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| *Vultures Knob>>>Mountain Bike |
What size frame of mountain bike should I get? |
I am looking for a new mountain bike and wanted to get the right size. I am 6'1" and weigh 230 lbs. My inseam in 34" Not going to try to win this one, only give a few pointers. Please don't measure your pants again when you go to look for bikes--unless you're looking for 20 year old bikes. Facts and figures about traditional standover height measures only work with traditional frames--never with compact geometry (modern) frames. Fit by reach. Here's how: Get a yardstick. Hold arms outstretched similar to a crucifix, but just one arm at a time. Press the 1" end of the yardstick against your ribcage at the armpit. Read the number that ends up in the center of your palm. Do both sides and use the smallest number. My reach is 25" Hold the yardstick paralell to the floor across the bike's top tube and also include the stem extension. A very similar measure is seatpost to handlebar pipe center to pipe center. This is the bike's reach. If a bike exceeds your reach, the result is a requirement to push backwards, applying considerable force to your spine, and spinal injury. So, the bike's reach should never be longer than your own reach. A bit shorter reach on the bike can make for greater comfort. Some mountain bike sport-centric applications actually require a smaller frame. Road riders do this because that's easier to sprint. Not sure why mountain riders do it. Too small is hard to steer, too large has severely limited distance and zero leverage for power. Test drive until you find the one that seems the most pleasant and the fastest--simultaneously. Don't settle for less. Simultaneous comfort and speed indicates fit. So, test drive, comparing several bikes against each other. This will give a better clue on the fine points of fit for your body. Look at it this way. The farther forward your body is, the more power goes into the front tire, towards pushing yourself onto the saddle and directly into the air above your rear end. None of this propels a bike despite the extremely small areodynamic advantage. For this reason, the XC racer (a road, trail, and gravel road bike) has a slightly longer reach than a full-suspension bike. Full suspension bikes are normally quite a bit smaller just for leverage. For the XC racer, cyclocross bike rules apply in the handlebars that are farther down must also be closer or zero leverage is the result. So, test drive a lot! You'll get it figured out demonstrated so much easier than a lot of text examples. My legs are almost as long as yours. I have a 19" bike, but have ridden a 21" bike for years also. For me, the 19" bike is more comfortable. (5'9", 141#, inseam 33") That really depends what kind of riding your planning on doing if your going for a cross country frame probably an 18 or 18.5 frame if your going into freeride or DH a 17" would do it. Keep in mind that from manufacture to manufacturer the angles can be quit different so test ride alot of bikes before you settle.By the way your the same weight as me just a tip whatever you get make sure its good and strong I've broken more than a few bikes in my day I'm currently riding a .243 and its pretty much the first bike i trust not to snap under hard landings.JEEZUZ had to add this after reading hlsj_99's long winded and uninformative comment buddy you need to trust the salesperson he knows more than you!!!! how in hell can you estimate the guys top tube length without knowing his reach or torso length????? as for your comment about size of frame and weight your right but .243 is a brand not a measurement (hmm a chin scratcher eh) awsome bikes check em out http://www.twofortythree.com/ Go to a bike store, straddle a couple mountain bikes and raise the bike to your crotch. When the top tube touches, the wheels should be 3-4 inches off the ground. This sounds hard, but for the most part you are going to be faced with 2 choices because frames tend to come in 2 inch intervals. For you it's going to be a 17,19 or an 18,20 inch frame depending on the manufacture. The standover height is important only so you can get both feet flat on the ground safely when standing over the top tube. The top tube length is going to be the deciding factor - the effective length - this takes into account the seat tube angle and the slope of the top tube. For someone your height look for an effective top tube between 22.5 and 23.5 inches. There are of course exceptions, but I can't see you! You will find that these numbers are pretty standard, there's not much new in the dimensions of a human. Your weight does not have an influence on your frame size. Different frames will react differently to different weights - it varies a lot. Once you find a bike you like the ride and handling of start looking at the stem. It is likely you can benefit from changing it. Do you want the handlebars closer to you, further away, higher, or lower? The stem