Mountain bike geometry is much more enjoyable than you might think. We won’t even ask you to solve the problem for X. You can forget about that flashback and reconsider what you know about geometry. Mountain bike geometry will allow you to predict how your bike will ride before you ever even touch it. We will show you how to better understand the components of the bike you ride. Let’s dive into the design of our bikes and discover their intended purpose.
Angle of the head tube
Head tube angle refers to the angle at which the head tube points toward the ground in degrees. A 90-degree angle head tube angle would mean that the tube points straight up and down. Imagine a shopping cart where the wheels spin in circles. Bikes have head tube angles that range from 63 to 72 degrees. This difference in degree can make a huge difference in how the bike handles. A bike with a steeper angle (a higher number) will give you better control and climbing abilities. A e bike with a lower angle (lower numbers), will give you slower steering and better stability at high speeds. A chopper is a motorcycle that can be used to race on the streets. Cross-country bikes are more comfortable at steeper angles, ranging between 68 and 72 degrees. A full-on downhill bike will be at a lower angle between 63 to 65 degrees. The angle of a trail bike’s headtube can vary from 66-68 degrees depending on its intended use.
Length of chainstay
The lower portion of the rear triangle that connects to the rear wheel is the bike’s chainstays. The length of the chain stays plays an important role in a bike’s playfulness. A bike with shorter 16-to-17-inch chainstays will handle and wheelie better than one with longer stays. A shorter wheelbase also improves cornering. However, too short chain stays can lead to problems. A slightly longer chainstay will keep the front wheel on the ground when climbing steeply, while a wider wheelbase can increase stability at high speeds. To achieve the perfect balance, you should carefully choose the length of your chain stays.
Bottom bracket height
The measurement between the bottom bracket’s center and the ground is called the height of the bottom bracket. Because of the low center of gravity, a lower height will allow for better cornering performance. However, bikes with extremely low bottom brackets will have clearance problems with the crankarms. Full-suspension bikes compress, and the bottom bracket height drops, bringing the crankarms closer together. This can lead to riders crashing into roots and rocks on technical sections of the trail. Cross-country bikes have a lower bottom bracket than trail bikes, enduro and downhill bikes. This is to aid in climbing difficult terrain. Trail, enduro, and downhill bikes, on the other hand, will perform better in corners and descents due to their lower center of gravity.
Wheelbase
The distance between the front axle and the rear axle of a bike’s wheels is its wheelbase. A bike with a longer wheelbase will have trouble cornering but track better at higher speeds. Bikes with a shorter wheelbase are more agile and can maneuver through tight turns and switchbacks better than bikes with a longer wheelbase. The longest wheelbase is often found on a downhill bike that was designed for speed and will have a longer wheelbase. Trail bikes have a wheelbase that is a happy middle, which allows for greater maneuverability at all speeds. XC bikes often have the shortest wheelbases of all the bikes. Cross-country race bikes are built to maneuver through tight corners quickly to cut down on lap times.
Standover height
In the days before bikes had horizontal top tubes, a bike’s height above the ground was more important than it is today. Modern bikes have sloping top tube designs that make it easier for riders to climb on and off their bikes. Sloping top tubes provide more clearance for cornering, allowing riders to move their legs and hips higher above the bike. Remember that the standover height should be greater than the bike’s measurement. Cross-country bikes have a more upright stance, as putting one foot down is less common.
Length of the top tube
It is important to know the difference between effective and actual top tube length. The bike’s actual top tube length is not relevant if it has a sloping front tube. The effective top tube length can be measured by drawing a straight line from the centerline of the steer tube to that of the seat post. This measurement is the best way to measure a bike’s dimensions.
Reach
The bike’s reach measurement can also be used to determine its fit. The reach measurement is taken from the same spot on the head tube but intersects with an imaginary line that runs up from the bottom bracket. Modern bikes have lowered seat tubes to provide additional clearance for dropper posts. This allows riders to stand higher than ever before and can even take on larger frames. A bike’s reach measurement will tell you how far forward a rider is. Some riders might prefer a smaller or larger frame, depending on how they feel. A bike with a longer reach will provide greater stability while one with a shorter reach will feel more agile.
Angle of the seat tube
The angle of the bike’s seat tube can be measured in degrees. It is usually between 72 and 78 degrees. The seat tube angles are intended to balance a rider’s weight and the crankset. Modern bikes often have a steeper seat post angle, which puts extra weight on the front of the bike during seated climbs. Dropper posts can also be used to move the saddle further away from the ground by having a forward (high-number) seat tube angle. Most bike saddles can be adjusted, which can allow the rider to find a position that is comfortable and takes into account weight distribution and knee alignment.
