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-   -   Is something bent here? (http://www.bikeforums.net/bicycle-mechanics/935977-something-bent-here.html)

Andy_K 02-27-14 02:04 PM

Is something bent here?
 
I've been having problems with my rear shifting. If I adjust the rear derailleur so that I can shift cleanly on the smallest cogs, I have trouble with shifting on the biggest cogs. If I adjust the rear derailleur so that I can shift cleanly on the biggest cogs, I have trouble shifting on the smallest cogs. I've taken steps to rule out the usual suspects (dirty cables, poor cable routing, worn cassette, worn chain, dirty derailleur pivots, muck in the shifter mechanism), so I think what's left is either a bent derailleur cage or a bent hanger.

I know it can be really hard to judge this kind of thing from pictures, but I thought I'd at least ask if anyone can see something obvious in these images.

The only thing I can see is that derailleur cage is kind of bowed, and I don't know if that's normal or not.

http://farm8.staticflickr.com/7417/1...37634f9a_c.jpg

http://farm8.staticflickr.com/7361/1...5b0ab535_c.jpg

It may be a trick of the camera, but it looks to me like the derailleur isn't lined up right with the cogs here. I don't remember seeing that when I was in the garage.

http://farm8.staticflickr.com/7303/1...29f2a343_c.jpg

I think this is the best pic I have of the hanger.

http://farm3.staticflickr.com/2863/1...b35bddbf_c.jpg


There's nothing here that looks definitive to me, but I was hoping maybe more trained I would see something.

Thanks for any help you can offer.

bobotech 02-27-14 02:09 PM

Quote:

Originally Posted by Andy_K (Post 16532779)



http://farm8.staticflickr.com/7361/1...5b0ab535_c.jpg

It may be a trick of the camera, but it looks to me like the derailleur isn't lined up right with the cogs here. I don't remember seeing that when I was in the garage.

http://farm8.staticflickr.com/7303/1...29f2a343_c.jpg

I think this is the best pic I have of the hanger.

Is it possible you have the cable attached to the derailleur cable retaining bolt backwards? It almost looks like the cable is routed to the wrong side of the bolt which would cause the ratio to be off causing shifting to be problematic at one end or the other of the gear range.

Can you take a picture of the cable mounting point so that it shows the retaining nut/bolts better than the above pictures so we could see how the cable is routed?

RPK79 02-27-14 02:12 PM

In that third picture it looks like it is at an angle compared to the cassette.

Andy_K 02-27-14 02:15 PM

Quote:

Originally Posted by bobotech (Post 16532800)
Is it possible you have the cable attached to the derailleur cable retaining bolt backwards? It almost looks like the cable is routed to the wrong side of the bolt which would cause the ratio to be off causing shifting to be problematic at one end or the other of the gear range.

Can you take a picture of the cable mounting point so that it shows the retaining nut/bolts better than the above pictures so we could see how the cable is routed?

Well, I've done that before and I know it does lead to exactly this behavior, so that was one of the things I checked. I'll take a picture tonight but I can tell you that it's like routing A in the image below, not routing B.

http://sheldonbrown.com/images/dura-...ble-anchor.png

Andy_K 02-27-14 02:31 PM

Quote:

Originally Posted by RPK79 (Post 16532814)
In that third picture it looks like it is at an angle compared to the cassette.

I definitely see what you mean. I'm not sure if that's camera distortion or if it's really like that. I'll take a closer look when I get home, but I was looking for that before. My perception isn't what it could be.

If it is at an angle, how can I tell if it's the hanger or the derailleur that's bent?

I'm thinking this process is likely to lead me to purchase a DAG-2. I generally buy tools as I need them, but I try not to buy tools that I'll only use a couple of times a decade. It sounds like the DAG-2 is handy to have around, but I'd hate to spend $60 on a tool only to have it tell me that what I really needed was to do was replace the derailleur.

RPK79 02-27-14 02:34 PM

Quote:

Originally Posted by Andy_K (Post 16532873)
I definitely see what you mean. I'm not sure if that's camera distortion or if it's really like that. I'll take a closer look when I get home, but I was looking for that before. My perception isn't what it could be.

If it is at an angle, how can I tell if it's the hanger or the derailleur that's bent?

I'm thinking this process is likely to lead me to purchase a DAG-2. I generally buy tools as I need them, but I try not to buy tools that I'll only use a couple of times a decade. It sounds like the DAG-2 is handy to have around, but I'd hate to spend $60 on a tool only to have it tell me that what I really needed was to do was replace the derailleur.

