Un-bending a rear derailler
#1
Senior Member
Thread Starter
Un-bending a rear derailler
If you look at the photo below, you may not be surprised to learn that the derailleur cage rubs against the spokes when it is on the largest cog.
From what I've read, it sounds like the way to fix this situation, in general, is to bend the hanger. Is that the right approach here? It is a Suntour GT in case that matters at all.
From what I've read, it sounds like the way to fix this situation, in general, is to bend the hanger. Is that the right approach here? It is a Suntour GT in case that matters at all.
#2
Senior Member
Join Date: Oct 2012
Location: Berkeley CA
Posts: 2,533
Bikes: 1981 Ron Cooper, 1974 Cinelli Speciale Corsa, 2000 Gary Fisher Sugar 1, 1986 Miyata 710, 1982 Raleigh "International"
Mentioned: 97 Post(s)
Tagged: 0 Thread(s)
Quoted: 929 Post(s)
Liked 1,289 Times
in
486 Posts
Usually it is the hanger that is bent, not the derailleur, so yes, removing the derailleur and bending the hanger is generally the correct remedy. Park even makes a special $80 alignment tool that threads into the hanger and helps you get the hanger perfectly aligned. Every bike shop worth its salt will have that tool. Either pay the mechanic to straighten it for you (should be a minimum charge) or go it alone with a big crescent wrench and eyeball it. For 5-speed friction shifting like you have it doesn't have to be perfect.
Likes For davester:
#3
Senior Member
Join Date: Nov 2004
Posts: 23,223
Mentioned: 654 Post(s)
Tagged: 1 Thread(s)
Quoted: 4722 Post(s)
Likes: 0
Liked 3,036 Times
in
1,874 Posts
In this case, the the mounting claw is not parallel to the cogs. It's hard to tell if the bend is completely in the claw but it appears to be the major contributor. The claw can be removed from the derailleur to be straightened. Once re-assembled, that will tell you if there is additional bend to look for elsewhere A lot of cyclists would just grab the derailleur and bend it back into position, which may fix the issue but still cause problems if installed on another bicycle, as you're not necessarily addressing the root cause.
Likes For T-Mar:
#4
Senior Member
Join Date: Nov 2015
Location: Dublin, Ireland
Posts: 1,256
Bikes: Bianchi Ti Megatube; Colnago Competition; Planet-X EC-130E; Klein Pulse; Amp Research B4; Litespeed Catalyst; Trek Y11
Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Quoted: 596 Post(s)
Liked 478 Times
in
258 Posts
If you don't want to fix it "properly" with an alignment tool directly on the rear derailleur mount, you could bodge it by using the correct sized allen key in the rear derailleur mounting bolt and *carefully* torque it (bend it) so it effectively straightens the rear derailleur hanger and the whole assembly lines up more correctly. There's probably a YouTube video...
#5
Senior Member
Thread Starter
In this case, the the mounting claw is not parallel to the cogs. It's hard to tell if the bend is completely in the claw but it appears to be the major contributor. The claw can be removed from the derailleur to be straightened. Once re-assembled, that will tell you if there is additional bend to look for elsewhere A lot of cyclists would just grab the derailleur and bend it back into position, which may fix the issue but still cause problems if installed on another bicycle, as you're not necessarily addressing the root cause.
I think I will give straightening it a go myself. It actually runs pretty well now (except in the largest cog of course) - it can only get better
#6
Senior Member
Join Date: Sep 2005
Location: Oakland, CA
Posts: 3,265
Bikes: '82 Univega Competizione, '72 Motobecane Grand Record, '83 Mercian KOM Touring, '85 Univega Alpina Uno, '76 Eisentraut Limited
Mentioned: 57 Post(s)
Tagged: 0 Thread(s)
Quoted: 1088 Post(s)
Liked 1,205 Times
in
701 Posts
Yes, that's the hanger claw. But recall Astronaut Chris Hadfield -- "There is no problem so bad you can't make it worse."
