Installing Aftermarket Bucket Seats in the MK RX-5
At GSM Performance, we’ve had a number of enquiries about fitting aftermarket bucket seats into the MK RX-5 range. These lightweight British sports cars are designed for drivers who want a raw and engaging experience, and they’ve built a strong following among enthusiasts who enjoy track days, road rallies, or simply spirited drives on a Sunday morning. The RX-5 combines sharp handling with classic kit car character, but its compact design comes with one big challenge – interior space.
The cockpits on these cars are extremely narrow, and that makes seat fitment a real issue. Standard aftermarket bucket seats are usually too wide or too bulky to fit comfortably between the transmission tunnel and the side panels. Customers who come to us asking about replacement seats for their RX-5 are often surprised to learn just how limited the options are.
That doesn’t mean upgrading is impossible, though. With careful measuring and the right products, we’ve found a small range of seats that fit well inside the RX-5 and provide the extra support, safety, and comfort drivers are looking for. In this blog, we’ll go through the different RX-5 models, explain why an upgrade makes sense, and highlight the narrow-fit seats we recommend for these cars.
The MK RX-5 Range
MK Sportscars designed the RX-5 as a modern interpretation of a lightweight British kit car, drawing on Mazda MX-5 running gear for proven reliability and performance. Across the range, all versions share the same compact chassis and narrow interior, but the engine choices and character of each model set them apart.
RX-5 140 – This is the entry-level model, powered by the 2.0-litre Mazda MX-5 engine producing around 140bhp. It’s not about raw power, but about balance and drivability. The RX-5 140 is often chosen by first-time kit car owners who want something that’s manageable, affordable, and still capable of delivering plenty of fun on track or on the road.
RX-5 250 – A step up in performance, the RX-5 250 makes use of the more powerful Mazda MX-5 2.5-litre engine. With around 250bhp in a lightweight chassis, this model is aimed at drivers who want something sharper and more aggressive without stepping into the world of full race-spec machinery. The RX-5 250 is a popular choice for track enthusiasts who want more power without sacrificing the everyday usability that makes the RX-5 range so appealing.
RX-5 VTEC – Sitting at the top of the range is the VTEC edition. As the name suggests, this model swaps the Mazda engine for a Honda VTEC power unit, unlocking a huge amount of performance and transforming the RX-5 into a car that can rival serious track machinery. With high-revving power and a screaming soundtrack, the VTEC model is the most extreme version of the RX-5 and is often built with competition or dedicated track use in mind.
All three models give you a slightly different flavour of the RX-5 experience, but they also share the same limitations when it comes to interior space. That’s why fitting aftermarket bucket seats into any RX-5 – whether it’s the 140, 250, or VTEC – requires careful planning and a focus on seats designed specifically for narrow cockpits.
Why Upgrade the Seats in an RX-5?
The MK RX-5 is built for driving enjoyment, but the standard seats can feel like a compromise. They’re fine for casual use, yet they don’t offer the support needed when you start pushing the car harder. Because of the RX-5’s lightweight chassis and sharp handling, drivers often find themselves moving around in the seat more than they’d like during quick direction changes, braking, or cornering. That movement may not seem like a big issue at first, but over time it reduces confidence and makes it harder to stay focused on the road or track ahead.
Aftermarket bucket seats solve this problem by giving you deeper bolsters and proper lateral support. Instead of bracing yourself against the steering wheel or the side of the cockpit, the seat holds you firmly in place, letting you concentrate fully on your driving. This is particularly important on track days or during spirited drives, where consistent support translates directly into better control.
Another major reason to upgrade is harness compatibility. Standard seats are not designed to work with racing harnesses, but many aftermarket bucket seats feature harness slots as standard. For RX-5 drivers taking part in motorsport or preparing their car for more serious events, this is essential. Proper harness routing adds a big step up in safety and ensures you’re fully secured in the car, even under heavy loads.
