(Photos: Daniel Sharp)
When you break it down, your bicycle only needs to do two things: Go and stop.
In our last column we discussed the go (chains), today we’ll delve into the stop (brakes).
The Pacific Northwest is known for many things, but one of the most insidious is the slow, grinding away of bike rims and brake pads. I’m no scientist; but my deduction? Our volcanic soils create tiny pumice particulate, which on rainy days get splattered all over your rims and brake pads turning them into tiny grinding stones.
You may think your bike mechanic’s hands are covered in grease, but most of the time you’re seeing a thick coat of black brake dust.
For simplicity, let’s call that rim grime “brake dust.” Brake dust is the product of the road grit and the rubber from your brake pad wearing down. You may think your bike mechanic’s hands are covered in grease, but most of the time you’re seeing a thick coat of black brake dust.
As your brake pads wear, they are lightly dry-lubricating the rim—to stop have you to pull harder on the lever and put more braking force on the wheel. Add some rainwater and you’ve got a wet lubricant, too, and slowing down isn’t so easy.
What’s a cyclist to do?
Take a dry, clean cloth (paying close attention to the part of the rim that contacts the brake pads) rub your rim clean. If it has been a while since you’ve cleaned your rims, get the bulk of the brake dust off with a dry cloth, then use a cleanser (Simple Green, soapy dish water, or rubbing alcohol are all good, gentle choices) to remove the rest. I don’t recommend using cleanser first as wet brake dust smears and is more difficult to remove.
This simple maintenance can add years to the rim life of your wheel and greatly improve your braking power.
Make cleaning you rims and part of regular maintenance: lube and clean your chain, then clean your rims (with a different rag- mind you) and the whole shebang should take less than 10 minutes.
What about that horrid “SCREECH!” your bike’s been making at stoplights?
To fix it, remove your wheels and examine the face of the pad where they contact the rim. Often you’ll find that they’re covered in a glossy sheen instead looking dull and grippy (like a pencil eraser). Slick surfaces don’t stop nearly as well (duh).
Take a small piece of sandpaper and buff through the shiny layer until the braking surface looks dull again. Don’t be surprised if you also notice a few small flakes of metal in the pads (this is from road grit getting caught and scraping away metal from your rim. It’s important to pick the metal from the pad or it’s constant scraping will bring your rims to an untimely death). If you notice more than a few metal flakes it’s best to start over with new pads (I recommend Kool Stop salmon colored pads — they’re grippy but gentle on rims).
Another sign that your pads need to be replaced is when your brake levers reach close to the handlebar. Peek down at your pads from above the bike. All rim brake pads come built with indents that serve as wear indicators. If one or more of the indents are worn away, it’s time for new pads. (See image above.)
Of course, you could always try disc brakes. Disc brake pads last two to four times as long as regular pads and they don’t loose stopping power in the rain.
Disc brake maintenance is super-easy as well. Occasionally wipe the rotors clean of debris with a dry cloth or wet with a bit of rubbing alcohol. Be careful not to expose the rotors to any oil—even from your bare hands.
Hope this brake-down was helpful. Feel free to share your tips, tricks and advice in the comments.
— Tori Bortman is the owner of Portland-based Gracie’s Wrench, a business that offers individual and group bike repair classes tailored to your needs. Column sponsorship is available. Please contact info[at]bikeportland[dot]org.
Or you could get a bike with drum/hub/roller brakes, which essentially never need any maintenance!
Exactly what I was going to say. I have a bike with drum brakes – they will need maintenance in about 10-15 years or so…
Ditto here – no more brake dust or wear on rims. I was kind of wondering why the tires on my other bike were always so dirty, then figured out it was the brake dust 🙂 No more of that problem. Not to mention the hub brakes don’t slip in the rain (great for Portland). Hub brakes and a chain case are really both major wins for a practical transportation bike in a climate like ours.
Tori, how do I know when to replace a rim due to wear? Is that something best measured at a shop with a mic? Are there some checks I can do at home? I tend to use parts up to near point-of-failure but obviously a rim is a significant safety concern.
Your shop mechanic can tell you in an instant. If your rim braking surface is no longer flat and starting to become concave, or if your rim braking surface is rough and gouged out, this might be time for replacement. If you’re able to find a brand new wheel to compare it to, the results will be fairly clear.
