On Rear Mech Longevity

from Rookie’s keyboard

Hello, friends

It’s rainy outside – and therefore a good moment to sit back and write another post for the site.

Today, I’ll talk about rear mech (RM) longevity.

The rear mech/derailleur is essential as it turns bicycles into highly efficient conquering machines.

With a click, you can find a cog and chainring combination that spares muscular energy and maximizes your mileage.

Shifting isn’t the only job of the rear derailleur. It has to maintain adequate chain tension too. All of that results in stress….constant stress. And yet – even somewhat cheap rear mech units last forever (outside of a hit).

A rear derailleur produced by a reputable brand (e.g., Shimano, SRAM, Campagnolo…etc.) has a very strong chance to outlive all components on a bicycle beside the frame.

There are numerous stories of people accumulating a very high mileage on their rear derailleurs (e.g., 20,000 miles/32 186 km) without a noticeable play in the joints or degradation in shifting.

A while back, I talked to a random bike courier about his bicycle. He told me that he’d built it entirely out of second-hand parts except for one of the rims. The bike had a rusty frame and components of mismatched colors.

The derailleur on the bike was a dirty 10-speed Shimano Deore RD-T610 bought second-hand from a local website. It had scratches all over the body,

The courier told me that he alone had amassed 10,000 miles/16000 km with that derailleur over the last year. The total mileage of the derailleur was impossible to know. Those numbers sound impressive but didn’t shock me.

I have a Shimano Altus RD-M310 (image below) on my hardtail – a low-end model in Shimano’s groupset hierarchy. The derailleur is not fancy, but I have only positive things to say about it; it’s cheap and has been performing flawlessly for years.

Shimano Altus RD-M310

For about 2 years, I was commuting on it in all kinds of weather, and it never gave me serious problems even though I’d only clean it once in a couple of months.

I also have a second-hand Shimano Tourney TZ 6/7-speed derailleur that came with an old-school German MTB under the brand of Kenhill.

The bike itself is over 20 years old, and I guess that so is the rear mech. Yet the derailleur still works.

The Most Common Sources Of Rear Mech Failure

The most common source of rear mech failure is……a hit.

Most derailleurs “retire” not because they’re “tired”, but because they’ve been destroyed during a fall or by an object wedged into the drivetrain (e.g., a rock, a tree branch…etc.).

It’s also possible for the rear derailleur to get pulled or pushed into the spokes of the rear wheel. This can happen as a result of a fall, a hit, or a fallen chain.

Mountain bikers are the most likely to mechanically break a derailleur due to the stunt elements of the sport (jumps, drops, manuals…etc.) and the high density of obstacles found on the terrain.

The Parts That Wear Out The Fastest

Joint play and deterioration of the jockey wheels and their bearings is the most common “overuse injury”

For that reason, jockey wheels are also the most frequently replaced part of the rear derailleur.

The most obvious sign of jockey wheel wear is the shape of the teeth. If they’re pointy and sharp like a ninja throwing star, then they have to be replaced.

Having said that, the process of getting a jockey wheel to that state is rather long.

A worn jockey wheel can cause slow shifting and some slipping.

However, if the chain is slipping, more often than not, the cause is a worn-out cassette rather than a jockey wheel.

But if the cassette, the chainring(s), and the chain are new, and yet the gears are still slipping after proper indexing, the culprit could very well be a worn jockey wheel.

The bearing of a jockey wheel can be problematic too. Worn or broken ball bearings do not roll smoothly, and in some cases, they may jam and cause the jockey wheel to seize completely.

Jockey Wheel Material

The jockey wheels found on most bicycles are made of nylon – a plastic with long and heavy molecules.

The main reasons for choosing it over other materials are:

Low weight, low price, decent durability. Plastic jockey wheels are cheaper than the more sophisticated metal ones.

Less wear on the chain. Nylon is softer than metal and easier on the chain than steel.

Stress resilience. Some people believe that a nylon jockey wheel has a built-in safety mechanism. If the bearing seizes, then the wheel could continue to turn by sliding around the outer shell of the bearing. It’s debatable to what extent this could happen in practice.

