K-Volve Kinematics — CP Platform
Engineering / K-Volve Kinematics
K-Volve / Metric
Five kinematic metrics. One concentric pivot architecture. Every number is a consequence of placing the main pivot where the drivetrain geometry wants it to be.
2.535
Mean LR
<2% variation — flattest in class
97.3%
Anti-Squat
At sag, 34/28t gearing (simulated)
49.1%
Anti-Rise
At sag — composed braking (simulated)
3–3.5°
Pedal Kickback
Motor-safe, idler-free
Every metric on this platform works in harmony. The anti-squat curve supports climbing without a lockout. The anti-rise keeps geometry stable under braking. The leverage ratio is remarkably flat for consistent damping. And the concentric pivot eliminates drivetrain interference. It's not just one clever number — the entire system is engineered as a whole.
— Fil Palmer, kinematic analyst & creator of @ebikeitalia6832
Bikelab Inc / Dirtlab 2026
The anti-squat values at sag are exceptional for a production e-MTB. Placing the pivot at the BB/motor axis is a genuinely clever engineering solution — the numbers speak for themselves.
Fil Palmer
The Paratu CP climbs effortlessly without a lockout — the suspension just works. Anti-squat geometry so well dialled you forget it is there.
EMBN
Short and punchy: this bike corners like it is on rails and the suspension is incredibly composed under braking. The numbers back up what you feel on the trail.
Alex Biketester
Nearly flat across 165mm. The frame does not fight you in the working zone. Every 1mm of terrain hit is treated identically at sag, mid-stroke, and near end-stroke. Damping adjustments mean the same thing at 20% travel as at 80% — because LR² barely changes.
Wheel force at full travel is 3.08× the force at sag — provided entirely by air spring compression and HBO, not by frame geometry. Volume spacers tune Layer 2 independently. HBO activates at shaft velocity, not at position — it doesn't exist until you hit something fast enough to need it. Both layers are tunable after the fact. The frame geometry never is.
Thermal advantage: Flat LR means lower peak shock shaft velocity — the shaft doesn't have to move faster at end-stroke to keep up with wheel movement. Competitors with 20–30% LR progression drive the shaft at increasing velocity through the stroke, generating more heat. The Paratu CP compounds this with a 230×65mm shock body — 12% more thermal mass than the 205mm standard on most enduro platforms. Less heat generated per run. More mass to absorb it. On a sustained 8–12 minute descent, the difference is measurable.
The idler eliminates chain-induced kickback — the cranks don't rotate backwards. But when the rear wheel hits an obstacle, kinetic energy flows through the hub into the freehub via suspension forces. That load is not chain-induced — the idler does nothing to dampen it. Motor freehub protection under impact is governed by anti-squat, not chain routing. At 97.3% AS, the Paratu CP's chain tension near-perfectly cancels the compression force. The motor sees near-zero net cyclic load on every hit.
On a high-pivot bike the chain wraps around the idler at an angle that changes as the suspension travels. The lower chain section — from the motor's chainring to the idler — carries tension that varies with that wrap angle through the stroke. As the suspension moves, chain tension on the motor side changes, creating a load cycle on the chainring, BB, and motor bearings. On a pedal bike this is negligible. On a motor producing up to 90Nm continuously, it is a real and repetitive load. The Paratu CP's concentric pivot keeps the chain angle to the cassette nearly invariant — the motor experiences no wrap-induced tension variation.
On an eMTB an idler pulley carries costs that don't exist on a pedal bike: ~2–3W of parasitic drag on a drivetrain already loaded by a mid-drive motor, one more bearing under the sustained tension of motor torque (regular maintenance required), ~80–120g of hardware, and accelerated chain wear on the idler-side length. Additionally, all high-pivot designs use 20–35% LR progression — the shock shaft moves faster at end-stroke, building heat on sustained descents. Paratu CP's flat LR keeps shaft velocity bounded. On a 10-minute enduro descent the difference in shock temperature is measurable.
