true that new bikes often have bent der. hangers.
It was easy to use the first time, - the directions are easy to follow. Now that I've used it a few times, it's super easy and really fast.

If you work on bikes, ride a lot, or have multiple bikes, (and like your derailluer to be straight) you need this tool.

Comments about Park Tool DAG-2:

This tool doesn't get the respect it deserves. I checked all my bikes (5) and found 4 of them to need adjustment. Not that shifting was bad, it just wasnt as good as I now realize it should be. The tool is very easy to understand in and of itself, however, it comes with instructions so that any level of mechanic can master the tool and its intended use quickly and easily. I cannot, honestly, think of anything negative to say of this tool. Park knows their stuff and this tool is a fine addition to any tool box.