Hope this helps!
In addition many rims have a groove in the middle of the braking surface that acts as a wear indicator. If the rim is worn down to the groove it is overdue for replacement.
most of our local soils aren’t volcanic, they are sediments deposited by the Missoula floods. OTOH, a lot of road aggregate is crushed volcanic rock, but not of the pumice kind.
Thanks for the geology lesson. I love to learn about the history of our hills, discuss theories and in the meantime I’ll keep hunting for the rim wearing culprit!
Aluminum is soft and it’s meant to wear when you brake, that’s why aluminum alloy rims work better in the rain than steel rims. Most of the black ick you get on your hands when working on brakes is not rubber from the pad or grit from the street, but rather, microscopic aluminum particles worn from the rim.
Good to know. Just another great reason to keep your rims cleaned and debris free.
Also, watch for the Shimano brake pads that are actually manufactured with pieces of aluminum molded into the pads, they are more common on hybrid city bikes and they are deadly on rims; some people don’t believe they exist and think that all that aluminum embedded in the pads if from the rim, but I assure y’all that they do. If you purchase a new bike with these pads, replace them as quickly as possible.
Burr is right about the black crud being aluminum. This stuff acts an abrasive and can wear through aluminum rims. When a rim is new the contact surface it flat. Over time it gets dished, over more time as the rim material gets thinner cracks will appear in the rim and the pads will wear unevenly and quickly over the irregular surface. Over more time with a big-assed Fred dropping anchor hard the rims get as thin as aluminum foil and strips peal away. My commuter bike is on it’s 3rd set of rims.
Cleaning the wheels (and the rest of the bike) often is a great way to prolong component life and to identify problems.
Many rims have their own wear lines; a groove incised in the surface of the rim. When you break enough, the groove wears away; at this point, the rim should be replaced, or at least checked by a mechanic.
Also, It should be noted that brake pads get old even if they are not worn out. In my experience brake pads tend to harden over the years, and are thus less effective at grabbing the aluminum (or steel) rim. Scuffing a bit with sandpaper can sometimes help, but often replacing the pads is the only way to restore effective braking. Great write up though – it reminds me that I need to check and clean my rims more!
If you ride down extensive hills doing a lot of braking, your pads can heat up to the point that when they cool down, they are much hader. You can rejuvenate them by grinding away some of the pad with a dremel or similar grinding tool
This is hands down my favorite bikeportland column. Thanks for this super-helpful awesomeness, Tori!
Like dan and sloe joe said, check the rims themselves, not the just the break pads. While the rim is wearing away the pads, the pads are wearing right back. Even if your rims don’t have a mark you can tell when they start to get a bit concave from the wear. Keep going long enough and the pad will eat right through until your rim unceremoniously explodes on you.
I read that the squeal can also come from brake pads that hit the rim flat-on. They recommended angling the brake pad so the front hits about 1 millimeter before the remainder of the pad. It’s referred to as “toeing in”. I can’t test this because I have roller brakes. 🙂
rim brakes are not only dangerous but also needlessly expensive. i used to spend $150-300 dollars every 1-3 years for a new commuter wheelset. after i switched to disc brakes i now have wheelsets with mileage well into the 5 digits.
PS: both avid and shimano make disc brakes that are fully compatible with both road and mtb gruppos.
Rim brakes are only dangerous if you don’t maintain them or lack the proper riding skills. Discs have their performance drawbacks as well plus, try finding a sub 20 bike with discs.
Now that Cyclocross bikes are disc-legal finding bikes at very close to the 20 lb point is not that hard. My mountain bike with discs is 23 lbs. Discs also have some performance bonuses too, like allowing the rims to be lighter. I’m not saying they are for everyone, but expect to see them continue to grow in popularity. Also note, that like any equipment, it pays to maintain them. Keep the pads dialed in close to the disc for best braking performance.
disagree. rim brakes have a limited life-span and its difficult to tell exactly when its unsafe to continue riding.
Hey Lazi Spinner, REALLY? no disc bikes under 20#?
Volagi.com 16lbs road bike with disc.