Some manufacturers bolt on external devices to compensate for excessive frame kickback — O-Chain (floating chainring carrier, absorbs ~8–12° at the crank), DT Swiss DEG hub (delayed freehub engagement, absorbs kickback at the hub), or e*thirteen eMTB-specific hubs (similar principle). These mask the symptom, not the cause. They add weight (~100–200g), cost (€150–350), and extra bearings to maintain. The table below shows native frame kickback first (what the geometry actually produces), then the device-adjusted figure these brands advertise. Paratu CP's geometry never needed any such device — but for reference, adding an O-Chain to the CP would reduce its already-imperceptible 3.5° to below 0.5°.
| Bike / Architecture | Native PK no device |
Anti-kickback hardware bolted on |
Resulting PK after device |
Motor Impact freehub / drivetrain |
LR variation | Note |
|---|---|---|---|---|---|---|
| Forbidden Druid · Deviate · Norco Sight/Range High-pivot + idler — pedal bike |
~0–2° | None needed (no motor) |
~0–2° | N/A | 25–35% | Correct solution for pedal bikes. No motor to protect. |
| Norco Sight VLT · Forbidden Druid E · Dreadnought E High-pivot + idler eMTB · Druid E 150mm / Dreadnought E 170mm · Avinox M2S |
~0–2° | None (idler handles crank PK) |
~0–2° |
MODERATE wrap angle shifts; suspension impacts hit freehub |
~25–35%† | Idler solves crank kickback. Motor freehub load from suspension impacts unaddressed by idler — governed by AS, not chain routing. |
| Amflow PL Horst Link 4-bar · Avinox M1 · 150mm |
Not published | None | Not published |
MODERATE-HIGH AS ~100-105% at sag (no PK data published) |
~21% | Horst Link 4-bar (DJI brand). AS ~100% at sag: Amflow white paper "approx. 100% at SAG"; Flow MTB review: 105%. AR 51–56% across travel (Flow MTB). LR ~21% progression (Cascade Components aftermarket reference). No PK degree published by Amflow or any independent source. |
| Amflow PX (2026) Horst Link 4-bar · Avinox M2S · 150mm |
Not published | None | Not published |
UNKNOWN no AS/AR data published |
Not published | Redesigned 2026 linkage. Amflow states kickback "significantly reduced" vs PL but has published zero kinematic numbers (no PK°, no AS%, no AR%, no LR curve). Avinox M2S: 150 Nm / 1500W peak. |
| Amflow PR (2026) Horst Link 4-bar · Avinox M2/M2S · 150mm |
Not published | None | Not published |
UNKNOWN no AS/AR data published |
Not published | Shares 2026 redesigned platform with PX. Same linkage claim — no published kinematic data. PR Carbon: Avinox M2 (125 Nm / 1100W). PR Carbon Pro: Avinox M2S (150 Nm / 1500W). Swappable 800Wh battery (expandable to 1280Wh). |
| Specialized Levo Gen4 FSR 4-bar · Shimano EP8 · 160mm |
~6° | None | ~6° |
MODERATE-HIGH ~100% AS — chain load not zero |
~20–25% | Good AS balance. PK at ~6° still transmits cyclic load through freehub on every hit. |
| Canyon Strive:ON · typical 4-bar Horst eMTB Horst-link 4-bar · Bosch/Shimano |
8–12° | None | 8–12° |
HIGH full kickback to motor every bump |
~20% | Traditional 4-bar. Motor lockout recommended on climbs. Worst PK in class. |
| Mondraker Zendit Zero dual-link · Avinox M2S · 165mm |
est. ≥8° (frame geometry, no hub fitted) |
DT Swiss DEG hub hub-body float absorbs kickback before freehub |
~4–6° still worse than CP native |
MODERATE-HIGH hub wears; residual kickback remains |
27% | Bolt-on hardware masks the symptom. Even with DT Swiss DEG, effective PK still exceeds Paratu CP native. Hub adds ~150g, cost, service interval. LR 27% → more shock heat on long descents. |
| Unno Mith Dual-short link · DJI Avinox · 160mm |
Not published | None published | — |
HIGH ~75% AS drops fast; motor bobs without lockout |
Progressive (first 30%) |
