What Is Mountain Bike Fork Offset

Mountain bike forks are the metal rods that connect the front tire to the rest of the bike. The fork’s offset determines how high or low a rider can set their handlebars.

Offset is measured in millimeters, and it is often adjustable. Riders with a smaller stature may want to go with a lower offset, while taller riders will want to opt for higher offsets.

It’s important to choose an appropriate mountain bike fork for your bike because it’ll affect both how you ride and how your bike handles.

What does fork offset affect?

Fork offset, combined with head angle, affects something called ‘trail’, and ultimately whether it’s a dog or a whippet on cdertain descents, thus explains bike fettler extraordinaire Chris Porter from Mojo. A bike feels great when descending if it has steering that is stable at high speeds and when in the turns.^[1]

Why does fork offset matter?

While a slack headtube increases stability, along with longer reach, you start to lose that front end feel and thus, losing traction. By reducing the forks offset, you are bringing the wheel back under the mass of the body, helping keep that traction, while still having a longer wheelbase and slack head tube angle.^[2]

What is offset in rockshox fork?

The diagram above shows how the front axle is offset so it is forward of the steering axis. A 2009 Gary Fisher Superfly with a G2 (note the ‘G2″ on the fork lower) 51mm offset fork.^[3]

How does fork offset affect bike 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.^[4]

Can I use a 29er fork on a 27.5 bike?

If you’re doing a 29er fork on a frame intended for 27.5, and you run a 29″ wheel, it will slow the steering down, raise the BB, and slacken the head tube. If you’re running a 27.5 wheel in a 29er fork, regardless of intended rear wheel size, it will make the handling slower and sloppy.^[5]

What’s the difference between 44 and 51 offset?

44mm vs 51mm Offset Mechanical trail has a similar difference. 44mm offset has 108.7mm while the 51mm offset comes in at 101.7mm. This means that the 44mm offset will have a bit more stable platform. If we wanted to design the same amount of trail into the 51mm offset fork we would need to decrease the headtube angle.^[6]

What is a 44mm offset fork?

A reduced, 44mm offset fork allows the rider to run a slacker geometry with a similar wheelbase, but still enjoy a stable steering platform without sacrificing traction, stability, and control.^[7]

Can I use a 29er fork on a 26 bike?

It would work, but there would be no benefit to it at all. It would probably just mess up the bikes geometry and add weight. You would only get more travel if the fork you put on has more travel than the one its replacing.^[8]

How do I find my fork offset?

Simply put, fork offset, or fork rake, is the distance between the front axle and the steering axis – the imaginary line running straight through the midpoint of the steerer tube.^[9]

How does fork rake affect handling?

The measurement is taken in millimeters on a line extending from a right angle from the steering axis and bisecting the center of the axle (the orange line). The effect fork rake has on a bike’s handling is straightforward. The more rake a fork has, the quicker its handling.^[10]

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.^[11]

How is fork rake determined?

Swivel the fork 180 degrees and measure to the same 2 points. Subtract the larger number from the smaller number and divide by 2. That’s your rake.^[12]