Comfort is also a factor. Narrow-fit bucket seats available for the RX-5 are designed with longer journeys and driver endurance in mind. With carefully shaped shells and the option of customised padding and trim, they can make a stripped-back kit car feel more accommodating without losing the rawness that makes it fun. For drivers planning long days at track events or extended road rallies, that combination of comfort and support makes all the difference.
Cobra Roadster 7 Sport Turbo Seats
When it comes to fitting bucket seats into a car as compact as the RX-5, very few options work without serious modification. The Cobra Roadster 7 Sport Turbo is one of the standout solutions. Specifically designed for kit cars and narrow-bodied sports cars, it offers the slimline construction needed to clear the RX-5’s door cards and transmission tunnel, while still providing the support you expect from a motorsport seat.
The seat’s narrow base and compact shoulders allow it to slot into the RX-5 cockpit without fouling panels or needing heavy adjustments. Yet despite its small footprint, it doesn’t compromise on functionality. Both the standard and Signature versions come with harness slots built in, making them fully compatible with multi-point harnesses for track and rally use.
Standard Roadster 7 Sport Turbo
The standard version of the Roadster 7 Sport Turbo provides everything you need in a compact, motorsport-ready package. It features:
- Narrow construction to maximise interior space.
- Harness slots to work with 4, 5, or 6-point belts.
- A strong steel-reinforced shell with comfortable padding.
- Trim options in vinyl or cloth to match your car’s style.
- Choose from a wide selection of colours, stitching patterns, and piping.
- Opt for premium materials like leather or Alcantara for a more bespoke feel.
- Add optional extras such as lumbar support or heating elements for everyday comfort.
This seat strikes a balance between affordability and performance, making it an excellent choice for RX-5 owners who want a straightforward upgrade.
Cobra Roadster 7 Sport Turbo Seat Dimensions
The main reason the Cobra Roadster 7 Sport Turbo works so well in the RX-5 is its extremely compact footprint. Most aftermarket bucket seats are too wide at the shoulders or base to slot between the RX-5’s narrow transmission tunnel and door panels. The Roadster 7 Sport Turbo avoids this issue with a slimline design that was developed specifically for tight cockpit spaces.
Key dimensions:
- Overall height: 920mm
- Shoulder width: 400mm
- External base width: 430mm
- Internal base width: 290mm
- Seat depth (front to back): 580mm
These measurements make the Roadster 7 Sport Turbo one of the narrowest FIA-style bucket seats on the market. With shoulders under 400mm, it clears the RX-5’s tight cabin without needing to remove or modify door panels. The narrow base also helps avoid interference with the transmission tunnel, a common issue when trying to fit standard-sized seats.
But the dimensions don’t just matter for the car – they matter for the driver too. With an internal base width of 290mm, the Roadster 7 Sport Turbo is best suited to slim-to-average build drivers. The snug fit ensures you’re held firmly in place during cornering, but drivers with a wider frame may find it too tight for comfort. That’s why we always recommend customers try the seat in-store where possible, or compare the measurements against their current seat to judge fitment.
Tillett Bare Shell Bucket Seats
For drivers who want the most minimal and lightweight option, the Tillett seat range is ideal. These bare shell bucket seats are designed with tight cockpits in mind, making them some of the best choices for the RX-5. With no bulky padding or extra trim, Tillett seats maximise interior space while still providing the rigidity and support needed for track use.
The seats are available in fibreglass for affordability or carbon fibre for ultimate weight savings and strength. Both versions share the same slimline design, making them perfectly suited for the RX-5’s compact cabin. Importantly, all of the recommended Tillett seats come with full harness slot layouts, so they’re ready for use with 4, 5, or 6-point racing harnesses.
Tillett B4
The Tillett B4 is one of the narrowest car seats available, designed specifically for lightweight sports cars and kit builds. With its ultra-slim shoulders and low base profile, it slides neatly into the RX-5 without clashing against the tunnel or side panels. The B4 is a true performance-focused seat, offering minimal weight and a very snug fit, best suited to slimmer drivers who want maximum connection with the car.
