Instructables
Resurface bike rims for up to 300% stopping power, even in wet conditions. Makes some bike brakes impervious to water, even submerged....

Step 1: Get some slate first

get a sample piece of slate used in construction....Slate is a grindable and fileable sedimentary stone, and is almost as hard as granite....an ideal chioce for a resurfacing stone on aluminum up to cast iron....

Step 2: Cut slate with a suitable tool

To cut slate, you neet to user a suitable tool and cut it with water as a coolant and lubricant. In this case I used fiberglass-reinforced cutoff wheels for a Dremel tool. This is Black & Decker part #RT1000 (426)....Be sure to round the wheel on a piece of scrap before you proceed to cut, and do not remove the wheel after doing so unless it is worn-out or shattered....but these wheels are supposedly shatterproof...

Nonetheless, always wear eye protection and do not cut or grind directly into your face

Step 3: Prepere slate for cutting

Have a suitable jar handy filled with water so you can dip it in and keep the stone soaked. Quench (dip) the slate before it dries out from the friction. Keep the stone wet as you cut or it will flake and chip and chew up your cutoff wheel prematurely. Room-temperasture water will work just fine, just keep it wet through the entire cutting process...you cannot keep it too wet for cutting, in case you had any doubt, and not only controls dust, but keeps everything cool and lubed enough...

Step 4: Cut your stone to desired size

Never force the tool, let the tool do the work, excess pressure is not necessary and will wear down your tools prematurely...The ideal speed for this is somewhere around 20,000 rpm, but you can cut at full speed if your rotary tool is not of the adjustable type. Do not cut in one place, just keep recutting the same groove over and over. As soon as the stone starts to dry around the cutting area, dip it again....beware the initial water spray as this will contain some of the slate particles which will be very unfriendly to the eye socket mechanism, hence the need for safety glasses at all times....

In this example I cut a small stone..I have cut larger stones for other purposes, but this is to give you the general idea...

Step 5: Now, lathe your bike rim

In this step, you will be lathing your anondized (coated) bike rim with the stone to provide a better braking surface. Note how I am holding the stone at one end...The wheel in this pic is rotating clockwise, with the pressure being put on the trailing-end of the stone. Be sure that the stone is filed flat on the surface you intend to use for honing...

Keep spinning the wheel manually while holding moderate pressure on the stone the entire time. eventually you will notice the anodization being scoured off, leaving bare aluminum...It is ideal not to let the wheel come to a complete stop in this process, as the stone will get a little clumsy on the recoil...

Step 6: Note the technique used

Note how I am using my right hand to spin the wheel and my left to secure the stone, using the bike fork as reinforcement. Hold the stone tightly so it doesn't get away from you, and be sure to over the entire side area of the rim by both moving the stone up and downb on the rim as you hone it, and placing it diagonally in both a toe-down and toe-up direction....Once you see a roughened surface, you know you are close to hiome....lighten the pressure once you see bare aluminum to hone the last of the anodization off...

Do this type of honing dry, you want some of the scoring, and some of the aluminum to collect on the stone to add to some of the abrasion. This methiod will also smooth the rim surface for more even braking throghout the rim's rotation...

Step 7: After removing all anodization...

Wipe the rim surface down with a clean, dry, disposable cloth to remove the excess dust, and then go for a ride, favoring the brake you just refinished for stopping to reseat the pads. This method can be repeated for when rims get glazed, but the advantage of this is that it gives a 400-grit sandpaper finish every time, without wasting sandpaper....

Now your aluminum bike rims will have much better braking power, even in the wet. This method has been tried-and-trued through just about all conditions, even completely submerged, so I suggest any with halfway-qaulity bikes to try this on their rims...

Just be sure to test braking power moderately at first, especially on the front, as this is what it is recommended for. This method is most ideal just before using the olegendary "Scott-Matthauser" brake pads, which you will find in orange...Following that, you will have bike brakes suitable for stopping a 3000lb car....

The finish you see is what you want to aim for...
 
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dwosullivan4 years ago
Did anybody else try this? i gave it a shot and it was super loud. waiting for my new brake pads to arrive so can't comment on stopping power, feel etc
Would this same method work on old 70s steel rims? Or is it just the softness of the aluminium that lends it so well to this process?
Gah, I was just doing some reading and I read that steel chromed wheels with side caliper brakes was the worst. Especially in the wet... I don't suppose you do have any tips do you?
Thanks.
Prometheus (author)  bad ass pope4 years ago
(sorry, this'll be a bit of a read)

Yes they are. Caliper brakes are weak and flexible, and rubber and steel are easily parted by a layer of water. Some will even tell you that they are downright dangerous in the rain, and to them I agree. The first way to make sure your brakes are working at their peak potential is to keep your wheels "true" (straight), and set your brakes properly on the rim (I think there's an Instructable on how do do this on this site somewhere). When squeezing the brakes, the front part of the pad should touch the rim first, and the pad should "land" squarely on the rim under hard pressure while the wheel is rotating. Maximum braking power should be achieved without the brake lever coming close to touching the handlebar-grip. For caliper brakes, the calipers shouldn't wobble, but also shouldn't be "sticky" (it's a terrible design, really).

