The right fluid for the right bleed!
Hydraulic disc brakes are now everywhere. Knowing your hydraulic fluids is a key to proper maintenance and safe, predictable braking performance. UBI’s Jake Sawyer has this primer:
In the realm of bicycle hydraulic disc brakes, there are two common categories of fluid: DOT fluid and “Mineral Oil”. DOT fluid is a hydraulic fluid designed to meet specific criteria put forth by the United States Department of Transportation and organizations such as the Society of Automotive Engineers (SAE). There are numerous ratings available for DOT fluids, with DOT 3, 4, and 5.1 being used regularly in the bicycle industry. Mineral oil is a bit of a misnomer, as it is easily confused with the clear, colorless oil sold over-the-counter at pharmacies. The mineral oil used in bicycle disc brake systems is an engineered hydraulic fluid designed for this specific application, and is in no way compatible or interchangeable with other brake fluids. Or the pharmacy’s mineral oil, for that matter!
DOT 3, 4, and 5.1 are polyethylene-glycol based fluids, a group of chemical solvents that have high boiling points and have very low compressibility. DOT 5 fluid is silicone based, and is not compatible with any bicycle disc brake. Because of the high temperatures generated during braking, and the relatively miniscule volumes of fluid contained in a bicycle’s hydraulic system, a hydraulic fluid with a very high boiling point is considered quite desirable. If a brake fluid reaches its boiling point, transforming from a liquid to a gaseous state, its ability to stop the bike is greatly reduced.
The various grades of DOT fluids refer to the boiling points of the fluid. DOT fluid is considered to have two boiling points: a dry boiling point and a wet boiling point. Polyethylene-glycol based fluids are hygroscopic, or water absorbing. Given the conditions that disc brake-equipped bicycles are often ridden in, this can increase fluid replacement intervals. As DOT fluid absorbs moisture from the environment, its boiling point is significantly lowered. DOT fluid is considered “wet” when it has absorbed as little as 3 percent of water by volume. “Wet” fluid can have a boiling point over 30 percent lower than “dry” fluid. Once a container of DOT fluid is unsealed, it immediately begins to degrade; this is why DOT fluid for bicycle brakes is generally sold in small volumes.
Conversely, the other type of fluid used in bicycle disc brakes, mineral oil, is hydrophobic, meaning it does not absorb water. Because of this, mineral oil is able to maintain its non-compressible properties for longer periods. This is not to say that mineral oil systems are immune to water contamination and performance degradation due to heat, only that the fluid itself does not mix with water. Because mineral oils are proprietary, they are not categorized like DOT fluids into grades. That said, mineral oils can have boiling points as high, or higher, than “dry” DOT fluids.
Dry boiling point Wet boiling point
DOT 3 205 °C (401 °F) 140 °C (284 °F)
DOT 4 230 °C (446 °F) 155 °C (311 °F)
DOT 5.1 260 °C (500 °F) 180 °C (356 °F)
None of this is to say that one type of brake fluid is better than another. But it is important to understand that the fluid a manufacturer specifies in a given system is the only fluid that should be used. DOT systems will often state that they can be used with more than one grade of fluid, but those fluids should never be mixed. If you’re changing from DOT 4 to say, DOT 5.1, the system should be completely flushed of one grade before being bled with another grade. In mineral oil systems, it is important to use only the manufacturer’s fluid. While not as readily available as DOT fluid, mineral oil is generally not difficult to acquire through your local bike shop.
A well-maintained brake system is extremely important. Hydraulic brakes should be bled at regular intervals, even if they feel fine. Murphy’s Law predicts that when you most need the control that hydraulic brakes can offer, a poorly-maintained system will show its weaknesses. A good rule of thumb might be to bleed brakes every six months, or whenever your pads are changed.
Want to know more about disc brakes? Check out UBI’s one-day Disc Brake Seminar. The next session is Saturday, April 19 in Portland.
We’re excited to announce that SRAM, Quality Bicycle Products (QBP) and UBI have teamed to offer two scholarships for women mechanics to attend either the Professional Repair and Shop Operation class or the Advanced Certification Seminar Week at UBI Ashland. QBP is hosting the application form.
You can read more about the scholarship here.
