Weight Rant
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by Lee Bridgers, Dreamride owner and founder
In summer of 2005 we completed a project bike that had the following names over the past five years: Moment, Rattler, Pagan. It finally came together as the Mutant. The Mutant is a perfect example of the philosophy of weight distribution that is the basis for the info provided below. Read up on the bike at DREAMRIDE MUTANT for practical application of weight placement. Dreamride also produces the FULLY, a six inch trail bike that balances weight concerns with high performance in the long travel cross country arena. At the other end of the weight-issue spectrum is the WHITE RIM 29ER, a bike that truly focuses on light weight out of necessity and specific use.
OK, you're a weight weenie. You want every gram shaved so that you can climb faster and handle the bike quicker. Well, weight is certainly a concern, but, in a world of full suspension, it is not as much of an issue as it used to be. Riding within the limits of light equipment can certainly limit your ability to go fast. Downhill cycling technology has changed the way we think as mountain bikers. If you ride with anyone who rides the very edge you will notice that they are more concerned with durability and travel than with weight. After years of BMX, motocross, screaming down ruts and a few trips to the hospital, the way moto bikers approach weight is the exact opposite from the way a weight weenie does: They pick up the bike, shake it a bit and pronounce it, "Too light!"
The most important factor when considering mountain bike components is rider to bike weight ratio. Obviously, if you weigh 250 pounds, a 23 pound bike would be dangerous. Race bikes for these heavy dudes can weigh in the neighborhood of 27 to 28 pounds and do not hold up for more than a couple of years of racing. Weight is also dependent on use and terrain. The "big boy" category demands that components are not compromised in strength. If you weigh 130 to 150 pounds, then you can go with DT Revolution or Titanium spokes, light rims and a feathery air fork and be able to ride without too much caution--ON MOST XC TERRAIN. A race bike can be built to 21 or 22 pounds for these lighter riders. If you weigh between 150 and 170 then you can probably go for the same set-up, but will have to think about the light components as you are riding, AND YOU WILL HAVE TO RESTRICT WHERE YOU RIDE. If you weigh between 180 and 220, then you are going to have to start thinking about stout components, especially spokes, rims and frame. IF YOU RIDE ROUGH TERRAIN AND RIDE FAST AND HARD, THEN NO MATTER HOW MUCH YOU WEIGH, YOU ARE GOING TO HAVE TO BUILD A STOUT BIKE.
SUSPENSION UPDATE: At this point in time air forks (especially those built by Marzocchi) are a viable alternative for heavier riders, but there are still quite a few out there that are questionable. Air pressure shoots up on compression when a 200+ pounder lands on a five foot drop. This instant high pressure can blow a seal and the fork leg in quesion looses all of its travel in a split second. Catastrophic failure of an air cartridge causes injury. Avoid forks with one sprung chamber in a single leg (the other leg acts as a damper for the spring in the other leg), the Maverick DUC, for example. Coil springs, however, will never let you down and work smooth as butter in one or two legs of the fork. In 2006 we went to full air suspension on the Dreamride Fully and a combination of coil and air on the Mutant. Newer Marzocchi long travel air and air/coil combo forks from Marzocchi have huge air volume, which means lower pressures and buttery operation. They also have springs in both legs for redundant cush, a wider tuning range and safety. Also, the Fox DHX-Air is now a stock item on the Dreamride Fully and an option on the Mutant freeride bike. It feels like a coil, allows a wide range of adjustment, is far lighter than the DHX-5 coil shock and holds up well under rough use. So, when things get lighter and they work, we cannot complain.
WHEELS
Light wheels can flex and change your line, even taco or break with a hard lateral impact. A tire mounted on wider heavier rims presents a wider footprint. The wide bead greatly reduces rollover and means a stiffer, more vertical sidewall. Wider grip and stiffer sidewalls allow you to reduce braking in turn and that means faster elapsed time. Stiff side knobs just rail you through. Large tires mounted on small rims wabble around as the bike is leaned into a turn and simply roll off the rim in a jump. Here's a news flash: Aluminum is lighter than rubber. Use a wide rim and a light tire for the best of both worlds. Read the information on 29er wheelsets at BIG WHEEL RANT for some serious information on the dangers of mistaking a larger wheel for a mountain bike full suspension component.
