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Derailleur broke in half!

Old 04-22-12, 11:29 AM
  #1  
LtotheK
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Derailleur broke in half!

I ordered a 2012 Men's Diamondback Edgewood hybrid online via Amazon because the bike stores here in Brooklyn are small & mostly have expensive bikes. My husband, who is experienced with bikes, put it together, and just after we finished riding over the bridge, the derailleur broke ... it didn't come apart from the screw(s) -- the metal part broke in half! It fell off & got lodged in my spokes and I came to a dangerous halt. WTF? From what I understand, it's a nice piece of machinery: Shimano Tourney TX35 6/7 spd Rear Derailleur w/ Hanger. Unfortunately, with Amazon, we'd have to return the whole bike to remedy the problem. So we just ordered the part and my husband will fix it. I was wondering if anyone has had this problem? I was just changing gears. Now I'm afraid I'm going to do it again. And I was having so much fun....!!
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Old 04-22-12, 11:45 AM
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I was wondering if anyone has had this problem?
Yes, it happens all the time. If the derailleur mount is bent, then the derailleur can snag the spokes when shifted inboard, ripping the derailleur apart and potentially breaking the derailleur mount (which should be a replacable part of the bike's frame for this exact reason).

Another scenario is when the derailleur's limit screws haven't been adjusted properly, which would be up to you as the assembler since you didn't buy it from a dealership. In that case, the derailleur can shift the chain right over the large cog and into the spokes, which may also result in the derailleur being dragged around by the wheel and ripped in half, etc etc.

When you install the new derailleur, make sure the frame's mount (called the "rear derailleur hanger") is not bent, here's a guide for that: https://www.parktool.com/blog/repair-...nger-alignment. If necessary, replace the RD hanger. Also make sure the limit screws are limiting the derailleur's range of motion so it doesn't shift the chain off into the spokes, here's info on that: https://www.parktool.com/blog/repair-...nts-derailleur.
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Old 04-22-12, 11:52 AM
  #3  
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Lots of brand names have been commodified and sold, so where Diamond Back
20 years ago
was an OK brand, sold inBike Shops that reputation did not follow
when the contract priorities were
Make it cheap .. sell it for cheap, sell it by volume, in a big box store,
rather than continue in the make it good
history the name should signify..

thing could have been banged up in shipping,
could have never been right in the 1st place..

Bike shops have a derailleur hanger alignment tool , worth going by
and seeing that it is right. service fee likely affordable..

Last edited by fietsbob; 04-22-12 at 11:57 AM.
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Old 04-22-12, 01:10 PM
  #4  
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Originally Posted by fietsbob View Post
Bike shops have a derailleur hanger alignment tool , worth going by
and seeing that it is right. service fee likely affordable..
Not going to help the OP because her bike uses a Tourney derailleur with an integral hanger claw that attaches to the rear axle.
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Old 04-22-12, 01:25 PM
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I would report the failure to the mfg of the derailer.
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Old 04-22-12, 01:25 PM
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From the photos at Amazon.com, it looks like it's the Tourney variant that mounts to a frame's RD hanger on this one. And if the RD got ripped off, it's a safe bet the RD hanger is now bent at the very least, and possibly due for replacement. With that in mind, I believe this is the hanger that would be called for: https://derailleurhanger.com/dh027.php


Last edited by mechBgon; 04-22-12 at 04:00 PM.
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Old 04-22-12, 02:28 PM
  #7  
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Originally Posted by LtotheK View Post
From what I understand, it's a nice piece of machinery: Shimano Tourney TX35 6/7 spd Rear Derailleur w/ Hanger
Lol
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Old 04-22-12, 03:48 PM
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It doesn't have to be a bent hanger, and likely isn't unless the hanger got bent between when the limit screws were set and the event happened. If the hanger was bent all along, and the limits set accordingly then the hanger wouldn't be a factor.

Of course the hanger could have bent along the way, but there again it wouldn't have made a difference unless/until the bike was shifted to a lower (more inboard gear).

The other (IMO more likely) possibility, especially if it broke while riding in a mid-range gear (and not shifting) is that the "B" screw wasn't adjusted correctly and the upper pulley engaged a sprocket through the chain. This is very common, and causes the RD to get kicked back, and can cause TD breakage. IMO this is the more likely cause since the event happened on the downhill side of the bridge, so the OP wouldn't have been shifting to low at the time.

If you look at the picture Mechbgon so kindly posted, you can see about 1" (2 links) of chain separating the pulley and sprocket. This is correct, but all to often the RD is riding higher and that clearance doesn't exist on some gears. Because Shimano upper pulleys change height as the cage rotates, the clearance has to be checked for all sprockets using all three chainrings, and the "B" screw adjusted to ensure clearance for the closest combination.
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Old 04-22-12, 04:06 PM
  #9  
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Originally Posted by fietsbob View Post
Lots of brand names have been commodified and sold, so where Diamond Back
20 years ago
was an OK brand, sold inBike Shops that reputation did not follow
when the contract priorities were
Make it cheap .. sell it for cheap, sell it by volume, in a big box store,
rather than continue in the make it good
history the name should signify..

thing could have been banged up in shipping,
could have never been right in the 1st place..

Bike shops have a derailleur hanger alignment tool , worth going by
and seeing that it is right. service fee likely affordable..
+1 Diamond Backs where great BMX frames back in 80's and they did sell some decent road and moutian frames. All of the early Diamond back stuff was actually higher end Japanese stuff rebranded for the US.
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Old 04-22-12, 04:49 PM
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The RD in #6 is not going to set you back much , just get another one..

