You are a bike mechanic. Whether or not you’ve ever thought of it that way, you possess skills that most people don’t. Maybe you think those skills start and end with changing a tire, but I disagree. You know the angle your brake levers should be at, and how to get them there. You know how your saddle clamps to your seat post and how to adjust it. You at least know your left pedal is reverse thread. From my years of being a professional
bike mechanic I can tell you that this makes you more qualified to fix a bike than most of the human population. And if you’re reading this article, it means you probably know what a derailleur-hanger alignment gauge is, and that fact alone rockets you well into the top 1%.
But very few of us own one. The hanger gauge is the sort of thing most of us let bike shops worry about. They’re bulky, they’re rarely used, and most notably, they’re expensive. The benchmark is the Park Tools DAG-2.2, and it’s $80. For a tool that you might go a year or more without needing, that’s a lot of cash to have hanging on the pegboard, if you even have
pegboard. But when you need a hanger gauge, you need it. So, what about a cheap one? How bad could they be? Well, that’s exactly what we’re going to find out.Coherny Professional Bicycles Hanger Alignment Gauge Alignment Ranging Tool for MTB and Road Bikes: $39.99
Yes, that’s literally what this thing is called on Amazon. But it’s not the only one. There are look-alikes out there from “SYCOOVEN” (yes, all caps) or one on AliExpress that’s just called “AG 2.0,” which is even a few bucks cheaper than my trusty Coherny.
The first thing I noticed about this tool is how well put together it feels. It’s entirely lathe-spun aluminum, and it’s oddly satisfying to slide the two telescoping elements in and out. It ‘s hard to tell scale in a photo, but it is not undersized or flimsy-feeling. It’s also significantly lighter than the Park DAG-2.2, and far more compact. Not that this is the sort of tool you’d pack on a trip to Whistler, but it wouldn’t be a bad luxury item to take on a road trip. It even can be quickly broken down to three narrow parts and would fit in a small toolbox.
Having used the very differently configured Park DAG-2.2 during my near 20 years of shop life, I was surprised how familiar it was to use the Coherny. I had expected the telescoping motion to be a problem, in that it would be loose or sloppy, but there’s actually a bit of smooth resistance that steadies the outer end at a constant distance from the axis so you can follow the rim. In fact, it was a little smoother than sliding the probe of the Park DAG-2.2 up and down its arm. Similarly, sliding the probe in and out on the Coherney was also easier because it is held in place by a tight plastic bushing, whereas the DAG-2.2 relies on a thumb screw that is best tightened and loosened every time the probe is slid in and out.
But on the other end, the “axle” that threads into the hanger, there is a considerable amount of play. You can’t tell when it is off the bike, but magnified by the length of the tool, there is about 17 millimeters of wobble, and it makes getting an accurate reading a little more difficult. I needed to set the probe to hit the rim at one end of that wobble and go from there, putting some pressure on the tool as I did my rounds looking for the direction of the bend.
I didn’t sense any further inconsistency in the rate of wobble as I went around, and this method did get me a straight hanger after checking it against the more robust DAG-2.2. It is imperfect, clumsy, and requires the extra step of flexing it towards the rim to actually know the shape of the hanger, but I have to admit that it’s better than eyeballing it.Park DAG-2.2 $83.95
Your local bike shop probably has a couple of these above its workbench. We often forget that Park is not the only dedicated bike tool brand out there, but they are the biggest and most popular. While there are several fancier gauges on the market (the $185 Abbey Bike Tools gauge is an absolute treat to use, and Park has a new DAG-3 for $120), the DAG-2.2 offers the most bang for the buck.
Part of that is its simplicity, albeit simplicity that might make you question the $84. But like the vast majority of Park Tools, the DAG-2.2 is made at Park’s headquarters in St. Paul, Minnesota. And as I learned using the apparently not-so-dialed Coherney alignment gauge, it’s not easy to do this right.
The axle assembly is what makes the DAG-2.2 stand out. It’s the heaviest part of this already heavy tool. The thick steel around the axle is meant to survive years of professional use, and the occasional professional fall to the shop floor. It also is designed not to stretch, flex or deflect under load. The Coherney tool seemed tight as a drum until the force was magnified by a 14-inch lever. The DAG-2-2 that I tested, which I’ve had for two years, had barely two millimeters of play compared to 15 on the Coherney.