Low AS = significant bob. Lockout required on climbs. Sag sensitivity ±2% changes ride character. |
| Orbea Wild LT 4-bar linkage · Avinox M2S RS |
Higher AS reduced 20% to compensate for PK |
None — AS deliberately sacrificed |
Reduced no published degrees |
MODERATE ~90% AS — 10% shortfall + climb efficiency lost |
~31% | Orbea traded 20% climbing efficiency to reduce kickback. Proof that other architectures cannot achieve both. AR ~60% = more nose-dive under braking. |
| Specialized Turbo Levo R FSR 6-bar · 130mm rally |
~6° | None | ~6° | MODERATE-HIGH | ~20% | 130mm — different travel category. FSR architecture identical to Levo Gen4. |
| Paratu CP Concentric Pivot · Maxon BikeDrive Air S · 165mm |
3.0–3.5° | None required geometry solves it |
3.0–3.5° already below perception threshold |
NEAR-ZERO 97.3% AS — chain tension cancels squat force |
<2% | 3.5° is imperceptible (<4° threshold). Motor load minimised by geometry — no bolted-on hardware needed or recommended. |
| Paratu CP + O-Chain (hypothetical — not needed, not recommended) | 3.0–3.5° | O-Chain (~€250) absorbs ~8–12° |
<0.5° effectively zero |
ABSOLUTE ZERO | <2% | Shown for reference only. If kinematics are done right, you do not need this hardware. Adding it anyway would be paying €250 to solve a problem that doesn't exist. |
Anti-Squat
97.3%How Anti-Squat Works
Anti-squat describes how effectively chain tension counteracts suspension compression under pedalling load. At 100%, the chain force exactly cancels the squat force — the suspension neither compresses nor extends under pedal input. The Paratu CP sits at 97.3% at sag with 34/28t gearing: the geometry does the bob-control work that on other bikes must be done by compression damping.
This means compression damping does not need to fight geometry. LSC can stay at 2–3 clicks or even fully open. The geometry handles the anti-squat. This has a direct consequence for budget shock compatibility — the coarse compression circuit on a budget shock is never exercised in the regime where it fails.
The eMTB Advantage
Maxon Motor Protection
The Maxon BikeDrive Air S delivers up to 90Nm of continuous torque through the drivetrain. Without near-100% anti-squat, this torque would continuously compress the rear suspension. The 97.3% AS at sag means the motor drives the bike forward, not into its own travel. The concentric pivot — positioned at the motor/BB axis — is specifically designed to maintain high AS across the eMTB gearing range.
Anti-Squat Through Travel
The AS curve declines steeply from 97.3% at sag to 38.7% at full compression. This is by design:
Zone 1: 0–76mm (Climbing Zone)
AS stays above 65%. Chain tension nearly balances squat force. The suspension absorbs every small input while the drivetrain feels rigid. The bike climbs like a hardtail with active traction.
Zone 2: 76–165mm (Descending Zone)
AS drops from 65% to 38.7%. The chain no longer balances the squat force — the suspension opens fully for impact absorption. The rider isn't pedalling in this zone, so low AS is correct. The bike transforms from climbing machine to impact absorber.
Gearing Effect on Anti-Squat
The bike self-adjusts: harder gears (where more power is applied) produce higher anti-squat. This is a consequence of the concentric pivot placement.
Competitor Comparison
Frequently Asked Questions
What does 97.3% anti-squat mean in practice?
At sag with 34/28t gearing, the chain tension almost exactly cancels the gravitational compression force on the shock. The bike climbs like a hardtail — no shock lock-out needed on technical climbs. The remaining 2.7% means the suspension stays microscopically active rather than fully locked, preserving traction.
How does gearing affect anti-squat?
