Anyone who knows anything about bikes, will tell you that fit is the #1 thing to consider when buying a bike. Each manufacturer has a particular geometry to get the most out of there designs. Getting a correct size frame will give a position that is optimal in getting the most from the bike. Whether it's a road or mountain bike.
The body is a remarkable piece of equipment. It can adjust itself to try to be as comfortable as possible in any situation. Thus, you find people who have been riding the wrong size bike for a long time. The body adapted.
We developed a fitting system that we have found to be the best on the web. WS Fitting System The design is based off a few different concepts that were distilled down to the core. Eddy Merckx, Lemond, and Independent Fabrications were all used in cross referencing sizing measurements.
We have also made some images to show you how to measure your own bike to not only cross reference the WS fitting system, but also for us to see what you've been riding and how your new fit will affect you. We have found that most people are fit incorrectly, so if your measurements seem vastly off on your own bike most likely you were misfitted to begin with. That means your new bike will give you another reason to go out and do longer rides.
I'm going to explain the measurements in detail and you can click on the image to get a view of how to take it as well.
1. Saddle Height - Saddle Height is based off of your true inseam. Not your pant inseam. To know that you have taken the inseam measurement correctly, you can approximate that your true inseam will be about 1-1.5" longer than your pant inseam. The saddle height is measured from the center of the bottom bracket, which is where the crank is bolted to the frame, to the top of the saddle measuring along the seat-tube.
2. Top Tube - Top tube makes up for the majority of your cockpit area. The major component being the stem, which we will get to a little later. This measurement can be tricky if you have a compact or sloping geometry. Which means the top tube slopes down towards the seat-tube. Both measurements are measured parallel to the ground. For a traditional frame, measure from the center of the head-tube back along the top tube to the center of the seat-tube/seat-post. If it's a compact frame, measure from the center of the headtube, parallel to the ground, going back to the seat-tube where ever the intersection is. With some compact frames that intersection will be at the center of the seat-post.
3. Seat Tube - If you go into a shop and they say, "Stand over this bike.", "yes, it's a perfect fit!" Then you know that employee or shop, doesn't know much about fit. The Seat-tube is a secondary measurement to the rider compartment. In an ideal situation you will get both a perfect top tube and a perfect seat-tube, but it doesn't always work out that way. Each manufacturer has a different view of fit and stem length. There are ideal stem lengths for frame sizes, but once again the human race doesn't have alot of consistency so not everyone has an ideal stem length either. To measure the seat-tube center to center, measure from the center of the bottom bracket, the same place as the saddle height, to the center of the top tube along the seat-tube. To measure the seat-tube center to top, measure from the center of the bottom bracket to the top of the top tube. Keep an eye on manufacturers measurements as some measure center to center and others measure center to top. Apples to apples.
4. Handlebar drop - This is primarily a comfort measurement. With the threadless stem/forks out today there are limitations as to how many spacers you can put below the stem. Generally the most is 35mm, although some go as much as 50mm. The more spacers under the stem the higher the bars. The higher the bars, the less weight on the front wheel which will take away some of the descending and cornering prowess. So a good rule of thumb is to go as low as you can, while still being comfortable. To measure your handlebar drop, measure from the floor, perpendicular to the floor, to the top of the saddle. Then measure from the floor, perpendicular to the floor, to the top of the handlebar. Subtract the saddle height from the bar height. 2" is the most common drop for good handling and comfort.
5. Stem Length - There can be vast discussions about stem lengths as to what length is best. The bottom line is that it still needs to fit. Your anatomical measurements give a "rider cockpit" that cockpit is your top-tube + your stem length. Yes there are other variables, such as straight post, offset post, seat angle, saddle length and such, but the "rider cockpit" calculation will get you 98% of the way there. Anything more will most likely need a higher scientific calculation, like going to UC Davis for a VO2 max metering and wattage. To measure stem length, measure from the center of the headset bolt to the center of the handlebar. Oversize bars can be tricky to measure, so make sure to go to the center of the handlebar and not where the faceplate meets the stem.
6. Your cockpit - As I stated above if you take the stem length (#5) you just measured and add it to the top tube length in measurement (#2) you will have your overall reach. If you go through the WS sizing system it will tell you an ideal "rider cockpit" based on your overall measurements. You can compare them to your existing bike and you'll get a sense of what your reach will be on your new bike. If your an avid cyclist and have been riding in a particular position for many years and find it comfortable and don't want to change, not a problem. The fitting system is designed to get you a perfect fit, but back flexibility, medical ailments or just plain riding style will also influence the outcome. We look at the measurements, but your feedback is what helps deliver the perfect fit.
WS Fitting System