The Floating Jockey Wheel

The upper pulley of Shimano derailleurs is designed to move a bit to reduce excessive chain noise and to compensate for slight imperfections in gear indexing.

The floating jockey wheel of Shimano is also patented and considered one of the reasons why it was so hard for SunTour to match Shimano’s shifting performance in the past.

Jockey Wheels Maintenance

Jockey wheels should be cleaned and inspected for wear regularly. Having said that, you don’t have to be a fanatic. A good rear derailleur can operate even when it’s not perfectly clean.

Most derailleurs come with bushings instead of bearings. Those types of pulleys would benefit from regular cleaning, but putting grease on them results in dirt accumulation rather than improved performance.

I also have bushings on my derailleurs, and the only maintenance I do is cleaning the parts once in a while.

The bushing/roller is above the bolt and goes into the wheel. The other two metal pieces are seals/caps and protect the bushing and the axle/bolt from dirt. This system is super simple, effective, and does not require a lot of maintenance. Hence why you find it on lower-end derailleurs.

Bushings may be considered primitive, but they’re less prone to problems such as sudden seizing thanks to the simplicity of the system.


More sophisticated jockey wheels come with ball bearings which require more intensive servicing consisting of the following steps:

1. Remove the jockey wheels from the derailleur. (You will need an Allen key.)

    Before removing the jockey wheels, you can take a picture with your phone. That way you won’t have to rely on your memory to remember the orientation of the jockey wheels when reassembling the derailleur.

    2. Clean the jockey wheels with a towel.

    3. Remove the spacers and the seals of the jockey wheels.

    4. De-grease the bearings and the seals.

    5. Put fresh grease into the bearings and put the seals back in place.

    This procedure could also revive a seized jockey wheel.

    Minimizing The Effect of Bad Weather

    Here are some tips that can reduce the effect of bad weather on a derailleur:

    1. Get a winter “beater” bike. (cheat winter)

    A cheap but otherwise functional bike can be easily turned into a very good winter/rain commuter. Even with lower-end components (e.g., Shimano Tourney), the bicycle should ride nice enough.

    By using it only on rainy/snowy days, you will spare your nicer derailleur while introducing some variety to your commuting experience.

    If you want to keep things simple during the winter for the sake of lower maintenance, you could build/buy a single-speed bicycle and eliminate the need for a derailleur.

    Of course, this option isn’t for everyone. Some cities have too many hills to cover the distance without gearing.

    2. Develop a clean & protect policy

    Cleaning the derailleur after every winter ride will prevent a lot of damage and prolong the life of the component.

    For example, you can wash the derailleur with water, dry it with a cotton towel/rug, and then spray it with WD-40 or a product with similar functions.

    The WD-40 will create a layer of protection reducing the chances of corrosion. It will also lubricate the mechanical components of the derailleur.

    If you want even more lubrication, you can put a few drops of the oil that you lube your chain with on the pivots of the derailleur.

    A Note On Shifting Issues

    The rear mech is often associated with shifting problems, but in a surprising number of cases, the culprit is found elsewhere.

    If you are experiencing inaccurate shifting, and the derailleur looks fine (straight), the sources of the issue could be:

    1. The derailleur hanger

    If the derailleur hanger is bent, it will cause funny shifting even if the derailleur itself is in perfect condition.

    2. Shifting cable + Housing

    A worn-out and/or improperly rooted shifting cable can create a great deal of shifting problems.

    Cyclists often buy new derailleurs and talk about how great they are in comparison to the old ones. Ironically, a lot of the improvement often comes from the new cable accompanying the upgraded derailleur rather than the mech itself.

    3. Worn cassette/Freewheel

    A worn cassette or freewheel can cause serious gear slipping, especially when combined with a new chain.

    If the derailleur hanger is fine, the next step to fixing slipping gears would be to change the cassette or freewheel as well as the chain.

    4. A contaminated shifter

    If the shifter is contaminated, it can cause shifting problems. In similar situations, one of the options is to take off the cap if it’s removable and spray WD-40 or a similar product while clicking the shifter up and down.


    Until next time,

    Rookie


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