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Old 12-12-20, 10:58 AM
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Moisture
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Comprehensive Frame Fitting Guide

As some of you may know, it's been quite a journey for me with regards to frame fitting. I hope that my methods of trial and error as well as research can help guide someone looking for a bike into t he right direction. Please be kind and offer feedback in a constructive manner, if need be.

With the average person being built different from one another, it is imperative to find a riding position which ensures that you are not leaning back or forward too much. You should feel a good centre of gravity by ensuring that you can easily lean forward or backwards without too much of your weight always being fore or aft.

- Skinnier people tend to prefer a more leaning over position to achieve the desired balance versus someone who is top heavy either with fat or muscle.

- Three main frame measurements to consider:

- Stack - make sure you find a bike with a sufficient stack, ideally so that you don't need to add several spacers or a stem riser in order to get your handlebars level with your seat.

- Reach - How close or far away the bottom bracket is from the bars. This will affect your balance, comfort and power trasnfer whilst pedalling out of the saddle.

- Top tube length, or Effective top tube - This is the measurement which determines how comfortable you are while sitting in the saddle. You can make small adjustments by sliding the seat fore or aft to get the best leverage over your cranks, but this is never a solution to a poor fitting frame.

- Standover height should never be used as a basis for a comfortable fitting frame.

- Crank arms should be in direct proportion to your inseam. This mostly a matter of comfort, but will always pay some dividends to overall performance as well as the way the bike is geared.

- Once you have the top tube length and reach set in order, you must make sure that the stem you are using is an ideal length for you. it's better to err on an overly short frame reach because you can always compensate with a longer stem.

- Drop bars vs flat bars- I find that drop bars only work well with a precisely fitting frame. As long as the bar is roughly your shoulder width, you should have an optimal level of manveurability. drop bars tend to decrease precision around twisty or tight turns, but the different hand placements and aerodynamic profile can be highly efficient for power transfer, especially during climbing and descending. flat bars tend to offer better control over the bike, but the rake of your fork and head tube angle also plays a role here.

As a general rule of thumb, if you can just almost touch the ground with your toes while sitting on the saddle, you got the seat height about right. Now, if your handlebars are lower than the saddle, chances are you may want to try out some spacers or a stem which is higher and/or closer to you. If that is not enough to reasonably level your handlebars, this is a solid indication that the frame is not a suitable size for you.

Generally speaking, there are two generic types of frame geometry.

Road or Gravel bike - generally a shorter reach, designed to compensate for the stretched out position of having drop bars and a lengthy stem. Lower bottom bracket. Faster handling.

XC, trail bikes, etc etc - These type of mountain bikes tend to have a pretty long reach. It's not ideal for gravel or road/urban rides.

For example, im really only comfortable on a bike with quite a short reach and top tube length. something you will typically find on an older style road bike, using a pretty short stem. This brings the cranks a bit further in front of the seat for better leverage while helping me bias my weight rearward. I like having my butt hovering over the saddle, so I can easily adapt my power levels by keeping weight off the seat and into the cranks or conserving energy by pedalling in the saddle more. This way, my weight is rear biased. However, being top heavy, this means I don't need extra top tube or stem length to bias my weight forward easily like you always tend to do with a mountain bike.
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