This simple tool helps you figure out your bike's Bottom Bracket Height or Drop by factoring in wheel and tire sizes, suspension travel, crank length, and SAG. Seems easy until you try to calculate for an enduro mullet bike to see how things change using specific Flip Chip positions. Yes, we skip most other geometry data because we just want to compare Crank Clearance using those specific BB numbers focusing on that measure. While the calculation doesn't account for any geometry point obove axles, it still provides a reliable estimate of ground clearance. You might have noticed some brands provide BB data incorrectly, which is why you can also double-check your own measurements with BB Calc. This way, you can ensure real numbers to compare them or use for example to choose the right crank lenght.
Knowing these values can help you understand your bike's geometry, cornering stability, and pedal or crank clearance.
BB Height is the vertical distance from the ground to the center of the bottom bracket. This measurement can be taken from geo chart or measured by user.
BB Drop is how far the bottom bracket sits below (or above) the wheel axles' centerline. This one is hard to measure so we need to trust provided geo chart of bikes manufacturer or... use our calc!
SAG refers to the amount of compression in the suspension (front fork and/or rear shock) caused by the rider's weight when sitting in a natural riding position. It is typically measured as a percentage of the total suspension travel and plays a crucial role in how the bike handles.
Honestly, you don't :) But if you're comparing different bikes before buying, ground clearance is often the most overlooked factor that impacts your riding experience. We all know angles, reach/stack, and wheelbase matter, but pedal/crank clearance can be just as important when you're trying to dial in your setup. Who likes pedal strikes? Enduro bikes can cost big bucks, and if you're a bit like us, you pick your weapon of choice wisely ;) We calculate two types of clearance: Ground Clearance (pedal axis) and Crank Clearance (actual clearance - which is a bit lower). We always knew this affects riding, and now you can check how this stands in different frame designs.
In short, using “average travel” to illustrate how the bottom bracket SAGs is a helpful approximation, but it’s not a perfect depiction of real-world suspension kinematics. On suspended enduro bikes (with the same wheel size and comparable front/rear travel) the BB is predictable, so approximating its placement by that average is a workable estimate. For a quick online geometry check—especially when comparing different bikes or wheel setups—averaging the travels is typically “good enough” to see how changes might affect pedal clearance and BB position. This approach is both simple and sufficiently accurate for most suspended bikes geometry comparisons. If you need pinpoint accuracy, you’d have to rely on a full link/leverage geometry calculator. However, for everyday usage or quick checks, we prefer our practical method.
It's your Secret Sauce for Customizing Every Ride :) Ever wished you could tweak your Enduro Bike on the go?
Flip Chip — the game-changing feature that lets you effortlessly switch how your bike handles. Whether you're shredding steep descents and need extra stability or tackling tight, technical trails that demand nimble agility, the Flip Chip has got your back ;) This nifty little gadget not only enhances your bike’s versatility but also optimizes your enduro riding. So, "what if" and "what when" you want to check your BB Positioning or compare with some other bike? You can do it here!
If you can't support our project that's fine. Have a blast using this online free version of BB Calc :)
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This tool is designed for people that understand how things may vary in different setups, especially when comparing 100% SAG just to estimate the limits of a particular design in terms of minimal BB Height.
BB Calc simplifies calculations by averaging Suspension Travel input, rather than having pinpoint accuracy. For those seeking more precision, the Vertical Travel option is available where we can factor in the travel that inpacts how the Bottom Bracket lands. This ensures users can account for real-world differences between the marketed suspension travel and actual vertical movement. It’s an important factor as suspension designs can result in varying vertical travel even if the stated travel is larger.
Also, for a simple calculator that aims to give you a ballpark figure, the overhead of implementing a chainstay-based weighted approach was not worth the added complexity. Most bikes with typical geometry are fairly close to the simple Half-and-Half method we had used here.
Additionally, the calculator includes adjustments for Wheel Circumference. Different rim widths influence how a tire sits on the rim, which directly impacts the circumference. Since this can vary significantly, the option to factor in such adjustments allows for more accurate calculations tailored to your specific setup. Not mentioning that it was fairly easy to implement using our simplistic Axle-to-Ground point of reference approach.
Another critical aspect when comparing bike geometry charts is the influence of the fork’s Axle-to-Crown length. This length affects both BB Height and BB Drop values. Unfortunatly in this Calculator we are not intrested in what happens above axles as we want to keep it as simple as possible :) So please do keep in mind that manufacturers may use different forks at same travel or own standards of publishing the measurements. Differences in particular models of front forks or suspension design can have a noticeable impact on bikes geometry. Being aware of this variability ensures a better understanding of how your setup compares to the manufacturers' charts and comparisons between different bikes.
By considering these factors, bbcalculator.com aims to provide results that are not only easy to understand but also flexible enough to account for real-world deviations.