It's probably tough to make a call form the pics but derailleur cage is angled inward at the bottom toward the tire. This is an older STX 8 speed, and it's riding rough through the outer sprockets. I'm thinking the derailleur should be perfectly vertical, and this hangar is bent. Contemplating the the best way to bend it back out. Wanted to get a few affirmations before I started bending though. Also, any ingenious methods for straightening would be appreciated as well.

Thanks

It looks bent. I use this tool. Your best bet is too take the hanger off and, using a vice and an adjustable wrench, bend the hanger carefully back to as straight as you can get it. Conversely, you can probably just buy a new hanger. What bike and year is it?

There is an actual appropriate tool for that: https://www.parktool.com/product/dera...nt-gauge-dag-2 .

When I have had this problem, I've used the tool at the local bicycle cooperative. If you don't have this option consider buying the tool or having a shop do it: the accurate alignment of the hanger is fairly important for accurate shifting.

If you really have to effect a ghetto repair don't yank on the derailleur itself. https://www.utahmountainbiking.com/fix/rhanger.htm is a search result I found. I've also heard of straightening with a hex key in the rear derailleur attachment bolt for emergency roadside repair.

Take a 6-pack to the local bike shop and they probably won't charge you to either let you use the proper tool or to do it for you.

That's about a $15.00 or $20.00 for a shop.

On a 7 or 8 speed I can usually align it adequately by eye to get the shifting to index correctly. 9-speed cassettes and above are spaced so closely that I need the proper gauge to set the alignment. I clamp a big crescent wrench over the derailleur. It's good to keep something screwed into the derailleur mounting hole to keep from ovalizing the hole.

You can buy an expensive tool, or pay a bike shop to do it, or you can DIY it in 30 seconds flat.

Stick a 6mm hex key into the upper pivot bolt, and bring it back into line by eye. The upper pivot bolt is strong enough to do the job, and will take the hanger with it the same way the tool does. Of course you won't get the precision that you could get with the tools gauge feature, but for an older 8s bike it's good enough for government work.

Looks like a steel frame, which can handle a bit of re-bending when needed.

I'm also thinking that my derailleur hanger might be slightly bent, and have been contemplating purchasing the Park tool...but nearly $60 for a tool that is very seldom used is not easy to justify.

A couple months ago my commuter (Trek FX 7.5 - 9sp) fell over on it's right side. Ever since, my shifts haven't been as smooth, and I can't use the second-to-largest rear cog, as the chain is constantly trying to jump off of it - especially on hill climbs. I've adjusted the cable tension / barrel nuts with no success. All other gears work fine, the chain just won't stay on the second-to-largest cog.

besides the 6mm allen that FB mentions i'll often add a slot blade screw driver wedged behind the hanger and the cassette/freewheel. Adds leverage without as much distortion to the der's mounting bolt's allen's fitting. Andy.

If the hanger is bent directly inward, that is with no twist, and there is not deraillsur damage then an eyeball straigtening is generally enough. I know from experience that's not always true, however. Sometimes the deraiilleur is twisted, and sometimes the dropout bend is not simple.

After a trip to Italy I was plaquedy by inconsistent shifting - some gears fine, others lousy and phantom shifts. I was unable to resolve it until I borrowed a dropout alignment tool. I found the hanger was bent in more than one plane, and once corrected I had no further problems. As a mechanic with 20 years experience,including a lot of both frame and drive train alignment I would advise you that if your attempt to resolve the problem fails take it to a good shop.

One of my coworkers at the shop would slide a threaded headset wrench (one of those flat, laser-cut Park tool dealies 30/32mm) behind the derailer hanger and use it to bend the hanger out. The one time I saw him do it, I checked his work with the Park DAG-2 afterwards and it was spot on. I was impressed.

I'm going to DIY it. Now I have a bunch of methods to choose from. I'll post with results.

Thanks all

I usually bend it back while ordering a new hanger, they are not that expensive.

Even a brand new hanger doesn't guaranty perfect alignment, so one way or the other you need to square them up.

I just stuck an Allen wrench in the pivot bolt and pulled it out. Thanks FBinNY!

Shifting is pretty good now, but not perfect. I'm noticing that the chain either runs rough (catches the next sprocket a little) at the top of the cog or the bottom depending on how I fine tune the cable tension. Aligned at the top, and I'm a little off at the bottom; aligned at the bottom, and I'm a little off at the top. I'm not sure if this has anything to do with the bent hangar though.

Odds are the alignment still isn't perfect. Here's a way you can fairly accurately verify vertical hanger alignment, though not twist. You'll need a small plumb line (weight on a string). Use the plumb to get the bike exactly vertical against the wall. Then shift to a gear where the RD cage is vertical. If all is right the upper loop will be directly above the lower since the sprocket and both pulleys are all in line. Check by placing the plumb line just touching the top loop of the chain just forward of the cassette. The lower loop should just kiss the line. A gap, or if it's leaning on the lower loop mean the hanger is bent out or in respectively.

As I said, twist is harder to detect, but you can get a pretty good idea by looking at the angle the chain meets the lower pulley in various gears. It will come from the outside in low gears, and the inside in low gears, and straight on in middle gears.

Personally I might use an allan key as an emergency repair, but I'd still use a professional alignment tool on it ASAP. The correct tool will easily detect a difference as small as 5mm from one side of the rim to another in any direction. That translates to an offset of less than 1/2 degree. My eyes are pretty good but not that good.

If you don't have the tool you can use a spare rear wheel to take the tools place. The rear axle uses the same size threads as the der. bolt. Remove the der. and replace it with the spare rear wheel. Use it as a lever to align both wheels and the repair is complete.

davidad is sometimes correct. Many Asian made wheels use the 10mx1tpm that most hangers use. And the 10mmx26tpi axles will still thread in and serve as a lever well enough. But those who have 3/8" (9.5mm) axles might want to think about this method. Espically with an Alu. hanger the loose fit could cause thread damage. Andy.

I disagree with eyeballung it. U need to be accurate.