Short answer: The Manthey Kit makes the 718 Cayman GT4 RS a more adjustable, higher-downforce track car without adding engine power. It replaces or adds aerodynamic panels, a wider four-position rear wing, an adjustable inverted-coilover suspension with a 20 percent stiffer front spring rate, and steel brake lines. At approximately 124 mph (200 km/h) with the wing in Performance position, Porsche reports total downforce increasing from 196 lb (89 kg) to 372 lb (169 kg). The trade-offs are a US list price of $53,946 before installation in May 2024, track-focused setup changes, and no published evidence proving a particular road-ride, comfort, tire-wear or ordinary track-day improvement for every driver.
This is therefore not a power upgrade or a wholesale brake conversion. It is a factory-channel aero, chassis and brake-hardware package intended primarily for circuit use, with road-legal components that must still be checked for local approval and configuration.
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What the Manthey Kit changes—and what it does not
The stock 718 Cayman GT4 RS already uses a naturally aspirated 4.0-liter flat-six rated at 493 horsepower in Porsche’s US description. The kit announcement does not claim an engine, intake, exhaust or software change, so the powertrain output remains the same in this comparison. The measurable focus is the air moving around the car, the way the suspension can be tuned, and the consistency of the brake pedal.
| Area | Stock 718 Cayman GT4 RS | Manthey Kit configuration |
|---|---|---|
| Aerodynamics | Standard bodywork and rear wing with three wing positions | Additional front and underbody aero, wheel-arch treatment, carbon rear-wheel aerodiscs and a wider rear wing with a new blade, larger endplates and four adjustment positions |
| Downforce reference | 196 lb (89 kg) total at approximately 124 mph/200 km/h with the wing in the specified Performance comparison position | 372 lb (169 kg) total at the same approximate speed and wing setting |
| Suspension | Standard GT4 RS chassis | Inverted adjustable coilovers, four adjustment positions, tool-free rebound and compression adjustment, and a front spring rate 20 percent higher than stock |
| Brakes | Standard brake plumbing and pads | Steel brake lines as standard in the kit; track pads are an optional Manthey item |
| Engine output | 493-hp naturally aspirated 4.0-liter flat-six in Porsche’s US description | No kit-related power increase is stated |
| Installation | Factory-built car | Ordered and installed through an authorized Porsche Center; country-specific availability and pricing apply |
The downforce figures are the same manufacturer comparison expressed in imperial and metric units, not two independent tests. They only apply at the stated approximate speed and wing setting.
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Every aerodynamic part added by the kit
Front flaps and air curtains
The front of the car receives additional flaps and air-curtain elements. These parts manage the high-pressure air at the nose and help control the flow alongside the front wheels. Their purpose is aerodynamic balance rather than additional engine cooling or power.
Wheel-arch Gurney flap
A Gurney flap is added at the wheel-arch area. It changes the local pressure distribution around the arch, contributing to the kit’s overall load and helping the front-to-rear balance work with the larger rear wing.
Carbon underbody and diffusers
The kit adds a carbon-fiber underbody with diffusers. Smoothing the floor and shaping the diffuser exit allows the underside to generate more aerodynamic load with less exposed turbulence than a simple collection of external spoilers. The cited descriptions identify the hardware, but do not provide separate front- and rear-axle load figures for each component.
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Carbon rear-wheel aerodiscs
Carbon-fiber aerodiscs cover the rear wheels. They are intended to reduce turbulence in the wheel area, where rotating spokes and tire surfaces disturb airflow. The discs are part of the package’s aerodynamic system, not decorative covers alone.
Wider, more adjustable rear wing
The rear wing is widened by 85 mm according to Manthey. It uses a new blade and larger endplates, and the kit provides four adjustment positions. Porsche’s US description contrasts that with three positions for the standard car. The additional position gives the owner more scope to match rear load to a circuit, tire and chassis setup.
Because the wing loads the rear structure more heavily, the rear engine cover is reinforced. This reinforcement is a structural response to the aero package, not an engine modification.
Optional rear-spoiler attachment and front-fender louvers
Manthey also lists an optional rear-spoiler attachment and carbon-finish front-fender louvers. The spoiler attachment can add approximately 4 percent rear-axle downforce when combined with the larger kit wing, according to Manthey. That percentage is a manufacturer-stated incremental figure for the specified combination; it is not a guarantee of a 4 percent increase in total vehicle downforce in every wing position.
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What the downforce numbers mean in practice
At approximately 124 mph (200 km/h), with the wing in Performance position, Porsche’s US release reports total downforce rising from 196 lb to 372 lb. Manthey presents the same comparison as 89 kg to 169 kg. In other words, the cited total is approximately doubled at that single speed and setting.
| Configuration | Total downforce at approximately 124 mph/200 km/h | Condition attached to the figure |
|---|---|---|
| Stock GT4 RS | 196 lb (89 kg) | Manufacturer comparison with the wing in Performance position |
| GT4 RS with Manthey Kit | 372 lb (169 kg) | Same approximate speed and Performance wing position |
Downforce is speed-dependent: the aerodynamic load falls rapidly as speed drops. A road driver traveling well below 124 mph will not experience the quoted load. The figures also do not tell you how much grip is available in a particular corner, because tire compound, temperature, surface, alignment, fuel load and driver inputs all matter. They are useful for understanding the kit’s design intent, not for predicting a universal lap-time gain.