Take the hanger off and lay it down on a flat table.

Andy_K 02-27-14 02:45 PM

Quote:

Originally Posted by RPK79 (Post 16532884)
Take the hanger off and lay it down on a flat table.

I think I have the technology to do that. :o

Thanks!

davidad 02-27-14 02:53 PM

If you have a spare rr wheel remove the derailleur and screw the axle of the extra wheel in(they have the same threads). If the wheels are parallel then the hanger is not bent. If not you can use the wheel as a lever to bend the hanger into place.

Andy_K 02-27-14 03:59 PM

Quote:

Originally Posted by davidad (Post 16532947)
If you have a spare rr wheel remove the derailleur and screw the axle of the extra wheel in(they have the same threads). If the wheels are parallel then the hanger is not bent. If not you can use the wheel as a lever to bend the hanger into place.

Really? I may end up getting the tool anyway, but that's pretty cool.

woodcraft 02-27-14 08:51 PM

I'm impressed that you've made it 6 yrs & 6,000+ posts on BF

without this issue coming up.


Cool idea about using a wheel as RD hanger tool- you should put that in the hints and tricks thread.

Duane Behrens 02-27-14 08:55 PM

One of the first bicycle-specific tools I bought was the Park hanger adjustment tool. Quick, easy to use, removes guesswork and worry. Easy to get it right and when you do, the RD is almost self healing.

Andy_K 02-27-14 09:58 PM

Quote:

Originally Posted by woodcraft (Post 16533906)
I'm impressed that you've made it 6 yrs & 6,000+ posts on BF

without this issue coming up.

You know, I was thinking about that too. I've ridden around 26,000 miles in that time and for all but the first year I've been doing my own maintenance. Even weirder is I've done 96 cyclocross races in that time. I did bend a RD hanger on a steel bike in one CX race, but the whole bike was so messed up that time that I took it into a shop for rescue. Oh, and this problem happened on a bike that hasn't been off road and hasn't been crashed.

Reviews of the DAG-2 seem to indicate that people use it a lot. Maybe I just have more tolerance for poor shifting than most people.

Incidentally, I tried the wheel thing this evening. The alignment was definitely off, but I'm not sure I got it back within limits using the wheel. In any event, it didn't fix the problem. I'll probably pick up the tool, but I think something else is going on.

Sixty Fiver 02-27-14 10:10 PM

With a 10 speed drive you only have to be off by about this much >< for the shifting to be off... the last photo suggested that the hangar or the derailleur might have been a little askew.

Using a wheel as an alignment tool is a brilliant trick, I still use an old Campagnolo derailleur tool that I repaired and the I used part of a hollow 10mm axle to replace the damaged bolt section.

It still requires a good eye... newer drive systems are just that much more precise and are affected by things that would not bother a bike with 8 or less speeds.

lopek77 02-27-14 10:34 PM

Quote:

Originally Posted by RPK79 (Post 16532884)
Take the hanger off and lay it down on a flat table.

One of the best low tech tips I saw on BF lol

Turtle Speed 02-28-14 01:55 AM

1 Attachment(s)
Quote:

Originally Posted by Andy_K (Post 16532873)
I'm not sure if that's camera distortion or if it's really like that.

Looks like more than camera distortion to me...

yellow line = alignment of cassette sprocket
peach line = alignment of derailer pulley


http://bikeforums.net/attachment.php...hmentid=366410

Duane Behrens 02-28-14 07:07 AM

Great graphic. As I recall, on a 10-speed the pulley should reside just slightly OUTBOARD when on the smallest cog, the difference decreasing as the bike is downshifted. In the gear choice shown, I would think the pulley should reside more or less directly beneath its cog. Eh?

dbg 02-28-14 09:13 AM

I apply the Park derailer hanger alignment tool to every old frame that comes through my workshop --and I end up tweaking at least half of them (and I'm not normally OCD). I think it's a great tool to have (that wheel trick above is cool).

You should always have a wheel (or at least an old hub) tight in the drops when attempting to bend the der hanger --especially on CF frames.

Looigi 02-28-14 10:19 AM

A dissenting opinion: In my experience, RD hanger alignment doesn't matter much if the stops and cable tension are adjusted appropriately. I've ridden my bikes with hangers or dropouts bent to various degrees and they were fine. Subsequent straightening and readjustment made no difference in shifting performance. It does make you feel better knowing it's all nice and straight though.

