Installing Aftermarket Bucket Seats in the MK RX-5
Kit car seat fitting guide
We get a steady run of questions about fitting aftermarket bucket seats to the MK RX-5. It is a light, seven style kit car built around Mazda MX-5 running gear, and owners use them for track days, road rallies and quick Sunday drives. The one thing every RX-5 shares is a very narrow cockpit, and that is what makes the seat choice hard.
Most aftermarket buckets are simply too wide to sit between the transmission tunnel and the side panels. Upgrading is still possible, though. With careful measuring and the right shells there is a short list of seats that go in and give proper support. This guide covers the RX-5 models, why an upgrade is worth doing, the narrow seats we point owners towards, and how they are mounted.
- The RX-5 140, 250 and VTEC share the same narrow chassis and cockpit
- There are no direct fit seat frames for the RX-5, so mounts are fabricated
- Cobra Roadster 7 Sport Turbo: 920mm tall, 400mm wide, base mount
- Tillett B6: a bare GRP shell, 40cm wide with the rolled edges cut off
- Tillett B6 Screamer is the FIA 8855-1999 version of the same shell
- Send us your height and waist and we will talk through the fit
The MK RX-5 range
MK Sportscars build the RX-5 as a modern take on the lightweight British seven, using Mazda MX-5 parts for the drivetrain. There are three versions, and while the engines differ, the chassis and cockpit are the same on all of them.
- RX-5 140: a naturally aspirated 1.8 litre MX-5 (NB) engine, quoted by MK at around 140bhp. The balanced, easy to live with version, and a common first kit car.
- RX-5 250: the same 1.8 MX-5 engine with a turbocharger kit, quoted at around 250bhp. Much quicker, and popular with track day drivers.
- RX-5 VTEC: a Honda K20A2 VTEC engine mated to an MX-5 gearbox. High revving and the most extreme of the three, often built for dedicated track or competition use.
Because all three share one cockpit, the seat advice below applies to any RX-5, whichever engine it has.
Why upgrade the seats in an RX-5
The RX-5 is light and sharp, and that is exactly why the seat matters. Under hard braking, quick direction changes and long corners, a seat with little side support lets you slide about. You end up bracing yourself against the wheel or the side of the car, which costs confidence and concentration.
A proper bucket holds you in place with deeper side bolsters, so your hands are free to steer and your feet are free to work the pedals. On a track day that consistency is the difference between a tidy lap and a messy one.
Harnesses are the other reason. Many RX-5 owners run a multi point harness for track use, and that needs a seat with harness slots in the right places. The seats below all have them. Comfort counts too: a shaped shell that fits you is far kinder on a long day at the circuit than a seat you are fighting against.
Cobra Roadster 7 Sport Turbo
Very few seats fit a cockpit this tight without modification. The Cobra Roadster 7 Sport Turbo is the one we point RX-5 owners to first. It was built for seven style cars: tall enough to give a taller driver proper shoulder support, and narrow enough to clear the tunnel and the side panels.
Its figures from our listing are what make it unusual. It is 920mm tall and 400mm wide, the tallest shell in the Roadster range and one of the narrowest seats Cobra build, at 9.5kg with a 580mm cushion. The cushion is short, but in a car where your legs are already stretched out towards the pedals that matters less than it would in a saloon.
Harness slots come as standard on the Sport Turbo, and it is listed as 4 point harness compatible. It is Road and Track approved, not FIA homologated, so it suits fast road, track day and kit car use, not a championship that scrutineers seats to FIA rules. It is a base mount seat, supplied as the seat only.
There is also a Signature version of the same seat, which opens up Cobra’s wider choice of trims, colours and stitching if you want the interior to be your own.
| Cobra Roadster 7 Sport Turbo | From our listing |
|---|---|
| Height | 920mm |
| Width | 400mm |
| Seat depth | 580mm |
| Weight | 9.5kg |
| Fixing | Base mount |
| Harness | Slots included, 4 point compatible |
| Approval | Road and Track |
A seat this narrow is a snug fit on the driver as well as the car. Garreth’s advice is to sit in one before you order if you can, or at least compare the measurements against the seat you have now. If you have a broader build, tell us your waist size and we will be honest about whether it will suit you.