Chelsey Reeves starts a suspension service at UBI Ashland. She works as a bike mechanic in the Sacramento, CA area.
Officer Adam Ferguson, Kent, WA P.D.
Those of us who use a bike just for leisure sometimes forget that a bike can also be a useful tool. We were recently reminded of this when Officer Adam Ferguson of the Kent, WA police department took our Introduction to Bicycle Maintenance course. His goal was to better handle his department’s fleet maintenance needs. Between class sessions on how to adjust derailleurs and true wheels, we had a chance to ask him a few a questions about what it’s like being a bike cop and how the bike adds utility to his job. UBI’s Craig DeAmbrose processed the suspect, took the mug shots, and conducted the interrogation.
UBI: For your job as a police officer, what are the benefits of being on a bike?
Officer Ferguson: The ability to get around in the crowded areas is incredible. We can often times respond in the downtown area faster than patrol cars can. We’re also quiet and can view crimes you would never see in a car.
UBI: How many bikes are there in the Kent Police Department fleet?
OF: We keep a bike for each person in the unit and we have two extras for CDU members. (CDU is a special unit for civil disturbances.) We have enough bikes to accommodate 8 officers.
UBI: How many bicycle officers?
OF: We are currently working with 4 officers and 1 sergeant. In April we are upping our team to 8 officers with 1 full time sergeant.
UBI: If you are assigned to bicycle patrol, is that all you do? Or do you split your time between other duties?
OF: We cover both bike duties and the marine patrol in the summer time. We have also been assigned to our CDU team.
UBI: How many hours on the bike for a typical shift/patrol?
OF: A typical bike shift for us is 10 hours. Actual riding time is probably half. The other 5 hours go to follow ups and writing reports.
UBI: What kind of special training is involved?
OF: All bike officers attend an IPMBA (International Police Mountain Bike Association) training that is specific to bikes. This is usually 1 week long.
UBI: What are the challenges with fleet maintenance?
OF: Time!!! Right now I am trying to take care of the fleet while keeping up with special duties and patrol.
UBI: Do officers generally like being assigned to bike duty?
OF: Some officers still prefer a car. The position for bike officer is a specialty position and officers have to apply and test to get on the team.
UBI: For patrolling by bike how does your uniform change? Any cycling specific clothing?
OF: We wear a brighter blue uniform to identify us better. We also have additional reflective items for road safety. The ballistic vest we wear is also an outer carrier. It has the same stopping power as normal vest but the outer carrier allows us to put a lot of the gear we usually wear on our belts and move it to our vest carriers. This eliminates a lot of the pinching at our waist.
Weight weenies need not apply: Officer Ferguson’s standard vest with gear.
What’s the weight of the bike with all normal gear attached?
OF: The bikes we have start at 26 pounds; we add about 15 pounds for bike bag and contents. Our vest runs an additional 15-18 pounds. Our batons are about 2-3 pounds, bringing a total to about 58-60 pounds.
UBI: What kind of duty/patrol does a bicycle officer typically do? Crowd control? Neighborhood patrol?
OF: We are mainly assigned to the downtown area. We usually focus on crowded areas like parks or the library. We are assigned to any functions like street parades, or public events. We can maneuver through the crowds easily and, when needed, we can use our bikes as a barricade pushing unruly crowds back.
UBI: Does the public respond to you differently on your bike as opposed to being in a car?
OF: Absolutely. I think we are more approachable and visible. I feel like the public likes seeing us in their area. Besides, we don’t usually give speeding tickets!
UBI: How do the seasons affect you? Is the unit less active in winter?
OF: We usually take advantage of winter as a time to overhaul the bikes and get ready for the next summer. We still patrol in the rain, but if it’s icy or snowy we have the option of jumping in a vehicle.
UBI: Anything else you think we should know?
OF: I think it’s important to note that bikes allow a more versatile use of our resources. Our department has talked about cross training our entire CDU team in bikes. They have seen countless CDU callouts like the Seahawks parade, where the regular CDU team members get posted to specific areas but the bike guys get assigned to escorting the parade. When you’re on a bike you can be a more effective officer during the events.
Ride around rifles? You need a rifle vest.