I would argue that what you are calling “brake dust”, that nasty black, greasy coating that covers your rims/tires is mostly a mixture of automotive fluids (dripped/spilled on roads) and microscopic particles of worn auto tires. Its especially bad if you ride in the rain (and who doesn’t?) and literally coats your rims/tire/spokes and even hubs. No arguing that there is automotive oil/fluids all over the roads, but have you ever wondered what happens to the rubber that “wears” off of the millions of auto tires in this country? Into the air and settles mostly on the roadways. So a nice, wet, sticky mess on your rims, add some grit, and you get worn brake pads and worn rims. Clean up with mild soap and water, check for wear, and your good to go!
The black grime on rims is not made of brake pad rubber or automotive products. It is mostly aluminum oxide from the rims. You won’t find it on a steel rim bike. Aluminum forms an oxide when exposed to air but in contrast to iron in steel the oxide conversion is one way so the oxidation process does not eat through the aluminum like rust eats through steel. The brake pads wear the oxide coating off and then more is formed. If you run your hands along any uncoated aluminum you will see the same black stuff even where there are no brake pads or road stuff around.
Aluminum oxide is used in sandpaper and other industrial abrasives.
Great column, thank you. Also love the armchair geologist theory!
this is a very helpful column, thanks!
Don’t use Simple Green on aluminum, such as rims(!). SG reacts with aluminum and weakens it, as well as can remove anodization. If you feel you absolutely must use SG, they make a version that is safe for aluminum (SG Aviation).
Thanks, Tori, and all you commenters — this is great stuff! Love the geology, BURR. And the Simple Green/aluminum reaction I’ve not heard of before..?
I had not heard of this reaction either, but I have seen a similar reaction with anodization and a citrus cleaner. If you want to use something more gentle, you can try some dish soap and water mixed. However, in my experience, it took a very strong and heavily applied solution of citrus cleaner before the aluminum/anodization was compromised, so using it judiciously will also work.
I’ve also seen rubbing alcohol used which might be a good choice.
When I apprenticed at my very first bike shop years ago, The proprietor eschewed fancy industrial chemicals and used Lemon Joy dish soap to clean everything. For especially greasy/dirty parts he’d use five parts Joy to about one part water; for everything else equal parts Joy and water. Very gentle on everything and doesn’t break down plastic or metal the way some industrial chemicals can.
Yeah but my dishwasher is too small for 700c wheels.
Re: Simple Green and aluminum:
A technicality, I know, but if you break something, it becomes broken; if you brake something, it slows and/or stops moving.
Similarly, if you peddle bikes, you are selling them; if you pedal them, you make them go forward.
I recently installed the Kool Stop salmon colored pads on my 20″ front wheel (the rear is 700C with disc brakes). I had extreme squealing problems, so I readjusted the pads with a dime under the rear edge of the pad for toe-in. This made them quiet except under the hardest braking.
So – is the answer to simply increase the toe-in, perhaps using a thicker coin in place of the dime? I have not yet measured the thickness of a dime to see how it compares to 1mm – don’t have a micrometer here at work….. (Before you ask – yes, I DID remove the dime after the adjustment) ;-}
“When you break it down, your bicycle only needs to do two things: Go and stop.”
Turning helps from time to time… 🙂
Seriously though, great article Tori, and good comments too! As a good who probably shouldn’t be touching my own bikes I really enjoy your column.
I’ve been meaning to invest in a set of dental calipers to measure rim thickness. from reading what others have reported on the net, I understand that 1.5mm thickness is common for a new rim. If it gets much under 1mm its time to consider replacement, and if it gets down to .5mm failure is to be expected. Having blown-out a rim sidewall at 30 mph, I do not want to repeat that experience if it can be avoided. Thank you Tori for writing an excellent column!
Baking soda works great for cleaning wheels. Get a big brush and a dish pan with hot water. Rinse well. Repeat if necessary.
re rim brakes being “dangerous”: Huh? I’ve ridden them for 25 plus years – that’s an exceptional problem, untypical for commuter riders.
Gone disc for my commuter 4 years ago and I wonder why anyone would EVER go back to rim for commuting.
Disc rotors wear out as well, it just takes much longer- 5 years for my rear rotor. I have a daily ascent/descent of 240 yards over 1 1/2 miles in my work commute, and many of the inclines are 1 in 10 or steeper.