Gears & Gadgets: Brake Adjustment
Gears & Gadgets, May 2015:
Brake Adjustment
This installment of Gears & Gadgets will focus on proper brake adjustment. Proper brake adjustment is crucial to riding safety and efficiency.
An instructor once jokingly told me “brakes just slow you down.” This was during a high-speed class in which we were learning advanced riding techniques. His statement, of course, was in reference to proper use of the brakes, including when to avoid using them. However, when we need them, we want to make sure they work properly and stop us in a safe manner.
Many public safety bikes, particularly older models, are equipped with linear pull brakes, aka “V-brakes.” About half of our fleet in Tacoma uses this style of brake. It is a very effective brake when properly adjusted (and when it is not raining). Many new public safety bikes - and mountain bikes in general - have shifted to using disc brakes, either mechanical or hydraulic.
V-Brakes
First I will focus on proper V-brake adjustment. Let’s assume the cables, housing, and pads are in good condition and don’t need replacing. Let’s also assume your wheels are mostly true and not causing excessive pad-rub from being all kinds of wonky.
Proper pad adjustment is crucial to ensure adequate stopping power and prevent premature wear of the pads, wheels, and tires. If the pad is rubbing on the rim or the tire, things will wear out very quickly. Spin the wheel, then watch and listen for brake rub. If you see the pad contacting the tire, double-check to make sure the wheel is correctly installed in the dropouts. I can’t tell you how many times brake rub is the result of a wheel installed in the wrong direction or not fully seated in the dropouts.
If, after you have made any necessary adjustments, the pad is still rubbing on the tire, you will need to use a 5mm allen wrench to adjust the pad. Loosen the offending brake pad, and then squeeze the brakes closed with the brake lever. Adjust the pad until it is lined up with the rim and not touching the tire. Tighten it down snug. Keep in mind: it may still need some minor adjustments once you release the brake lever, but this is a good starting point. Re-engage the brake lever and see if the pad is properly lined up on the rim. If needed, loosen the pad again and make minor adjustments until it is properly lined up. I often toe the front of the brake pad slightly in towards the rim to help prevent brake squeal.
Now, if the pad is lined up properly and is rubbing on one side of the rim (not on the tire), we need to adjust the spring rate. On each side of the brakes towards the base (pivot point), there should be a small Phillips head screw on the outside of the brake. Turning the screw in (clockwise) will put more tension on the spring, and turning the screw out (counterclockwise) will release tension. If the left side pad is rubbing on the rim, you want more spring tension on that side and less on the opposite side. The first thing I always do is actually release the spring (a long metal rod) from the brake. I bend the spring outward to give it a little more tension. I then reset the spring and re-evaluate. If that trick doesn’t work, I will then turn the tension screw in about a half- to a full-turn. I re-evaluate, and if it is still rubbing, I will then loosen tension on the opposite side. It’s a game of give and take, and finding the right balance. Ideally, you want equal distance between the pads and the rim on both sides.
If your brake levers are too loose (remember the “rule of thumb”), first attempt to adjust them using the barrel adjusters on the levers. Remember, barrel adjusters are for minor adjustments, not major ones. If needed, you can add or remove cable slack at the brakes using a 5mm allen wrench.
To check if your pads are worn out, look at the face of the pad that touches the rim. There is a wear strip that will indicate if they are worn out and need replacing. If they are glossy, rough the surface using emory paper. Glossy brake pads won’t help you stop very well. Clean your rims as well, using a shop rag and rubbing alcohol. Don’t use solvents or other chemicals to clean your rims; they can contaminate the brake pads you just worked so hard to adjust. Installing new brake pads is fairly easy, and can be done so following the adjustment guidelines above.
Disc Brakes
Now let’s talk about disc brakes. Some disc brakes can be very finicky and a pain to set up properly. It is not uncommon for there to be a rub on the disc that you just can’t seem to get rid of. I’ve never met a disc brake that can’t have the disc rub fully adjusted away, but some models require tons of patience and a bit of luck.
Spin the wheel and listen for the pads rubbing on the disc. If you don’t hear anything, you’re doing better than most. It is not uncommon for a disc to be slightly out of true, causing periodic rubbing. If this is the case, you can use a disc truing tool or a crescent wrench to true the disc. While slowly spinning the wheel, look and listen for the disc rubbing on the pads. If you can see exactly where the disc is rubbing on the pad, use the disc truing tool to bend the disc in the opposite direction of where it is rubbing (if it is hitting the left pad, bend the disc slightly to the right at the rubbing point). Keep working the disc until it is as true as you can get it.
