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My Bucket Seat Is Too Big. How Do I Pad It Out?
Seat fit, your questions
A call came in last week that we get more often than you might think. The caller had a Corbeau Revenge XL, it was a bit too roomy, and they wanted something cheap and quick to tighten it up. They were thinking a bit of padding, nothing as involved as a moulded insert.
Cally took the details and passed it over, and it started a proper argument on the shop floor. Cameron's first question was how big is a bit big. Garreth's was whether it was ever the right seat in the first place.
They are both right, and which one of them is more right depends on how much room there is in that seat.
- Padding is for the last inch. If the shell is a whole size out, a smaller shell is the answer
- On an FIA 8855-1999 seat, a cushion between you and the seat can be up to 50mm thick
- Anything added to an FIA seat has to meet the ISO 3795 flammability standard
- Side kidney cushions close up a seat that is too wide at the waist and ribs
- A flattened cushion set makes any seat feel bigger than it is. Fresh cushions come first
- A moulded insert, foam or bead and resin, is the proper made to measure fix
- