Questions tagged [derailleur-rear]

Questions referring to the derailluer responsible for moving the chain along the cassette

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16
votes
4answers
5k views

10 gears to singlespeed

My second hand Hercules bicycle came with 10 gears. Two gears in the front and five in the back. The gearshift does not work well and since I cycle in the same gear all the time anyway, I consider ...
15
votes
4answers
13k views

What options do I have if my rear derailleur breaks when I'm out on a trail?

I ran into an unfortunate situation earlier this week. I was out on a mountain bike trail, alone — just me and my hardtail. I'm pedaling, when I suddenly hear a CRUNCH and my bike stops. The hanger ...
15
votes
3answers
63k views

How can you identify if a Shimano rear derailleur is medium or long cage?

I have a 2013 Shimano XT rear derailleur. It is part of a 2x10 drivetrain. How can I find out if it is a medium or a long cage one? The picture below shows the derailleur.
14
votes
6answers
13k views

Why is a derailleur guard present only on more affordable bicycles?

Looking at http://decathlon.co.uk, I see a derailleur guard only on more affordable bicycles, e.g. this one. This one does not have it, and there seems to be no obvious way to install one. Are ...
14
votes
1answer
30k views

Which pulley is which on my Shimano STX RC derailleur?

I disassembled my rear derailleur to clean it; when I removed the sprockets they basically looked the same; both jet black and caked with all sorts of black grease-like-stuff. I figured they were the ...
13
votes
2answers
1k views

Bike chain slips in a strange way

I bought a new bike about a month ago. And it made a strange sound from the first ride , I thought the sound was because it was new and will disappear with time but it didn't. The sound is like a ...
13
votes
6answers
6k views

How to remove the broken ball end of a small hex key that is now stuck inside the socket

While trying to replace the yoke of my derailleur I made the mistake of using a multi-tool hex key that was not able to handle the torque necessary for the task and snapped while the head stayed ...
13
votes
5answers
8k views

Why doesn't Shimano use shadow technology on road derailleurs?

Shimano has been using their 'Shadow' technology on their high-end mountain bike rear derailleurs (> Deore) for many years. In addition to the benefit described in the images below (from here), ...
12
votes
3answers
6k views

Why is cross chaining 'bad', but 1x is OK?

When you run 1x, aren't you basically force to cross chain?
11
votes
3answers
2k views

Busted my bike hub & derailleur (I think) - how bad is it?

I screwed up :( Background leading to my foolishness: I've been straining my bike quite a bit with hills and inclimate weather, and I haven't been able to find my maintenance kit since I've moved, so ...
10
votes
4answers
2k views

Upper pulley wheel suddenly totally off chain

Went for a bike ride today and thought the chain had slipped. Stopped and found the upper pulley wheel of the rear derailleur assembly was completely out of contact with the chain (please see photo)! ...
10
votes
2answers
16k views

What exactly is Shimano's Shadow Plus technology for rear derailleurs?

A couple of years ago, Shimano debuted their Shadow Plus technology for mountain bike rear derailleurs. What is it and why would you want it? If it's such a good idea, why hasn't it been copied by ...
10
votes
7answers
5k views

Do oversize pulley wheels increase derailleur capacity?

Do the large custom pulley wheels and cages increase the capacity of a derailleur significantly? There are reasonably priced ones on E-bay with 16t pulley wheels. Every demo of these I've seen says ...
10
votes
2answers
2k views

Chain popped out of derailleur and wrapped around itself - how? why?

During my ride yesterday, I've hit a really weird mechanical and would love to understand. So here's the situation - I'm riding along, start on a hill, stand up and push some power, suddenly hear ...
10
votes
3answers
501 views

My derailleur completely "opened" up. It is now almost a straight line. What have i done to my derailleur?

I had a flat on the side of the road. So I took my wheel off to replace the tire with a temp to get me home. When I reinstalled the wheel, the derailleur "opened up" completely...what have ...
9
votes
3answers
19k views

When to replace rear derailleurs

What is the typical life cycle of mid-range rear derailleurs assuming no accidents? More precisely, what's the average mileage after which it's better to replace it rather than doing tuning all the ...
9
votes
2answers
13k views

Do I have Direct Mount or Hanger Mount?

