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Questions and answers about sports

If I replaced the fork on my cyclocross bike with a track fork, what would be the effect on the bike geometry?

5 min read

Asked by: Justin Unruh

How does bike geometry affect ride?

The higher the bottom-bracket height, the higher the centre of mass of the rider, and so the more the bike tends to pitch when faced with bumps, hard braking or steep gradients. In this sense, a lower bottom bracket improves stability in much the same way as a longer wheelbase.

How does fork offset affect handling?

By reducing the fork rake (offset), the head angle remains the same for stability at high speed and down steep and rough trails, but the wheel is closer to the steering axis for better handling, especially at slower speeds.

What difference does bike geometry make?

A bike’s geometry determines two very important things: how the bike handles and your position on it. At one extreme are bikes designed for racing. Their geometry will typically give you more edgy handling for a ride that’s more responsive.

Does bike geometry affect speed?

The short answer is that ‘it depends‘. Some viewers commented that maybe it just doesn’t matter. It absolutely does matter and indeed the geometry of the bike is the most powerful way that we can change the riders experience of the bike.

How does fork length affect head angle?

Geometry changes



As the fork gets longer, it raises handlebars up and slackens the head tube angle. As a rough estimate, each 20mm of travel added will correlate to a one-degree difference in the head tube angle.

What is aggressive bike geometry?

Aggressive geometry puts your upper body down lower for aerodynamics and the bikes tend to favor a more twitchy handling traits. Relaxed geometry has you sitting in a more upright position and the bike is setup to feel more stable at speed.

Does fork offset change headtube angle?

Both the headtube angle and fork offset can change the length of the trail number. By making the head tube angle slacker (decreasing the angle) you will make the trail longer. By reducing the fork offset, you will also make the trail longer.

Does fork offset change wheelbase?

A common one is the thought that a reduced offset fork will pull your front wheel towards you, significantly reducing the wheelbase length. In actuality, the change is negligible. In the case of a 29’er with a 65 degree head angle, going from a 51mm to a 44mm offset fork will reduce your wheelbase length by 5.78mm.

How do I choose a fork offset?

If you’re buying a new bike and cornering is your weakness, choosing a reduced offset fork can help. If you’re trying to race enduro or downhill competitively, a reduced offset fork can give you a slight edge. Ultimately, I think reduced offset forks work best on longer and slacker bikes with big travel.

What is a relaxed geometry bike?

The saddle is positioned back and set low while the top tube is lengthened for a riding posture that is relaxed and creates a stronger feeling of balance for the rider.

What size bike should a 5’9 Man ride?

Road bike sizing chart

Rider Height (feet/inches) Rider Inseam (inches Bike Frame Size (centimeters)
5’4″-5’7″ 28.5″-30″ 52-54 cm
5’6″-5’9″ 29.5″-31″ 54-56 cm
5’8″-5’11” 30.5″-32″ 56-58 cm
5’10”-6’1″ 31.5″-33″ 58-60 cm

Which is more important stack or reach?

For a given reach, a greater stack puts you into a more upright riding position; your hands will be moved upwards and your body position will rise more towards the vertical.

How do you adjust the geometry on a bike?

Quote from video: You can change the geometry the bike. Without spending any money at all so if you've got that option then grab your allen keys swap things around try it back-to-back on your favorite bit of trail.

Can I put 150mm forks on a 140mm bike?

You’ll be fine either way. It’s only when you go up or down more than 25mm in travel that you really have to worry: You’re likely to end up negatively effecting your geometry and risking damage to the frame.

How does fork length affect reach?

Any increase in fork travel will slacken the bike and shorten its reach. Slacker head angles boost confidence in steep descending terrain, but they make a mountain bike less agile at climbing technical singletrack as well as unbalancing the bike by moving the rider’s weight backward.

What does a steeper head angle do?

A steeper head angle makes the bike much more responsive at lower speeds and can help the rider manoeuvre the bike through slower, tighter, and more technical terrain.

How does seat tube angle affect ride?

Seat tube angles range from about 70-75 degrees. A steeper angle moves the saddle forward while a shallower angle moves it back. Steep is fine for racers. It allows them to ride hard in an aero crouch, as the more open hip angle doesn’t constrain breathing or power transfer.

Is a 67 degree head angle slack?

The head tube angle is the angle of the head tube in relation to the ground. A “slack” angle is anywhere from 63 to 66 degrees. This means the fork of the bike is going to stick out farther, creating a more stable ride at high speeds, but also be slower handling.

What is a relaxed geometry bike?

The saddle is positioned back and set low while the top tube is lengthened for a riding posture that is relaxed and creates a stronger feeling of balance for the rider.

How do you change a bike in geometry?

Quote from video: It means a shorter stroke length when hitting the same bumps will use less of the bikes travel. That means it's it's higher in the travel and consequently keeps the geometry steeper.

Which is more important stack or reach?

For a given reach, a greater stack puts you into a more upright riding position; your hands will be moved upwards and your body position will rise more towards the vertical.