Riding down a mountain trail, enjoying the sights and sounds of nature, when suddenly an annoying screech cuts through the peace and quiet. That terrible creaking is coming from your brakes. This jarring noise ruins the whole experience and leaves you wondering what’s going on with your bike. Understanding what causes brake squeal and learning how to fix it will have you back on the trails in no time.
What Is That Awful Noise?
The screeching or squealing noise coming from your brake is called brake squeal. This happens when the brake pads rub against the rotor as you apply the brakes. The vibration causes the components to resonate at a high frequency which produces that nails-on-a-chalkboard sound. Several factors can contribute to and exacerbate brake squeal on mountain bikes.
Why Do My Brakes Squeal?
There are a few common culprits of noisy mountain bike brakes. Contamination between the pads and rotors is often the problem. Things like oil, dirt, sand particles, or other debris end up embedded in the pads and rotors. As you apply the brake lever, these particles vibrate against the rotor producing noisy squeals and squeaks.
The composition and hardness of the brake pads also impacts noise. Organic pads generally provide better modulation and less noise than sintered metal pads, but organic pads wear out faster. Humidity can cause slight variations in size of brake pads, just enough to alter vibration frequencies and induce squeal. Even your riding technique matters – braking too hard or not “toeing in” the pads correctly can lead to noise.
But perhaps the most common cause of annoying brake squeal is that the rotor itself has become warped. Heat from braking causes rotors to warp over time. This uneven surface vibrates against the pads generating that irritating resonant squealing.
How To Fix Squeaky Brakes
Luckily several easy solutions exist to quiet noisy brakes and get rid of annoying squeals while riding. Here are four effective ways how to stop brake squeal on your mountain bike.
Clean contaminated brake pads
Carefully inspect each brake pad, looking for embedded particles, uneven wear, glazing, cracking, or excessive wear. Use a coarse file brush and gently scrape debris off the pad surfaces. Avoid damaging or filing down the pad material itself during cleaning. Next, use a clean rag with isopropyl alcohol to thoroughly wipe down the rotor and remove any oil, grease residue, or other contaminants. These steps clear out the squeal-inducing particles between the pad and rotor surfaces which should eliminate any vibration noise.
However, if the rotors have become deeply grooved or uneven due to significant embedded debris, they may need to be replaced. Uneven rotor thickness causes vibration and noise. Inspect thickness variation using a dial indicator while slowly spinning the wheel. Any sections over 0.15mm variance require resurfacing or rotor replacement.
Replace worn out brake pads
Carefully measure pad thickness using calipers and inspect for glazing or uneven wear patterns. Organic pads should be replaced once they reach 2mm or less in thickness. Sintered metallic pads under 3mm need replacement. If one pad set shows significantly more wear than the other, the caliper alignment may be off causing uneven pressure. This would require brake service to realign components.
When installing new pads, make sure they are the identical model and composition as the existing set for proper compatibility. Use brake cleaning spray to remove any oil or film on new pad surface and rotor contact points. Proper “toeing in” of pads prevents uneven pressure application and noise-inducing vibration. This involves adjusting the leading pad inward slightly so the front contacts rotor just before the trailing pad.
Resurface the brake rotors
Inspect rotors closely for uneven wear, grooving, cracking, bluing, or gouging. Use a Park Tool Rotor Truing Fork to check for lateral true of the rotor and identify any warped sections. Carefully bend back small warped portions by hand with gentle pressure. For more significant warping beyond 0.15mm variance, the rotors will need resurfacing or replacement.
Resurfacing eliminates dips and high spots by filing down some material to achieve a flat smooth rotor surface again. Use 220-400 grit sandpaper attached to a flat block. Work slowly and evenly across entire rotor surface, checking frequently with a straightedge. Remove no more than 0.25mm depth when resurfacing to avoid weakening the rotor. This should eliminate warped sections prone to vibrating against pads and causing squeals.
New rotors may have a protective film requiring removal with isopropyl alcohol prior to use to prevent squeaking. And rotors that show significant gouging, pitting, or cracking require replacement as resurfacing would overly compromise structural integrity when worn that deep.
Upgrade your brakeset
If cleaning rotors and pads, replacing worn parts, and resurfacing fails to solve chronic squealing, consider upgrading your entire brake system.
Higher end mountain bike brake systems incorporate vibration dampening technologies into pad shims and caliper hardware which inhibits resonance frequency build up and noise. Materials like aluminum, titanium, phenolic resin, and compression springs integrated into pad backing plates provide dampening interfaces between the pad and caliper. Upgraded brakesets also include insulator bushings where caliper mounting bolts pass through frames or forks which reduces potential vibration points.
Premium level brake calipers position pads closer to the rotor for more consistent alignment and pressure application which prevents uneven wear and debris build up – two primary causes of squealing. Four piston opposed calipers generate higher clamping force for improved modulation with less noise. And they incorporate cooling fins and cross-drilled rotors to better dissipate heat buildup and minimize warping over time.
Higher end brake lever and hydraulic line systems maintain more consistent fluid pressure control resulting in smooth even braking power transfer and pad contact further eliminating potential vibration noise sources.
Consider upgrading to compressionless brake housing lines and polymer coated stainless steel braided hose for maximized mechanical power transfer to calipers reducing spongy brake lever feel which can impact stopping consistency.
Prevent Future Noise Issues
An ounce of prevention equals a pound of squeal-less riding. Here are some key tips to stop brake squeals before they happen:
Clean Rotors and Pads – Regularly remove built up contaminants with isopropyl alcohol and gentle abrasion to prevent embedded particles that cause vibration and noise. Inspect thickness and wear patterns with each cleaning.
Lubricate Moving Parts – Caliper mounting bolts, bushings, and contact points should be cleaned and lubricated to maintain smooth operation necessary for noise-free operation. Avoid getting lube on rotors or pads.
Check Pad and Rotor Thickness – Replace excessively worn pads early to maintain optimal braking performance. Measure and document components during cleaning to identify wear trends early.
Resurface or Replace Rotors – Resurface any warped rotors to 0.15mm tolerance levels or less. If rotors show deep gouging or cracking, replace immediately before catastrophic failure occurs while riding.
Stubborn squeals still persist? Consider upgrading your entire brake system if basic steps fail to resolve chronic squealing issues. High end brakesets run quietly requiring less continual maintenance.
In summary, brake squeal stems from multiple causes but usually indicates contaminated pads and rotors or uneven rotor warpage. Fortunately several easy fixes exist – clean parts thoroughly, replace worn pads, resurface or replace rotors if warped, lubricate and inspect caliper mounting points, and consider upgrading entire brake system. Investing some quick regular maintenance into brakes results in smooth predictable operation letting you fully enjoy the peace and quiet on the trails.