Duane Behrens 02-28-14 01:39 PM

Quote:

Originally Posted by Looigi (Post 16535269)
A dissenting opinion: In my experience, RD hanger alignment doesn't matter much if the stops and cable tension are adjusted appropriately. I've ridden my bikes with hangers or dropouts bent to various degrees and they were fine. Subsequent straightening and readjustment made no difference in shifting performance. It does make you feel better knowing it's all nice and straight though.

As of this moment, your experience conflicts with advice and counseling from Shimano, Park, Zinn and a host of other so-called experts, all of whom state that adjusting a derailleur without first straightening the hanger can become an exercise in futility.

On the other hand, prior to Columbus everyone knew the world was flat.

RPK79 02-28-14 01:42 PM

Quote:

Originally Posted by Duane Behrens (Post 16536006)
As of this moment, your experience conflicts with advice and counseling from Shimano, Park, Zinn and a host of other so-called experts, all of whom state that adjusting a derailleur without first straightening the hanger can become an exercise in futility.

On the other hand, prior to Columbus everyone knew the world was flat.

More recently Freidman proclaimed that the world is flat.

Andy_K 03-19-14 01:44 PM

Updating for the sake of the archives.... This ends a bit like one of those mystery novels where you weren't given enough information to actually solve the mystery until the answer is revealed.

I did a whole lot of things, including straightening the derailleur hanger, that probably made incremental improvement but didn't come close to fixing the issue. I took it in to the LBS and after their first line mechanic couldn't fix it, he passed it on to another guy who noticed that the shift cable seemed to have worn a small groove in the frame where it exits the downtube. (Did I mention that this bike has internal cable routing?) He put a small piece of cable liner between the place where the cable exits the frame and the bottom bracket cable guide. As of right now, that fixes the problem and my shifting is great. I guess it remains to be seen how long the cable liner lasts/stays in place.


In other news....

Quote:

Originally Posted by Looigi (Post 16535269)
A dissenting opinion: In my experience, RD hanger alignment doesn't matter much if the stops and cable tension are adjusted appropriately. I've ridden my bikes with hangers or dropouts bent to various degrees and they were fine. Subsequent straightening and readjustment made no difference in shifting performance. It does make you feel better knowing it's all nice and straight though.

Measuring with the Park DAG-2, my alignment was about 5mm off -- so I guess 1mm out of spec. That probably didn't make a huge difference.

However....since I bought the tool, I decided to check out the hanger on my CX race bike, even though I thought it was shifting OK. That puppy was off by 20mm top-to-bottom and about 10mm front-to-back. I straightened it out, and the shifting does seem a bit more perfect, but like I said it was working before. So maybe I am just too tolerant of sub-par shifting, but it also seems to me that Looigi isn't entirely wrong.

Retro Grouch 03-19-14 02:02 PM

Quote:

Originally Posted by Looigi (Post 16535269)
A dissenting opinion: In my experience, RD hanger alignment doesn't matter much if the stops and cable tension are adjusted appropriately. I've ridden my bikes with hangers or dropouts bent to various degrees and they were fine. Subsequent straightening and readjustment made no difference in shifting performance. It does make you feel better knowing it's all nice and straight though.

Why would anybody choose not to check it out? It's not a big deal to check and, like you said, it feels better knowing it's all nice and straight.

fietsbob 03-19-14 02:45 PM

the old Campag R tool was not that precise , as Friction shifting was less critical,

than the indexing schemes of to day are ..

goldfinch 03-19-14 10:05 PM

This week I had the pleasure of straightening a bent one piece derailleur hanger on an old steel bike someone gave me (rather than throwing in the trash). It was bent so far that you couldn't screw the adjustment tool onto it. At the co-op the mechanic and I first just bent it very roughly straight, stuck it in a vice to get the twist out of it, then used the DAG-2. At first, we both blew it. The wheel was way out of true and we didn't account for that when using the tool. So, the bike didn't shift right. I am happy to say that I figured out the problem. I trued the wheel and I got the hanger straight. I put on a used old derailleur and the bike is now shifts perfectly. And I don't have a clue what to do with the bike. I'll probably give it to the co-op, given how much they have helped me this winter.

A good lesson in using the DAG-2. I think I want one for my birthday.

Sixty Fiver 03-19-14 11:06 PM

Quote:

Originally Posted by fietsbob (Post 16593096)
the old Campag R tool was not that precise , as Friction shifting was less critical,

than the indexing schemes of to day are ..

The human eye (with 20/20 vision) can see a difference of just under 4/1000 of an inch at a distance of 12 inches.


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