Something you can try is to roughen the rim a little. What you need is a portable drill and a grinding stone (gray-wheel) on it. Using the same method as with the wire-wheel, hold the wheel at a 45-degree angle relative to the braking surface (when looking at the wheel from the side) and use the drill to spin the rim, like the pic below. Don't put too much pressure or you may grind too deep and weaken the rim.  As the wheel turns, the grinding stone will draw a line around the rim. It doesn't have to look pretty, it's more effective when it isn't.

The idea is to scuff the rim diagonally so the pads have a little more to bite into. Be careful not to grind too much, you just wanna ugly that mirror-finish so your brakes will work. Wet performance will almost exist, and dry performance will improve.

If for some reason above is not an option, an even quicker and dirtier way is to cut some durable and coarse sandpaper to cover the pads like little booties, and ride the bike while holding the brakes down lightly (be sure you aren't sanding the tires!) to score the rim surface. This is even less effective, but it's better than leaving them the way they are. Be careful as your braking power will be dramatically increased while doing this, so don't honk on the brakes hard or go too fast. This can be a good thing, but using this for a fix would eventually cause a blowout by grinding the rim away.

Above all, NEVER wax the rims, and try to keep them clean, because oil from car exhaust and just on the road can gather on the rim surface, and eventually the pads themselves. Don't use the pads that were on the back wheel on the front, because they are likely already contaminated with oil from the chain (not to worry though, any more braking power and the rear wheel locks anyway). If your pads are glazed, use a file to take some material away and get rid of that shine. Using a hacksaw to cut 2 or 3 shallow slots diagonally in the pad should give water someplace else to go. Observe wheel rotation and cut the slots so that when installed, they angle opposite the angle of the front forks so that they sling water outward from the rim.

Don't cut too deep (maybe about 2mm or so), and don't cut too much. Too deep, and the pads will deform under braking. Too much and you won't have enough surface-contact for braking.