I'm very very new to bicycles and obtained a little project for me to work on, hence the amount of rust on the parts currently but I'm not sure if I have a direct or hanger mount derailleur? I'm 100% ...
9
votes
3answers
5k views

Is my derailleur hanger too bent?

I bent the (steel) derailleur hanger on my 9spd cassetted (steel) Bianchi Volpe about 1.5 yrs ago, and I just did it again, but worse. This time the derailleur got sucked into the wheel and really did ...
8
votes
3answers
3k views

Has a bike been made with a rear derailleur above the chainstays?

The question title pretty much sums it up, but has a bike with an alternate drivetrain style like this been made? This would mean a derailleur mounted essentially upside down with the tension pushing ...
8
votes
3answers
6k views

Rear derailleur got caught in the spokes, what could be a root cause

I have several problems on this bike. Here are the elements that have failed and other pieces of information: the chain has derailed past the largest sprocket the rear derailleur has rotated 180 ...
8
votes
4answers
2k views

Rear derailleur lifespans

How should I know when my rear derailleur is getting worn? I can measure/inspect chains, tyres and brakes; gears tend to show problems on a new chain if they're worn. But when changing my chain at ...
8
votes
2answers
4k views

Rear derailleur cage hits largest cog on cassette

I got a new rear derailleur for my wife's bike after a stick turned the original one into a twisted mess of metal. The derailleur is a Shimano Acera, the cage is slightly longer than the original. ...
8
votes
2answers
28k views

Eagle chain B-gap adjustment without plastic tool

SRAM makes this plastic tool for adjusting the B-gap on their Eagle derailleurs. My question is, if I want to measure this distance without this tool (say with a caliper instead), how should I go ...
8
votes
1answer
258 views

Do all or virtually all rear derailleurs actually have linear actuation ratios?

Adapter devices such as the Jtek Shiftmate and Wolf Tooth Tanpan are designed with the notion that the actuation ratio of the rear derailleurs they're being attached to are dead linear. So, for ...
7
votes
5answers
4k views

Pedals spin freely in cold conditions

I recently bought a second hand Giant Upland SE and to be frank, it is my first bike with multiple gears. The bike functioned normally for the first day or two. I could use all the gears. When the ...
7
votes
1answer
10k views

How do I tell if jockey wheels need overhaul or replacement?

I am refurbishing a bike and am deciding how much to clean out the rear derailleur. It's in pretty good shape. But after I take off the chain, I tried spinning the jockey wheels with my fingers (...
7
votes
2answers
908 views

Rear derailleur moves forward when pedalling stops

Can you please help me to resolve the issue I am having? When I stop pedaling rear derailleur moves forward by inertia. This happen almost every time i stop pedaling and start coasting. I have a video ...
7
votes
2answers
3k views

What could have caused a rear derailleur to end up in the back wheel suddenly?

This is a similar question to What exactly happened to my rear derailleur? but with some significant differences. My bike had recently been serviced (about 3 weeks/500 km previously). All that had ...
7
votes
3answers
26k views

Choosing a rear derailleur for 11-42t cassette on a SRAM 10-speed 1x system

I have an 11-42t 10 speed cassette and a 42t narrow wide chainring. I cannot work it out definitely whether a Sram long cage rear derailleur will work with it. I think that this one should work but ...
7
votes
7answers
1k views

why would my chain slip on the road, but not when the bike is on a stand?

The chain on my bike has started to slip a lot -- every couple of seconds when riding. It happens, as far as I can tell, in every gear, and is unrelated to shifting. The precise nature of the problem ...
7
votes
1answer
1k views

Derailleur can't shift to 51-T sprocket. Deore CS-M5100 + RD-M5100

ISSUE: When attempting to shift to the largest cassette sprocket, the side of the derailleur cage contacts the 51t sprocket, so the chain is not able to go up the gear. WHAT I DID: My drivetrain was ...
7
votes
2answers
1k views

How to install the cable for this rear derailleur?

For two months so far I'm trying to fix my bike. I bought a used bike and the shifting was not good. So I bought new cables and tried to make the rear derailleur work, but without any kind of luck. ...
7
votes
4answers
25k views

Can the Tensioner Spring go Bad on a Rear Derailleur?