Tillett B6 bare shell seats
For the lightest and most minimal option, Tillett bare shells make a lot of sense in an RX-5. There is no bulky padding or trim, so the shell takes up as little of the cockpit as possible while still giving the support you need on track. The original version of this guide also named the Tillett B4 and B5; neither is on our site at the moment, so we now point RX-5 owners at the B6 family.
The standard B6 is a black gloss GRP shell weighing 4.5kg to 5.1kg, with a Dinamica covered headrest panel. You choose the width: 40cm with the rolled edges cut off, or 44cm with them left on. In a car as tight as the RX-5, the 40cm is the one to look at. It suits a 32 to 36 inch waist, is Road and Track approved and is side mounted.
If your championship asks for an FIA seat, the B6 Screamer is the same family homologated to FIA 8855-1999, and both widths keep the approval, so cutting the rolled edges to 40cm does not lose it. It weighs a little more at 5.8kg to 6.1kg, is 30 degree HANS compatible, and Tillett recommend a five or six point harness with it. An FIA seat has a limited life, so tell us what you compete in and when, and we will check the date suits.
The B6 XL is the same shell 30mm wider inside, for a 36 to 40 inch waist. Its external width is 43cm with the edges cut off, so we have not included it as an RX-5 recommendation. Measure your tunnel and sill before considering one.
All the B6 shells are supplied as the seat only, so you will need brackets as well. Our guide to the best Tillett seat for a Caterham or Westfield covers the same family in similar seven style cars.
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Seat installation in the RX-5
Fitting seats to an RX-5 takes more planning than in most cars. Its kit chassis and compact interior mean seat manufacturers do not make vehicle specific frames for it, so there is no direct bolt in option. Some fabrication is always part of the job.
The usual approach is custom floor mounts that line up with the chassis rails, giving the seat a solid base. From there the fixing depends on the seat. The Tillett B6 shells are side mounted, so they need side brackets, which also let you set the angle and height. The Cobra Roadster 7 Sport Turbo is a base mount seat and bolts to the mounts underneath.
Because fabrication is involved, we always suggest working with a specialist who has fitted seats in narrow kit cars before. Getting the position right matters: too high or too far forward and you lose comfort, control and head room under the roll bar. If you are running a harness, the mounting points need to be right for it too, and our guide on how to fit a motorsport harness covers the angles and anchor points.
Choosing between Cobra and Tillett
Both work in the RX-5’s cockpit, but they give a very different experience.
Cobra Roadster 7 Sport Turbo
- Padded and trimmed, so it is more comfortable for longer drives.
- A choice of materials and colours, with more still on the Signature version.
- Easier to live with in a car that does road miles as well as track days.
- Heavier than a bare shell, and snug for broader drivers.
- Road and Track approved, not FIA.
Tillett B6 family
- Very light bare GRP shells, around 4.5kg to 6.1kg depending on the model.
- The bare shell leaves the most room in the cockpit.
- An FIA 8855-1999 option in the B6 Screamer.
- Little padding, so it feels more like a race car on the road.
- Side mounted, so it needs side brackets as well as floor mounts.
If your RX-5 does plenty of road miles alongside track days, the Cobra is usually the better fit for how you use the car. If it is mainly a track or competition car, a Tillett B6, or the B6 Screamer where an FIA seat is needed, keeps the weight down and gives you the support you need.
Our wider guide to narrow racing seats and which model fits your car is worth a look if you are comparing more shells. For a personal recommendation, send us your height and waist measurements and we will talk through which of these suits your build.
Are there direct fit seat frames for the MK RX-5?
No. Seat manufacturers do not make RX-5 specific frames, so the mounts are fabricated to line up with the chassis rails.
Is the Cobra Roadster 7 Sport Turbo FIA approved?
No. It is Road and Track approved, which suits fast road, track day and kit car use, not events that scrutineer seats to FIA rules.
Which Tillett seat is FIA approved?
The Tillett B6 Screamer, which is homologated to FIA 8855-1999 in both its 40cm and 44cm widths. The standard B6 is Road and Track.
Does the seat choice change between the RX-5 140, 250 and VTEC?
No. All three share the same chassis and cockpit, so the same narrow seats apply to each.
Can I use a harness with these seats?
Yes. The Roadster 7 Sport Turbo has harness slots and is listed as 4 point compatible, and the B6 shells are listed as 6 point compatible.
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Narrow seats for a narrow carRoadster 7 Sport Turbo or Tillett B6
The Cobra for road and track comfort, the Tillett B6 or B6 Screamer for the lightest track seat.
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