If you can afford it or are otherwise willing, replacing them with aluminum rims would be best (or at least the front, where 85% of your braking is). They are lighter, faster ("an ounce off the wheel is worth two off the frame"), and more durable than steel wheels.
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Wow, that pretty much needs an Instructable of it's own! Thanks for the advice, much appreciated :-)
Prometheus (author)  bad ass pope4 years ago
Not so well on steel rims, and you are exactly right. For steel rims, just use a wire-wheel on a portable drill (remove the tire first, of course). While you're at it, pull out the rubber rim strip and check for rust and protruding spokes. If any stick up, grind them down (never cut spokes because the cut part can become a dangerous projectile, and it'd ruin the threads).
Karletto5555 years ago
synthetic steel can be used too 
Subfightr5 years ago
If I do this will i have to resurface my brake pads as often? Does this make a difference in that?
Prometheus (author)  Subfightr5 years ago
If you keep your rims relatively clean, you might actually have to do it less...
vadvaro8 years ago
What are the disadvantages of this process, does it reduce the life of the wheel due to accelerated corrosion, or some other reasons? Just wondering why the manufacturers are not already doing this.
mfr's don't do this because it removes the purpose of anodizing the alum. in the first place. Anodizing protects Al from oxidation -- the Al is going to change from shiny to dull rather quickly as a layer of oxidation builds up (this protecting the alum underneath).
Prometheus (author)  trebuchet037 years ago
No, manufacturers don't do this because it is of greater cost to machine the anodization off again, and more cost-effective to just anodize the entire tim surface. Any experienced cyclist (perhaps such as "dhej" below) knows that anodization makes for a poor braking surface. If you are concerned about corrosion on the braking surfaces, try riding more than once a year lol... When was the last time you saw rust on the braking surfaces of a daily-driven car?
Constantly. The steel of the rotor flash rusts very quickly. Even a light rain, while the car is sitting will make the rims flash rust. However, the first contact of the pads with the rotors removes the rust.
Prometheus (author)  leebryuk6 years ago
Not quite that fast, but the cast iron used for brake rotors and drums (I think you meant rotors and not rims) is over 98% pure, and the purer the steel, the faster it will oxidize, as with many metals.
I've drilled some auto brake disks and I'm pretty sure that they are steel. I think they are alloyed with a small amount of lead to make them machine easy. Yea, this is totally off topic, and they might still be 98% pure, but they are not cast iron.
Prometheus (author)  kill-a-watt6 years ago
They may not look it after all the machining, but I can assure you they are made of high-carbon cast-iron. Cast iron comes in far better grades than vintage cookware. However, they are not alloyed with anything to make them easier to machine (you want them to resist wear and cutting as much as is reasonable), they are alloyed with nickel and zinc to make them slightly more tolerant of the heat spectrum they regularly withstand. Lead would make the rotors glaze more easily, and lead is a slippery metal as well. You'd want to alloy with lead for things like bearing blocks or cast-iron housings.
OK, I just got a google education of cast iron vs. cast steel and I did not realize that cast iron covered such a broad swath of alloys, I was using the classic definition. In that sense i was right. BTW, the firearms industry is loath to call anything they produce "cast iron", it's still "cast steel" {1}, even though that term is falling out of use. The postulation of lead is from how easy it was for me to drill and tap holes in a few old brake rotors. Even though you need the rotor to be tough, you still have to machine the things to the proper size. This stuff was easy to machine. There must be some specific alloying magic being used. I see a lot of brake rotors that are made in China. If they can't keep the lead out of the cheap plastic stuff that gets passed off as toys nowadays... {1} Actually, it's just "steel", as most manufacture don't even want to admit many parts are investment cast vs. forged. Oh, and Glocks are made out of "polymer", never "plastic".
Prometheus (author)  kill-a-watt6 years ago
No fault of your own...The reason you had such an easy time drilling them was not the rotors, but the carbide bit you were using. Steel may be strong, but is absolutely no match for carbide. Carbide makes even chro-moly seem soft by comparison. The comparison is like that of aluminum to granite. The magic is in the tools you are using. If you look at drill-bits for concrete, you can see the carbide spade at the tip, or concrete saw blades with the carbide tips at the slots. Cast-iron is used because it resists warping from sudden temperature changes and stresses. It also retains it's "temper" better in abusive situations, such as a friction-brake surface like brakes and clutches. The lead content from China was in the paint used for the toys, however, because lead improves the finish and color-consistency of the paint, and the ease of casting with "pewter" parts when it is alloyed into it. "Iron" was generally used to describe a cruder form of steel, but that is no longer true anymore. Rest assured, the observation is of no fault of your own. "Cast iron" is (generally speaking) a crude form of steel, but a very dense one. Technology now allows us to identify and categorize varying grades of any metal or alloy and their strongest suits for an application.
Yes, I meant rotors the second time. Flash rusting is a problem in Florida. Pretty much any rain will cause rotors to have that wonderful red cover the surface. The first few feet of breaking will abrade it smooth. By saying it is a problem I should refer to it as a cosmetic issue. But people rarely notice it. Most never look at exposed rotors anyways.
Prometheus (author)  Calorie6 years ago
You do have a point however, in that enough rust at a time can cause noisy brakes, as the particles get lodged int he pads.
Yep, your right. I meant rotors and not rims. But I still see flash rusting on the rotors after a light rain that has had a chance to splash up on cool rotors.
Actually rim manufacturers often machine the braking surfaces of their anodized rims. Off the top of my head Alex, Mavic, and Velocity all offer machined rims where they have ground down the braking surface to reduce chatter and allow smoother, more efficient braking. Mavic machined rims are noted with UB, Alex marks them with CSW, and I don't know what Velocity calls them but I know they do it. So basically, this is a poor-man's solution for taking a cheap rim and giving it better braking characteristics. That's pretty sweet, especially since good aftermarket wheelsets often run almost as much as bikes.