#7
Senior Member
Join Date: May 2011
Location: Seattle WA
Posts: 2,841
Bikes: 2009 Handsome Devil, 1987 Trek 520 Cirrus, 1978 Motobecane Grand Touring, 1987 Nishiki Cresta GT, 1989 Specialized Allez Former bikes; 1986 Miyata Trail Runner, 1979 Miyata 912, 2011 VO Rando, 1999 Cannondale R800, 1986 Schwinn Passage
Mentioned: 72 Post(s)
Tagged: 0 Thread(s)
Quoted: 796 Post(s)
Liked 522 Times
in
367 Posts
Or you can buy a whole new vintage looking RD from Amazon for about $10 or get one from a bike co-op
#8
Senior Member
Join Date: Mar 2013
Location: Maryland
Posts: 3,799
Bikes: Lots of English 3-speeds, a couple of old road bikes, 3 mountain bikes, 1 hybrid, and a couple of mash-ups
Mentioned: 53 Post(s)
Tagged: 0 Thread(s)
Quoted: 887 Post(s)
Liked 335 Times
in
225 Posts
Just remove the wheel and chain, and then fix the claw or buy a new one. What @T-Mar said about everything else. A dropout with no integrated hanger is not too hard to align - if it needs aligning at all. I may have a Suntour hanger in my stash if you need one.
#9
Bike Butcher of Portland
Join Date: Jul 2014
Location: Portland, OR
Posts: 11,630
Bikes: It's complicated.
Mentioned: 1299 Post(s)
Tagged: 0 Thread(s)
Quoted: 4677 Post(s)
Liked 5,790 Times
in
2,279 Posts
A tip I picked up from @Andy_K:
Most rear QR hubs are M10 x 1mm pitch.
Most derailleur hangers are the same thread.
Remove QR, thread in your wheel, carefully bend. It's easy to see if the rear wheel on your bike is parallel with the "tool" wheel.
Most rear QR hubs are M10 x 1mm pitch.
Most derailleur hangers are the same thread.
Remove QR, thread in your wheel, carefully bend. It's easy to see if the rear wheel on your bike is parallel with the "tool" wheel.
__________________
If someone tells you that you have enough bicycles and you don't need any more, stop talking to them. You don't need that kind of negativity in your life.
If someone tells you that you have enough bicycles and you don't need any more, stop talking to them. You don't need that kind of negativity in your life.
#10
Senior Member
Join Date: Oct 2012
Location: Berkeley CA
Posts: 2,533
Bikes: 1981 Ron Cooper, 1974 Cinelli Speciale Corsa, 2000 Gary Fisher Sugar 1, 1986 Miyata 710, 1982 Raleigh "International"
Mentioned: 97 Post(s)
Tagged: 0 Thread(s)
Quoted: 929 Post(s)
Liked 1,289 Times
in
486 Posts
Or you can buy a whole new vintage looking RD from Amazon for about $10 or get one from a bike co-op
#11
Senior Member
Thread Starter
If you don't want to fix it "properly" with an alignment tool directly on the rear derailleur mount, you could bodge it by using the correct sized allen key in the rear derailleur mounting bolt and *carefully* torque it (bend it) so it effectively straightens the rear derailleur hanger and the whole assembly lines up more correctly. There's probably a YouTube video...
Likes For mmcc73:
#13
www.theheadbadge.com
Join Date: Sep 2005
Location: Southern Florida
Posts: 28,510
Bikes: https://www.theheadbadge.com
Mentioned: 124 Post(s)
Tagged: 0 Thread(s)
Quoted: 2420 Post(s)
Liked 4,381 Times
in
2,090 Posts
If you're not confident bending the hanger back, just replace the existing one: https://www.ebay.com/itm/Sunrace-Der...wAAOSw8Dxc3sNB
-Kurt
-Kurt
#14
Bad example
Join Date: Nov 2015
Location: Seattle and Reims
Posts: 3,042
Bikes: Peugeot: AO-8 1973, PA-10 1971, PR-10 1973, Sante 1988; Masi Gran Criterium 1975, Stevenson Tourer 1980, Stevenson Criterium 1981, Schwinn Paramount 1972, Rodriguez 2006, Gitane Federal ~1975, Holdsworth Pro, Follis 172 ~1973, Bianchi '62
Mentioned: 36 Post(s)
Tagged: 0 Thread(s)
Quoted: 816 Post(s)
Liked 176 Times
in
83 Posts
I am a fan of using a Crescent wrench to straighten hangers. I have been pretty successful with indexed derailleur hangers as well, although the Park tool is definitely a better choice for that.