Tillett B5
The Tillett B5 builds on the B4’s design but with slightly more width and comfort. It’s still compact enough for the RX-5, but the extra room makes it a more versatile choice for drivers who find the B4 too tight. Like the B4, it’s available in fibreglass or carbon fibre, giving buyers the option to balance cost and performance. The B5 is a popular middle ground, providing the minimal footprint needed for the RX-5 while accommodating a wider range of body types.
Tillett B6
The Tillett B6 offers the most comfort of the three while still staying narrow enough to fit inside the RX-5. It has slightly deeper bolsters and a shape designed for longer stints, making it a better option if you plan on using your RX-5 for extended track days or road rallies. While still compact, the B6 is the most accommodating of the three recommended models, and is a great choice for taller or broader drivers who still need a slim seat.
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Seat Installation in the RX-5
Installing bucket seats into an RX-5 requires more planning than with most cars. Because of the car’s unique kit chassis and compact interior, there are no vehicle-specific subframes available from seat manufacturers. This means you won’t find a direct bolt-in solution – instead, some level of fabrication will always be required to secure aftermarket seats properly.
The most common approach is to fabricate custom floor mounts that line up with the RX-5’s chassis rails. These mounts provide a safe and solid foundation for the seat, and from there, you can bolt on side mounts or runners depending on your setup. For fibreglass and Tillett shells, side mounts are essential, as they allow the seat to be positioned at the correct angle and height. With Cobra Roadster 7 Sport Turbo seats, you can choose between side mounting or direct base mounting, depending on your preference and how much space you want to save.
Because fabrication is involved, we always suggest working with a specialist who has experience fitting seats in narrow kit cars. Getting the seat position right is crucial – too high or too far forward, and you’ll lose comfort and control. Done correctly, a custom installation ensures the seat not only fits the car but also supports you in exactly the way it should.
MK RX-5 Vehicle Guide
Choosing Between Cobra and Tillett
When deciding on seats for your RX-5, the choice often comes down to Cobra Roadster 7 Sport Turbo or Tillett bare shell seats. Both work well in the RX-5’s tight cockpit, but they offer very different experiences.
Cobra Roadster 7 Sport Turbo
Pros:
- More comfort thanks to padding and trim options.
- Available in a wide range of materials and colours.
- Signature edition allows full customisation with stitching, piping, and upgrades like heating and lumbar support.
- Easier to live with for longer journeys or dual road-and-track use.
Cons:
- Heavier than a bare shell seat.
- Internal base width is tight, making it less suitable for broader drivers.
- Less minimal than a Tillett for those chasing every kilogram of weight saving.
Tillett B4, B5, and B6
Pros:
- Extremely lightweight, with carbon fibre versions saving even more weight.
- Bare shell design maximises available cockpit space.
- FIA-approved with full harness slot layouts.
- Excellent for dedicated track use where minimalism is key.
Cons:
- Less comfort for road use, with no padding or upholstery beyond the shell itself.
- Limited trim options – focus is purely on performance, not style.
- Requires drivers to accept a more stripped-back, race car feel.
Which to Choose?
If your RX-5 will see plenty of road miles alongside track days, the Cobra Roadster 7 Sport Turbo is the better option. It balances narrow fitment with comfort and the ability to tailor the look and feel of your car’s interior.
If your RX-5 is primarily a track or competition car, then the Tillett B4, B5, or B6 is the way to go. The bare shell design keeps weight to an absolute minimum while ensuring you have the support and safety needed in demanding conditions.
Final Thoughts – Narrow Seats for a Narrow Car
Fitting aftermarket bucket seats into the MK RX-5 isn’t straightforward, but it is possible with the right products. The Cobra Roadster 7 Sport Turbo and the Tillett B4, B5, and B6 ranges are the best options we’ve found, thanks to their slimline designs and narrow dimensions.
While the RX-5’s cockpit limits your choices, these seats provide the lateral support, harness compatibility, and lightweight design needed to get the most out of this exciting little sports car. With fabrication work and careful measuring, upgrading your RX-5 seating is a challenge worth tackling.