Suspension and chassis: more adjustment, not a published comfort upgrade
Inverted adjustable coilovers
Porsche and Manthey developed special inverted coilovers for the kit. The struts have four adjustment positions, and rebound and compression damping can be adjusted without tools. Inverted construction places the larger-diameter portion of the damper at the upper end, a layout commonly used when stiffness, heat management and track-service access are priorities.
The package is offered for cars with or without front-axle lift. A buyer does not have to give up the lift system simply because the car receives the Manthey suspension, but the exact compatible configuration must be confirmed with the Porsche Center before ordering.
20 percent higher front spring rate
The front spring rate is increased by 20 percent over stock. A higher rate resists body motion and can support the additional aerodynamic load at speed. It also changes the forces reaching the tires and chassis, which is why damper settings and alignment need to be considered as a system rather than adjusted in isolation.
The official descriptions do not publish instrumented ride-quality, compliance, cabin-noise or comfort measurements. The higher spring rate and track-oriented damper range explain why the kit is not automatically a better daily-road setup, but they do not prove that it will be uncomfortable on every road or in every setting.
What the adjustment range is for
Four-position dampers and a four-position wing let an experienced driver tune the car for different circuits and conditions. A high-speed circuit may reward more rear load, while a slower layout may make aerodynamic drag and balance more important. The useful result is adjustability: the kit gives a specialist more ways to arrive at a stable setup than the standard car. It does not mean every position is appropriate for public-road use or every tire.
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Braking changes: firmer plumbing, optional pads
Steel brake lines are standard in the Manthey Kit. Porsche says they improve pedal feel and the delivery of braking power by reducing the expansion associated with flexible rubber lines under pressure. The change affects pedal consistency and control; it is not described as a replacement of the GT4 RS braking system.
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Track-oriented brake pads are optional in Manthey’s overview. Pad choice affects friction, temperature range, dust, noise and cold performance, so a circuit pad can be sensible for repeated hot laps but less convenient for a road car used in traffic. The cited material does not specify a single pad compound or a universal street/track recommendation.
Track towing loops and cosmetic carbon parts are also optional. They should not be confused with the steel lines or the core aerodynamic and suspension package.
How much faster is a GT4 RS with the kit?
The headline result is a manufacturer comparison at the Nürburgring Nordschleife. With Porsche brand ambassador Jörg Bergmeister driving, the Manthey-equipped car recorded 7:03.121 on the 20.8-kilometer course. Manthey says that was 6.179 seconds quicker than the stock 718 Cayman GT4 RS’s run from the prior year.
| Item | Manufacturer-stated detail |
|---|---|
| Manthey-equipped lap | 7:03.121 on the 20.8-km Nürburgring Nordschleife |
| Reported difference | 6.179 seconds quicker than the prior-year stock-car run |
| Driver | Jörg Bergmeister |
| Tires | Optional Michelin Pilot Sport Cup 2 R tires on both cars |
| Kit-run conditions | 18°C and overcast skies |
| Verification | Manthey says the lap was certified by a notary |
This is meaningful evidence that the complete package can produce a faster manufacturer-run lap under the stated conditions. It is not an independent back-to-back test and does not establish a 6.179-second gain for every driver. The comparison uses a professional driver, a specific circuit, specific optional tires and different-year runs. Weather, track temperature, traffic, preparation and driving strategy can all affect a Nordschleife time. The result also says nothing direct about a short technical circuit, a wet day, ordinary road tires or a driver who is still learning the GT4 RS.
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Manthey describes the kit’s road-legal components as retrofit items sold through Porsche Centers. That statement is not a blanket approval for every country, vehicle specification or optional combination. Before installation, ask the dealer to confirm local type approval, registration implications, noise or lighting requirements and whether the selected aerodynamic parts are legal where the car is driven.
The available material does not measure ride comfort, compliance over potholes, tire wear, visibility, fuel consumption, wind noise or ease of parking. It also does not demonstrate that the extra downforce is useful at normal public-road speeds. Those are unanswered ownership questions, not evidence that the car will be unusable on the road.
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For a road-biased owner, the practical issue is setup discipline. The car can be road legal while carrying hardware designed to work hardest at circuit speeds, and the wing and damper settings can be changed. A dealer or experienced Porsche race-preparation technician should document a sensible road setting and explain how to return to a track setting without losing the alignment or adjustment baseline.