Another benefit of Officer Ferguson’s visit was the chance get up close and personal with his bike and some of the gear he carries. If you’ve ever seen a police bike, you’ve probably noticed that they’re not usually just a standard mountain bike with a sticker on it that says “Police”. The bikes used by many law enforcement agencies are typically mountain bikes that are purpose-built for use by police. The bikes that the Kent Bicycle Police Unit use are no exception. They use a stock Kona Kahuna Deluxe 29er
as the base for their patrol bike and change up a few things to make it ready for duty:
*Stock knobby tires get replaced with high volume slicks. High volume slicks are better suited for the urban areas they patrol in and offer a good mix of traction and smooth rolling.
* A rear rack is installed to carry various gear. It has such a wide stance that it also ends up protecting the rear derailleur and rear disc brake as well. This secondary function of the rack is particularly important because officers often have to “dump” the bike while in pursuit of a suspect. As you can imagine, dumping the bike at high speed can be pretty hard on exposed parts like the disc caliper or rear derailleur.
*A fork steer tube extender with a high rise stem is added for rider comfort and better visibility. To those of you who might be turning your nose up at the extender and upright stem, consider the 18lbs of bullet proof vest and gear an officer has to wear for a 10 hour patrol. If you had to do the same, you’d probably find yourself wanting the same set up. Occasionally officers will have to wear a secondary vest if a suspect is armed with a high-powered rifle. The second vest adds another 15 pounds and protects against higher velocity rifle rounds.
*Just like its four-wheeled, internal combustion counterpart, Kent police bikes get a full siren and light set up. The siren is mounted on the front with some flashers and some LED strips mounted to the rack on the rear. Everything is activated by a handlebar mounted control box.
“Do you know why I’ve stopped you today?” Officer Ferguson’s bike has a full siren and light assembly. Note also the stem riser that allows him to ride comfortably wearing a ballistic vest.
If you’re interested in learning more about bicycle mounted police you can go to www.ipmba.org which is the home page for the International Police Mountain Bike Association. There’s lots of great info, including a history of bikes used in police forces stretching back to the 19th century.
Note the transition of the ovalized down tube and seat tube into the head tube.
Back in the day, Jeff Lindsay built Mountain Goat Cycles out of his shop in Chico, California. If you’re a mountain biker of, ahem, ahem, a certain age, you lusted after a Mountain Goat. You know you did. So when our student Chris showed up at UBI Ashland with this circa 1985 classic Mountain Goat — from Chicago, no less — out came the camera. And the memories. There may be some weird synchronicity that this happened the same week that Oakley re-released the EyeShade. The universe works like that. But we digress. Here is more of Chris’s Mountain Goat:
Lindsay had these fork crowns cast by Henry James.
Ovalized down tube. The paint is original. Sweet!
Oh yeah! Not just a Shark Fin, but a Shark Tooth to match. Note the XT U-brake with the derailleur cable routed through the brake boss.
Chris has a period-correct drive train. Clean, too!
To help you get the suspension dialed on your mountain bike, UBI instructor Jake Sawyer prepared this three-part primer. This week, part three:
Last week’s article covered rebound damping, which controls how quickly a spring can return to its neutral state. This week we examine the other side of the equation, compression damping – that is, how quickly the spring compresses. Varying the compression damping of a fork or shock can have a drastic effect on the feel and behavior of a bicycle’s suspension.
If you’ve ever pedaled out of the saddle and felt your bike’s suspension ”bob” or wallow, you are experiencing too little compression damping for the conditions you are riding in. On a long, fast, technical descent, less compression damping can be a good thing. But when the trail turns up, the lack of damping can cause excessive feedback at the pedals or handlebars, making the bike unpleasant to ride, and robbing energy from the rider.
When the trail flattens out or steepens, more compression damping is beneficial. Manufacturers use different terms – “platform”, “threshold”, “lockout” – to describe the same thing: a form of increased low-speed compression damping. While internally the damping effect is typically caused by limiting of the flow of oil through the circuitry of the damper, there are many external controls that manufacturers have devised to allow the rider to adjust compression damping. Often, the adjustment takes the form of an on/off lever – open or locked-out. This is most common on non-gravity oriented bikes. Bikes designed for more aggressive forms of riding will often have adjustments that work more like a dimmer switch for a light. These offer a range of damping, but not a full lock-out.