FRAMES
Strength is the primary weight issue. When looking for places a bike can be lighter and retain strength look first at the frame. A triangulated frame can weigh far less than a beam or interupted design and still be stronger due to the inherant physics of the triangle. The strength of a triangulated frame is then bolstered with gusseting (a good gusset is not welded to the frame on the end away from the frame joint--the gusset should be able to move at some point), butting (this shaping of the tube can be done externally or internally), or the tubes can be simply thicker (a straight gauge tube is superior to a butted tube when it comes to stiffness and the ability to resist denting--an externally butted straight gauge tube is best). Strength in a triangulated frame is increased by the stoutness of the three sides. Brace a single joint of the triangle with another tube inside the triangle, and bing--no more triangle. Any four sided shape is not going to hold up like a triangle.
SMALL COMPONENTS
When looking for places where weight has a direct impact on strength look at spindles or any part that bears weight but is not triangulated or supported at either end. The handlebar is a good example, as is the stem. Bottom backet spindles and crank arms need to be well engineered or just plain beefy. If you land hard on an ultralite part it could bend or sheer off. If your seatpost is carbon fiber and REALLY LIGHT it could fail catastophically. Carbon fiber part defects can be invisible to the eye, so you never know what you are getting. Friends don't let friends ride carbon fiber, especially on a bike that is going to be going off of drops. That said, I do spec carbon fiber parts I have grown to trust. Seatposts, however, are not one of those.
WEIGHT=MOMENTUM
A rarely considered rationale for heavier parts, is that weight increases momentum, which in turn allows you to roll up and over nasty obstacles, allows you to be more stable in the air or in hard turns on rough terrain. A certain balance between the weight of your bike and your body is important. During technical moves over large obstacles the momentum of the bike and your body can be used to see-saw onto, over and through the section. There is a balance to be struck between weight for durability and momentum and the rider's ability to overcome the inertia of the machine at rest and in motion. The bike has to respond to the pitiful horsepower put out by the human body. A forty pound bike is probably at the limit for a pedaling bike, but a thirty pound SUSPENSION bike really cannot be considered "heavy." Out of my own experience, 25 to 38 pounds is where the weight of a suspension mountain bike, a true trailbike, should be. I'm not talking hardtails here, only full suspension. A hardtail is fine in the 21 to 29 pound range and when the speeds get up to the point where things break you are probably aready out of control. Just where the weight of your bike falls will be dictated by your own weight and just what you plan on doing with the bike. Naturally, for slow speed twisting, smooth trails, light is right, but as the terrain becomes rougher and the speeds go up, the weight simply has to increase for the sake of strength and momentum. Suspension allows this speed. Momentum allows control, stability and comfort over rough stuff. This is why a Cadillac is so smoooooth.
WHERE IS THE WEIGHT?
There are places on a bike where weight has a greater effect on performance and handling. Stout and heavy hubs have very little effect on how a bike feels. Their weight is low on the bike and at the center of the wheel. Weight on the wheels that is not rotational (at the outside of the wheel) is not as noticed when the bike is in motion. The reason disc brakes do not seem to detract from the bike's performance, even though they are quite a bit heavier, is that they are at the center of the wheel, not up on the bike's frame. Rims are at the outer edge of rotational weight, so they have a much more serious effect on accelleration. A heavy saddle or tools inside of a seat tube mounted pack cause the bike to resist subtle weight shifts during cornering or while making quick moves around and over obstacles. Weight that is carried low is always prefered to weight carried high. Weight at the center of the wheel is always prefered over weight at the outer edge. That said, a heavy rim and tire will make you much more stable when going fast over anything. The more the outer edge of the wheel weighs, the better the gyroscopic effect of the spinning wheel. To get a good picture of how important gyros are, grab your brakes while you are in the air on a jump and you will fall like a rock. If you let your wheel spin, your flight will be smooth, stable and controlled. The wind resistance of the tread also has great effect on this phenom. Of course, don't try this if you are not already a jumper. Using the spinning weight of a wheel is one of the more subtle skills in jumping. Grabbing the front brake means the front end falls. Grabbing the rear brake means the rear falls. If you ever get a chance to watch Robby Knevel in the middle of a huge jump, watch how he feathers the throttle to change the rate of his rear wheel gyro and in turn makes the front or the rear of the bike rise or fall.
