Flip Chip Geometry: The Complete Guide

The flip chip system on both the Paratu CP and Iuhu CP is one of the most functional pieces of geometry engineering on the frames. Five positions, three named chips, and a geometry range that spans from composed trail riding to genuine enduro aggression — all without touching a single other component on the bike.

Here is a complete explanation of how it works, what each position does, and how to choose the right setup for your riding.

How the flip chip works

The chip is not a simple spacer. It is an eccentric disc that sits inside the bore of the lower yoke — the rocker arm that connects the rear shock to the linkage. When you rotate the disc and re-install it, the bore centre moves in space. That offset shifts the axle path, which changes the chainstay length, bottom bracket height, head tube angle, and seat tube angle all at once.

There are five distinct positions in total:

• FORWARD +5mm — maximum offset toward the shock
• FORWARD +2.5mm — half offset toward the shock
• CENTER 0mm — neutral, no offset
• BACKWARD −2.5mm — half offset toward the wheel
• BACKWARD −5mm — maximum offset toward the wheel

Each position requires a specific rear wheel size. This is not a preference — it is a hard mechanical constraint set by chainstay clearance.

The locked pair rule: chip position and rear wheel size

The chip position and rear wheel size are a locked pair. You cannot mix them freely.

• FORWARD chip positions (+5mm, +2.5mm): 29" rear wheel only
• CENTER chip (0mm): 27.5" rear wheel only
• BACKWARD chip positions (−2.5mm, −5mm): 27.5" rear wheel only

Running a CENTER chip with a 29" rear wheel is an invalid setup. The chainstay clearance is designed around the 27.5" tyre at CENTER and BACKWARD, and a 29" tyre in those positions will contact the frame. Always change wheel and chip together.

FORWARD chip — 29+29 setup

FORWARD is the most common starting point for most riders. With the chip at +5mm offset and a 29" rear wheel, the geometry is at its most relaxed:

• HTA: 63.9° at 150mm fork
• STA: 77.8°
• BBH: 340mm

This is the base geometry the frame was designed around. The 63.9° head tube angle at 150mm fork is what most enduro and aggressive trail riders will recognise as a correct modern setup. The bike runs a full 29" front and rear — maximum rollover, maximum stability at speed, and the most forgiving handling in rough terrain at high speed.

FORWARD +2.5mm sits between FORWARD and CENTER: geometry is slightly steeper than +5mm but still requires a 29" rear wheel.

CENTER chip — 29+27.5 mullet setup

CENTER chip at 0mm offset requires a 27.5" rear wheel, creating a mullet configuration: 29" front, 27.5" rear.

• HTA: 64.1° at 150mm fork
• STA: steeper than FORWARD — better climbing position
• BBH: lower than FORWARD due to smaller rear wheel

The 27.5" rear wheel lowers the back of the bike slightly, which steepens the effective seat tube angle and changes how the bike corners. Many riders find the mullet setup more agile through tight switchbacks and faster to accelerate, while still retaining the 29" front for rollover and stability. The CENTER chip is the choice for technical, slower terrain where agility matters more than raw high-speed stability.

BACKWARD chip — most aggressive, most niche

BACKWARD positions (−2.5mm and −5mm) also require a 27.5" rear wheel. The geometry effect is a further steepening of the STA and a change in BBH relative to CENTER:

• HTA: 64.2° at 150mm fork (−5mm position)
• STA: steepest of all positions

BACKWARD is the most aggressive climbing and technical position. The steep STA keeps your weight forward on climbs, which is especially useful on long sustained steep pitches. Most riders will not regularly ride in BACKWARD, but it exists for those who want to push the geometry toward its most aggressive end.

How fork travel changes everything

The geometry numbers above are all at 150mm fork axle-to-crown. Fork travel changes the head tube angle by approximately −0.024° per millimetre of axle-to-crown length. That means:

• 140mm fork: HTA steeper by ~0.24° vs 150mm
• 160mm fork: HTA slacker by ~0.24° vs 150mm
• 170mm fork: HTA slacker by ~0.47° vs 150mm
• 180mm fork: HTA slacker by ~0.71° vs 150mm

Both frames accept 140mm through 180mm travel forks. Use the geometry calculator to see the exact HTA, STA, and BB height for any combination of chip position and fork travel.

Choosing your setup

For most riders starting out on either frame, FORWARD +5mm with a 29" rear wheel is the right starting point. It is the geometry the frame was optimised around, and it covers the vast majority of enduro and aggressive trail riding scenarios.

Move to CENTER chip with a 27.5" rear wheel if you ride primarily technical, tight terrain where corner agility and the lower standover of a mullet setup suit you better — or if you are a smaller rider who finds the 29+29 setup too long through corners.

Try BACKWARD if you are climbing-focused, want the steepest STA available, or are experimenting with how far the geometry can shift.

The geometry is reversible. Changing chip and rear wheel takes less than 30 minutes with basic workshop tools. There is no reason not to experiment.

The full interactive flip chip guide — including the chip simulator and geometry values for every position — is available at dirtlab.com/pages/mullet-flip-chip-guide.