In the last couple of years, some manufacturers have gone to a multi-platform compression damping system. Think of this as a three-way switch on a lamp – off, low, and high. This method of adjusting takes away much of the guesswork for the rider. Manufacturer terms such as “Climb-Trail-Descend” or “Lock-Pedal-Unlock” clearly define what position should be used in a given situation.
As with rebound damping adjustment, there is a degree of personal preference involved with compression settings. However, like rebound, there is a fairly small window of adjustment between having too much or too little damping. If your bike is equipped with one of the multi-platform dampers found on many new bikes, the guesswork is taken care of. Are you going uphill, pedaling along a trail, or descending? The same is true of on-off style dampers.
If your bike has a range of adjustability in its damper, a process like that described in the rebound article would be called for. Ride the same section of trail repeatedly, and adjust your compression damping one click at a time until you dial in the best balance between pedaling performance and bump absorption for your riding style and conditions.
We hope this series has helped you gain a basic understanding of how the external adjustments of your suspension system(s) influence the ride characteristics of your bike. Use this knowledge to get the most performance – and the most fun – out of your bike! Want to know a lot more about suspension? Check out UBI’s Suspension Technician Seminar! Or, if you’re working for a Fox dealer, our Fox Master Tech Clinic.
A space has just opened up in the March 24 – April 4 Steel Brazing Frame Building class in Portland. Joseph Ahearne, shown above tucked behind a frame building jig, is the scheduled instructor.
Here’s your chance to build your own lugged or fillet brazed frame and have it ready to ride in time for the season. You can sign up by clicking this link.
It’s been a few years since UBI has showed up for one of the US’s oldest and biggest bicycle shows, the Seattle Bike Expo, but the statute of limitations has run out on the misdemeanor mayhem charge our Administrator racked up during the last visit, so goshdarnit, we’re going to be there again this year!
Come on by booth number 522 and say hello, learn all the latest UBI gossip, and register to win something cool.
March 1 and 2. See you there.
To help you get the suspension dialed on your mountain bike, UBI instructor Jake Sawyer prepared this three-part primer. This week:
Without damping, any form of suspension is just a glorified pogo stick. After an undamped spring compresses (say, by hitting a bump on the trail), it returns almost all its stored energy to the rider, creating suspension that is unpredictable and difficult to control. This is bad! A damping mechanism regulates how that stored energy is returned to the rider, and offers a smoother ride and ultimately, more control. This is good!
Damping settings can take a while to get tuned exactly to the rider’s liking and are closely tied to spring rate. The best part about tuning your damping? You get to ride your bike! It is worth noting that damping settings may change based on terrain. For example, it might be necessary to speed up rebound (less damping) at the top of a particularly rocky descent. Conversely, if riding at a terrain park with large, widely spaced hits, slower rebound (more damping) may be required.
Step 1. Turn all external compression adjusters to open. This may be expressed as “Descend”, or the direction opposite of
Step 2. Determine the current rebound settings of your fork. Record the number of clicks from full open (less damping). This is a red knob or dial on Rock Shox and Fox products, a blue knob or dial on Manitou.
Step 3. Make note of the total number of clicks available from fast to slow. Check with your bike’s manufacturer for recommended baseline settings. If the manufacturer’s settings are not available, start in the middle of the range. This will be the baseline adjustment.
Step 4. Go ride! It is a very good idea to select a short section of trail – one less than a quarter mile – that offers a little bit of everything that you like to ride.
Step 5. Beginning with the baseline settings, determine where to go from here. If the fork feels too bouncy or twitchy, try adding a click of rebound damping. If the fork feels sluggish or does not return over rapid consecutive bumps, called “packing up”, remove a click of damping.
Step 6. It may be necessary to repeat steps 3 and 4 several times until the desired feel is attained. It is a good idea to keep note of the settings being run, and once the fork is dialed to your liking, make note of them for future reference.
Step 7. If you are unable to attain the desired feel of your fork, consult a reputable bike shop for guidance. Or it may be time for UBI’s Suspension Technician Seminar!
