Archive for the ‘Bicycle Gear’ Category

29ers: You’ve got a Bigger Future

Wednesday, June 11th, 2008

For many of us, there is a larger world ahead where our bicycles roll more smoothly and with less effort, than in the present era. As evidenced at the recent North American Handbuilt Bicycle Show, bicycles with 29 in. or 650B sizing are in increasing demand for their grace and efficiency on the trail.

At this point, due to the availability of compatible parts, the 29 inch standard has the strongest following.of the larger wheel standards. Many designers and builders of 29ers have developed geometry that strikes a balance between the early, sluggish 29ers and common 26er handling. One limitation in developing these bikes has been suspension systems. White Bros. was among the first fork manufactures to sign on to the 29 inch standard, followed by Marzocchi, Rock Shox and Fox. Now, virtually every type of rear suspension platform is being manufactured in a 29er, as well, with most offerings in the 3-4” travel range.

The recent fusion between singlespeed/fixed and 29er is more than the product of crusty bicycle mechanics’ opinionated hybridizing. Cyclingnews.com’s extensive testing is showing that 29ers are more efficient in many situations. Less scientific testing has come to other conclusions.

So who should make the leap to 29er? Think of these larger wheels as a continuation of the spectrum of wheel sizes: 20, 24, 26, 650B, 29. The more you like epic rides, are over 5’ 6’’ tall, or are skilled, the more likely a 29er should be in your future. Because minimum standover height on these bikes is about 28.5”, you should be about 5’6” or taller for a hardtail, and 5’8” or taller for a dual suspension bike.

Wild Rose is excited to offer a wide range of 29ers from Jamis, Fisher, Intense, and Surly. Jamis has some great deals on 29ers including the stealthy Exile singlespeed for about $1000. With 8 years experience in 29ers, Fisher has carried over it G2 geometry, with reduced trail forks for better handling, in the HiFi Dlx 29er. Intense has just introduced the Spider 29 with VPP, which is likely the fastest, plushest 29er being produced. And, if you’re looking for old school durability and value, Surly’s Karate Monkey is more likely to take you into old age than your spouse. Come in and take one for a bigger ride.

Anatomy and Function of a Disc Brake

Wednesday, June 11th, 2008

Last month a friend of mine asked my advice about replacing the disc brakes on his full suspension mountain bike with Shimano V-brakes. Of course I asked, “why?” He responded that he had been having quite a bit of trouble with the pads rubbing on the rotors. “I’ve tried everything,” he said. Finally his frustration boiled over on a White Rim Trip. He decided then he would switch back to cable brakes.
“What was everything?” I wondered. “Does he understand how bicycle hydraulic brakes work? Did he know all the possible adjustments?” despite appearing very complicated, the bicycle hydraulic disc brake is very simple. It just takes a little time to get to know each of the separate parts and their function.
The hydraulic brake system consists of four main parts: the brake lever and master cylinder, the caliper, the rotor and the brake line.
The brake lever is the one component that the rider interacts with. It consists of the body, upon which a master cylinder is attached, and the part we squeeze called the lever blade. The master cylinder is the reservoir for the brake fluid. It also contains a piston, which moves fluid into the brake line. The brake lever has two, sometimes three adjustments to be made. First, the horizontal angle of the lever can be changed on the handlebar. The most comfortable angle is adjusted to place the hand, wrist and forearm in a straight line. Next, a small screw in the lever body adjusts the resting position of the lever blade from the handlebar grip, called reach. Generally the reach is set closer for small hands and further for large. On some upper end models, it is also possible to adjust how much the lever blade moves when squeezed, called throw. Throw and reach are not purely independent of each other. For example, it might be challenging to have short reach and long throw.
On the action end of the system are the rotor and caliper. The rotor is a piece of machined steel or aluminum, or combination of both mounted to the wheel. They are not as fragile as they appear. However, they will bend under extreme force. Brake rotors come in different sizes; a larger diameter will provide more braking power. Changing the rotor size requires an adapter, specific for that brand, size and position (front or rear).
The brake caliper is mounted to the frame or fork; depending on the brand and size it may or may not have an adapter. The internal parts of the brake caliper include the brake pads and one, two or four moving pistons. These pistons, along with fluid behind them, are what squeeze the brake pads against the rotor. The brake pads and pistons are self-adjusting (more on this later). The caliper is adjustable laterally to provide clearance for the rotor to pass through. This can be done a couple different ways. Some manufacturers use thin washers between the caliper and mounting adapter to change the position of the caliper. The second method has the caliper manufactured with oval bolt holes.
Connecting the system together is a brake line consisting of a plastic inner liner and either plastic or metal on the outside. The fluid that moves through this line may be DOT automotive brake fluid or a specially designed mineral oil.
The way this all works is pretty simple. When the brakes are actuated, fluid moves from the master cylinder, through the brake line and into the caliper. Voila! We stop. It is easy, but there is more.
When the lever is squeezed, a piston pushes fluid from the reservoir through the brake line, into the caliper, forcing the pistons to clamp the brake pads against the rotor. In a two (or four) piston caliper, the fluid is routed behind each piston. When the brake is released, fluid returns back to the master cylinder. However, as the brake pads wear the pistons remain extended to keep a constant distance from the rotor. This is the self-adjustment mechanism. Therefore an increasing amount of fluid will remain in the caliper instead of returning to the reservoir.
Sometimes the self-adjustment needs a little help. Maybe the brake lever got bumped when the wheel was out. More often, heat from use may cause the rotors to change shape. That same heat will also affect the brake fluid and any air in the brake line in the form of expansion. The hydraulic brake is a closed system. Therefore, any expansion has nowhere to go, and it presses the pistons out. Usually when the brakes cool all returns to normal. Occasionally it may not. One or both pistons might not retract to its proper position in the caliper and the brake will continue to rub.
In any case brake pad clearance will need to be reset. If the brake caliper is positioned correctly, this can be accomplished a couple ways. One way is to gently press the rotor against the brake pad that is rubbing. Another method is to remove the wheel, and insert a plastic (!) tire lever or brake pad spacer between the pads to move the pistons. However, when the brake pads are new, the pistons are fully retracted and don’t have much room to move. Remember that closed system? With each of these methods, the pistons are reset back into the caliper. The brake pad clearance will be reset the next time the brakes are actuated.
“Aren’t disc brakes complicated?” is a question often asked by new bike shoppers. Yes, and no is my answer. In detail and design, the hydraulic bicycle brake is very complex. On the other hand, with an understanding of the basic principles, there is no reason to be fearful of them. This understanding, combined with good maintenance habits will keep your bike friction free and stopping smoothly. As for my friend’s brakes, he called soon after with a question about his new brakes. “How do I stop squealing brakes”, he asked. “I have a solution, but it’s expensive”, I replied.