Anti-squat is gearing-dependent. At 34/50t (largest cassette cog), AS drops to approximately 72%. At 34/10t (smallest cog), it rises above 115%. The 97.3% figure at 34/28t represents the gear most used during sustained climbing. In practice, the bike self-adjusts: harder gears (where you push more power) have higher AS.
Why is high anti-squat important for an eMTB?
A Maxon BikeDrive Air S delivers up to 90Nm of continuous torque. Without near-100% anti-squat, that motor torque would compress the rear suspension on every pedal stroke. High AS means the motor drives the bike forward, not into its own suspension. No compression damping needed to fight motor-induced bob.
How does the Paratu CP compare to other eMTBs on anti-squat?
Most competitors sit at 85–100% AS at sag. The 6-bar linkage (160mm eMTB) matches at ~100%. The VPP (160mm) sits at ~92%. The 4-bar Horst (170mm) at ~96%. The Paratu CP's 97.3% is calibrated rather than maximised — just below neutral to keep the suspension microscopically active while eliminating perceptible bob.
Anti-Rise
49.1%Braking Stability Explained
Anti-rise measures how the rear suspension responds to braking forces. At 100%, the rear end stays perfectly neutral under braking — no extension, no compression, no attitude change. The chassis stays level, the rider stays centred, and weight transfer happens through the tyres rather than through suspension geometry changes.
The Paratu CP's anti-rise curve (kinematic simulation) peaks at 49.7% near sag and declines smoothly to 38.8% at full compression. This declining profile means the bike is most stable exactly where stability matters most — in the normal riding position under hard braking.
Why This Matters on Trail
Steep Technical Descents
The Paratu CP runs 49.1% anti-rise at sag (kinematic simulation) — tuned so the rear stays composed and predictable under hard braking, while the suspension stays active to absorb terrain in the steepest chutes.
Braked Corners
Corner entry under braking is where most enduro time is lost or gained. Low AR bikes change their geometry as the rider brakes into a corner — the front dives, the head angle steepens, and the wheelbase shortens. The Paratu CP maintains its geometry through the braking phase, giving the rider a stable, predictable platform for corner entry.
The Physics of Forward Axle Path + High Anti-Rise
Complementary Design
The Paratu CP has a forward axle path, which creates a small harshness penalty on square-edge hits compared to rearward-path designs. Low chain growth in the working zone (~11mm sag to +80mm, kinematic simulation) keeps drivetrain feedback low when the rear is driven hard into obstacles. The net result is a bike that absorbs terrain differently from a high-pivot design.
Competitor Comparison
Frequently Asked Questions
What does the CP platform's anti-rise tuning mean?
Anti-rise describes how braking forces interact with the rear suspension. The Paratu CP runs 49.1% at sag (kinematic simulation) — tuned so the rear stays composed and predictable under hard braking, giving a calm, planted platform through braked corners and steep chutes.
How does the Paratu CP compare on anti-rise?
The Paratu CP runs 49.1% anti-rise at sag (kinematic simulation) — tuned for composed, predictable braking rather than a maximised headline number.
Leverage Ratio
2.535 LRWhy 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.
What the LR curve does not show is the effective end-stroke progression the system produces. Three mechanisms stack on top of the flat geometry in harmony: the air spring's internal volume diminishes as the piston travels deeper, generating a non-linear rate increase; the HBO high-speed bleed circuit builds hydraulic resistance as shaft velocity rises through deep travel; and the concentric pivot's chain tension vector increases its opposition to compression at larger travel angles. None of these appear on a geometric LR graph — yet together they deliver the end-stroke resistance and bottom-out protection a rider feels, while remaining fully independent of each other and independently tunable. The flat geometric curve is not a limitation. It is the enabling condition that allows air spring volume spacers, HBO knob and HBO shim stack to each do their job cleanly, without fighting or being amplified by a progressive linkage underneath.
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.
Pedal Kickback
3-3.5 degConcentric Pivot: Kickback by Geometry
The Paratu CP's concentric pivot is positioned at the motor/BB axis, keeping the chain's effective pivot close to the chainring's rotational axis. This means chain-length variation through the stroke is minimised at the source — no idler pulley needed, no additional drivetrain complexity, no bearing maintenance.
