K-Volve: Kinematics Evolution

Performance-Focused Kinematics

Modular Travel Options & Multi‑Use Concept

A key strength of the Paratu and Iuhu CP platform is that rear travel is defined by shock stroke, while the eye‑to‑eye length stays constant at 230 mm. This means you can change rear travel without introducing big, unwanted geometry side‑effects. The frame has been calculated to work this way from the start.

Rear travel options at a glance (230 mm eye‑to‑eye):

• 230 × 65 mm stroke → 165 mm rear travel (full‑travel enduro mode).
• 230 × 62.5 mm stroke → 160 mm rear travel (light‑enduro / all‑mountain mode).
• 230 × 60 mm stroke → 155 mm rear travel (short‑travel enduro / aggressive trail mode, often marketed as ~150 mm).
• 230 × 57.5 mm stroke → 145 mm rear travel (trail/adventure mode).

Because the pivot layout and eye‑to‑eye are fixed, the bike’s core geometry – reach, stack, seat angle, and head angle around sag – stays very similar across these options. You adjust how much travel you have available and how the bike feels deep in the stroke, without ‘breaking’ the handling. In practice, this gives riders a genuine multi‑use frame they can reconfigure over time.

Example build concepts:

• Full‑on enduro build – 170 mm fork / 165 mm rear (230 × 65): for maximum capability in steep, rough terrain. Works brilliantly with modern air or coil shocks. Typical complete bike weights: ~17.5–19 kg depending on spec.
• Light enduro / all‑mountain build – 160 mm fork / 160 mm rear (230 × 62.5): a slightly lighter, more nimble setup for big days in mixed terrain. Typical complete bike weights: ~17–18 kg.
• Trail‑biased build – 150–160 mm fork / 145–155 mm rear (230 × 57.5–60): for riders who prioritise agility, efficiency and lower overall weight but still want real descending capability. Typical complete bike weights: ~16.5–17.5 kg.

For the manual and website, you can present this as a modular system: one frame, multiple personalities. Riders can start with a lighter trail or light‑enduro build and later move to a full‑travel enduro setup simply by changing shock stroke (and, if desired, fork travel), without needing a new frame or accepting dramatic geometry compromises.

2. Suspension Concept & Ride Intent

The Paratu and Iuhu CP frames share the same core kinematic platform: a concentric main pivot with a horizontal shock layout. The goal is a bike that pedals efficiently enough for big days out, stays calm under braking, and remains predictable and supportive through the full travel – without the complexity, drag, and setup sensitivity of extreme high‑pivot layouts.

The axle path is slightly rearward‑biased and close to the rear wheel's arc, so the suspension works with the tyre and terrain rather than fighting them. Anti‑squat starts above 100% in the climbing gears and drops smoothly as the bike moves into the travel, which gives you a very stable pedalling platform without the harshness and pedal feedback that can come with more aggressive kinematics.

3. Axle Path & Chainstay Behaviour

Across the usable travel, the rear axle follows a gently rearward‑biased path that closely follows the wheel’s natural arc relative to the ground. Horizontally, the axle moves from only a couple of millimetres rearward at the top of the stroke to roughly two centimetres at full travel. The axle‑path angle starts just over 90° (slightly rearward) and gradually opens out towards the end of the travel, so the wheel can move back and up into square‑edged impacts, then transition to a more vertical path deeper in the stroke.

In practice, this gives you a rear end that: (1) tracks well in repeated hits without hanging up, (2) grows the rear centre just enough for high‑speed stability, and (3) avoids the exaggerated rearward movement that can make some bikes feel long, lazy, and hard to manual or change lines on slow, technical features.

4. Anti‑Squat & Pedalling

Anti‑squat has been tuned around real climbing gears (approximately 34 × 28T) and realistic sag positions. At top‑out, the system sits around the mid‑100% range, which helps the bike feel lively and efficient when you stamp on the pedals as you settle into sag, anti‑squat drops towards ~100%, giving a balanced feel: enough support to keep the bike from bobbing, but not so much that the suspension locks out or feels harsh.

Through the mid‑stroke and into the last third of the travel, anti‑squat continues to decline. This is deliberate: once you are deep in the travel, you are usually descending or dealing with impacts, not trying to sprint. The bike stops ‘pushing back’ against your pedalling and instead focuses on staying glued to the ground. The result is a suspension feel that riders describe as ‘efficient but never nervous’ rather than ‘stiff and dead’.

5. Chain Growth & Pedal Kickback

Because the axle path is only mildly rearward, chain growth is moderate: slightly negative above sag, essentially zero at sag, then building to around 1.5 cm by full travel in the measured climbing gear. This puts the Paratu and Iuhu CP frames well below most extreme high‑pivot systems in terms of potential pedal kickback.