The probe on the DAG-2.2 is probably the only slightly frustrating bit. If it were held in place with constant friction like the Coherney or that Abbey tool I once had the pleasure of using, it would make one rather frequent action in the process of hanger alignment a lot easier. Hanger straightening needs to be done slowly, especially in the era of thru-axles, when hangers are far stronger and take far more force to straighten. It’s done in small steps, so the probe needs to be re-positioned a couple times during the process. But as we established already, this is a tool that most of us won’t use that often. A few seconds of fiddling is worth the accuracy if you want it done right.The Verdict
As for which of these two tools is the right choice for a de facto bike mechanic like yourself, I really have to say it’s worth it to pony up for the Park. Although a cheap gauge eventually did get me good results, I had to put a lot of thought into it on the way. And that’s coming from someone who worked in bike shops for nearly two decades, using a hanger gauge several times a week. For the vast majority of us who will not be using it often, a tool that gives accurate, reliable results will make a crucial task (which is as crucial as ever in the era of 12 speeds and 52-tooth cogs) far easier and more repeatable. It’s worth it.
If you’re a pro and working at a shop, the first thing you should do if there are shifting complaints is a hanger check, it’s probably top-ten for most used tools at my bench.
For better than 2 decades I wondered what it was and how could I get one.
It always bothered me that the wheel was used as the basis for adjusting a deraileur.
I googled TL-RD10 and low and behold, there it was. So thank you.
Someone somewhere should make a centering gauge to fit modern dropouts.
For those of you who have no idea what I am talking about... manualzz.com/doc/53871177/shimano-tl-rd10-service-instructions
Either way, as socratease said, and as you've learned from experience (the best way!), it's good practice to check any hanger after installation, regardless of whether it's new or not.
Only downside would be the chubby head on rare occasions doesn't have enough space to move / bend the hanger into shape. I've adjusted a couple 1000's hangers with this tool and it's like new..
Also, it true a lot of new hangers can require a little tweak to get them right out of the box, but usually what you find is the dropout is slightly misaligned and the hanger is attached to a frame that isn’t completely straight. Unless it’s a steel frame, you’re not aligning dropouts. However if a new hanger isn’t straight it’s worth your time to put dropout gauges in the frame and visually check the frame.
The three bikes I’ve bought in the past two years all needing hanger alignment from the get go. So yes.
I use the dag 3 or more times a year. I think it is necessary tool
Drilled out square tube
11 mm bolt
Few 11mm nuts
Under $20 and have a nice ghetto derailleur hanger gauge tool that works as good as these
Not surprising given year-round PNW riding. Bikes get tossed. Fact if life. And ha gers get bent. Not often - but often enough.
The cool thing is - it bolts right on, adjustment is really straight-forward (fiddly, but clear & easy), and it's more than beefy enough to make the bend, when a bend is necessary - over & over & over again. Like all my Park branded tools. Great value, and works.
Frankly I might be pressed to purchase a less expensive tool, if I was absolutely sold that it woud work as easily, have my back, and go the distance. And I din't already have my trusty dusty DAG. I mean..., all you really need from a.practical standpoint, is massively improved. Right?
Another 40 bucks? I spend that on beer, in one evening out with my friends on an evening. So there's that, eh? $40 ain't breaking my bank, as meager as it is. And t's a WAY better investment on a sure thing.
It has nothing to do with a perfectly true wheel. Flat spots welcome too.
@noapathy: where you going with this
Most new hangers I’ve installed were crooked out of the packaging, most brand new frames also show up with bent hangers.
If you don't have any friends in any shops, should you be doing any of this biking thing?
And also, if many of you ride as much as you say you do, you're not looking at the hanger just once a year. If you're only looking at it once a year, should you be doing any of this biking thing?
@barp I was talking specifically of those tools you only might need once in forever, like in this case.. I would definitely not recommend using tools at shops for free for most other resons! I have most things at home, except a few tool that don’t make the cut due to price vs realistic amoun of time I’ll spend using it. This definitely is in that group as I’ve had to use it twice in a decade, and I was working at a shop myself when it happened lol
Join Pinkbike Login