is all about the position of the handlebars relative to the other fixed points on the bike. Remeber you onlytouch the bike at three points when riding - the seat, the grips, and the pedals. These items are worth some thought before you lay down your money because they will all influence the bike-rider combo. I could go on and on but that is enough! HAve fun. Owned a lot of bikes, never trusted a salesperson Your Inseam and Frame Size We'll talk primarily about fitting a road bike, and make notes about fitting a mountain bike where appropriate. The best frame size for a cyclist is as small vertically as possible, with enough length horizontally to allow a stretched out, relaxed upper body. This frame will be lighter and stiffer than a larger one, and will handle better and be more comfortable than a smaller one. Determine Your Proper Frame Size To determine your proper frame size, you鈥檒l first need to get an accurate inseam measurement . Stand with your back against a wall, your bare feet 6" apart on a hard floor, looking straight ahead. Place a book or carpenter鈥檚 square between your legs with one edge against the wall, and pull it up firmly into your crotch, simulating the pressure of your saddle while riding. Have a helper measure from the top edge of the book to the floor, in centimeters. (You can convert inches to centimeters by multiplying inches by 2.54.) Repeat two or three times, for consistency, and average the results to get your inseam length. Bike Sizing Worksheet 禄 Frame Size Frame size refers to the length of the frame鈥檚 seat tube. Pro frames are measured along the seat tube in one of two ways, center-to-top (C-T) or center-to-center (C-C). C-T measures the distance from the center of the bottom bracket to the top of the top tube or seat lug (See image bellow). C-C measures from the center of the bottom bracket to the center of the top tube. Since C-T measures to a point higher on the frame, a frame measuring 55cm C-T would also measure roughly 53.5鈥?4cm C-C, a difference of 1鈥?.5cm. To size your C-T road frame, we use a guideline of .67 x inseam length. For example, if you have an 85cm inseam, your C-T frame size would be .67 x 85cm, or 57cm. LeMond鈥檚 formula, from his former coach, Cyrille Guimard, establishes C-C size by the formula .65 x inseam length, which yields virtually the same frame size when you add the 1鈥?.5cm difference between C-C and C-T. Larger riders (6'0" and up) may find that this formula puts them on a too small, and uncomfortable, road frame. A taller cyclist who wants a more comfortable frame may be better off selecting a frame 27鈥?8cm less than inseam length, C-T. For a mountain bike, we start by recommending a frame in the range of 10鈥?2cm smaller than you take in a road frame. For example, if you ride a 55cm C-T road frame, look for a 43鈥?5cm (17鈥?8") C-T mountain frame. Click for larger view. Frame Dimensions ------------------------------... A1 Seat Tube Length (C鈥擳) A2 Seat Tube Length (C鈥擟) B Top Tube length (C鈥擟) C Stem Length (C鈥擟) In many ways, though, it is more important to fit a mountain frame by the top tube length needed, rather than by the seat tube length. For instance, you might be able to get to the proper frame clearance, saddle height and neutral knee position (see below) on either a 17" frame or a 19" frame. Yet the 19" frame will likely have a top tube 1" longer than the 17" frame, which changes your stem length accordingly. Or, one manufacturer鈥檚 17" frame may give you a 22" top tube, while the next one鈥檚 17" gives you a 22.8". More on this below鈥?just make sure that you鈥檒l be able to work out your top tube and stem length for a given frame. Bike Sizing Worksheet 禄 Saddle Height With the right frame size, you鈥檒l be able to set your correct saddle height, which will be within a centimeter of .883 x inseam length, measured from the center of the bottom bracket to the low point of the top of your saddle. This allows full leg extension, with a slight bend in the leg at the bottom of the pedal stroke. LeMond recommends that you then shorten this length by 3mm when using clipless pedals. Also, you might consider a slightly taller saddle height if you ride with your toes down and your heel raised. Most importantly, make any changes in saddle height gradually, and give your body time to adapt to the new position. Bike Sizing Worksheet 禄 Neutral Knee Position Next, put your bike in a stationary trainer, raising the front wheel to level the bike. Check your position with a video camera or mirrors in front and to the side, or with the help of a friend. Position your cleats with the ball of your foot directly over the pedal axle, and in line with any natural "toe-in" or "toe-out" foot position. Warm up by riding easily for 8鈥?0 minutes. Then, as you continue to look ahead, slowly stop pedaling, and bring the cranks to rest at horizontal, parallel to the ground. Check the position of your forward knee relative to the pedal spindle 鈥攆or a "neutral knee position," you鈥檒l be able