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*Edit Me* - New FAQ addition on brake squeal.
Howdy. i posted a couple days ago asking for tips and thoguhts on
brake squeal. i was not, as i had naievely hoped, immediately inundated with secretive tricks and age-old wisdom, so i did the best i could with my own knowledge and the archives, and present the following for you to pick apart. post if there are any glaring mistakes, additions, etc. when i quoted sections from posts, i attributed with a name and email address. if it shoudl be just a name, or just an email, or neither, let me know. best anthony --- Practical Steps towards quieting squealing brakes. Toeing in brakes is the most basic and widely known advice. A few specifics regarding various types of brakes: V-brakes. Start with no pad toe-in. If they squeal, try toeing them in a little. Aim for no more than 1/32". A lot of toe in is unacceptable as there is not much cable travel to spare and you get mooshy action. Cantis. Start with them slightly toed in. Possible starting point might be width of a dime at first contact of front of pad. Popular wisdom seems to be quite supportive of toe angle experimentation with cantis. If they squeal, try a steeper angle. 1-3mm is a good realm to stay in. Road brakes. Start with no toe in. Many calipers do not have hardware (spherical washers) to toe in pads. There are many aftermarket brake pads that toe in easily, so that is one good option if they squeal. Unlike beefy brakes like cantis and v's, you can generally bend a road caliper to toe the pad in. This is, of course, a cinch with flimsy department store calipers. It was common practise with older road calipers like centerpulls, and there is even a park tool made specifically to do this. Modern road calipers, dual pivots especially, are pretty beefy and don't take as kindly to 'metalworking'. Some new calipers come noticeably off kilter, either toed in the wrong way, or otherwise misaligned. It is said that cold setting these new calipers is a bad thing, as anytime you bend aluminum there is some risk of damage- present or future. However, I see mechanics in shops bend (very small bends, mind you) modern road calipers with regularity. No problems- Yet. YMMV. An alternative to bending calipers to achieve road caliper toe in is to take the pads off the calipers and sand them on a belt sander, or with a block of wood and sandpaper, such that they are toed in. Disc brakes. see bottom of article. If appropriate toe-in doesn't work, things to try, in rough priority: -clean rim. you might even do this before toeing in. soap and water generally work. or, you can try an appropriate solvent. Alcohol, and acetone seem to work. Automotive brake cleaner has also been suggested. Alcohol is much better for you than acetone, acetone is a stronger solvent. Brake cleaner doesn't sound like something you'd want to drink either, but sometimes you have to make sacrifises. -Make sure pads are correctly oriented. Pads where orientation matters generally have an arrow that indicates rim revolution direction. Art Harris writes: "If you have any of the "asymetrical" pads, make sure the longer end is towards the rear." If there is no indication of correct orientation, you could try turning them around, or switching them left for right to see if that changes anything. -sand rim. or scotchbrite. machined rims have a roughness to them already, but sanding can sometimes help with these anyway. with some rims, steel wool, or a 400 grit swipe is all it takes. 125 grit is the last resort, and your rims better be pre-machined or the fine scratches will look pretty ugly and nobody will talk to you on the club ride. -take brake system apart and rebuild clean, lubed, and tight. neglected points would be a little grease between pad washers which can make a difference. -clean pads. also make sure there is no foreign matter embedded in the pads. -sand pads. or scotchbrite. if that doesnt work, file pads. You can also try sanding areas of the pad away. Sanding a bevel into 1/4 of the leading edge of the pad has been suggested a few times. -uneven toe in. toe in one pad only, or one pad more than the other. -Toe-OUT. yes. toe the pads the wrong way. As little as 1/64" all the way up to 'generous' toe-out. this decreases braking power, but if you keep it conservative it should not be a problem with modern brake systems. -change pad, either material or construction. a cartridge pad is stiffer than a disposable brake pad. in addition, some cheaper pads may have inferior tolerances and not seat as firmly onto the caliper. changing material can make a big difference. -for bossed calipers (cantis/v's) a brake booster stiffens the system. -aftermarket adjustments to brake calipers. Shimano, for example, sells shims that adjust the play in some of their bossed brakes. This was specifically to address squealing problems in parallel-push calipers, IIRC. -change brake calipers. stiffer might help. or just changing something can do the trick. higher quality does not necessarily mean less squealing, but it generally is a step in the right direction. -you do have aluminum rims, don't you? Misc. Tips and Tricks. Popular wisdom on R.B.T To sand your rims, and clean any contaminants off at the same time, you can do it while riding. From a variety of posts, your options include riding in the rain, or through puddles, or mud, while braking a lot. Putting an abrasive on the rims while riding such as bathtub cleaner, etc, laying on the