TRAINING ON A LIGHT BIKE TO RIDE A HEAVY BIKE
I have a lot of bikes available to me in this business. I ride from a pool of 10 bikes, weighing from 21 to 34 pounds. I prefer the heavier bikes (29 to 34 pounds) for guiding and for play on really rough stuff, but ONLY if I take the time to train for carrying the weight around by spinning my light 21 pound 29er or road bike for miles and miles. Of course, Moab terrain is quite different than hardpack mountain singletrack and areas with extended climbs on smooth roads where the extra weight of long travel becomes unnecessary. On the smoother trails I prefer the 29er over the suspension bikes. As the season moves into October, after months of training, I end up on the heaviest bike, the Mutant. Power is where it's at. Getting stronger means you can handle a much more capable rig. Get it to the top and on the way down be thankful for the forgiveness. After thirty years on off-road bikes, I have learned that if you want the thing to be lighter, loose some weight off your huge ass.
REPETITIVE MOTION INJURIES
This update comes as I have just figured out a specific injury I have been dealing with over the past three years. My hip began to give me serious problems a few years ago. I tried a number of treatments, avoiding surgery at all costs. Age certainly plays a part in this, but not as much as you would think. At its worst, the hip kept me from traveling, caused me great pain in the morning when I got out of bed, and scared the crap out of me when the pain became sharp and sudden. I finally figured out the source(s) of my problem and now I deal with mild intermitent "warning" pain, rather than constant torture. What were the causes? 1) Sleeping in the same position for decades. 2) Riding too heavy a bike constantly. 3) My position on that heavy bike. 4) Diet. Solutions? 1) Move to the other side of the bed (the greatest relief came from this simple choice). 2) Ride a light bike for training and a heavy bike for work. 3) My position on the heavy bike, the Mutant, remains the same as far as the saddle is concerned, but I now use the extension control on the fork much more, effectively changing my position from behind the pedals to over the pedals by lowering the fork height while climbing or during a distance trek. 4) I eat better. No more restaurants! Only one beer at a time. No liquor. No white flour. Avoid acidic foods. Knees are another issue. On a heavy bike it is essential to spin those pedals for momentum, and keep the torque for short bursts. I know fellows who have blown up their knees by riding a heavy freeride bike as their main rig. If you experience joint pain while pedaling, something isn't right. I blew up both knees in the 70's riding a 40 pound singlespeed Schwinn cruiser. There is no excuse to ride a pig like that at this point in time.
NOW, FOR THE "BOTTOM LINE"
The heavier the bike, the more the damage done to the environment and to the image of our sport in the eyes of the general public. A bike that weighs over 30 pounds is going to make you do stupid stuff. It will make you lust for ski lifts and shuttle rides. It leads you off trail. It will enable you to do things that you could not do on lighter equipment--stuff that maybe you should not be doing for ethical reasons. Young riders coming into the sport tend to go for stuff that looks like a motorcycle. Young riders are dumb as a post, a bag of hammers, a box of rocks, so they gravitate to anything marketed to them as "extreme." So, we are seeing the "youthification" of mountain biking resulting in sixteen year olds jumping off of their dad's garage for sport, as the image gets more and more extreme------ahhh, "extreme." Did you know that the Rat Olympics recently changed their name to the Extreme Rat Challenge? Did you see the CNN feature on "Extreme Babymaking" followed by a story about a sixteen year old kid holding police at bay with a rifle (he ended up dead--extremely so--at his own hand). Extreme sports produce extreme results. I hope all you whipper snappers are prepared for the devastation of global warming and terrorism in your backyard, because that is exactly where the "extreme" logic leads. What is the worlds greatest extreme sport? WAR! What is the most extreme experience one can have on earth? VIOLENT DEATH AT AN EARLY AGE. Enjoy your heavy bike, but real men ride 21 pound singlespeeds over the same terrain that whipper snappers enjoy on a 45 pound pig
http://www.dreambike.com/weight.htm
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