Should you worry about a little disk brake rub?

My approach to disk brake troubleshooting is simple. I approach it like everything else on the bike. It starts with diagnosing the origin of the problem in the simplest, cheapest and fastest way. Key elements? Don’t get your fingers caught in the rotor (disk). There are many different problems that can occur with disk brakes just like rim brakes. The number one complaint you will come across is brake rub.

Brake rub is usually accommodated with a noise like a squeal or screech. There are a few ways to determine the severity of the brake rub. Is it stopping the wheel too soon? Is it always noisy? Is the rub something you cannot live with? Most of the time the wheel should be spinning freely and quietly. What will usually get your attention or your ridding buddies attention is a noisy disk brake, sometimes with the brake applied and sometimes not. Whats happening here is one or more brake pads are lightly touching the brake rotor. 

If it’s noisy when applying the brake lever that is a sign of some form of contamination. The easiest to deal with is dirt, the harder one to remedy is oil. Dirt on the disk brake or the brake pad can be addressed on its own. Most cases it will clean itself in due time. Oil contamination on the other hand will have destroyed the brake pads almost immediately and will now be considered garbage. The brake rotor or disk can be cleaned with isopropyl alcohol.

Remember this, cleaning the brake rotor will also strip off the good brake pad material and the disk or brake rotor will need to be reintroduced to the brake pads material again. This can be done by braking gently several times in the parking lot. You are basically coating the brake disk with brake pad powder making the contact surface of the brakes rotor tacky or increasing the resistance.

Sometimes the rub is not enough to stop the wheel but maybe just enough to create brake noise and not enough to notice the resistance when pedaling. My first suggestion is do not attempt a brake adjustment unless it is something you cannot live with. The reasoning for this is that there is not a lot of room between the brake pads and the rotor for adjustment in the first place. Attempt this only if you have patience and are willing to master the adjustment. 

There is approximately a millimeter in a half (1.5mm) on each side of the brake pad and rotor and thats being generous. Don’t get discouraged you can still be very successful with a little practice. Repetition is key for learning any new task. Become comfortable with the uncomfortable. I hear that term a lot in sports and I think the same applies here with brakes rubbing the rotor. If you are experiencing a brake rub of some sort there is no immediate danger for your safety or the health of the bike in any way in most cases.

You may be experiencing a light brake rub or disk brake drag and not even know it. I suppose there is a possibility of heat developing from brake drag but it is not enough to create problem. In order for there to be concern from a bad brake rub the wheel would not be able to spin several times before it stops. This is all relative to how hard you spin the wheel when testing. This is something that is hard to learn if you are not used to working on your bike or with your hands. Videos may not be enough to help you with “the feel” of something. Thats where getting hands on help can be beneficial. 

A.R.

The many beautiful layers of the rear derailleur.

The Different Personalities of the Rear Derailleur

When adjusting a rear derailleur I like to break it down into segments. There is a starting point I like to refer to as home base or restarting the computer. This is the place you will start when first installing a rear derailleur on to the bike and the the place you will start when you get confused and need to re-establish what exactly is going on. Home base, just like playing hide n go seek as a kid, you need to establish common meeting ground. It will also help you to find the problem of why the rear derailleur is having trouble.

The derailleur and the chain will be referred to synonymously. The chain is going nowhere unless the rear derailleur tells it to move. The chain and the shifter should always be on the same page. It’s up to you to keep track at all times. One of the best ways to do this is to pay close attention to the clicks in the shifter at all times. If you hear or in some cases feel a click then there should be chain movement. 

One click should equal one gear change of the  rear derailleur (cassette or cog, chain). In some cases two clicks of the shifter can happen very quickly but are often missed by the operator and the operator ends up lost immediately. People are surprised at how intricate a shifting system can be. There are a lot of variables and every bike has a different temperament. Not all derailleurs and bikes are created equally. 

You must take into consideration the age of the component and the level or model. Cost plays a big part I this. Typically the more you pay the better the materials, engineering and quality in most cases. What this means is the more you pay the lighter the part and performance is enhanced. If a rear derailleur, shifter, cable and housing are tired or dirty and has many miles on it then you must take this into consideration as well.

If the moving parts of the component are not working the way they use to when they were new, this usually means the pivot points in a rear derailleur are not as tight, there is more play between hinges. All this adds up to looseness or play that may not be felt all the way back to the shifter. It’s like having a worn out shoe or loose shoe laces. Your foot will slide even it is a small amount but this will add up over time causing a blister. 

When this happens to a rear derailleur some of this can be addressed with the barrel adjuster until it can no longer, then what? How do you diagnose a worn out rear derailleur? How can you tell if the derailleur alignment is incorrect? Which one is to blame? Stay tuned. 

A.R.

I hate patching tubes.

Bicycle repair service in willow Glen CA. The shop is easily accessible and located on the corner of Pine ave and Jaunita Ave. You can find it between the major streets if Bird ave and Lincoln ave in San Jose. This is a neighborhood friendly bike repair shop that caters to family bikes to serious bike racers. We cover basic repairs like flat tires, brake and derailleur adjustments to ground up bare frame bike builds. We cover the serious mountain bike that rides in the Santa Cruz Mountains to all sorts of weekend warriors and commuters.

Replacing a Tube vs. Patching a Tube

Bike repairs can fall into different categories. The most common are flat tire repairs or often called tube replacement. Bicycle tubes are replaced now a days rather than repaired by patching. Patching can be unpredictable. If the patch is not applied correctly it can and will fail. Usually by the ends of the patch coming up by loosing adhesion.

The most common error when repairing a tube by patching is the preparation. If you are in hurry and do not scuff the area enough or most commonly not covering a big enough area for adhesion. The size of the prep area should be twice the diameter of the patch size you are using.

Scuffing of the area should easily be seen after the patch is applied. This goes for the glue as well if you are using a patch kit with glue. The area the glue should cover should be at least a size in a half if not doubled in size of the patch size. Using a little extra glue could mean the difference between a long lasting patch job or the patch failing off the the next day. Another important detail is trying not to touch the prep area with your fingers. Any dirt or natural oil from your fingers can contaminate the adhesion process.