| Technical Facts About Bikes | ||||
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Do you know what components make up a typical hardtail (no rear suspension) mountain bike? Below is the list: |
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The types of brakes available have changed greatly over the past 20 years. Although there has been a great change on how it looks and where the braking systems is located, the basic idea of using frictional force to slow down the moving parts still remains the same. In all cases of braking, there is the wheel that turns and a stagnant piece of material that presses against the moving material to slow down the bike. The material and topography of the surface in contact determines the frictional coefficient. The overall frictional force is a function of the force applied, ara of contact, and the material properties. There are five different types of brakes available. First type is known as the plunger brakes which are used in children’s bicycle and tricycles. The way in which this functions is by pulling a lever on the handlebar, which in turn pulls a cable that presses a metal shoe or rubber shoe against the outer part of the tire. This type of performs very poorly in wet weather conditions for the reason that the tires gets wet very easily. It also causes wear and tear on the tires as well. The second type of braking system is the internal-expanding hub brake. This is similar to that of an automotive hub brake. They were popular amongst medium-weight “roadsters” back in the 1930’s, however this system lost popularity due to its weight compared to rim brakes. Since the brake itself is contained in the hub, it performs better in wet weather; however, since the braking system is contained in the hub, it causes maintenance problems. Third type of brake is the “coaster” hub brakes or also commonly known as backpedaling brakes. This system can be operated when you rotate the pedals backwards. They are entirely unaffected by any whether conditions, so they are reliable in that sense. They are also very effective for rear wheels however, it is not feasible for the front brake since our hand cannot generate as much force needed to operate the coaster brakes. Some downside of this braking system is that if derailleurs are used (only good for single speed bikes) or the chain brakes off, the breaking system no longer works. The fourth type of brake is the rim brake, which works by a pad or “block” of rubber usually made of rubber elastomer that is forced against the rims of the wheels. This is a very light system; however, it is very sensitive to water. Most of the lightest bikes made today have rim brakes. Depending on how the rim brakes are set up and the mechanism for pulling the cable, the braking force applied the rims are very different. For example, the older types of brake that uses a cable to pull two brake pads perpendicular to the braking force is not very effective at providing a good frictional force. A better designed rim brake is known as v-brakes. For v-brakes, the cable pulls on the brakes parallel to the braking force. Since one is directly attached the cable and the other brake pad suspended, it causes both of the pads to close simultaneously and at a great force. The fact that they are horizontal allows for more frictional force to be applied to the rim of the wheels. Finally, the fifth type of brake is a disc brake. They can either be mechanical or hydraulic disk brakes. Since the disks are located in the center of the wheel by the hub, they require significantly higher braking force than for rim brakes. Although this is the case, it has benefits in that it keeps mud and excess water from the ground away. This type of biking system is also found on motor cycles, race cars, and air crafts. (bicycling sciece) I personally have tried all but the plunger brakes. Comparing them, from my experience, the most effective ones are the v-brakes (rim brakes) and hydraulic disc brakes. At the same time, there is a rim brake that is hydraulic as well, which works phenomenally well. The down side to hydraulic brake is that it they are heavy and require high maintenance. For this reason, riders whom care about the weight of their bikes do not use this system. The downside to cable brakes is that the cables stretch over time and they just be adjusted constantly. At the same time, significantly more force must be applied by your fingers to get the equal amount of force as hydraulic brakes. One major characteristic that I personally like about the hydraulic brakes is that, if they are bled properly (the brake fluid placed in correctly with the absence of air bubbles), the brakes feel very ridged and firm. What I mean by that is that for a cable brake, you can keep on pulling on the brake levers because they stretch; however for a hydraulic brake, because liquid is an incompressible fluid, there is a limit to how much you can press the brake lever. This is great when you need to lock your wheels for tricks, for instance trials riding and freeriding. At the same time, you fingers will not get as tired of pressing the brake when hydraulic brakes are utilized. It might be hard to think that one may get tired of pressing brakes, but when you are doing a downhill riding, it is critical that you keep your hands on their brake and press them constantly. At such extremes, speaking from experience, even with hydraulics brakes, your finger can get cramps. So imagine riding with rim brakes, I don’t think I would have made it down the hill.