My bike chain has been "skipping", so I've gone through the obvious: I replaced the chain I replaced the smallest cassette cog, which was showing significant wear After my replacements I noticed ...
7
votes
1answer
10k views

Effects of jockey wheel sizes & types

I'm wondering about the variations in jockey wheels / derailleur pulleys and what differences they make; There's a lot of conflicting and confusing information out there, so I'm after some general ...
7
votes
2answers
960 views

Why are there so many types of mech hanger?

I have just stripped the threads on my mech hanger and I'm in the process of buying a new one. There are so many different types, even for one manufacturer, I was wondering what the reason for this is?...
6
votes
6answers
4k views

Should I adjust rear derailleur as my chain seems too close to each other

I am learning to replace chain and freewheel (So far so good). After I put new freewheel and new chain on, the chain are too close to each other at the back now (as you can see in the photo). I think ...
6
votes
4answers
743 views

Swapping wheels and cassettes with Shimano GRX 600/800

I am in the market for a gravel bike. I plan on getting a second set of wheels for road rides. This bike will most likely have Shimano GRX 600 or 800 2x and an 11-34 cassette. Assuming the rear ...
6
votes
2answers
612 views

What is this part called?

I built a new YT Capra yesterday, and it had a part I had not seen before. It was not mentioned anywhere in the instructions, but it was needed to get the rear mech the correct distance from the rear ...
6
votes
1answer
663 views

Does the initial position of the B-tension screw matter?

When I'm installing a rear derailleur, should the B-tension screw be in a high or low setting or does it not matter? I've tried searching for information on this but no one seems to mention this so it ...
6
votes
2answers
236 views

Is there excessive lubricant on my new rear derailleur?

I just received a new Shimano Deore rear derailleur, which has large gobs of lubricant in two locations (one clearly visible in photo). This seems excessive. Do I leave it, or are they expecting you ...
6
votes
3answers
715 views

Recovery from a cycling mishap

I took my bike for the first ride of the season yesterday and unfortunately it was pretty short. As I was cycling through the rear gears I hear a plinking sound and then a large clunk. I stopped ...
6
votes
3answers
565 views

What is going on with my derailleur?

I was on a ride a few months ago and while shifting, my chain came out of my derailleur. So this is a little confusing. Let me explain. The chain was resting on the outside of the bottom part of the ...
6
votes
1answer
2k views

Why has the Centeron pulley disappeared on many Shimano rear derailleurs?

I have no idea if it's only some mechs or all nowadays but a while back I noticed its absence. Always thought it was a clever design to aid alignment when things were slightly out of adjustment. ...
6
votes
0answers
202 views

Why did Shimano change their rear derailleur design going from a torsion spring to a tension spring inside the parallelogram?

The older Shimano rear derailleurs (pre 7700) use a torsion spring inside the parallelogram. But with the release of the 7700 group they switched to a tension spring which they continued using ever ...
5
votes
7answers
19k views

Is gasoline an effective restoration material to use?

A fellow rider just picked up an old mountain bike which has some rust and plenty of gunk in the gears to wash out. He intends to use gasoline to clean the entire bike. This is the first I ever heard ...
5
votes
2answers
19k views

Can I just fit a cassette with more gears with the same derailleur?

I've got a Boardman Road Sport which I use for commuting and doing reasonable length rides during the week etc. I have Shimano Claris as my rear derailleur and so is some of my groupset. I would like ...
5
votes
2answers
5k views

Replace rear deraileur without breaking the chain

I currently have a Shimano Dura Ace 10 speed rear derailleur with a 12-25 cassette. For some hilly rides I'd like to change to a 12-30 cassette. The maximum the rear derailleur can handle is 28, so ...
5
votes
1answer
882 views

Stock 10 Speed Shifters with 9 Speed Transmission [closed]

I have a bike that was built with 10 Speed Campagnolo Veloce Shifters, 9 speed Veloce rear derailleur, and SRAM 9 speed cassette and chain. I found a page on the builder's website that states they do ...
5
votes
1answer
24k views

Misadjusted B-screw: symptoms?

What are the typical symptoms of incorrectly adjusted B-screw in the rear derailleur? How does it manifest itself when shifting? Obviously, if the cage pulley interferes with the cog, the problem is ...
5
votes
3answers
2k views

Why rear derailer has limit on front chainring difference?

Just as an example, Shimano RD-M786-SGS (as most other RDs) specification says "Max. front difference: 22T". Why is rear derailler limited in front max difference? It is clear that it is ...

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