It may be necessary to change your rebound settings if going on a trip to a different area with drastically different terrain and trails. If time is taken to establish a good baseline, usually only one click in either direction should be needed. Just repeat the process for the new trails at the beginning of the ride and adjust as needed. Enjoy!
Next week…. Compression and lockout.
To help you get the suspension dialed on your mountain bike, UBI instructor Jake Sawyer prepared this three-part primer. This week:
No form of bicycle suspension will operate as intended unless something called “sag” is properly set from the get-go. Sag can be defined as the amount of suspension travel that is used with the rider on the bike on a smooth level surface. It is usually expressed in the form of percentage of travel. For example, if a 120mm fork compresses 30mm with the rider’s weight on the bike, it has 25% sag.
How much sag is needed is based on the intended use of the bike. An XC race bike might need as little as 10-20% sag, whereas a long travel all-mountain or downhill bike might use as much as 30-40% of its total travel in sag. Proper sag adjustment allows the bike to conform to both the positive and negative variations in terrain. Setting sag is usually quite simple, and can have a drastic effect on the comfort and handling of a bike.
Setting sag only takes a few minutes, and a few tools.
You will need:
• a machinists rule or calipers (metric)
• the sag indicator that came on your fork or rear shock (that little O-ring thingy) or a zip-tie
• a shock pump (for air spring equipped forks and shocks)
Step 1 - Get geared up. Make sure to carry the same load you would typically ride with: full hydration pack, toolkit, food, etc.
Step 2 - Turn any external compression adjusters (the blue knobs) to the open position (unless you’re riding a Manitou, which has red adjustor knobs).
Step 3 - Step onto the bike, with all your gear. If possible, ride around a bit, cycling the suspension, boing, boing.
Step 4 - While still on the bike, set the sag indicator on your fork or rear shock all the way against the dust wiper/seal. If your sag indicator is missing, a small zip-tie will work.
Step 5 - Taking care not to cause the front end to dive during braking, slowly come to a stop and CAREFULLY step off the bike.
Step 6 - Measure the distance the sag indicator has moved away from the dust wiper.
After dismounting, measure from the top of the dust wiper to the sag indicator.
Step 7 - Divide this distance by the total travel of the fork. Multiply by 100. For example, a 160mm fork with 65mm of sag has 40.6%. For rear shocks, measure the stroke of the shock. Stroke is the difference in the shock’s length, eye-to-eye, from fully extended, to fully compressed. It is expressed in millimeters. This is not the same as rear wheel travel!
Step 8 - Adjust your sag by using the appropriate method for your suspension system. For air springs you will need a high quality shock pump. If you find your sag is too great for your intended riding style, add air to the shock. If your sag is too low, release air from the shock. Coil spring systems usually have a collar for adjusting preload. Turn the collar in the correct direction depending on whether your sag is too much or too little. If the range of adjustment needed for a coil spring is not sufficient, a different rate spring may be required.
Finding the appropriate amount of sag for your bike can be a matter of personal preference for more experienced riders. However, many manufacturers state an ideal range for a given model/category of bike, which can give you a good starting point. A few rough rules of thumb can help get you started.
• XC Race: 10-20% sag
• Trail and All-mountain: 20-30% sag
• Downhill/Freeride: 30-40%
Winters can be kind of quiet around the shop. Why not spend some time acquiring new skills? UBI has several career Development Seminars on the way in February.
First off, we have another installment of our Chris King seminars coming in Portland. Here’s your opportunity to be one with the sound of Angry Bees, as we take you through the maintenance and overhaul procedures for Chris King headsets, BBs and hubs. Be ready to super-serve your customers with your newfound King wisdom! The seminar is Saturday, February 1 at UBI-Portland, and you can register for it on line.
The next session of our popular Fox Master Tech Clinics will happen in Ashland, Saturday, February 22. This clinic, team-taught by UBI and Fox techs, gets you major hands-on time with the latest Fox CTD damper technology, and the cost of the seminar includes a brand new 2014 Fox fork of your choice. Which means, yes, you go home with a brand new fork. Plan to spend the whole weekend so you can get some rides on Ashland’s mountain bike trails. The Fox Tech Clinic is open to employees of Fox dealers only. On line registration is available now.