I would report the failure to the mfg of the derailer.
warrantee flow chart usually goes back thru the Dealer , FWIW,

Amazon probably just middle-manned the transaction,
that is what happened when I bought a book thru Amazon UK
seller was actually a book shop.

Last edited by fietsbob; 04-22-12 at 04:54 PM.
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Old 04-22-12, 05:02 PM
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It doesn't have to be a bent hanger, and likely isn't unless the hanger got bent between when the limit screws were set and the event happened.
The force required to tear a RD in half is almost certainly going to leave the hanger damaged. I regret to say I have personal experience with this
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Old 04-22-12, 05:27 PM
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Originally Posted by mechBgon View Post
The force required to tear a RD in half is almost certainly going to leave the hanger damaged. I regret to say I have personal experience with this
Me 2.
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Old 04-22-12, 05:50 PM
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[QUOTE=LtotheK;14130333]I ordered a 2012 Men's Diamondback Edgewood hybrid online via Amazon because the bike stores here in Brooklyn are small & mostly have expensive bikes. My husband, who is experienced with bikes, put it together, and just after we finished riding over the bridge, the derailleur broke ... it didn't come apart from the screw(s) -- the metal part broke in half! It fell off & got lodged in my spokes and I came to a dangerous halt. WTF? From what I understand, it's a nice piece of machinery: Shimano Tourney TX35 6/7 spd Rear Derailleur w/ Hanger. Unfortunately, with Amazon, we'd have to return the whole bike to remedy the problem. So we just ordered the part and my husband will fix it. I was wondering if anyone has had this problem? I was just changing gears. Now I'm afraid I'm going to do it again. And I was having so much fun....!![/QUOTE]

I saw that alot when I was working in a shop and I would suspect that as stated, the derailleur was not adjusted properly and or slightly bent. when you shifted into the easiest gear the derailleur got jammed in the spokes and got ripped in two. Unless the bike is properly adjusted it is quite likely to happen again.
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Old 04-22-12, 07:21 PM
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Originally Posted by mechBgon View Post
The force required to tear a RD in half is almost certainly going to leave the hanger damaged. I regret to say I have personal experience with this
I agree.

Certainly after something like this the hanger wouild need to be at least straightened, if not replaced. But in the earlier post which you quoted, I was discussing causation, not consequences. As I said, the bent hanger wouldn't have caused the problrm, unless the limits were misadjusted, or the hanger was bend subsequent to the adjustment.
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Old 04-22-12, 07:37 PM
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Happened to me too, long ago. Bought a beater bike for $25, test rode it, everything seemed ok until I shifted into the biggest cog. Destroyed the RD and bent the hanger badly but didn't break any spokes.

Not the manufacturers fault at all, this is a simple RD adjustment error. Low limit screw prevents the RD from going into the spokes like that. Of course, if the RD or hanger was bent after everything was setup then a failure like that could've occured.
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Old 04-23-12, 01:28 AM
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Agreed, it was a problem with the rear derailleur adjustment. That is why it is better to buy a fully assembled bike from a dedicated bike shop rather than buying one in a box and trying to put it together yourself. Setting up a bike is not a simple thing, and many of the problems that people have with it cause safety issues - it shouldn't be attempted unless you really know what you're doing.
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Old 04-23-12, 02:33 AM
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I assemble this model all the time. Like all other bikes, I have to adjust both high and low limit screws because they are not set properly from the factory. Not a problem unique to this model, or Diamond Back bikes for that matter. Occasionally I'll have to tweak the derailleur hanger, but nothing outrageous. These newer Tourney rear derailleurs are actually nicer than those made a couple years ago. Coupled with the trigger shifters, I've never had a problem getting the rear to shift perfectly. Usually I have problems with the front since the crankset is not the best-wobbly/out of true.
Not to sabotage your husband's competence, but we see people all the time claim to have "experience" with bikes. "Experience" is relative.
If you want to ride without worrying, you should test it gently. Gently and slowly shift the right hand thumb shifter into the easiest gear and slowly pedal forward, keeping an eye on the rear derailleur to be sure it is not moving so far inward that it contacts the spokes of the rear wheel. If it doesn't do this, you should be able to ride with confidence this same problem won't repeat.
Or you could sneak the bike into a shop and ask them to take a quick peak.

Last edited by vredstein; 04-23-12 at 02:38 AM.
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Old 04-30-12, 08:28 AM
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Thanks everyone -- soooo much great advice here! After reading through the replies, my husband realized that he didn't adjust it properly & he felt so bad he bought the new one. After he switches out the old one, we're going to take it to a bike shop for adjusting.

Here's my new question: Since it's a new bike, do I really need to spend $60 on a full tune up, or is it okay to spend only the $15 for the derailleur adjustment? Meaning, is there anything else (besides the derailleur) that could be dangerous if not properly adjusted?
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Old 04-30-12, 08:34 AM
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Meaning, is there anything else (besides the derailleur) that could be dangerous if not properly adjusted?
The brakes are the first thing coming to mind. Inadequately-fastened pedals falling off, inadequately-fastened handlebars or stem coming loose are a couple others. If the front derailleur isn't clamped sufficiently, or its limit screws allow overshifts or excessive range, it could get in trouble too (snagging the crankarm as it goes by, for example). If you take it in for a tune-up, make sure to explain that you assembled it yourselves, so the shop knows not to make any assumptions about stuff being fastened properly as if it came from a Diamondback dealer.
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