If the disc is rubbing the full diameter on one pad, the caliper needs adjusting. Start by loosening the caliper, often with a 5mm allen wrench. Don’t unscrew the bolts too much; just enough to loosen the caliper. Then, while spinning the wheel slowly, activate the brake lever. This, theoretically, should center the caliper on the disc. Tighten down the bolts on the caliper. Release the lever, spin the wheel, and listen for brake rub. If it’s quiet, you’re done…if not, let’s continue.
Perhaps it is better but still not perfect, so some fine-tuning is in order. Loosen the caliper bolts just enough to be able to move the caliper. Slowly spin the wheel, watching and listening for the pads rubbing on the disc, and move the caliper around. Being able to see exactly where it’s rubbing is crucial, although sometimes very difficult. I often adjust the bottom part of the caliper first until I can see that it is perfectly centered over the disc, then tighten the lower bolt a little (not completely snug). Then I’ll adjust the upper part of the caliper until I can see that it is perfectly centered. Ideally, the bottom part of the caliper will not have moved and the entire caliper should now be centered. Snug down the top bolt all the way, and then finish off the bottom bolt. Again, patience and luck are often key when adjusting the calipers over the discs.
Depending on the make and model of the disc brakes, there are other adjustments you can make to eliminate pad rub. Avid BB5 and BB7 mechanical disc brakes have pad adjustment dials on the calipers. I can’t speak for other mechanical disc brake models as I have not had much experience outside of Avid’s. Most entry-level and mid-level hydraulic disc brakes generally have very little adjustment at the user level. That’s why proper setup as described above is important. The nice thing about hydraulic disc brakes is that once they are properly set up, very little maintenance is needed other than pad replacement or an occasional bleeding.
Pad Replacement
To replace pads on hydraulic disc brakes, first remove the wheel. Remove the pads according to the manufacturer’s specifications. Then, using a soft tool (tire levers or a flat-head screwdriver wrapped in a shop cloth), push the pistons back into the calipers. You should see them actually moving back into the caliper. Once the pistons are pushed back all the way, install new brake pads. Make sure you clean the discs on the wheels, using rubbing alcohol on a shop cloth. Again, don’t use any chemicals or degreasers to clean the discs as that will contaminate the pads. Place the wheel back onto the bike and check for proper alignment. If you are getting pad rub, refer to the last few paragraphs to adjust them.
It is not uncommon for disc brakes to squeal, howl, and be down-right nasty sometimes. Loud disc brakes are generally a sign of contaminated brake pads. Generally the best option is to invest in a new set of pads, and make sure the rotors are thoroughly cleaned before coming in contact with the new pads. However, there are a few tricks to try before buying new pads. First, clean the rotor with rubbing alcohol. Then, remove the pads and scuff them up with an emory cloth. Re-install and give it a go. If the noise goes away, lucky you. But chances are, the noise will return.
The next method is a bit more fun, but has the potential to ruin the pads completely. If you’re already considering buying new pads then this method won’t bother you. You will need a bottle of rubbing alcohol and a lighter or matches. You probably also want to have some means of extinguishing a fire, such as a hose or a fire extinguisher. Safety eyewear is also recommended here.
Remove the pads and place them face-up on a concrete surface, away from any flammable materials. Douse them in rubbing alcohol, giving the alcohol about 30-45 seconds to soak into the pads. Keep in mind that alcohol evaporates quickly, so you won’t want to wait long. Use a lighter or match to set the pads ablaze. The alcohol will boil until it has burned away.
Theoretically, the contaminants within the pads (oil, etc.) will also burn away with the alcohol, leaving you with a clean pad. The fire will put itself out when all of the alcohol has burned away. I’ve done this successfully with Shimano resin pads, but haven’t tried it on other brands or types of pads. I suppose it’s possible that doing this will ruin the pad, so doing some research on the internet wouldn’t be a horrible idea if you are considering this method. If all else fails, like I said, new brake pads are the best way to go.
All this talk about alcohol has made me thirsty. Until next time, ride safe and have fun.
The information described in this article is meant as a resource. Please know your own personal limitations when it comes to bicycle maintenance and do not attempt to repair anything you don’t understand or do not have the proper tools for.
If you have any questions, or suggestions for future topics, please feel free to email me at jared.williams@ci.tacoma.wa.us
About the author: Jared is currently a Police Patrol Officer for the Tacoma Police Department. He loves to tinker, and can often be found obsessing of the mechanical state of his bicycles. Jared is the owner and operator of Piggies On Wheels, LLC, which exists for the purpose of public safety bicycle education. To learn more, go to https://www.facebook.com/PiggiesOnWheels.