Okay, we all know the best way to find your next frame is to test ride everything that floats your boat. However, it’s usually much easier said then done – finding frames in your size and in stock is not easy. Standard manufacturer data doesn’t usually tell me enough about how a bike will ride, so I dorked out and put together a set of formulas that uses manufacturer data to spit out more usable geometry info. The default data is for mini-dh/all-mountain frames in medium size, but you can plug in whatever frames you want.
How to use this -
First, download the file at - Bike Geometry Formulas (you can view the file right on the site, but to enter in additional frames you'll need Excel)
Plug in the following data – head angle, top tube (inches), static bb height (inches), wheelbase (inches), chainstay length (inches) and rear travel. There’s a millimeter to inches converter formula in the sheet if you need it, as well as a formula for converting BB drop to static bb height.
Output:
The resulting data is for COMPARISON use only. The data without a reference point isn’t very useful. It’s best to use bikes you have ridden as controls to compare other bikes to. Also, remember garbage in = garbage out, the data is dependent on it’s source – if you use crap measurements you’ll get crap accuracy.
BB/WB: Ratio of sagged bb height to overall wheelbase. This is a tricky data point because rear travel is not usually measured vertically. That said, bikes with a lower percentage may have a lower center of gravity.
Front to Center: Front axle to the center of the BB. Gives you an idea of how much room you have in the front end.
Standing Horizontal Reach: Similar to top tube measurement but starts at a point directly above the BB and ends at the center of the stem on the steerer. This is much more useful then a top tube measurement as it reflects reach when you're standing. To make the data comparable the calculation uses the same height between the BB and the stem on all frames. You can enter a control value for preferred stem height, but if it’s too low it won’t be realistic – the point you’re measuring would be in the headtube or lower. The default measurement is 24”. Use your own measurements from your current bike if you wish (measure floor to the center of your stem on the steerer and subtract static bb height).
Front to Bar: Horizontal measurement from the front axle to the center of steerer tube based on preferred bar height. Gives you an idea how far out in front of your bars your front wheel will be.
Rider Center vs True Center: Center between bb and bar reach versus center point between the axles. Gives you an idea about the forward/rearward bias of the bike.
Once you have the sheet loaded with the frames you're interested in, just sort the list by column criteria to find the bikes that meet your preferred specs.
How to use this -
First, download the file at - Bike Geometry Formulas (you can view the file right on the site, but to enter in additional frames you'll need Excel)
Plug in the following data – head angle, top tube (inches), static bb height (inches), wheelbase (inches), chainstay length (inches) and rear travel. There’s a millimeter to inches converter formula in the sheet if you need it, as well as a formula for converting BB drop to static bb height.
Output:
The resulting data is for COMPARISON use only. The data without a reference point isn’t very useful. It’s best to use bikes you have ridden as controls to compare other bikes to. Also, remember garbage in = garbage out, the data is dependent on it’s source – if you use crap measurements you’ll get crap accuracy.
BB/WB: Ratio of sagged bb height to overall wheelbase. This is a tricky data point because rear travel is not usually measured vertically. That said, bikes with a lower percentage may have a lower center of gravity.
Front to Center: Front axle to the center of the BB. Gives you an idea of how much room you have in the front end.
Standing Horizontal Reach: Similar to top tube measurement but starts at a point directly above the BB and ends at the center of the stem on the steerer. This is much more useful then a top tube measurement as it reflects reach when you're standing. To make the data comparable the calculation uses the same height between the BB and the stem on all frames. You can enter a control value for preferred stem height, but if it’s too low it won’t be realistic – the point you’re measuring would be in the headtube or lower. The default measurement is 24”. Use your own measurements from your current bike if you wish (measure floor to the center of your stem on the steerer and subtract static bb height).
Front to Bar: Horizontal measurement from the front axle to the center of steerer tube based on preferred bar height. Gives you an idea how far out in front of your bars your front wheel will be.
Rider Center vs True Center: Center between bb and bar reach versus center point between the axles. Gives you an idea about the forward/rearward bias of the bike.
Once you have the sheet loaded with the frames you're interested in, just sort the list by column criteria to find the bikes that meet your preferred specs.
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