Bent hanger... or bent derailleur?

[ayjay]

Hello all!
First post, bit of a lurker.

I recently bought a second hand hybrid for next to nothing and am finding this has its rewards and problems.

This is the issue... the rear gears shift from small to large cog wonderfully, but down the other way is guesswork. It misses cogs out or shifts one gear out of sync then shifts two with the last shift. After a bit of research here I checked the shifter (all ok), the cogs, the chain, none of which seem worn.

However once I came across the bent hanger possibility I thought I'd check the derailleur visually against the one on my perfectly fine no-issues mountain bike. The hybrid swings noticably outward towards the bottom of the derailleur rather than slightly inward as my mountain bike does. Though looking at these photos, I'm wondering if it's the derailleur itself that's bent?

Is there an easy way for me to check this without splashing out unnecessarily on hanger alignment tools?

The derailleur hanger is a shimano megarange job, whereas the mountain bike is a shimano alivio.

I've attached the photos.
Al

The mtb
[attachment=2324]

The hybrid (problem child )
[attachment=2325]

[cyclerUK]

Your local bike shop should have a tool and should only be a couple of dollars for them to check and adjust.
Probably not worth buying the tool as you say.
Besides looking from the rear of the bike, also look down from above.
The derailleur should be parallel to the sprockets.
I suppose you could bolt a piece of straight bar to the hanger and take some measurements from the rim.
Pull and tug on the derailleur to see if there is any wear on the pivots etc. Check that the hanger securing screws are tight as well.
I have "straightened" hangers using an adjustable spanner. Gently does it though.

[ayjay]

Thanks for the reply. I'll have a chat with the local bike shop. Thing is I took it in there not so long ago to get the gears adjusted. They replaced a worn cable and dialed the gears in, but as I rode on and things bedded in it became clear after only about 15 miles that I still have shifting issues.

They were minor issues til a certain person (cough) was stupid enough to bounce it down the road. It had its vengeance by sitting on me so we're on speaking terms. Naturally enough I've dialed the gears back to how they were thanks to the videos on this site, but not smoothly shifting to the smaller cogs is proving rocky in traffic.

[dave_sd]

It's probably the hanger. You don't need the official tool to straighten the hanger...a 5 mm hex wrench will work in a pinch. Put the long end into the bolt head like you are going to remove the derailleur, and start very gently bending it to straighten it out. The hanger is replaceable if you break it.

I bought the park tool because I mountain bike a lot and didn't want to go to the shop every time I bent the hanger.

[JohnV]

Why is it that mostly all the MTB and medium priced bikes (my hybrid included) have removable hangers but most of the medium to high end road bikes (including mine) don't? It can't be because of the weight of the hanger adding to the weight of the bike. I just hope my rear derailleur on my road bike doesn't get bent in the event of a crash.


Update: My bad! After looking at it much, much closer, the two small screws that hold the hanger were covered up by the slightly oversized skewer cap. It didn't help that the hanger was painted the same color as my dropouts (black) and is such a tight fit, that the seams were almost invisible. Lesson learned: look before you post.

[cyclerUK]

Usually only steel bikes have integral hangers. Most other frames, Ali, Carbon, Ti have replaceable ones. Problem is there are so many types that to get a replacement could be tiresome.
http://www.sjscycles.co.uk/page/find/?name=gear%20hanger&page=1#page=3

[ayjay]

Cheers for the reply. Seeing how this bike cost so little I did a little adjusting using the wrench as suggested. To start with it seemed better but having dialled the gears in again and gone for a ride, it felt pretty much the same as before. At least it is now responsive when going into the wrong gear.

Had another look at the rear cassette and spotted something I hadn't before. It doesn't seem to be worn evenly which I'm guessing is a result of years of the rear wheel not being entirely true? Anyway take a look at how the teeth are pointing in erratic directions! The tooth in the middle of this photo (3rd smallest cog) is pointing towards the top of the shot whereas the one to it's left isn't. This probably isn't helping things.

[attachment=2331]

[dave_sd]

The gear teeth have different profiles by design to aide in shifting (not saying that yours aren't messed up like you suggest). Try a new cassette. there could also be a lot of friction in the cable housing which could cause what you're describing, so you could also try a new cable and housing.