__________________
Keeping Seattle’s bike shops in business since 1978
Keeping Seattle’s bike shops in business since 1978
#15
Senior Member
Join Date: Nov 2013
Location: Near Pottstown, PA: 30 miles NW of Philadelphia
Posts: 2,186
Bikes: 2 Trek Mtn, Cannondale R600 road, 6 vintage road bikes
Mentioned: 83 Post(s)
Tagged: 0 Thread(s)
Quoted: 472 Post(s)
Liked 1,028 Times
in
404 Posts
Keep in mind that the hanger or claw needs to be parallel to the wheel, all the way around. Best to start with a nicely true wheel. Otherwise always check at the valve stem. Check it both top to bottom and back to front. You can check more spots but diminishing returns. I find that getting it to within 1/8"at the rim, back to front and top to bottom is sufficient. Yes, less fussy with friction shifting but is very nice when friction shifting is so smooth and predictable.
I find that around half of the bikes that come into the shop have bent hangers, even right out of the box. Some top to bottom, some back to front, some both. All my own bikes get checked and adjusted.
I find that around half of the bikes that come into the shop have bent hangers, even right out of the box. Some top to bottom, some back to front, some both. All my own bikes get checked and adjusted.
Likes For Prowler:
#16
Senior Member
Join Date: Nov 2015
Location: Dublin, Ireland
Posts: 1,256
Bikes: Bianchi Ti Megatube; Colnago Competition; Planet-X EC-130E; Klein Pulse; Amp Research B4; Litespeed Catalyst; Trek Y11
Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Quoted: 596 Post(s)
Liked 478 Times
in
258 Posts
I agree on the frequency of bent hangers, it made me go buy the proper Park alignment tool. Expensive, but I've gotten great mileage out of it. If you have multiple bikes and/or like to tune & build up your own, it's very useful to have on hand.
#17
Senior Member
Join Date: Oct 2012
Location: Berkeley CA
Posts: 2,533
Bikes: 1981 Ron Cooper, 1974 Cinelli Speciale Corsa, 2000 Gary Fisher Sugar 1, 1986 Miyata 710, 1982 Raleigh "International"
Mentioned: 97 Post(s)
Tagged: 0 Thread(s)
Quoted: 929 Post(s)
Liked 1,289 Times
in
486 Posts
If you're not confident bending the hanger back, just replace the existing one: https://www.ebay.com/itm/Sunrace-Der...wAAOSw8Dxc3sNB
-Kurt
-Kurt
#18
Extraordinary Magnitude
Join Date: Aug 2009
Location: Waukesha WI
Posts: 13,642
Bikes: 1978 Trek TX700; 1978/79 Trek 736; 1984 Specialized Stumpjumper Sport; 1984 Schwinn Voyageur SP; 1985 Trek 620; 1985 Trek 720; 1986 Trek 400 Elance; 1987 Schwinn High Sierra; 1990 Miyata 1000LT
Mentioned: 84 Post(s)
Tagged: 0 Thread(s)
Quoted: 2607 Post(s)
Liked 1,695 Times
in
934 Posts
I resemble that remark.
__________________
*Recipient of the 2006 Time Magazine "Person Of The Year" Award*
Commence to jigglin’ huh?!?!
"But hey, always love to hear from opinionated amateurs." -says some guy to Mr. Marshall.
Commence to jigglin’ huh?!?!
"But hey, always love to hear from opinionated amateurs." -says some guy to Mr. Marshall.
#19
www.theheadbadge.com
Join Date: Sep 2005
Location: Southern Florida
Posts: 28,510
Bikes: https://www.theheadbadge.com
Mentioned: 124 Post(s)
Tagged: 0 Thread(s)
Quoted: 2420 Post(s)
Liked 4,381 Times
in
2,090 Posts
OP's pic most definitely shows a bent hanger though. I'm giving the dropout the benefit of the doubt. The stamped Raleigh dropouts tend to get chewed down by the axle cone nuts - if the dropout is bent. I don't see that here.
-Kurt