If your chain slackens when spinning in reverse, here’s the remedy.

from Rookie’s keyboard,

Hello, friends

I’ve developed the habit of writing for RJ.com at night, so here’s the nightly post.

This evening I will tackle a fairly common scenario on older (or “unmaintained”) bikes.

When you spin the pedals in reverse (and sometimes when you coast), the chain slackens (loses tension) and “rests” on the drive side chainstay. When you start pedaling forward, it regains tension and snaps back into place.

The most likely route of the problem is a contaminated freewheel/freehub that cannot rotate freely because the pawls are sticky.

When you backpedal, the rear cogs barely move and the chain “clmbs up”.

When the chain is prevented from moving freely, it drags the cage of the derailleur towards the front of the bike.

The spring in the derailleur cannot counteract the pull and the chain sags.

When you resume pedaling, the rear cog moves forward, and the chain is mobile and free again.

The remedy is super simple – degrease and re-lubricate the freewheel or the freehub.


Freewheels are an older system that combines a set of rear cogs and a ratcheting mechanism in one unit.

The freehub comes with its own ratcheting mechanism and is combined with a cassette which does not have moving parts.

If you have an older, low-end bicycle, chances are that you have a freewheel. If your bike is new and mid-range or above, you have a freehub + a cassette.

To know with certainty, you will have to remove the rear wheel and examine the hub and the cogs.

A freewheel will have different cutouts in the middle compared to a cassette.

The lockring has two “dots”.

A freewheel
A cassette

If you have a freewheel, you will need a freewheel removal tool that corresponds to the freewheel type.

Freewheel removal tool

99% of freewheels use a multi-spline tool. Some older ones (e.g., Suntour’s models) require a 2 or 4 notch removal tools that are hard to find because those freewheels are rare.

If you have a cassette, you will need a cassette removal tool and a chain whip which are readily available at every bike shop.

Cassette Removal Tool

Once you get off the freewheel, it’s time to degrease it. The simplest method is to spray degreaser such as WD-40 at the back.

Wash the freewheel with soapy water, dry it, and re-lubricate it by dropping oil in the same area.

You couldtechnically disassemble the freewheel entirely, degrease and re-grease it. However, this method is more difficult and requires more experience. I wouldn’t bother.

If the freewheel is beyond repair, replace it.


If you have a freehub with free ball bearings, you will have to disassemble it, (you will need 2 cone wrenches) clean it and re-grease it.

If the hub uses sealed bearings, it’s not meant to be serviced, and you will have two options:

  • А rough service

You can spray WD-40 or another degreaser into the crack shown below. As you do it, rotate the driver to spread the chemical into the ratcheting mechanism. Then, re-lubricate it with oil.

  • Replace the Hub

If the rough service doesn’t help, the freehub is practically dead and will have to be replaced.

This procedure is more difficult, expensive and less user-friendly because you will have to re-lace the entire wheel to a new hub which may demand spokes of a different length.

The task isn’t extremely challenging for cyclists with experience, but it requires a good number of tools – a truing stand, a dishing tool and a spoke wrench.


A Loose P-tension Spring

In 99% of cases, the culprit is either the freewheel or the freehub.

Occasionally the derailleur is problematic too.

If the P-tension spring of the derailleur has slipped or is broken, the derailleur’s cage will remain pulled forward and thus be unable to tension the chain.

The P-tension spring of many entry-level derailleurs is not serviceable, and there’s no way to get to it without damaging the derailleur. You will have to replace the entire unit.

On some models, however, it’s possible to disassemble the derailleur and re-attach the P-tension spring.


A Super Long Chain

In some cases, an excessively long chain may be the source of the problem. If the chain is far longer than needed, the derailleur will fail to fully stretch it.


By the way, if you want to learn how a rear hub works (and why its pawls could have such a profound effect), consider reading this post.

Until next time,

Rookie


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