The 7 Best Derailleur Hanger Alignment Gauges

Editor's Notes

September 09, 2020:

It was a fairly straightforward round of updates, with most of our previous selections maintaining their spots. We did, however, replace the Unior 1602/2 with the Unior Genie 1602/5 – a collapsible model that’s said to have tighter tolerances than its predecessor – and switched out the Park Tool DAG-2 for the Park Tool DAG-2.2 — which features a design with improved clearance, allowing it to accommodate thru-axle derailleur hangers. And, in an effort to expand our rankings, we also included the Coherny Professional on our list — a budget-friendly model that many hobbyists will find serviceable, although it may not work with some small tires, as found on BMX bikes and children's bikes.

Beyond that, there isn’t much for us to say here that we haven’t already touched on in our July 11, 2019 editor’s note for this page. While accuracy, durability and weight are all important considerations in this category, with our top-end models costing as much as seven times more than budget picks, price is likely going to be the biggest driver in most user's purchase decision, here. While The Shimano TL-RD11 and Abbey Bike Tools HAG remain excellent options for gearheads and those with big budgets, the Park Tool DAG-2.2 is the model we recommend for most, as it seems to present the best balance of affordability and quality.

If that still lands outside your price range, more low-cost options from lesser-known brands are beginning to pop up in this category, which was looking quite sparse just last year, and they may be worth investigating. However, with few reviews available, we decided to hang tight before adding any to our list this time around, with the exception of the Coherny Professional, which many users seem to find agreeable.

July 11, 2019:

For a bicyclist, sluggish gear shifting can be the result of several problems, including poor limit setting, chain lubrication or cable tension. In fact, and especially in the case of rookie cyclists, your problem could be something as simple as human error. However, there is one common issue that you might have trouble diagnosing without the proper tool: a bent derailleur hanger.

In the case of most well-made bicycles these days, your rear derailleur – that’s the device hanging off your horse that’s responsible for doing most the heavy lifting, changing gears for you – bolts onto a derailleur hanger. The derailleur hanger, in turn, is bolted onto your bike frame. Typically made of soft aluminum, derailleur hangers are frail by design – intended as a deliberate weakest link, and meant to sacrificially bend in case of a collision. The idea being is that the hanger will bend in lieu of your bike frame, leaving you to replace an inexpensive part instead of a costly frame.

The problem with pliable hardware like this is its potential for nuisance bending, caused by impact as negligible as another bike leaning up against yours. Even a small bump can cause a deviation in the parallelism between your bike’s cassette and derailleur. Some bike mechanics have reported that brand new bikes routinely arrive from manufacturers with their derailleurs out of alignment. All this goes to say that, with several inexpensive options available on the market, a derailleur hanger alignment gauge is a smart acquisition for cyclists of all skill levels.

Essentially, the tool works by the user setting their bike up (ideally on a repair stand), then removing their rear derailleur from its hangers and installing the tool's mounting bolt in its place. From there, the mounting bolt acts as a fixed pivot point and, assuming that your tire's true, allows you to test for inconsistencies in distance from the tool to various points along the tire. If a variance is detected, the tool can act as a pry bar, allowing the user to gently bend the hanger back into place.

A few things to keep an eye out for while you’re shopping:

Is this a tool for your workshop/garage, or will it live in your panniers/backpack? If your answer leans toward the latter option, you might want to consider investing in a tool with a compact design. Both the Shimano TL-RD11 and the Abbey Bike Tools HAG are options that offer a combination of professional performance and prime portability – through telescopic bodies and the ability to store the device’s measuring arm inside its main shaft. These offerings are also well-suited as on-the-road gear by their impressively light design – weighing 1.1 pounds and 1.5 pounds respectively.

Is your tool going to work on your bike? Although it appears that many of the tools ranked on this page are compatible with most modern bicycles, frame clearance can still be an issue when working on some bikes, especially those with thru axles. New designs have started to account for this deficiency by including narrower mounting bolts. Examples of these new designs include, but are not limited to, the Unior 1602/2 and the Park Tool DAG 2 – which just included a narrower profile on the mounting bolt of its latest edition.

How accurate do you need this tool to be? While the consensus seems to be that a variable of less than four millimeters (measured at any two points along your rim) should be sufficient to warrant acceptable shifting, some of these offerings are engineered for much greater accuracy. Abbey Bike Tools is one company that’s not afraid to advertise the precise measuring power of their HAG. As we are playing a game of millimeters when it comes to these tools, any amount of lateral play should be considered detrimental to its accuracy. So, while a bit of tolerance in this respect will afford you the option of purchasing one of the lower-priced offerings in this category, if you’re the sort of person who needs to have the best of everything, this might be one of those situations where you need to be prepared to get what you pay for, or pay for what you want.

Beyond that, I’d say make sure you keep an eye on warranties in this category, especially if you’re thinking of shelling out for one of the pricier options – many of these companies appear to be quite proud of what they do, and offer lifetime warranties to the original purchasers of their products – absolving you from reinvesting in a replacement tool down the road, and freeing your finances up to be invested in something better (maybe a new bike computer?). And, last but not least, while this recommendation certainly doesn’t discount your need for this tool, let me gently suggest that you also look into investing in a backup derailleur hanger. It’s a cheap part, and it can be tough to find one that’s compatible with your frame, so don’t wait until it’s too late, order one up right now. Even with your new alignment gauge in tote, it can’t hurt to keep an extra hanger on hand, as they are prone to breaking – especially after they’ve been bent back into shape a few times.

Don’t forget your helmet and gloves when you hit the trail/road, and happy cycling!