Bucket Seats For A Locust Seven: What Fits And What To Measure First
Seat guide, Locust Seven
Somebody asked us this week what goes in a Locust, the Mazda engined one, and Cameron gave the answer he gives every Seven owner: roughly the same seats as a Caterham or a Westfield. Narrow cockpit, no roof, tunnel down the middle. The shortlist barely changes.
Then Garreth pointed out the bit that does change, which is that nobody built your Locust in a factory.
- Same shortlist as a Caterham or Westfield, because the cockpit problem is the same
- A Locust is a kit car, so measure yours. No two were necessarily built alike
- The number that decides it is the width across the base, not across the shoulders
- 40cm or 44cm on a Tillett is chosen when the seat is built and cannot be cut afterwards
- Not being scrutineered? The Cobra Roadster 7 at £569.00 was drawn for Seven style cars
- Both FIA options: the Tillett B6 Screamer at £1,234.36, or the Sparco Sprint at £252.00
- On the Screamer, both widths are homologated, so 40cm does not cost you the approval
Your Locust is not the same as the next one
This is where a kit car parts company with a Caterham. Caterham build theirs on a jig, so if you tell us the model we can tell you the cockpit. A Locust came as a chassis and a pile of parts, and somebody put it together in a garage, possibly in the eighties, possibly not the person who owns it now.
Which means we cannot quote you a Locust cockpit width and neither can anybody else. Get a tape in the car before you get a wallet out.
Measure between the transmission tunnel and the sill, at the floor, where the base of the seat will actually sit. Not across the top where your shoulders go, because on a Seven that is rarely the tight bit. Then do the other side, because on a hand built chassis the two are not guaranteed to match.
The 40cm decision, and why you only get one go at it
Tillett build the B6 and the W1i in two widths. 44cm with the rolled lip round the leg area left on, 40cm with it cut off. Four centimetres does not sound like much until you are trying to get two seats either side of a tunnel in a car this narrow.
The catch is that it is specified when the seat is made. It is not a thing you can take off afterwards with a cutting disc, and it is not a thing we can change once it has arrived. Tillett themselves say the 40cm is what turns up in Lotuses and Caterhams, which tells you where they expect it to go.
So measure, then decide, then order. In that order.
Sparco Sprint FIA: the cheapest way to satisfy a scrutineer
If the car is going to be scrutineered and the budget is the thing you are working around, this is the one. FIA 8855-1999 for £252, which is remarkable, and it does it by using a steel shell where everything else at this end of the market uses fibreglass.
Steel is heavier. We are not going to pretend otherwise, and neither does our listing: if your series scrutinises seat material or a minimum weight, check the regulations before you order. For club hillclimb and sprint work where nobody is weighing your seat, Garreth thinks it is a lot of homologation for the money.
- £252.00 inc VAT, part BRR0003B0
- FIA 8855-1999
- Steel shell, which is where the price comes from
- Base mount or side mount, so it suits a flat kit car floor
- 32 to 36 inch waist, all heights, 6 point harness compatible
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Tillett W1i: the light one, if your roll bar does the head work
The W series came from single seaters and formula cars, where there is no room above your shoulders for a headrest. So the W1i has not got one. The shell sits lower and more compact than a B6 and it weighs 1.9kg, which in a car that might scale under half a tonne is worth having.
It is a four point seat and the head protection is the roll bar’s job, not the seat’s. On a Seven that is usually how it works anyway. Cameron fits more of these into narrow cars than anything else in the range.
- £520.08 inc VAT in GRP, part W1i-40-Black-GRP
- 1.9kg shell, the lightest thing here by a distance
- 40cm with the rolled edges off, 44cm with them on
- No headrest, road and track approval
- Base mount or side mount, 4 point harness
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Tillett B6: the one most people end up in
A proper Tillett shell without paying for paperwork you will never be asked for. It has the moulded headrest the W1i does not, it takes a six point harness, and it is civil enough that you can drive to the circuit in it and still want to drive home.
Weight is 4.5kg to 5.1kg and Tillett are open about seats varying by up to ten per cent, so take that as a range. The same 40cm and 44cm widths apply.
- £952.56 inc VAT in GRP
- 4.5kg to 5.1kg shell
- Moulded headrest with a Dinamica covered panel as standard
- 6 point harness compatible, road and track approval
- 32 to 36 inch waist on the standard shell
-
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Cobra Roadster 7: the one built round the bulkhead
If you are not being scrutineered, this is the other seat that belongs on the list, and it got there from a different direction to the Tilletts. Cobra drew it specifically for Seven style cars.
The clever bit is the back. In a Seven the thing you are fighting is the rear bulkhead, and most buckets sit square against it and waste the space the angle has already taken. The Roadster 7 is shaped to follow that angle, and what it recovers goes into legroom. That is why a general purpose bucket so often does not work in these cars, and it is not only about width.
- £569.00 inc VAT, part COBROAD7
- 400mm base, 460mm across the shoulders, 750mm tall, 720mm deep, 7kg
- Base mount, 4 point harness compatible, road and track
- All waist sizes and all heights
- Hand trimmed in the UK, made to order, so allow four to six weeks
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There are dearer versions of the same shell if you want them. The Sport at £639.00 inc VAT comes with the harness slots, and the Signature at £639.00 is the same seat again in a wider choice of trim. The fit does not change between any of them, so pick the shell because it goes in and pick the version because you like it.
