23 votes

What exactly is the "clutch" doing on a Shimano M8100 rear derailleur?

I'll try to answer the question of exactly how the clutch works. In essence, the Shimano clutch design uses a one-way bearing that allows the cage to freely rotate clockwise, but adds friction if ...
MaplePanda's user avatar
  • 15.6k
21 votes

Upper pulley wheel suddenly totally off chain

The derailleur is supposed to be mounted to the dropout at the hanger, circled in red here. It is not. It should have been mounted using a bracket that runs between the hanger and the part circled in ...
Adam Rice's user avatar
  • 30k
20 votes

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

If you carry a multi-tool which happens to include a chain tool, you could also convert your bike to a single speed. If you do so, you would have to replace the chain afterwards as well (since you ...
cookiemonster's user avatar
18 votes
Accepted

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

The chain is too long. Presumably you did not cut it down to size it when you installed it. All chains are sold with excess length and must be sized to the bike. The length required depends on the ...
Argenti Apparatus's user avatar
18 votes
Accepted

What is this U shaped metallic piece with 2 holes?

Looks like a derailleur guard It mounts to the rear drop out on the derailleur side. It protects the derailleur from some impact damage. EDIT: 06/19/2021 The comments seem to be running strongly ...
David D's user avatar
  • 21.3k
17 votes

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

Derailleur guards are rarely found on more expensive bikes for several reasons: Protection: These guards only protect from minor contacts. Forces that would bend a typical derailleur would also bend ...
anderas's user avatar
  • 1,288
17 votes
Accepted

What exactly is the "clutch" doing on a Shimano M8100 rear derailleur?

I assume you're talking about Shimano's 12s XT rear derailleur. For disambiguation, 8100 could also refer to the 12s Ultegra groupset. However, the Ultegra group doesn't have a clutch, and I believe ...
Weiwen Ng's user avatar
  • 31.6k
16 votes
Accepted

Bike chain slips in a strange way

You can see in the video how the teeth on the cassette rotate quickly at the moment it slips(at :05 seconds), while the spokes of the wheel actually stay slow, then jolt forwards to catch up. This ...
Swifty's user avatar
  • 12.8k
14 votes

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

If you want to change your cassette to something with more gears, then you will need to replace the rear shifter and possibly the rear derailleur. A cheaper option would be to get a wider range ...
Kibbee's user avatar
  • 21.7k
14 votes

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

Another suggestion: Scooter it. The bike is functional but the drive train cannot transmit power. So one solution is to scooter along with one foot on the opposite pedal, and your other foot ...
Criggie's user avatar
  • 124k
14 votes
Accepted

New bike is making rattling noise

The noise happens every time your foot is in the same point of rotating the pedal. It sounds to me like the chain is catching on the front derailleur once per rotation. Not unusual and not difficult ...
Swifty's user avatar
  • 12.8k
13 votes

Pedals spin freely in cold conditions

The pawls in your freehub are most likely getting stuck, causing them not to lock and transfer the force from the cassette to the wheel. In your case as the bike is new it is probably due to it being ...
Toby's user avatar
  • 344
13 votes
Accepted

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

It doesn't matter how it's set when you first begin the installation. If it were out so far that it prevented the guide pulley from clearing the large cog at all, that would be a problem, but you'll ...
Nathan Knutson's user avatar
13 votes
Accepted

Threading Shimano chain, over or under lug?

Shimano seems to keep a lot of their documentation online, you can find your specific manual there. For example, the site gives this picture for DEORE XT RD-M8000 derailleur. Essentially, the ...
Ross's user avatar
  • 373
13 votes
Accepted

Are brifters meant to spin/slide on impact, by the choice of a low attachment-bolt torque?