brakes, and rinsing it off afterwards with a waterbottle can work too. Mellerio: I have tried everything under the sun to quiet XTR v-brake squeal on my Cannondale Headshok Fatty SL. A Shimano Carbon Brake Booster works because it dampens the vibration. This led me to find other solutions to dampen vibration. I tried rubber bands around the pivot arms, etc. and nothing worked. Today I tried placing a 1/8" O-Ring between the v-brake and the brake boss mount. I tightened down the v-brake, compressing the O-Ring and took the bike for a spin (without the carbon booster). No squeal!!! [Although in the rain they still squealed] From Mike Jacoubowsky: First, just for kicks. try reversing the front wheel. From Gmaker: -Observe the wheel from above in very good light. -Very slowly apply brakes. -Carefully check if the wheel deflects slightly in one direction as a result of one pad applying more force than the other *just when they hit*. This can happen even though the pad standoff appears equal and the pads seem to move evenly. Adjust pads to stop this. Counter-intuitive, and unproven, From K. Becker: Here's an unconventional cure for brake squeal: Put a little wax on the rims or the pads, rubbing them lightly with a crayon or a candle works well. I've used this method on several of my neighbor's bikes, since the metal used for brakes on cheap bikes is often too brittle to toe-in. The wax actually seems to improve the performance, although if you used too much it might decrease it, so apply sparingly. From Neil, at the shop I work at If all else fails, or you are in a hurry, brushing a little talcum power on the brake pad seems to take squeal away. Unsure about how long it lasts. The Kool Stop Salmon Legend: A Red Herring? Koolstop salmon pads are highly recommended on r.b.t for their power and quality. On my own bike, I can feel a marked difference in power when running the KS salmons. However, all is not golden. Some or all of these salmon pads seem to be particularly resistant to de-squealing with some setups. Many posts volunteer alterations you can make that may or may not cut down on squeal, including sanding off the plow tip, sanding a bevel into the pads, sanding in a 'toe-in', etc. Many suggest koolstop dual compound pads for bikes in need of quality pads but with serious squealing issues with the full-salmons. Another possibility to reap the benefits of grippy salmon is to use the KS salmon cartridges with a stiff metal cartridge holder. Things that can cause a brake that wasn't squealing before to start squealing; -coating the rim with a substance that exaggerates the stick-slip behavior of pad on rim. examples include getting oil or grease on the rim surface, or biking through wet grasses as mentioned in the FAQ. Fix: clean the rim. -Too clean. This is one that has happened to me. It seems that some amount of dirt or abrasive on the rim can keeps things quiet for squeal-prone brake systems. I once cleaned the rims on one of my squeal-prone rides with alcohol, and suddenly my brakes were squealing after months of silence. I cleaned again. More squeal. I figured it was impure solvent, so i upgraded to acetone, and cleaned them with that. still squealing like a pig. I had to lightly sand the rims and toe them in more to shut them up. -pads wearing down and developing new resonant properties. re-toe in, sand, or whatever it takes. -bad karma. call your mother, clean your bike, feed your dog, and hope for the best. Disc brake squeal: Y'know how all the manufacturers say not to get oil on your rotors/pads while setting up/bleeding your brakes? Well. Now you know. Clean them. Clean the pads. Clean everything. Some companies say that cleaning pads of oil is useless and hint that they might need replacement. YMMV. Below find some tips. In addition to these, check that everything is clean, lubed, and tight. As a last resort, you could try sanding the rotor itself. From Tony Raven: 1. Clean the disc with [solvents such as] methylated spirits and make sure it does not get oil or wax on it - washing the bike with wax containing car shampoo can cause the problem as can clumsy spray lubrication. 2. After cleaning the disc, take the pads out, place fine emery on a flat (glass?) surface and rub the pad surface on the emery in a figure of eight motion to remove any glazing that may have formed. 3. Put the pads back (in the same place as they came from, don't mix them up) with a smear of copper grease between the pad and the piston. 4. Chamfer the leading edge of the pads 5. Ride in wet abrasive mud From Rich Wood: lightly coat the back of the pads with copper grease. You might need to put a strip of aluminium tape on there first to stop the grease contaminating the pads. Thank you to: Everyone. I couldn't possibly cite everyone who's posts contributed to this accumulated knowledge, so a big thank you and an electronic hug will have to do. |
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*Edit Me* - New FAQ addition on brake squeal.
A couple of really cosmetic findings:
Cantis. Start with them slightly toed in. Possible starting point might be width of a dime at first contact of front of pad. "Width of a dime" is not very widely known length unit, in particular outside of the US. Is it about 1mm? -clean pads. also make sure there is no foreign matter embedded in the pads. If there is, how to get rid of it? Or is replacing the pads the only cure? Thanks for the newborn FAQ! Konstantin Shemyak. |
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