Fitting sports seats when your car has no direct-fit frame
There is no seat frame listed for my car, so can I still fit sports seats? We hear that from owners of classics like the MGB and the Karmann Ghia, and from owners of newer cars no frame maker has covered. Yes, you can. The seat still needs something solid to bolt to: a universal frame or a base a fabricator makes, with the side mounts, sliders and seat from us, and Cameron checks your car before anything is ordered.
- Every part on this page is a live SportSeats4U listing, prices checked on 13 November 2026
- Cameron checks your floor, your seat and your measurements before anything is ordered
- Side mounts, sliders and seats come off the shelf; only the base is made for your car
OMP Universal Weld In Seat Frames
£107.40inc VAT, one kit as listed
The one universal frame we list. It is welded in, so the base becomes part of the car, and the side mounts, sliders and seat bolt on top.
- Two 35 x 35mm steel tubes, 600mm long
- Four weld in plates and four support brackets with M8 bushings
- Takes side mounts, a base mount seat or sliders
- Permanent, so it needs someone who can weld properly
Why we wrote this guide
As a retailer we source seat frames from as many makers as we can, from Planted Technology to Sparco, OMP, Cobra, Corbeau, PCI Racing, M2 Motorsport and SW Motorsport. Between them they cover most of the cars people search for on this site, so it is rare for us to have nothing at all. Now and then it happens, mostly with a classic and once in a while with a car so new that no frame has been made for it yet.
Those owners still want sports seats, and the seats fit once the right base is under them, so when our finder shows no frame for your car it links to this page. Here are six such cars, each checked in our finder on 13 November 2026 with no direct-fit frame or side mount listed.
Six cars we list no direct-fit seat frame for
Ford Mustang (S650)
The current Mustang: we list frames for the S550 before it, and nothing yet for the S650.
Audi RS3 8Y
A new car with nothing in our finder yet: no frame, bracket or side mount.
Ford Capri Mk1
We list roll cage parts for the Mk1, and no seat frame.
BMW 2002
Cage parts are listed for it, with no seat frame or side mount.
Hillman Imp
The small rear-engined Imp has cage parts listed and no seat frame.
Volkswagen Karmann Ghia
It sits on a widened Beetle floor, so the Beetle frames we list are the wrong part for it.
What Cameron checks before anything is ordered
The frames on our site for each car are the full range we sell, so with none for yours the build starts at the floor, and the first job is Cameron’s. Before he puts a parts list together he wants five things from you.
- The registration, so he knows the exact car and year.
- Photos of the floor where the seat sits now, ideally with the standard seat out, showing the mounting points, the tunnel and the sill.
- The seat you want, or the shortlist. Whether it bolts through the base or through the sides decides everything that goes under it.
- Your height and waist, and whether you drive in a helmet. Headroom is usually what sets how low the base has to be.
- Whether you are keeping the standard seat belts, and where the buckle lives today.
From that Cameron works out the stack, from the floor up, and tells you which parts we supply and which part your fabricator makes. Drop us an email or click to open a chat with the photos and he will come back to you.
How a seat goes in, from the floor up
A direct-fit frame is only a base cut to suit one car’s floor points, and with that taken away, every other layer of the job is the same as on any other car.
Bucket seats bolt through their sides, so the order runs floor, base, sliders if you want them, side mounts, then the shell. Reclining sport seats bolt through their underside to runners, which bolt to the base.
| Layer | What it does | Where it comes from |
|---|---|---|
| Seat | Bolts through its sides (bucket) or its base (reclining) | Off the shelf |
| Side mounts | Carry a bucket seat and set its height and angle | Off the shelf, any standard side mount |
| Sliders or runners | Fore and aft adjustment, if you want it | Off the shelf |
| Base | Fixes to the floor and gives the rest a flat, strong platform | The OMP weld in frame, or made by a fabricator |
| Floor | Takes the load through the car's own mounting points or welded plates | Your car |
Base mount reclining seats skip the side mounts: runners bolt straight to the seat.
The numbers your seat brings with it
Whoever makes the base needs the seat’s numbers before they cut anything, because the holes in the base, the runner and the seat all have to line up. Our seat bolt patterns explained guide covers each brand in detail.
| Seat | How it fixes | The number to give your fabricator |
|---|---|---|
| Sparco and OMP base mount seats | Through the base | 345mm x 271mm |
| Corbeau base mount seats | Through the base | 291mm or 345mm wide, runner chosen to match |
| Cobra base mount seats | Through the base | 291mm wide on most frames |
| Most bucket seats (Sparco, OMP, Cobra, Mirco, Sabelt) | Through the sides | Standard 290mm side hole spacing, M8 bolts |
| Corbeau bucket seats | Through the sides | Standard spacing, M10 bolts |
Recaro direct-fit frames are not being made until the end of 2027 and Recaro seats are not expected before 2027.
When the base and the seat end up on different patterns, adapter bars bridge the gap without new holes in the base: the Corbeau to Sparco base mount adaption bars do the job between the 291mm and 345mm patterns, and the Endurance adapter bars take a seat from a 405mm base.
OMP universal weld in frames: the off-the-shelf base
This is the one universal seat frame we list. Two square steel tubes are welded to the floor, running from the inner sill across to the centre tunnel, and they make a permanent platform for side mounts, a base mount seat or sliders. OMP’s kit also carries four weld in plates and four support brackets with M8 bushings.
It stays once welded in, so on a car with real value or originality a bolted base from a fabricator is often the kinder route. On a dedicated track or competition build it is the quick answer, and with a good welder and a car you are building to keep, Garreth would start here.
