Can You Side Mount A Big Tillett Seat Like The B10 XL Straight To The Floor Of A Mini R53?
An owner with a Mini R53 asked us whether a big Tillett seat, something like the B10 XL, can go on side mounts bolted straight to the floor with no subframe. He had looked at the Cobra Mini side mounts, and Garreth steered him away from them because they do not have enough adjustment or bolt holes to do the job. Two of our own R53 customers have bolted FIA side mount seats to the floor with Endurance Motorsport multi-point brackets. So the mounting works, and the question for a wide Tillett is whether the shell fits the cabin.
- Built from our two R53 customer cars and our Tillett fitting guide
- Tillett shell widths taken from our listings
The floor route works in an R53, and the width of a big Tillett decides the rest
Two R53 customers bolted FIA side mount seats straight to the floor with Endurance Motorsport multi-point M8 side mounts. Tillett do not make a Mini kit, and the XL shells are wide for a car this tight, so we measure the cabin and compare the holes on your exact model before anything is ordered.
- Endurance multi-point brackets bolt to the R53 floor with no frame or runners
- The B10 XL is listed at 45cm with the rolled edges cut off and 48.5cm with them left on
- The largest seat we know fits an R53 is the Mirco RTS-2, at 590mm across the shoulders
- The seat is fixed, so it suits one driver
What the customer asked
The owner has a Mini R53 and a big Tillett in mind, along the lines of the B10 XL. He wants side mounts that go straight to the floor, with no subframe like the Cobra, Sparco or OMP frames. He found the Cobra Mini direct fit side mounts and asked whether they would do it.
Garreth would not recommend them for this. They have no height or angle adjustment, and there are not enough adjustment or bolt holes to place a seat exactly where you want it. The R53 owners who came to us before him did it a different way, and that is the route this page follows.
What the Cobra Mini side mounts do
Cobra make 4mm steel side mounts for the Mini that use the factory bolt points, so nothing is drilled, and they put a side mount seat low in the car. They are fixed, with no height or angle adjustment, which keeps the seat solid in one position. They suit stripped out cars, because they cannot be fitted with the carpet in place.
We recommend the Cobra Mini side mounts only for the seats Cobra say fit them. Cobra’s own table lists the Imola Pro-Fit and Suzuka Pro-Fit in standard width, the Sebring Pro-Fit LP in standard width and the Ultralite, and the listing strongly recommends using the mounts with Cobra seats. The wider GT versions are not on the table, and neither is a Tillett. Our Cobra Mini side mount guide has the full table.
The floor route our R53 customers used
The first customer wanted a Mirco RTS-2 as low as it would go, right back against the roll cage. He used Endurance Motorsport Multi Point M8 side mount brackets bolted directly to the R53 floor, with no base frame and no runners. He made three small changes: no frame, one hole on each bracket opened out slightly so it met the Mini’s factory bolt holes, and some carpet trimmed back to clear the wider spacing. The full story is in our guide to mounting a seat super low in an R53.
The second customer is 6ft 3in and was cramped on Sparco R100 reclining seats. He fitted a pair of Sparco Evo L seats on the same brackets and said the installation was relatively straightforward and did not need much modification. The rows of holes in the brackets gave plenty of height and tilt adjustment, and the R53’s flat, wide floor mounting points take them with no subframe. His car is in our Evo L customer car guide.
Both seats are side mount only, with M8 fixings at the standard 290mm side spacing, which is what the Endurance brackets are made for.
A pair of side mount seats on the floor of an R53
The bigger Tillett shells and the R53 cabin
The R53 is tight and the door cards come in close. The Mirco RTS-2 uses the space right up to the door cards and the centre tunnel, so we treat its size as the limit: 590mm across the shoulders, 500mm at the base and 915mm tall, from Mirco’s drawing. Our R53 guides say to avoid XL seats unless you have measured the car carefully, and a wider or taller seat than the RTS-2 is unlikely to go in.
That is the point to settle before a big Tillett. Tillett quote one width for each shell, taken with the rolled edges either left on or cut off, so it is not the same measure as Mirco’s base width. We compare them at the car, between the tunnel and the sill, with you in the seat. These are the widths on our listings:
| Tillett shell | Width, edges cut off | Width, edges left on | Notes from our listing |
|---|---|---|---|
| B6 | 40cm | 44cm | Standard B6 suits a 32 to 36 inch waist |
| B6 XL | 43cm | 47cm | 30mm wider inside, 36 to 40 inch waist |
| B8 | 43cm | 44.5cm | Twin moulding, shaped for a bigger car |
| B10 | Not listed | 44.5cm | Cut away sides to keep the standard three point belt, higher headrest, quoted to 100kg and around a 36 inch waist |
| B10 XL | 45cm | 48.5cm | Same cut away sides, 30mm more room inside, against 44cm on the standard B10 |
Two things on those listings matter in an R53. The B10 and B10 XL have a higher headrest than the B6, which counts when the roof is low. And the B10 XL listing itself says the extra width is a real difference in a saloon with a close transmission tunnel, so measure before you order. If a big Tillett is the seat you want, the narrower edges cut off version is where we would begin.