to drop a plumb line from just below the front of the forward kneecap, and have it bisect the pedal spindle and ball of your foot below. Remember to not raise or drop your heel or hip as you check this. Then, move the saddle fore or aft, as needed, to achieve this neutral position. The neutral knee position serves as a good starting point for most cyclists, though many adjust it from here: long distance (stage) racers and mountain bikers often move the saddle back by 1cm or more, for power, and sprinters may move it forward, 鈥済etting on top of the gear鈥?for quick acceleration. One more note on frame size and geometry: if you cannot move the saddle back far enough to get your knee to the neutral position, you should look for a frame with a more relaxed seat tube angle, or consider a slightly larger frame; if you have trouble moving the saddle forward enough, look for a steeper seat tube angle on your next frame, or consider a smaller frame. For most frames, a seat tube angle shallower by 1掳 moves the seat lug 1cm back, relative to the bottom bracket. Finally, recheck your saddle height. If you鈥檝e moved your saddle forward or back, you鈥檝e effectively shortened or lengthened your saddle height, and will need to readjust it. Bike Sizing Worksheet 禄 Top Tube and Stem Length Next, dial in the correct "reach" to the bar, or horizontal fit. Proper reach gives you easier breathing, better neck and lower back comfort, and better weight distribution and bike handling. That "ideal position" varies here more than anywhere else for cyclists, depending on riding style, flexibility, body proportions, and frame geometry, among others. And, your upper body position will evolve with more hours in the saddle. That is, you may find that you develop a lower, longer position as your fitness and flexibility improve. As Phinney notes, though it may be difficult to achieve a truly flat back, we cyclists should all strive to be 鈥渓onger鈥?across the top of the bike. Unfortunately, there is no formula for sizing the top tube and stem that works as well as the inseam method. One indicator comes from glancing down at the front hub while riding in the drops; your view of the the front hub should be obstructed by the handlebar. LeMond recommends that your elbows, bent at 65鈥?0掳 with your hands in the drops, should be within an inch or two of your knees at the top of your stroke. Measure your current bike鈥檚 top tube and stem. Then, decide how you鈥檇 like to alter that fit; add the top tube length to the stem length to get your overall top dimension. The very reason we stock stems in 1cm increments, from 7cm to 14cm, is just to let you dial in your best top tube and stem length. Bike Sizing Worksheet 禄 Handlebar Size Road handlebars come in several widths and bends. Most cyclists select a bar that is just as wide as their shoulders, measured as the distance between the shoulder joints. A wider bar opens the chest for better breathing and more leverage, but is less aerodynamic. You鈥檒l need to find your own balance between the two. Bike Sizing Worksheet 禄 Crank Length, Gearing Choosing the right crank arm length, like the rest of this, comes down to your size and riding style. Longer cranks give you more leverage, helpful if you like to push big gears at a low cadence (climbing, time trialing, etc.). On the other hand, if you like to spin at a high cadence, you鈥檒l do better with standard cranks. As a starting point, we often recommend 170mm cranks on 54cm C-T road frames and smaller, 170鈥?72.5mm cranks on 55鈥?1cm frames, and 172.5鈥?75mm cranks on 62cm frames and larger. Mountain bikes generally get cranks 2.5鈥?mm longer than road bikes; that is, you might want a 175mm crank on your mountain bike if you鈥檙e set up with a 172.5 on your road bike. We offer a wide range of gearing options for chainrings and cassettes. Depending on your strength and terrain, you鈥檙e welcome to specify the close-ratio gearing generally used for racing, or wider ratios for hilly terrain or more recreational riding. Bike Sizing Worksheet 禄 A Final Note One of the objections your local shop may have to your purchasing a bike through the mail is that it cannot be fitted correctly. For the resourceful cyclist, the opposite is true. The retail shop often offers a cursory fit that involves the customer standing over the top tube of a few bikes on the floor; frames 5cm (2 inches) apart rather than 1鈥?cm apart in sizing; no stem sizing, no bar sizing, no crank sizing, no wheelbuilding options. Compare that with the program we have for you. The Colorado Cyclist offers quality and variety in professional road and mountain bikes, at significant savings鈥攁s well as a great fit! Bike Sizing Worksheet 禄 OUR BIKE FIT GUARANTEE We guarantee the fit of your new bike with this simple promise: After you've ridden your new bike for a few days, let us know if you need to swap out the bar or stem, or make other adjustments, and we'll make it right for you. |
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