To Tube, or Not to Tube?

Wednesday, June 11th, 2008

At the turn of the century one of the hottest new technologies was the tubeless tire system. Now, it seems to be all but forgotten. Unlike many components, there are just not that many new developments to be made to keep this performance enhancer in the limelight. In fact, many mountain bikes come equipped with tubeless compatible components and their owners don’t know it. As salespeople, sometimes we even forget to mention it. But using a tubeless tire system can increase the performance and enjoyment of our rides. There are two distinct types of tubeless systems available today.
In order to create a tubeless tire system, an airtight seal was needed in the rim bed. Mavic accomplished this by developing a method of installing the spokes from the hub side of the rim, leaving the inner rim bed completely sealed. The rim bead seat was also redesigned to provide an airtight seal and Universal System Tubeless (UST) was born. The tire companies Hutchinson and Michelin designed special tires that use a stronger bead wire to withstand the increased stress of the airtight bead seal. In addition, the UST tire has a layer of rubber inside the casing to complete the air containment.
Why go tubeless? The benefits of tubeless tires include lower rolling resistance, greater traction and less punctures. Without a tube, the rider can use lower tire pressure with less risk of pinch flats. With lower pressure, the tire contact patch is larger which provides more traction. The rolling resistance is decreased because with the lower tire pressure because the tire deforms and rolls over more objects instead of being deflected.
However, benefits do not come without cost. Upgrading to a UST wheel set with tires will cost several hundred dollars. Weight is always an issue on a bicycle, especially when it comes to wheels. A tubeless wheel set is of comparable weight, but the tubeless tire is a little heavier than its non-tubeless counterpart with tube. Installation can be frustrating if the tire does not inflate right away. Also, air pressure of approximately 60psi is needed to seat the bead completely; not an easy task without a floor pump or compressed air. Finally, the tire is still subject to punctures from sharp objects, and pinch flats can still occur if the tire pressure is too low. Instead of pinching a tube, the tire will have two punctures in it.
A lower cost alternative to UST tubeless is a tubeless conversion kit. While Bontrager manufactures a kit for its own brand, the most popular conversion kit is made by NoTubes.com. The tubeless conversion is made possible by a rim strip and valve combination that seals the rim spoke holes and provides an airtight bead seat. Therefore, any UST tire can then be used. More often though, a standard tube tire is used with a liquid sealant inside.
The benefits of a tubeless conversion kit are many. First, it provides all the performance enhancements of a tubeless tire system at a much lower cost. Second, the wheels are much lighter weight if used with sealant and a tube type tire. Finally, puncture resistance is increased with the sealant and seating the bead is often easier.
Tubeless conversion kits also have own their drawbacks. Installing or removing the sealant can be messy. Latex based sealants are prone to drying out, needing to be “refreshed every couple months or so. Similar to UST tubeless, initial inflation and sealing can sometimes be a challenge. Tire selection is reduced due to manufacturers recommendations.
Replacing tires is often a task that no one wants to do. New tires are not nearly as glamorous as a new shock. But look at the stacks of tires in any race truck and you will see how important tires are to performance. The correct tire and the benefits of tubeless could be just what you need to put a little excitement into your riding. Ten years later, what’s next? Road tubeless.

Tips for Tubeless
* Follow the manufacturers recommendations and instructions.
* Upon initial inflation, lubricate tire beads with soapy water. Use as little pressure as necessary to seat the bead and wear safety glasses.
* When using sealant, immediately after seating the beads, shake the tire horizontally to better distribute the liquid.
* Start with initial pressure 5psi less than with tubes. Decrease slowly until comfortable or you reach 30psi. Inadequate pressure leads to pinch flats and decreased control.
* When performing repairs, unlock as few tire beads as necessary. That means one.
* Inspect tire casings, treads and inflation pressure often
* Tubeless conversion for Cyclocross.