Assessing bent derailleur hanger?
 

visually, my hanger appear very slightly bent. I am considering removing it and testing with a straight edge but then I wondered;

1. are hangers always manufactured perfectly straight?
2. is ANY amount of bend acceptable?
3. is it acceptable to attempt to straighten it with a hammer on an anvil?

1. No
2. Maybe
3. No
Adjust hanger while mounted on the bike. Use the Hanger Alignment Tool. Ust the correct tool for this job.

Use a proper hanger or derailleur alignment gauge pick a spot on the wheel like the valve hole and use that to straighten it if you know what you are doing, otherwise just have a shop do it. The correct tool is not necessarily a cheap tool and the job is one you want to do with accuracy and some knowledge on the topic to not make it worse.

I would not recommend the just bang on it or bend it with other tools "method" as I am sure some one will suggest because it worked for them. Just do it right and then not have to worry.

You can't test a hanger for correct alignment with it off the bike.
The process of aligning the hanger on the bike, places bends in it that are customized to your frame.
Even if you were to purchase a brand new hanger, these custom bends will be required to align it for use on your frame.

Hope that helps

Barry

If you don't have the tool you can check the alignment by removing the deer. and screwing in a spare or borrowed rear wheel. They are both 10X1 mm. If the wheels are parallel, there is no problem., If not use the spare wheel to realign the hanger Once. Aluminum doesn't take to a lot of rebending..

What brand & model alignment tool do you guys recommend?

Mostly not, unless your frame has an alignment issue.

Then my Cervelo R3 has a significant alignment issue.

Barry

Then take your frame to someone who has the tools to check alignment and make whatever correction the frame may or may not need.

...if you are going to use it a lot (like professionally), this might matter. But they all work about the same, so for home use, get something that's cheaper.
For some reason, this is one of the tools that has spawned all sorts of high end, beautiful tool versions. They don't do a significantly better job than the cheaper ones, if used properly.

Here's one for 25 bucks.

Here are my top choices:
Abbey HAG (I own this personally)
EVT Tru-Arc
Park DAG-3
Shimano RD-TL11
Park DAG-2.2
Wolf Tooth Pack Hanger Alignment Tool (portable)

Yes some of these tools are maybe initially expensive but a precision tool that lasts a long time and does the job well is well worth it. You will not regret spending money on high quality tools you will regret having to buy cheap tools over and over again and potentially doing damage to different parts on your bike.

Make sure you read the instructions well or watch some videos on the tool you end up with. Having this tool and knowing how to use it is helpful but if you don't want to do it your local shop can do it but having the tools and knowledge is pretty awesome.

If the hanger is bent BADLY, then smacking it with a hammer while off the frame is a way to Temporarily straighten it out and make it usable.. BUT it May Crack and it WILL BE WEAKER...trying to straighten a badly bent hanger ON the Frame MAY ALSO BEND THE FRAME.

note any offset or cutout portions of the hanger and take steps to not mess up those areas.... and i advise only hitting the outside of the hanger,not the inner side. and avoid hitting any Threaded Holes to limit damage to those threads.

THEN ORDER A NEW HANGER. Once they bend, they get WEAK and WILL BEND or BREAK easily after "straightening"

You don't say if there is a problem with the shifting. If the bike shifts correctly through the gears there is no need to mess with the hanger. Otherwise, as others have said, you need the correct tool to align it.

Hammer, yes, yes, always, and please post video.

A HAG is the right tool, but if you don't have one, an old school front wheel will work. You can take the hanger off, and check it on a flat surface, but its the combination of the hanger and the dropout when attached that is important, so make sure it's secured properly on the frame, and then align when mounted. An adjustable wrench will work also. If you aren't very experienced, (and even if you are) having a spare is never a bad idea. You want to determine where you want to end up, and make one adjustment there, you don't want to make a bunch of little adjustments.

Except the fact that a Bent Der. hanger causes more rapid wear on derailleur rollers, Der. cages, Sprockets, and the chain.... :innocent:

It can do that without affecting shifting at all? :innocent:

Using a DAG (not "HAG") involves a series of "Little adjustments", and checking those adjustments in a vertical alignment with the wheel, then doing the same in a horizontal plane, then re-checking the vertical align, and then re-checking the horizontal align..... and then i do one last verification check of both alignments.... :thumb:

people have different levels of "affecting"... and will often ignore what you or i may call a "problem."

example: Eliminating sluggish and variable shifts from the rear of a Box store bike is nearly impossible, but millions of them roll around not shifting correctly by our standards... the owners never know the difference until they buy an upgraded der. or a better bike.

another example: a twisted hanger can and does cause advanced wear, but the bike may still "shift" fine...

and another: the hanger was bent, so the owner grabbed the der and bent it back to roughly vertical... it was out in two more planes... still bent, but back in position enough to allow sluggish and variable shifting,which the owner is ok with, but you or i would not be satisfied with.

Sure, standards vary. I was just trying to think of a time when a bent derailleur hanger didn't manifest as some obvious symptom, like: indexing works better/worse in one chainring vs another, shifts are sluggish, RD wants to ding the spokes in the big cog, or just unusual amount of noise. Unless I was setting up a friction-shifting bike, I'd expect one of those alignment gauges to confirm and quantify something I'd already noticed.

operative words in your reply .. "I" and "I'd"

look at things from other possible perspectives.

Obviously we are all an "I". Tangents are fun, but the OP has not offered any evidence that his RD hanger is actually bent. For all we know, his eyes are just fooling him. So I propose getting out of the weeds and discussing symptoms first.

he also has Moved ON.. you should too. you've now advanced to insulting the eyesight and intelligence of the OP.

bye bye.

also see: the thread opening post... "Slight bend"

LOL, what a stretch! Anyone can make mistakes eyeballing these things, no offense was intended. If OP said he was done, I missed it.

Feel free to put me on ignore if it helps keep your blood pressure down. :)

and to anyone saying a Der. Hanger should not be pounded on.. MOST Der. hangers are made in a stamp mill.... under thousands of pounds of POUNDING and SHEARING force
and "checking with a ruler" is a great way to check them for a "slight bend".

next time, you "experts" should advise doing the ruler check on the inner side since it was the downside during STAMP FORGING and is one of the Reference Surfaces during the MACHINING step of the processes involved in making a Der. hanger.

to thermonicscott.. now you're building a strawman. I hope you defeat your imaginary opponent! :D
i'm going riding now... a fast downhill awaits my attention... the comencal is aired up and ready to fly.