The kickback curve is perfectly linear: 0° at sag, rising smoothly to 8.14° at full travel. No spikes, no abrupt transitions. The chain growth curve follows the same linear profile: 0mm at sag to 15.93mm at full travel. This linearity means the drivetrain load on the suspension is predictable and does not spike in the middle of the working zone, where repeated-hit harshness actually appears.
Maxon Motor Protection
Drive Relief
The Maxon BikeDrive Air S motor uses a precision freehub mechanism rated for specific cyclic loading patterns. High pedal kickback (10–15°) creates back-driving forces that exceed the freehub's comfort zone, accelerating wear and creating potential failure modes. The Paratu CP's 3.0–3.5° working-zone kickback (kinematic simulation) keeps the motor within its design envelope even on the roughest terrain. Combined with 97.3% anti-squat, the motor experiences near-zero suspension-induced disturbance during normal operation.
Why Chain Growth ≠ Harshness
15.93mm chain growth sounds high compared to high-pivot bikes with idler pulleys that approach zero. But chain growth and pedal kickback are not proportional — the relationship is governed by pivot geometry relative to the chainline, not growth magnitude alone.
The 97.3% AS Factor
At 97.3% anti-squat (kinematic simulation), the chain force and gravitational compression force on the shock are near-balanced. The 15.93mm of chain growth acts on a system where the kinematic baseline is already neutral — the residual felt disturbance is much smaller than it would be on a bike with the same growth but 70–80% anti-squat.
Smooth Distribution
11mm distributed smoothly across 80mm of working-zone travel is ~0.14mm per mm of wheel travel — a near-constant rate. VPP frames typically show chain growth that accelerates hard as the virtual pivot rotates. A smooth rate means no mid-stroke spike where repeated-hit harshness actually appears.
Flow Trail Feel
Some riders on flow trails prefer moderate kickback — it makes the bike feel "supportive" when pumping. The Paratu CP delivers support differently: the 97.3% anti-squat keeps the rear from sinking when you pump, not the kickback. The felt difference is a quieter drivetrain with the same pop. Some riders coming off bikes with 10°+ kickback may initially read this quietness as "less alive." A test ride resolves the difference within one run.
Competitor Comparison
Kickback measured at 10T engagement (standard 12-speed cassette). Chain growth in the working zone (sag → +80mm) is the rider-felt metric.
Frequently Asked Questions
What is pedal kickback and why does it matter?
Pedal kickback is the backwards rotation of the cranks caused by rear suspension compression. It's felt as a 'kick' through the pedals when hitting bumps. High kickback (10–15°) fights the rider's pedal input and can damage eMTB motor freehubs. The Paratu CP's 3.0–3.5° is low enough to protect the Maxon motor while keeping the drivetrain quiet through rough terrain.
How does the Paratu CP achieve low pedal kickback without an idler?
The concentric pivot places the main suspension pivot at the motor/BB axis — close to the chainring's rotational axis. This minimises chain-length variation through the stroke. An idler pulley design achieves the same result by mechanically decoupling the chain path, but adds 2–3W of drag, bearing maintenance, and ~100g of mass. The Paratu CP achieves comparable results through geometry alone.
Is 8.14° of total kickback a problem?
No. The 8.14° at full compression is never experienced during normal pedalling — riders don't pedal through the final 40% of travel. In the working zone (sag to +80mm), kickback is 3.0–3.5°, which is best-in-class among non-idler frames and comparable to idler-equipped designs. The relationship between chain growth (15.93mm) and kickback (8.14°) is governed by pivot geometry relative to the chainline, not growth magnitude alone.
Does the Maxon motor benefit from low kickback?
Directly. The Maxon BikeDrive Air S uses a precision freehub mechanism. High kickback creates cyclic back-driving forces through the freehub, accelerating wear and creating potential failure modes. The 3.0–3.5° kickback means the motor freehub operates within its design envelope even on the roughest terrain. This is a reliability feature, not just a comfort one.