Prometheus (author)  dhej7 years ago
Lol...hence the birth of this idea after much frustration with wire-wheels and sandpaper...
rhubarb6 years ago
Thank you for the good instructable, as well as the engaged and respectfully toned discussion. I have a few question I hope you can answer. In the instructable you tell folks to "get a sample piece of slate used in construction." I'm wondering if you have a suggestion as to where to get such a small sample of material. You seem to have tried sandpaper at first. Did you try it with a small sanding block? Is it even worth trying, or does the paper wear through so quickly as to not merit the effort? Additionally I would value some elaboration on the cutting of the stone. How do you ensure that the grinding surface of the cut piece of stone is flat? Thanks
leebryuk6 years ago
Aluminum oxidizes immediately in the presence of oxygen. It's a great advantage of the metal. The oxide is very thin (on the order of atoms.) Perhaps what is being referred to is that messy glaze. If you want really rocking rims, search around for a ceramic coated set. They have superb wet response and grit/sand doesn't wear on the surface. It a ceramic coating on the braking surface of the rim. The only down side is that they require special brake pads, and they are getting harder to find.
Prometheus (author)  leebryuk6 years ago
If you are referring to "glazing" as it is used for brakes, the glaze is the film that develops as a result of a chemical breakdown of the pad rubber as it is streaked away, combined with the polishing of the surface, which cause chatter that prevents constant pressure on the rim...much like if you see a tractor-trailer lock up it's brakes; some wheels "jackrabbit" on the pavement surface, far reducing the braking effectiveness. Pure aluminum stock is immediately attacked by oxygen by bonding to the aluminum atom where exposure occurs, but it cannot reach beyond a few microns. Bicycle rims are not made of pure aluminum, but an alloy which consists mainly of aluminum, often 7505 or some other 7000 series (alloyed with zinc, copper, chromium, and magnesium) to increase strength and rigidity, and increase corrosion resistance. Ceramic rims are better than plain aluminum, but the purpose of this instructable project was stated best by you on the down side. Ceramic rims also don't take well to side impacts as the substrate cracks and traps the very contaminants they were meant to defeat. This is why they are getting harder and harder to find. Aluminum rims remain the most economically-prudent means for bicycles today and what this project is aimed at. Doing this to anodized aluminum rims gets you nearly the same response as ceramic, at 10% the cost, however your input is relevant and valuable to this project, and I appreciate the counterpoint.
I agree. I think the real demise of ceramic rims was disc brakes. I imagine you still come across ceramic rims at official cyclocross events. I don't think they allow disc breaks yet, but it is a matter of time. Cycling is slow to change. Aluminum rims are cheap and cheery. The only downside is on low quality rims is where the hoops are welded. You get that uneven weld. That's not an issue with rims that are a couple of dollars more. Trust me when I say that I believe bicycling should be cheap and accessible. The US has become way to elitist about cycling in general. Everything has to be expensive and carbon fiber. After many years in the bike industry I will say that I enjoy my utilitarian bike the most. It has internal hub gears and the brakes are basically enclosed hub (Shimano Roller) brakes. Cheap, always reliable and since they are enclosed they are not effected by the weather nor do they leave that messy black brake muck on you after a wet ride to town. Mine has a completely enclosed chain case, and I have ridden it in the winter snow and salt for years without a problem. Best transportation money I ever spent.
berserk7 years ago
OK, I understand why you would want to remove the anodized layer from your rim. Why is this method better than sandpaper, though? And, how long does it last before enough of an oxide layer builds up so you have to re-do it? I replaced an old cantilever brake on my older recumbent with a V-brake from a donor bike - great improvement. Bike shop told me you would need a differend lever - while not ideal, the cantilever lever works as long as your wheel is relatively true and you can adjust the brake closely.
Prometheus (author)  berserk7 years ago
The reason I use a stone is because it not only does not wear down like sandpaper will, but also does not leave any residual abrasive behind. It also helps to maintain a level surface for the pad, whereas sandpaper with your finger can grind a concave surface into the braking surface, and does not help to even the surface at the bonding joint. Finally, it does not gouge grooves that would only reduce actual braking performance and help to trap contaminants that would do the same, including smeared brake material. Assuming you ride your bike more than 5 feet every year, an oxide layer cannot build because the brakes will not give it a chance to oxidize. Even if it did, just a few revolutions would cull it all away. The only need to repeat this process is to de-glaze the rim after a likely 300-2500 miles, to resist hydroplaning of the pads. The stone gets it "just rough enough". I haven't had to repeat the process yet, so I can't give you an honest mileage estimate. Brake types can vary within their category quite a bit, the key is the leverage they truly have vs brake-lever leverage/travel vs brake-pad friction. This method is to help improve the pad/rim relationship, because there is no such thing as brakes that work "too perfectly".
nice one i use to scype my brake pads in wet weather (like snow tyre conversion) it invloved a small cutting implement and a bit of care being in tyres I decided to use a a pattern of smooth curved strokes (curving downwards) this creates channels which allow water to run away from under the pad getting rid of that deadly delay between working brakes and a soggy doom
ben_06148 years ago
They are not doing this because everyone would be flipping over their handlebars from the 300% braking power
Prometheus (author)  ben_06147 years ago
If you know how to use your brakes properly, this is not a problem...Ride in the rain and you will see the benefits of this.