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(Wilson, Bicyling Science) This is how a hydraulic disc brake works. More specifically, the illustration is a schematic of Hayes Disk Brakes |
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| About Suspensions | |
Suspension is a critical part on the bike that absorbs the bumps, shocks and vibrations that the bike may encounter while riding. These absorptions of bumps, shocks and vibrations provide more comfortable riding. In some cases, suspensions can prevent injuries. An example of this would be free riders riding off drop-off (ledge) that is 20ft high. Without the suspension, the rider can easily snap off his/her wrist. Although suspension provides comfort, they also provide extra weight to the bike, which is downside. Due to this weight increase of the bikes, road riders do not utilize suspensions. The road bikers would some times file their seat post down to cut any excess weight. At the same time, road riders do not face the worst bumps, it is not a necessity. On the other hand, cross country riders utilize suspension since it allows for them to perform better. There are many variations and types of suspensions available. The more common type of suspension is the suspension for the front. There are spring based suspensions, oil based suspensions, air based suspensions, and hybrid suspensions. Depending on what the usage of the bike is, different types of medium are utilized to match the needs. The lightest types of suspension that can be purchased are the air based suspensions. In ’98, Rock Shox released a suspension called SID (superlight integraded design) that was air / spring hybrid suspension. What it means by air/spring is that for compression, the air acts as a dampener and the spring is used for rebound. This was the lightest suspension in the market at that time. In year ’99 air/air suspension came out. This time, both the compression and rebound was air. Although this allowed for weight drop, there were problems associated with this design. If the rider rides at rough grounds and causes the suspension to “bottom-out” which is basically hitting the bottom of the length that it can travel, since no spring is available to stop the shaft, the shaft can puncture a hole in the bottom. This causes a problem because once the air leaks, the suspension can no longer be utilized. At the same time, air based suspensions require a lot of maintenance and is very hard to adjust. For extreme riding, spring and oil based suspensions are most common. In all springs, some oils are placed in cartilages to lubricate the springs; however, there are suspensions in which the liquid oil is used to dampen the shocks. These are heavy duty suspensions intended for downhill and freeriding, where is it common to have drops of greater than 6ft. Some of the well made heavy duty suspension can with stand 60ft drops. (Yes some riders are crazy enough to do these jumps) The heavy duty suspensions come in two styles, single crown or double crown. Double crown allows for stiffness and more support incase the tube that connects the suspension and the frame decides to give out. Along with the different types of medium used to dampen bumps from the riding surface, and also different enforcement for the fork connection with the frame, the travel of the suspension varies with the intended usage. Typically, cross country riders only utilize about 60mm of travel. Although this was the case until few years back, this is changing slowly to about 80mm. Since cross country riders are not jumping off large gaps like downhillers, they do not require such large travel. On the other hand, free riders and down hill bikes usually require larger travels. The travels for these purposes are usually in between 100mm to about 200mm of travel. Such long travel is needed to decrease the impact from drops and jumps that the rider may experience while riding. Due to increased technology, suspensions made today are extremely light or extremely durable. At the same time, there are many unique designs and features that are added. For instances, there are suspensions that can be locked out (suspension stops acting like a suspension – like a solid bar) by a single lever. Such feature is useful when climbing uphill. Lots of energy is lost by the rider if the suspension is moving the bike up and down. The vertical movement does not add to the overall output of power by the pedals. Another example of a variation is a front fork known as “Lefty” by Cannodale bicycle. The unique thing about “Lefty” is that the fork attaches to the front wheel with only a single bar on the left. A normal fork has two bars with the wheel in between; however, Cannodale came up with a way to keep the stability of two bars using just one leg. The usage of one leg would cut down the weight of the suspension significantly since less material is needed. |
This is a picture of a XC single crown fork. Year 2005 SID, Rock Shox
http://www.flyingball.com/fball/Dsc03084.jpg This is a pictuer of "lefty" fork. Cannodale makes this cool looking fork
This is a picture of a double crown fork. This can be used for downhill riding or freeriding. |