Axle Path
8mm fwdTwo-Phase Axle Path Architecture
The Paratu CP's axle path follows a two-phase design: near-vertical in the initial stroke for climbing efficiency, then progressively forward-sweeping in deep compression for obstacle management. The path angle transitions linearly from 95° at full extension to 72° at full compression, with a total forward displacement of 19.94mm.
Phase 1: 0-76mm (Initial Stroke)
Forward displacement: just 1.65mm over 30mm of wheel compression from sag. The path is within ±2° of vertical. Braking bumps, roots, and small rocks - the terrain in this zone - create forces that are predominantly vertical. A near-vertical path means the wheel moves straight up and over, with no lateral kick in either direction. Superior to both a rearward path (which kicks the wheel backward on braking bumps, breaking line) and a strongly forward path (which creates chain tension).
Phase 2: 76-165mm (Deep Compression)
Forward displacement accelerates from 1.65mm to 19.94mm. At impact speeds in this zone (major rock strikes, drops, roots at speed), the forward arc means the wheel rolls over the obstacle rather than deflecting from it. The progressive increase in forward angle changes the effective mechanical advantage against the shock, adding a geometric resistance component that combines with air spring progression and HBO.
Chain Growth Analysis
The Paratu CP has 15.93mm of total chain growth and 8.14° of pedal kickback at 34/28t. Despite the chain growth figure, the drivetrain-induced harshness in the working zone is minimal:
Working Zone Chain Growth: ~11mm
Full-travel chain growth (15.93mm, kinematic simulation) is the marketing figure. The rider-felt metric is chain growth from sag to +80mm - the repeated-hit zone where harshness is perceived. The Paratu CP's ~11mm in this window is the lowest of any non-idler frame in the segment. Idler-equipped pedal bikes can achieve lower values but at the cost of 2-3W continuous drivetrain drag and significant weight penalty.
Working Zone Chain Growth Comparison
Working zone (sag ? +80mm) is the rider-felt metric. Full-travel chain growth is the marketing figure but not where harshness is perceived.
Axle Path Competitor Comparison
Frequently Asked Questions
Is forward axle path actually better than rearward?
Forward axle path is correct for this bike's use case, not universally superior. A rearward path absorbs horizontal impact forces better - the wheel deflects away from obstacles. For DH at 60kph hitting a rock face, rearward is better. For eMTB enduro at 20-50kph on technical terrain, the near-vertical initial stroke and progressive forward sweep is the correct answer for balanced climbing efficiency and descending capability.
How much forward displacement does the Paratu CP have?
Total forward displacement at full compression is 19.94mm. But in the working zone (0-76mm from sag), forward displacement is just 1.65mm over 30mm of wheel compression. The path is within ±2° of vertical in this zone. The forward sweep accelerates only in the deep compression zone (76-165mm) where large impacts occur.
What is the axle path angle?
The path angle transitions linearly from 95° at full extension (near-vertical) to 72° at full compression (progressive forward sweep). This linear decline means there are no abrupt transitions - the bike's character transforms smoothly from climbing efficiency to impact management.
How does the Paratu CP compare to a high-pivot bike on rough terrain?
The comparison requires precision. A high-pivot bike — whether a true Horst-link or a faux-bar virtual pivot above the chainstay — produces significant brake-induced chatter: the pivot geometry causes the rear end to extend under braking, creating the characteristic head-nod on rough, braked descents. Both designs generate chain growth through rearward axle sweep; the concentric pivot's specific advantage is that the chain angle relative to the motor axis never changes through the stroke, keeping drivetrain torque delivery and freehub loading consistent. On rough terrain the Paratu CP's rearward axle path through the working zone handles small-bump compliance, while the concentric pivot eliminates the idler maintenance, wrap-angle variation, and parasitic drivetrain weight of the high-pivot approach. These are different engineering priorities, not a smoothness trade-off.
Left: high-pivot + idler (reference competitor). Right: concentric pivot (Paratu CP) — chain angle stays constant, no idler required.