Description of the malfunction:
The pedals of the bicycle are spinning when pushing/walking the bike even though there’s a cassette freehub or a freewheel that’s supposed to be in coast mode.
This phenomenon is commonly known as “ghost pedaling“.
The root of the problem:
The most likely culprits behind this phenomenon are:
- а broken freehub body;
- overly tighten cones of the rear hub;
- tight chain;
Structure and Function of the Rear Hub
A basic understanding of a cassette freehub’s operation is necessary when diagnosing the described issue.
The image above shows the fundamental anatomy of a rear hub.
The enclosure of the hub (black body) is known as a hub shell.
The hub shell spins around the axle and stores the bearings of the hub and the ratchet ring.
The next photo depicts the freehub body – the unit responsible for the ability of the bicycle to coast/freewheel when the rider is not pedaling.
When the freehub body is spinning clockwise (pedaling), the pawls open and bite against the ratchet ring which is press-fit into the hub’s shelf.
The bond between the pawls and the ratcheting ring connects the freehub body, and consequently the cassette, to the hub shell and allows the transfer of power to the rear wheel.
During coasting and backpedaling, the connection between the freehub body and the shell is interrupted.
In consequence, the hub shell continues spinning, but the freehub body remains stationary and so do the chain and the pedals.
The illustration above shows what happens during pedaling – the freehub body is spinning anti-clockwise (backward pedaling) whereas the hub shell and consequently the wheel remain stationary.
During coasting, the freehub body and consequently the cassette and the chain remain stationary while the ratchet ring keeps spinning and “brushing” the pawls of the freehub body.
The sliding of the ratchet against the pawls is the source of the clicking sound that you hear when coasting/freewheeling.
When you are walking/pushing your bike, the hub immediately enters “coast mode” because there’s nothing to spin the pedals.
Sources of The Problem
If the pedals of your bike keep spinning even when you’re walking it, the most likely sources of the problem are:
1. Seized or Broken Pawls
One of the ways to know with greater certainty whether the pawls are malfunctioning is to lift the bicycle upside down or clamp it on a bike stand and then spin the pedals backward.
If the rear wheel is spinning along with the pedals, then there’s a very high chance that the pawls are either too dirty or broken.
Over time the grease lubricating the pawls will mix with dirt and harden.
The contamination will partially or fully reduce the responsiveness of the pawls, and they may seize against the ratchet ring.
One of the possible solutions is to spray a degreaser into the opening of the hub while spinning the freehub body to spread the chemical over every pawl.
Then, you will also have to lubricate the hub with light oil to keep the mechanism running smoothly. Stay away from thick oil as if may prevent the pawls from moving freely.
If you don’t want to bother with two different chemicals (one for cleaning, one for lubrication), you could consider using a product that does both.
A common example would be Boeshield T-9 Bicycle Lubricant which cleans and lubricates bike components.
If you have a freewheel rather than a cassette hub, you can use the same method.
The only difference is that you will have to clean the freewheel itself rather than the hub.
If this method fails to produce results, you may have to disassemble the hub to fully service it.
Keep in mind that the freehub bodies of cheaper hubs are not meant to be serviced, and there’s no way to open them without total disintegration. In that case, you will have to buy a new freehub body.
If you have a higher-end freehub, there’s a greater chance that its freehub body is serviceable. Search for the manufacturer’s instructions on how to service it or bring it to a reputable bike shop.
If a pawl breaks a small piece of it may get stuck in the hub and occasionally bite against the ratchet ring. The end result will be sporadic ghost pedaling when the bicycle is coasting.
To fix this issue, you will have to replace the broken pawls, the freehub body, or the entire hub.
2. Tight Cones
Over-tightened cone nuts of the rear hub could be another source of ghost-pedaling.
The cone nuts are important “regulators” that are a bit tricky to set-up.
If they’re too loose, there will be play in the hub; if they’re too tight, the wheel won’t spin freely. Both situations are not desirable.
A tight cone nut could be preventing the freehub body from operating independently by pulling the driver body into the hub shell.
In consequence, the freehub body fails to disengage and keeps rotating along with the hub’s shell. The chain and the pedals have no choice but to spin too.
If this is the source of the problem, readjustment of the cone nuts will be necessary.
Note: If you have a Shimano freehub, only the cone on the non-drive side of the hub is designed for adjustment.
Shimano is among the few manufacturers sticking to a cup and cone system due to its simplicity and the ability to service it more easily.
Other producers use cartridge bearings for their hubs. In that case, you wouldn’t have to deal with a cone but with an end cap.
If the end cap is overly tightened, it will create a similar effect and prevent your bicycle from coasting.
Hence why manufacturers install a special mechanism meant to keep the end cap where it’s supposed to be.
One example of such implementation would be SRAM S30 AL gold/RACE/SPRINT & S27 AL COMP hubs. Those models have a set screw that retains the end cap to prevent unintentional adjustment.
If the screw is set improperly, or the mechanism underneath is malfunctioning, the coasting of the bike will suffer.
3. Tight Chain
A tight-fitting chain can also be a source of ghost pedaling.
During coasting, which is what happens, when you’re walking your bike, the freehub body and the cassette are technically resisting against the ratchet ring which is spinning and brushing the pawls.
The contact between the ratchet ring and the pawls may cause small movement of the freehub body and consequently the cassette.
If the chain is really tight and there’s no slack, the subtle movement of the cassette may be enough to spin the chain a bit and with it the pedals.
4. A New Hub
If the hub is new, the grease in it may still be too thick. This may be enough to stop the pawls from disengaging as quickly as possible.
In this scenario, simply riding the bicycle should resolve the issue because the lubrication will spread evenly over the bearings.
Sometimes this is the case even for expensive hubs. I’ve heard of people experiencing ghost pedaling with Chris King hubs for a bit due to fresh lubrication.
5. An External Object
If there’s an external object stuck between the largest cog of the cassette and the spokes, the bicycle will not be able to coast effectively.
One example would be a piece of a rag used to clean the cassette. Even a small stray from it can cause the problem, especially if the material is strong cotton. Another possibility would be grass or a thin and flexible sprig.
Examination and cleaning of the cassette should suffice to eliminate the ghost pedaling if the problem is external.
6. Improperly Assembled Hub
The rear hub contains many pieces that come in a specific order. If the hub hasn’t been assembled properly after servicing, one or more parts may be causing extra friction preventing the freehub body from operating as intended.
Frequently Asked Questions
I’ve been told that it’s normal for the pedals to spin when I remove my feet from them. Is that true?
If the bike has a freewheel or a cassette hub, this shouldn’t be happening except for a brief second.
If the hub is new, however, the grease in it as well as the resistance of the cassette could be making it difficult for the freehub to disengage even when the pedals are “free”.
If this is the case, the issue should go away after a couple of rides as the grease “softens”.
If the hub is old, it’s probably malfunctioning.
I have a single-speed bicycle, but my pedals are spinning as if it’s a fixed-gear. Why?
A broken or contaminated freewheel is the most likely problem.
Also, if your bicycle has a flip-flop hub (one side is a freewheel, the other a fixed cog), check to see if you’re actually using the freewheel.
The bike shop or the previous owner may have put the wheel in “fixie” mode.
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Very informative. Thank you!