- £107.40 inc VAT, one kit as listed
- Two 35 x 35mm steel tubes, 600mm long
- Four 80 x 60 x 3mm weld in plates
- Four 60 x 40 x 3mm support brackets with M8 bushings
- Welded between the inner sill and the centre tunnel
What a fabricator makes, and what to hand them
We do not have frames made to order for single cars. The answer for a car with no frame is a custom install: a fabricator makes a flat, strong base that fixes to your floor, and everything above it comes from us. Many fix it to the car’s own seat mounting points, which leaves the floor as it was, but how it fixes is their call once they have seen the car.
A good fabricator will ask for most of this anyway, so having it ready saves a second visit.
| Hand over | Why it matters |
|---|---|
| The seat itself, or its bolt pattern or side hole spacing | The holes in the base have to match it |
| The side mounts and sliders you are using | Their feet set where the base holes go and how wide it is |
| Your seated height and helmet use | Sets how low the base can sit |
| Where the standard seat bolted down | Usually the strongest place to fix the new base |
| Where the seat belt buckle goes | Motorsport bases carry no belt fixing, so the buckle needs a planned, solid home |
| Cameron's notes on your car | The measurements and the parts list in one place |
Side mounts: any of these fits a standard bucket
Side mounts are universal by design. Any of the four below bolts to any standard side mount bucket seat, so you choose them on height adjustment, material and price. The Endurance steel M8 pair is the simple one with one fixed height. The Endurance multi point brackets have several rows of holes, so the seat can go up or down after the base is in, which helps when the base is new and the driving position is still being found.
Planted’s steel 90 degree mount is FIA approved and built around the vertical side fixing most competition seats are designed for. The QMS listing is two pairs in one order, enough for two seats. Cameron’s tip on all of them: a Corbeau shell uses M10 fixings where most brands use M8, so tell us if yours is a Corbeau and we match the bolts to it.
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From £34.80 Incl. VATPayPal CreditSelect options This product has multiple variants. The options may be chosen on the product page
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Sliders and runners, if the seat needs to move
A car that more than one person drives wants a seat that moves. Sliders go between the base and the side mounts on a bucket seat, and straight under a base mount reclining seat. They suit road cars and track days. A competition car normally runs the seat fixed, and a slider lifts the seat a little, so measure the headroom first if a helmet is part of the plan.
The Sparco kit bolts to the 345mm x 271mm pattern, so it suits Sparco, OMP and Corbeau base mount seats, and under side mounts it moves a bucket. The Endurance kit is the entry option for side mount buckets. PCI’s universal sliders bolt down with four bolts each, adjust across a wide range of widths and are made to add movement to a fabricated mount.
Adapter bars, when the base and the seat disagree
Sometimes the base or the sliders end up on the wide 405mm pattern and the seat you want is narrower. These steel bars bolt across the sliders or frame rails at 405mm and take the seat at 345mm or 291mm, so nothing has to be redrilled.
They are sold as a pair, which is one seat. From the floor up the order is base, sliders, bars, then the seat. They add a little height under the seat, so Cameron allows for that when the cabin is tight.
- £47.40 inc VAT, a pair for one seat
- Bolt down at 405mm wide
- Take a seat at 345mm or 291mm
- Stack: base, sliders, bars, seat
Common questions
There is no seat frame listed for my car. Can I still fit sports seats?
Yes. The seat needs a strong base under it, and without a direct-fit frame that base is either the OMP universal weld in frame or one a fabricator makes for your floor. The side mounts, sliders and seat are the same parts any other car uses.
Can you get a frame made for my car?
We do not have frames made to order for single cars. A fabricator makes the base, and we supply everything that bolts to it. Send Cameron your floor photos and the seat you want and he will give you the parts list and the numbers to hand the fabricator.
Will the frame for a similar car fit mine?
Only the frames listed for your car are ones we stand behind, because floors differ even between close relatives: the Karmann Ghia sits on a widened Beetle floor, so a Beetle frame is the wrong part for it.
Do I have to weld anything?
Only if you choose the OMP weld in frame; a fabricated base can often bolt to the car’s own seat mounting points, and your fabricator decides once they have seen the floor.
Can a bucket seat still slide forward and back?
Yes, with a pair of sliders between the base and the side mounts. That suits road use and track days, and a competition car normally runs the seat fixed. Cameron will tell you which sliders suit your seat.
How do I find my seat's bolt pattern?
Our seat bolt patterns explained guide lists each brand. If you have the seat already, measure across the bolt holes and send the figure with a photo, and Cameron will confirm it.
What we would do with a car that has no frame
Garreth
Garreth's top tip
Choose the seat before anyone cuts metal, because the seat's pattern and its side mounts decide the shape of the base.
On a build you are keeping, the OMP weld in frame is quick and strong. On a car with value in its originality, have a fabricator bolt a base to the standard points and keep the floor as it left the factory.
Cameron
Cameron's fitting view
Floor photos with the old seat out tell me more than anything else. I look at where the old seat bolted down and how much room the tunnel leaves, then I work out the stack and the height.
Plan the seat belt buckle at the same time as the base: a motorsport base has no belt fixing, and it is far easier to give the buckle a solid home before the base is finished.
No frame listed for your car? Start with Cameron
Ring us with your registration and the seat you have in mind. Cally, our digital receptionist, takes your details and Cameron comes back to you with the parts list and the numbers to give your fabricator.