[RobAR]

Hey ayjay! I honestly do not see ANYthing wrong with the tooth profiles in the last pic of the cogs. As Dave stated, they're designed that way to assist in ease of shifting for indexed systems.
What has me concerned is that, in your 2nd post, you said that the LBS replaced a bad cable. Did they also replace the housing?

What you describe - shifting from small to larger cogs is fine but, coming back down is sporadic - is very indicative of a housing problem. Either Dirty, excessively Worn, or a section too Short. Something is causing a bind that your drlr spring can not easily overpower.

Also, I would say that (by looking at the pic of the drlr on the hybrid) it looks as if the hanger is okay but, the cage (with the 2 pulleys in it) is most definately not aligned correctly. It's way too far outboard. Looks as though it was bent at the lower main pivot. That could compound the cable housing problem.

[ayjay]

Thanks again for the replies guys.
I don't recall if the housing was replaced or not but I'll check that when I'm back from my hols (away for a week ). If it was replaced is it something that would ordinarily be lubricated in some way or is it left dry?

[dave_sd]

Brand new cable housings should be left dry since the inner plastic lining hasn't been chewed up by a cable yet. It's wise to eventually drip some tri-flow into the housings to keep things sliding smoothly.

[Joe_W]

Oh, and it could be not only the cable / housing but also the spring in the rear dérailleur. After a while it will be worn (weak, soft, un-spring-y, whatever is the correct phrase) and will not have enough strength to pull the RD to the small sprockets. Had that on several bikes, spent, dunno, EUR 15 each and now it works like a charm. Will have to do it on the next bike soon...

[ayjay]

(05-11-2011, 05:36 AM)Joe_W Wrote:  Oh, and it could be not only the cable / housing but also the spring in the rear dérailleur. After a while it will be worn (weak, soft, un-spring-y, whatever is the correct phrase) and will not have enough strength to pull the RD to the small sprockets. Had that on several bikes, spent, dunno, EUR 15 each and now it works like a charm. Will have to do it on the next bike soon...

Interesting suggestion Joe, what kind of age have those bikes been?
I kinda have a vendetta against this derailleur now I must admit! Just change freaking gear! I recently rode my mtb around having got really annoyed trying to sort out the gears on the hybrid. Changes like a dream in comparison. Utterly smooth. Just a stupidly heavy bike to be riding up tarmac hills!

[Joe_W]

About 20 years old, but they had not been ridden (much) for a while and the problems did start earlier (I think, I didn't know too much about bikes back then).

Looking at the pictures again: Maybe take a look at the B-tension screw? It is hard to tell, but I think the upper pulley is quite far away from the sprockets (though this does depend on the gear you are in etc.)

[ayjay]

Being a weird derailleur it has no B-tension screw, only the high and low ones plus the normal adjuster at the end of the cable. I came to the same conclusion as yourself there and actually held the pulley closer to the sprockets whilst the chain was running round trying to shift down a gear. As it got nearer it shifted, seemed to behave a bit, then slowly moved back to where it was.

[Joe_W]

What is the marked screw? Isn't that what you'd be looking for? (I hope the pic is uploaded correctly... not sure, is not displayed in the preview...)

[ayjay]

wrong bike That's the mtb.
Oh and an update: The cable housing was indeed replaced at both ends.
Moving the derailleur about by hand and letting go seems to result in it resting in a slightly different location each time. I'm beginning to wonder if replacing the whole of the rear derailleur makes sense.
The modern equivalent seems to be this one which does have the tension screw:
http://www.discountbicycles.co.uk/biz/product.php/4816/4517/shimano_tourney_rdtx71_6_7_speed_rear_derailleur_pin

[mrdunk]

im not sure where in the world you are but if you decide to get a new rear derailleur check this link out you might save a few bob
http://www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_503755_langId_-1_categoryId_165694#dtab

[ayjay]

Cheers MrDunk! I am in the UK as it happens. However, weirdly enough Amazon sell the same derailleur for 2 pounds less. At a tenner including delivery, plus a few more quid for a chain tool (kinda helps to take out the chain really ) it's a bit of a steal and worth a go. At the same time I'll hunt down a few other bits and bobs.

[mrdunk]

if you go back on the halfords link and find the bike tools section theres a tool set for about £30 thats got everything you'll ever need for basic maintenance i got 1 myself a few weeks ago and i think its saved me a good ton in labour charges