On trail, this means you still get enough chain growth to help anti‑squat do its job when you are on the gas, but when the rear wheel is driven into the travel by roots or rock impacts, the cranks are far less likely to be pulled backwards under your feet. The suspension can move quickly and freely without the drivetrain trying to hold it back. The bike feels connected and supportive when you are pedalling, yet remains remarkably calm in rough sections.

6. Anti‑Rise & Braking Behaviour

Anti‑rise values sit comfortably below 100% and decrease as you move deeper into the travel. Around sag the system is roughly in the 50% range, trending lower towards bottom‑out. In simple terms, this means braking forces neither lock the suspension solid nor cause the rear end to jack itself down aggressively when you grab a handful of rear brake.

The benefit for the rider is intuitive: you can brake later and harder on rough descents without the rear wheel skipping or chattering. The chassis maintains its attitude instead of pitching violently forward, so you keep more grip, more control, and more confidence on steep, loose terrain.

7. Leverage Curve, Progression & Tuning Options

The leverage ratio on the Paratu and Iuhu CP frames is intentionally close to linear, with a gentle progression of roughly two percent from the start to the end of the stroke. The average leverage sits in a range that works well with both modern air shocks and coils.

In feel terms, this gives you: (1) a supple initial stroke for traction and comfort, (2) a very supportive mid‑stroke that holds the bike up in berms and compressions, and (3) a controlled end‑stroke that relies on shock tuning – rather than a wildly progressive frame rate – to manage bottom‑out. The bike responds clearly to damping and volume‑spacer changes, which makes it easy for riders and suspension tuners to ‘dial in’ the feel they want.

Because the frame progression is subtle, bottom‑out control is handled primarily by the shock. This is an advantage for riders who want to tailor the end‑stroke ramp‑up to their weight, style, and terrain:

• Trail / lighter riders can use a standard air shock with moderate volume reduction for maximum grip and comfort.
• Aggressive and heavier riders can add volume spacers or choose a more progressive air can, using hydraulic bottom‑out (HBO) if available to provide a firm, predictable catch on very hard hits.
• Coil shock users benefit from the consistent leverage and can fine‑tune end‑stroke support with HBO or secondary bottom‑out bumpers, without needing an impractically stiff spring.

The key message is that the frame provides a neutral, tunable platform. Riders can build anything from a highly sensitive all‑day trail bike to a race‑ready enduro setup simply by changing shock type, spring rate, volume spacers, and (where available) HBO settings.

8. Ride Frequency, Comfort & Support

The natural suspension frequency is tuned to sit in a comfortable range around sag for a typical rider, with a slight increase deeper in the travel as the effective spring rate rises. Practically, this means the bike feels planted and ‘calm’ when you are seated and pedalling, yet gains support and pop when you start to push harder into the terrain.

Small chatter is absorbed without the bike wallowing, and bigger G‑outs or landings generate support instead of that vague, bottomless feeling that can make it hard to predict how far into the travel you are. This balance between comfort and support is one of the defining ride characteristics of the Paratu and Iuhu CP frames.

9. Geometry Stability Through the Travel

Because the axle path is only moderately rearward and the main pivot is concentric, geometry remains consistent and predictable as the suspension moves. Total wheelbase growth is on the order of two centimetres from top‑out to bottom‑out, with most of that occurring in the rear‑centre while the front‑centre stays effectively constant.

Pedalling and cornering around sag, the bike feels compact, responsive, and easy to manual. As you move deeper into the travel at higher speeds, the extra rear‑centre length adds stability and grip, without ever making the bike feel like it has ‘gone long’ or folded itself underneath you. Riders get the best of both worlds: a playful, reactive feel in the top half of the travel, and a calm, planted chassis when they are pushing hard.

10. Horizontal Shock & Concentric Pivot – Design Benefits

The horizontal shock layout with a concentric pivot is not just a packaging choice – it is a key part of the ride feel. The layout allows the shock to be driven cleanly and consistently, which reduces side‑loading on the shock body and bushings. This improves small‑bump sensitivity and long‑term durability while making service intervals more predictable.

From an engineering standpoint, the concentric main pivot keeps the relationship between the crank axle, chainline, and suspension motion simple and robust. There is no separate idler or complex multi‑link to manage, which reduces friction, noise, and wear.

From a rider’s perspective, the benefits are straightforward: (1) a quieter, smoother drivetrain, (2) fewer moving parts to service, and (3) easier shock access for setup and swaps – all while maintaining the carefully tuned kinematic behaviour described above.