Park ToolDAG-2 Derailleur Alignment Gauge(Return to Product Page)

Easy to use as long as you have a fairly true wheel to use as a reference point for your adjustments. My Evo has a fairly delicate derailleur hanger, probably so it bends before breaking carbon dropouts. So, it didn't take much effort to knock it out of whack or to put it straight. Probably should use it on my other bikes as it might clear up pestering shifting issues.

It's a very easy and intuitive to use tool that helped me realign the derailleur hanger in 5-10 minutes and it saved me time from a trip to the local bike shop.

This is an essential tool for a home mechanic. After a couple years and numerous random bumps I was surprised at how far out of alignment my derailleur hangers were on numerous bikes. You could have a bike shop check it for you, but if you do all your own maintenance (like me) this is an essential tool that you can't get good alignment without. It pays for itself immediately.

If you ride much, you will eventually want to use this. Even if it is just to check for peace of mind.

I hope you don't need this tool very often because it took me a week to just get over the worst of the injury of having crashed hard enough on the derailleur side to bend the hanger. Once you are back on your feet there is no replacement for this tool, any other method is guesswork and leads to crappy shifting. Just take your time when threading this into the hanger you are fixing, it is already bent and you don't want to make things worse by stripping the threads. Once you get past that this tool makes it easy to be ready to reinstall the derailleur (assuming it survived the crash) in just a matter of minutes. Not only did this tool save me some money not having to go to the shop, it saved me a lot of embarrassment about falling on wet leaves turning into my own driveway. Gad.