The dimensions, side by side
This is the table to hold a tape measure against. Both of these are road and track seats, so the choice between them is about shape and space, not paperwork.
| Cobra Roadster 7 | Tillett B6 | |
|---|---|---|
| Width at the base | 400mm | 350mm |
| Across the shoulders | 460mm | 425mm outside |
| Height | 750mm | 810mm |
| Front to back | 720mm | 695mm |
| Weight | 7kg | 4.5 to 5.1kg |
| Mounting | Base mount | Bottom or side mount |
| Harness | 4 point | 6 point |
Cobra figures from their own listing, Tillett figures from Tillett's B6 dimension drawing.
Read the top row first. The Cobra wants 400mm at floor level and the Tillett wants 350mm, so if your Locust is genuinely tight between tunnel and sill the Tillett is the one that goes in. For context, Cobra point out that an ordinary sports seat sits somewhere between 500mm and 560mm at the base, which is exactly why people try one in a Seven and give up.
The Cobra is the lower seat by 60mm and the roomier one across the shoulders, so if your car has the floor width for it, plenty of people find it the easier seat to spend a day in.
Tillett B6 Screamer: the FIA one that stays narrow
This is the B6 you buy when the scrutineer is going to look. Homologated to FIA 8855-1999, and here is the part that matters in a Locust: both edge configurations are homologated. Cutting it down to 40cm does not cost you the approval.
That catches people out on other brands, where the narrow version quietly is not the homologated one. If you need FIA paperwork and you need to fit between a tunnel and a sill, that combination is not as common as it ought to be.
It weighs 5.8kg to 6.1kg against the road B6’s 4.5kg to 5.1kg. The extra is the homologated construction, and there is no way round it at this price.
- £1,234.36 inc VAT in GRP
- FIA 8855-1999, and both 40cm and 44cm are homologated
- 5.8kg to 6.1kg
- 6 point harness compatible
-
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The five together
| Seat | Approval | Weight | Harness | Price inc VAT |
|---|---|---|---|---|
| Sparco Sprint FIA | FIA 8855-1999 | Steel, heavier | 6 point | £252.00 |
| Tillett W1i GRP | Road and track | 1.9kg | 4 point | £520.08 |
| Cobra Roadster 7 | Road and track | 7kg | 4 point | £569.00 |
| Tillett B6 GRP | Road and track | 4.5 to 5.1kg | 6 point | £952.56 |
| Tillett B6 Screamer GRP | FIA 8855-1999 | 5.8 to 6.1kg | 6 point | £1,234.36 |
All five are sold as a seat on its own. Mounts and harnesses are separate.
How they go in
Tillett’s own advice for a cockpit this narrow is to bottom mount instead of side mount, and they publish hole centres for both on the B6 drawing. In a Seven the floor is usually flat and accessible, which makes bottom mounting straightforward and keeps the seat as low as it will go.
If you want the seat to move at all, there is a runner kit that suits the B6 and the W1i for £22.80 inc VAT. On a car you built around yourself you may not want one, and plenty of Seven owners bolt the seat where it lives and forget about it.
One thing to avoid. There is a Tillett low profile kit that people find while searching and assume is for cars like this. It is not. It solves seat to roofline clearance in low roofed GT cars, and your Locust has no roof, so it is solving a problem you do not have.
Send us a photograph of your floor with a tape across it and we will tell you what the seat wants to sit on.
Common questions
Is a Locust really the same as a Caterham for seats?
For the shortlist, near enough. Narrow cockpit, no roof, tunnel in the middle, so the same shells come up. Where it differs is that a Caterham cockpit is a known quantity and yours is whatever the builder made, which is why we keep going on about the tape measure.
Which of the five would you fit?
Depends entirely on whether anybody is scrutineering the car. If not, the W1i for the weight or the B6 if you want the headrest. If yes, the Screamer if the budget is there and the Sprint if it is not. There is no wrong answer among the five, only a wrong answer for your car.
Can I cut the rolled edges down myself to get it narrower?
No. It is a build option, specified before the seat is made. Taking a cutter to a finished shell is not a fix and on the Screamer it would be the end of the homologation. Decide the width at order, which means measuring first.
Will two seats definitely fit side by side?
In most Sevens, yes, at 40cm. In yours, we genuinely do not know until somebody measures it, and neither does anyone who tells you otherwise. Two measurements and a photograph settles it in one phone call.
Does the Sparco Sprint fit a narrow cockpit as well as a Tillett?
It is a different shape and it was not drawn for a Seven the way the Tilletts effectively were. It base mounts, which helps on a flat floor. Send us your measurement and we will tell you honestly whether it goes in, because at that price it is worth knowing either way.
What about harnesses?
Seven type cars have their own listings with the strap lengths cut to suit, which is better than a universal set with a yard of spare webbing in the footwell. Tell us which seat you have gone for and whether you need four point or six, and we will put the right one with it.
Measure it, then ring us
Tunnel to sill at the floor, both sides, and a photograph of the cockpit. That is all we need to tell you which of the five goes in and which width to order it in.
Kit cars are the jobs Cameron enjoys most, mainly because no two turn up the same. Ring the showroom on 0115 9893488 and we will go through it with you.
