Leverage Ratio — Paratu CP
K-Volve Kinematics / Leverage Ratio
K-Volve / Metric 05
Leverage Ratio
2.51–2.57 across all 165 mm. Flat by design. Every damping click produces a predictable result at any point in the stroke — and the shock runs cooler than any progressive competitor on sustained descents.
2.535
Mean LR
±0.025 across full stroke
<2%
LR Variation
Flattest of any production enduro
3.08×
End-Stroke Ratio
Air spring + HBO sag → bottom
4-5%
LR² Variation
Damping authority nearly constant
The leverage ratio curve is almost perfectly linear through the mid-stroke — I measured less than 5% variation across the working range. This means every damping adjustment translates predictably across the entire travel. Shock tuning becomes straightforward because the suspension isn't fighting against a progressive or regressive rate.
— Fil Palmer, kinematic analyst & creator of @ebikeitalia6832
Why Flat Leverage Ratio?
The mountain bike industry has converged on 26–30% progression as a target for long-travel enduro bikes. That target originated before modern air spring technology and externally adjustable HBO circuits became standard. It was the correct answer to: how do we build end-stroke resistance into the geometry so a simple spring and damper can avoid bottom-out?
The Paratu CP was designed around a different question: how do we build a chassis where the suspension engineer has maximum independent control over each aspect of ride character? The answer is a flat LR that decouples the geometry from the end-stroke, combined with an air spring and HBO system that provides all the necessary wheel rate increase dynamically.
Damping Consistency Through the Stroke
The Arithmetic
Wheel rate scales as (spring rate) × LR². Damping authority at the wheel scales with LR. On a frame with 25% progression — LR going from 2.5 at sag to 2.0 at end stroke — the damper's authority at the wheel at end stroke is only 64% of what it is at sag, because (2.0/2.5)² = 0.64. That means when a rider turns LSC two clicks, the adjustment behaves very differently at 20% travel than at 80% travel. On the Paratu CP, the LR² ratio varies by roughly 4–5% through the stroke. A click is a click, at every stroke position.
Thermal Stability
Progressive frames drive the shaft at increasing velocity through the stroke for a given wheel speed. Higher peak shaft velocity = more oil shear = more heat accumulation. On a sustained 8–12 minute descent, progressive frames show measurable damping fade. The Paratu CP's flat LR keeps peak shaft velocity bounded, so the shock runs noticeably cooler over a long run. Combined with the 230×65mm shock body (12% more thermal mass than a 205mm shock), the Paratu CP sits in the best third of the segment for thermal performance.
Three-Layer Bottom-Out Defence
The flat LR means the linkage provides no geometric end-stroke resistance. Instead, three independent systems combine to prevent bottom-out — and each can be tuned independently:
Layer 1: Air Spring
With 2 positive volume spacers, the DVO Topaz T3 compresses from ~8.5cm³ at sag to ~3.2cm³ at full compression — a 2.66× volume reduction. Pressure rises from 190psi at sag to ~584psi at full travel. Wheel force increases from 942N to ~2,896N — a 207% increase.
Layer 2: HBO Circuit
Hydraulic Bottom-Out is velocity-sensitive, not position-sensitive. At 50kph hitting a rock, HBO force can exceed 1,000–2,000N additional resistance. At 5kph touching the same rock, HBO barely activates. No kinematic curve achieves this dynamic behaviour.
Layer 3: Volume Spacers
Every air shock — from entry-level to premium — contains a positive air chamber that compresses exponentially. Volume spacers work identically in a Deluxe Select as in a DVO Topaz T3. The physics are price-independent.
Natural Frequency Profile
Undamped natural frequency at 85kg system mass: minimum 1.614Hz at sag — most compliant at the rider's resting position. Frequency rises progressively to 2.476Hz at full compression. This is the correct profile: most compliant where compliance is needed (normal riding), building firmness where firmness is needed (large impacts). The steep end-stroke rise is the mathematical expression of the flat LR combined with a steeply progressive air spring.
Budget Shock Performance
On most enduro bikes, expensive components exist partly to compensate for geometric limitations. The Paratu CP removes those limitations at the frame level:
97.3% Anti-Squat
Compression damping doesn't need to fight bob. LSC can stay at 2–3 clicks or fully open. The budget shock's coarse compression circuit is never exercised in the regime where it fails.
Constant Velocity Window
A budget shock's fixed valve stack operates correctly and consistently from sag to full compression on the flat LR. On a progressive frame, the same valve stack is calibrated for the wrong shaft velocity at end stroke.
Price-Independent Physics
The Paratu CP with a budget RockShox Deluxe Select set up correctly outperforms most competitor enduro bikes with a mid-tier DVO Topaz T3 on pedalling efficiency, small-bump sensitivity, and line-holding.
Competitor Comparison
Thermal Index: combined air-spring + damper heating relative to Paratu CP = 1.00. Lower is cooler. Based on 10-minute sustained descent at ~2,000 cycles.
Frequently Asked Questions
Why is a flat leverage ratio better than progressive?
A flat LR means your damping adjustments behave consistently at every point in the stroke. On a progressive frame (25-30% LR change), turning LSC two clicks makes a different adjustment at 20% travel than at 80% travel — the click is a moving target. On the Paratu CP, LR² varies by only 4-5%, so a click is a click at every stroke position. The flat curve also keeps peak shaft velocity bounded, reducing thermal fade on long descents.
Won't a flat LR make the bike easy to bottom out?
No — because the leverage ratio is only one component of the total wheel rate. The Paratu CP uses a progressive air spring (2 positive + 1 negative volume spacer) combined with HBO (Hydraulic Bottom-Out) to deliver a 3.08× wheel-force ratio from sag to full compression. For comparison, the VPP (160mm) with 29% kinematic progression delivers only 2.29×. More total ramp, from a system that is velocity-sensitive rather than position-sensitive.
What about thermal fade on long descents?
Damper heat scales with shaft velocity squared. The Paratu CP's flat LR bounds peak shaft velocity at 2.52× wheel velocity. Progressive competitors sit at 2.70-2.80×, producing 13-23% higher peak damper power dissipation. Combined with the 230×65mm shock (largest practical air volume), the Paratu CP runs in the coolest third of the segment on sustained descents.
Does a budget shock work on a flat-LR frame?
Better than on any other frame. A budget shock's fixed valve stack operates in a near-constant velocity window throughout the stroke on the Paratu CP. On a progressive frame, the same valve stack is calibrated for the wrong shaft velocity at end stroke. Additionally, 97.3% anti-squat (kinematic simulation) means compression damping doesn't need to fight bob — LSC can stay open, avoiding the harshness that budget compression circuits produce when tightened.
See It in Action
Visual Analysis
Validated by
Supporting Video
Slow-motion trail footage, shock-shaft rig test, or drone-orbit of the frame showing the leverage ratio effect in action.