Garreth’s advice is to come and sit in the seat first, with your height and waist measurements to hand. Our Mini R53 and R56 bucket seat guide lists other seats for the car if the shell turns out too wide.
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Where Tillett brackets differ
Tillett fit their side mounts to the seat in their own way, so we look at the seat before we look at the bracket. Our Tillett compatibility guide lists what we check. A standard B6 or B6 XL is sold in a bottom mount and a side mount version, and only the side mount version has the inserts for side brackets. The B7 uses integrated side mount positions.
Tillett’s generic side mounts, the STBI, STBO, VTBI and VTBO, carry a common 2 degree angle for the B6, B7, B8, B9, B10 and C1 families. Inward brackets tuck under the shell and give the smallest footprint, which is the useful one in a tight cabin, and outward brackets spread away from it and make the fasteners easier to reach.
Tillett’s guidance for fixing a seat to the car is to use the manufacturer’s vehicle kit or a properly engineered mounting structure. The vehicle kits in our guide cover Lotus, Mazda MX-5 and the Emira, and none of them is for a Mini. So there are two routes for an R53: the Endurance brackets at the floor, if the Tillett’s side holes match the 290mm spacing and M8 thread they are made for, or a Tillett bracket on a floor interface made to suit the R53. We compare the holes on your exact model before we say which.
A fixed seat, and what that means
Both customer cars have no runners, so the seat cannot slide. That suits one driver who knows the position, and a shorter driver sharing the car would struggle. Tillett also say their adjustment runners are intended for road use and advise against them in a race car.
A fixed seat keeps nothing moving under hard braking and cornering. Moving the seat also changes where you sit relative to the lap, shoulder and buckle anchorages, so we check the belt geometry again with you in the seat, and our harness fitting guide shows the angles.
What to send us
Photographs between the tunnel and the sill usually settle more than a remembered bracket code. Send us these and we will say what goes in.
| What we need | What it decides |
|---|---|
| The exact Tillett model, width option and side mount or bottom mount | Whether the shell has inserts for side brackets, and how wide it is in the car |
| A photo of the floor between the tunnel and the sill | Inward or outward brackets, and where the carpet needs trimming |
| Your height, and whether you wear a helmet | How low the seat has to sit in a car with a low roof |
| One driver or shared | Whether a fixed seat suits, or whether you want adjustment |
| Your harness plan and cage | Where the belts anchor once the seat has moved |
Common questions
Can I bolt side mounts straight to the floor of a Mini R53?
Yes. Two of our customers did it with Endurance Motorsport Multi Point M8 side mounts on the R53’s flat floor mounting points, with no subframe or runners. One hole on each bracket was opened out slightly and some carpet was trimmed back.
Will a Tillett B10 XL fit an R53?
We cannot say from the listing alone. It is 45cm wide with the rolled edges cut off and 48.5cm with them left on, and the R53 is tight. We compare it at the car, between the tunnel and the sill, before you order.
Do the Cobra Mini side mounts suit a Tillett?
No. We recommend the Cobra Mini mounts only for the seats Cobra say fit: the standard width Imola and Suzuka Pro-Fit, the Sebring Pro-Fit LP in standard width and the Ultralite. They are fixed with no height or angle adjustment and suit stripped out cars only.
Will the Endurance brackets fit a Tillett?
They suit seats with the standard 290mm side hole spacing and M8 fixings. Tillett brackets are matched to their own shells, so we compare the holes on your exact model before you order.
Does a standard Tillett B6 take side mounts?
Only the side mount version does. The B6 and B6 XL are also sold as bottom mount seats, and a side bracket cannot add inserts the shell lacks.
Can I run the seat on runners?
Our customer cars use no runners. Tillett say their runners are intended for road use and advise against them in a race car.
How big a seat will the R53 take?
The largest seats we know fit well are the Mirco RTS-2, at 590mm across the shoulders, 500mm at the base and 915mm tall, and the Sparco Evo L. Avoid XL seats unless the car has been measured.
What should I send you?
The exact Tillett model and width option, a photo of the floor between the tunnel and the sill, your height, whether the car is driven by one person, and your harness plan.
What we would do
Garreth
Garreth's top tip
Keep the Cobra Mini mounts for the Cobra seats on their table. For a Tillett, take the floor route our R53 customers used: Endurance multi-point M8 side mounts straight to the floor, with the seat set as low as the rows of holes allow. It gives you the adjustment the Cobra mounts cannot.
Come and sit in the big Tillett first with your helmet, because in an R53 the width and the roof decide.
Cameron
Cameron's fitting view
Send me the Tillett model code and a photo between the tunnel and the sill. I will check the shell width against the cabin, compare the side holes with the 290mm and M8 the Endurance brackets are made for, pick inward or outward, and show you where the carpet needs trimming.
With the seat in, I check the belt angles before anything is tightened for good.
Want a big Tillett in your R53?
Tell us the seat model, the car year, your height and whether you drive alone. Cally, our digital receptionist, takes your details, and Cameron comes back with the mounting route.