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US price published in 2024
Porsche’s May 10, 2024 US announcement listed the Manthey Kit at an MSRP of $53,946 before installation. It separately listed a supplementary carbon package at $5,890. These are dated US figures, not a current worldwide price list, and installation was excluded. Taxes, labor, options, exchange rates and later price changes can alter the amount you actually pay.
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| Published item | Figure and qualification |
|---|---|
| Manthey Kit | $53,946 US MSRP, announced May 10, 2024, before installation |
| Supplementary carbon package | $5,890 US figure in the same announcement |
| Current local price | Not stated; verify with an authorized Porsche Center |
Where it is ordered and installed
Porsche’s announcement states that US owners can order the optional kit through authorized Porsche Centers, which handle installation. Manthey says road-legal components are sold through Porsche Centers worldwide, with country-specific pricing. The center is therefore the correct place to check parts availability, labor, compatibility with front-axle lift, and the exact option list for your chassis.
Warranty position
Manthey says the manufacturer warranty is unaffected by the road-legal retrofit components. That statement should be confirmed in writing for your market and the exact parts being installed. Ask the dealer which warranty applies to the components, who performs warranty work, and whether any non-Manthey modifications could change the result.
How to decide whether to retrofit your car
| Your priority | Stock GT4 RS is usually the simpler choice | Manthey Kit is more relevant when |
|---|---|---|
| Public-road use | You value the factory setup and want the least expensive configuration | You accept track-oriented hardware and have verified local legality and a workable road setting |
| Track days | You attend occasionally and are still developing driving, tire and alignment technique | You attend frequently and can use the damper, wing and alignment adjustments effectively |
| High-speed circuits | You do not need additional aerodynamic tuning | Higher-speed corners and repeated sessions justify more load and setup range |
| Budget | You prefer to spend on instruction, tires, brakes or events first | The dated US price and installation cost fit your plan for a specialized package |
| Engine performance | You want more horsepower | You are satisfied with the unchanged 493-hp engine and want chassis performance instead |
The kit makes the strongest case for an owner who regularly drives on track, uses appropriate tires, understands setup changes and can exploit extra aerodynamic load. A casual driver may obtain more consistent improvement by learning the stock car, attending instruction and choosing suitable tires and brake pads before spending on a large retrofit. That is a decision framework, not a claim that the kit lacks value for occasional users.
A sensible dealer conversation before ordering
- Confirm the exact car. Give the Porsche Center the vehicle identification number, model year and whether the car has front-axle lift. The suspension is offered in lift and non-lift versions, so compatibility should be established before a quote is accepted.
- Request a complete, itemized quote. Separate the kit, supplementary carbon package, optional brake pads, optional spoiler attachment, labor, taxes and any alignment or setup work. Do not treat the $53,946 US announcement figure as a current all-in price.
- Ask for the legal documentation. Have the center confirm which components are approved for your country and whether any registration, inspection or insurance notification is required.
- Define the intended setup. Tell the installer whether the car will be road-driven, used for track days or transported to circuits. The wing position, damper settings, tires and alignment should be recorded as a baseline rather than left undocumented.
- Clarify warranty coverage. Obtain the dealer’s written explanation of the manufacturer warranty and the coverage for the retrofit parts, including the procedure if a component later needs replacement.
- Plan consumables. If you select optional track pads or the Michelin Pilot Sport Cup 2 R tires used in the lap comparison, verify fitment, availability and whether you can safely drive the car to and from the circuit on that configuration.
What the official evidence establishes—and what it leaves open
- The kit adds aero, adjustable suspension and brake-line hardware; the cited announcements do not claim more engine power.
- The 196-to-372-pound (89-to-169-kilogram) downforce comparison is tied to approximately 124 mph/200 km/h and the Performance wing position.
- The front spring rate is 20 percent higher, and the coilovers provide four positions with tool-free rebound and compression adjustment.
- The Nordschleife result is a manufacturer comparison using optional Pilot Sport Cup 2 R tires on both cars, a professional driver and stated weather conditions.
- The result does not predict an identical gain for another driver, circuit, tire, temperature or road surface.
- Road-legal retrofit availability and an unaffected manufacturer warranty are stated by Manthey, but local approval and exact terms still require dealer confirmation.
- No cited material establishes a measured change in ride comfort, noise, visibility, tire wear, fuel use or normal-road lap-time benefit.
Bottom line: a faster setup tool, not a faster engine
The Manthey Kit changes the GT4 RS where a track driver can use it: it adds substantially more aerodynamic load at a specified speed, gives the chassis a wider adjustment window and improves brake-line feel. The unchanged engine output and the absence of a wholesale brake conversion are important parts of the comparison. Its $53,946 US price before installation in 2024, plus optional parts and local costs, makes it a specialized retrofit rather than an automatic upgrade for every owner. Choose it when the track, tires and setup work justify the expense; keep the stock car when road comfort, simplicity and occasional circuit use matter more than maximum adjustability.
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