I am not privy to the design philosophies of SRAM, Shimano or any manufacturer and as such my answer is based solely on my own experience. I have crashed on bikes with both Shimano Sora and Dura-Ace ...
newguise's user avatar
  • 146
12 votes
Accepted

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

TL;DNR A Shimano 'Shadow Plus' or SRAM Type 2 dérailleur (aka clutch dérailleur) means you can change the chain tension by flicking a lever. For completeness - back in the late 2000's, Shimano ...
mattnz's user avatar
  • 50.5k
12 votes

10 gears to singlespeed

I've got a 2nd hand Hercules too and I've done this exact thing. Get a quality chain tool and look up some videos on Youtube about how to remove and re-link a bike chain. I pretty much winged it as I ...
Poster's user avatar
  • 121
12 votes
Accepted

Momentum of rear derailleur wheels?

The derailleur wheels are small and light weight, so have very small moment of angular inertia. The bearings they run on need to withstand a significant force due to the action of the chain, not just ...
Penguino's user avatar
  • 761
12 votes
Accepted

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

Updated based on your edits and comments. The severed piece of metal circled in the 3rd image is one of the cage plates, and was originally attached to the lower (idler) pulley bolt. Beyond ...
DavidW's user avatar
  • 5,188
12 votes

Upper pulley wheel suddenly totally off chain

Your rear derailleur has failed. Look closely and if it is floppy there's either a broken spring, or a lug has been torn off. To my eyes, the whole derailleur has become separated from the hanger in ...
Criggie's user avatar
  • 124k
12 votes

Is it okay for my rear derailleur to be as "compressed" as this when in the lowest gear on the bike?

There's no issue with it looking like that while in small-small. It's very normal. The derailleur's total capacity number defines what large/large combination is supported while still allowing the ...
Nathan Knutson's user avatar
11 votes
Accepted

Is gasoline an effective restoration material to use?

Gasoline aka petrol, is a volatile fluid that will dissolve grease and oils. It will penetrate, soften, and loosen impacted and congealed dirt and dust. Petrol / Gasoline will NOT fix your rust, nor ...
Criggie's user avatar
  • 124k
11 votes

I need a new derailleur

You need to tighten the cable. Also, check that you're not missing a limiter screw, because that looks plain dodgy. Once the limiters are set up, follow these steps: 1)Set the gear shifter in the ...
yollooool's user avatar
  • 1,033
11 votes

Bike chain slips in a strange way

Confirming @Swifty's diagnosis. It's the freewheel mechanism. Take it back to where you purchased it and demand full refund or at least a complete new rear wheel. Don't let them try to repair the ...
Argenti Apparatus's user avatar
11 votes
Accepted

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

Every time I've seen a correctly adjusted rear derailleur go into the spokes while riding it was because something made the chain jam in the rear derailleur and the force of pedaling tore it off and ...
David D's user avatar
  • 21.3k
11 votes

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

Argenti's answer is correct - your chain is too long. Personally I don't bother calculating the numbers from the manufacturer's specs. I can generally assume that this combination of cassette/rear ...
Criggie's user avatar
  • 124k
11 votes
Accepted

Impossible to properly adjust rear derailleur indexing

The number one cause of poor shifting is excess cable friction somewhere along the line. You describe "hesitant" shifting coming down from largest cog to the next. This is a symptom of ...
Jeff's user avatar
  • 10.2k
11 votes
Accepted

Best drivechain for beach, seaside, coastal, winter, generally salty environment?

As someone who lives on a peninsular and services bikes, I'll throw in my oar, though there's probably overlap with other answers. My own bike has a Sturmey Archer 3-speed hub, gates belt drive and ...
Noise's user avatar
  • 13.9k
11 votes

Can you use a shimano Tourney Rear derailer with a 1 x 11 (11- 52 ish) sprocket?

Not a chance. Rather than asking for each one, here's how you work it out for yourself. Google up shimano tourney RD-TX800 spec or whatever model you're looking at. There will be some link to ...
Criggie's user avatar
  • 124k
11 votes
Accepted

Removing and re-using a Shimano Tourney deraileur hanger - vintage road bike

The claw adapter piece of the Tourney you have isn't designed to be removable in any way. All you need is one of these, called a claw adapter:
Nathan Knutson's user avatar

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