Clunking and banging sounds result from bike components banging against each other on another bike part. And this can be for many reasons, all of which can be avoided.

The biggest culprits for clunky noises are the chain(slap) and cables.

Downhill mountain bikes are the most abused, but also the quietest bikes out of the box.
Watch the Pro’s bikes getting handled with a good look at the noise-canceling accessories.

If you ever watched a mountain bike race live or watched raw videos, you probably noticed they are extremely quiet for the beating they get.

So it can be done with a few extra modifications and dampening material in the right spots.

Reduce chain rattle noises

A big part of mountain biking is hustling down rough trails, that give the rider and bike a good shake.

Watch some slo-mo footage and you’ll see how the chain gets tossed around, banging against the chainstay and seatstay (the rear part of the bike frame above and below the chain).

Shorter chain for less slack

The amount of can be reduced by increasing the tension on the chain in two ways: reducing chain length and/or increasing the pull by a clutch derailleur.

The former is free and only requires a chain tool, while the latter can get pricey depending on the drivetrain.

A good rule of thumb for chain movement is 2 finger-widths up or down while on the largest gear. Any less than that is definitely too tight and risks damage.

In fact, new chains come too long for most bikes and need to be reduced in length before replacement in any case.

chain stay rubber guard for noise
Modern mountain bikes come with rubber guards as chain stay protection and noise reducers pre-installed.
Something easily fitted by yourself aftermarket.

Rubber chainstay protectors

With a reduced range of movement for the chain, there is still no way to prevent it from slapping onto the chainstay, the part of the frame right beneath the upper chain line.

Luckily, this common problem is solved extremely easily by covering that part of the frame with rubber.

They come in various shapes and sizes. I personally got simple adhesive rubber tape on the cheap end of the spectrum while solutions like STFU or Velocity Hucking Systems with air pockets offer the best noise-canceling for a higher price.

Generally, softer is better here. Don’t go for thin or plastic frame protectors.

IMG 1146
“Slaphappy” adhesive rubber strips from Easy Frame.

The free, but not-so-pretty DIY version would be the old inner-tube-wrapped-around-and-held-on-by-zip-ties hack.

Chainring guard

Bash guards are primarily designed to prevent lateral chain movement and the chain ring from hitting rocks and roots.

With a lower guide roller, they also increase chain tension and reduce chain slack by pulling it up by roughly an inch.

IMG 1148
A rubber chain guide roller on a bash guard keeping chain slack in check.

Proper chain length is something to keep in mind with a chain guide like this. It needs to be a couple of links longer than without one.

Also, a lower guide roller is not a stand-alone part and has to be mounted to an ISCG chain guard, so it’s an expensive and little impactful method to reduce noise if that’s your main focus.

Stop cable rattle

The other main source of clunking sounds are the shifter cable and brake hoses. Even more than with the chain, restricting movement is the name of the game here as the options are more limited for cable management.

With internal cable routing, the options are somewhat limited. And that cable canal is actually the loudest part on my downhill bike, where I’m unable to eliminate the rattle inside the frame.

So, outside cable routing may be preferable for reducing bike noises.

Shorten cable hoses

The same principle as with the chain slack applies here. The shorter the cable hose, the less room it has to flap around.

And the hoses too need to have at least a little slack so they don’t bend in sharp angles and also allow the handlebar to turn in its full range of motion.

Cables and hoses can be cut with simple, sharp wire cutters. Universal pliers won’t do here. But keep in mind: measure twice, cut once.

Turn the handlebar all the way from one end to the other to check the cable length from the head tube to the handlebar.

Along the frame it can be as tight as possible, it just has to allow the rear suspension to go through its entire travel.

bike cables wrapped with duct tape
Not pretty, but gets the job done: duct tape around my cables to reduce noises.

Attach cable hoses to each other

A great way to prevent the hoses to clap against each other is to combine them straight up. There are rubber connectors, that come with some bikes.

But those tend to move around or not hold the cables that reliably.

A method many riders use is to put regular duct tape around brake hose and shifter cable on the same side, that go parallel to each other.

I also tied the brake hoses together right in front of the stem, where they go on top of each other – a great place to bang against one another.

both brake hoses on a MTB cable tied together
Both brake hoses on my downhill bike cable-tied together to reduce them flapping all over the place

Rubber grommets

Finally, there’s the rubber side of the house again. Especially with internal cable routing, there is always a little wiggle room for the hose inside the channel.

While there is no reliable way to eliminate that inside the frame, rubber grommets help on either end of the cable canal.

It may not look like much and can be cumbersome to install aftermarket, as the brake or shifter system needs to be disassembled to be able to pull out the cables.

But the difference is well noticeable. Maybe combine such an upgrade with another maintenance job. That’s not something I would do on its own.

IMG 1152

Other banging noises

Tighten bolts

Bolt checks should be part of the regular maintenance schedule. A couple of bolts should even be checked before or after every ride.

Namely: Axles, stem bolts, and linkage bolts. The seatstay clamp, grips and brake levers aren’t a bad idea either but, not quite as susceptible to loose bolts.

No noise-reducing accessories can help you when you ride with loose bolts. It’s loud and dangerous for you and the bike all at once.

For a quick tune-up mid-ride, I always carry a multitool on trail rides in my hip pack or backpack. It’s rare but my axles can get quite loose on a full day of rough downhills.

Frame design

One thing you can’t change on the bike, but is definitely worth considering is how the frame’s rear end is designed. What you want is a stable, relatively simple design with not so many moving parts and slim tolerances.

Any imperfections in design or movement in the bearings will lead to quite some movement in the rear wheel accompanied by some annoying noises.

The rear suspension design is why I didn’t go for the otherwise great Canyon Sender downhill bike but the YT Tues.

The Canyon bikes pre-2022 had quite loud rear ends, that only became increasingly louder with more bearing wear.

So, no matter which suspension design philosophy the manufacturer employs, the lesser moving parts, the better.

Also, wider rear triangle designs generally are more stable and bulletproof.

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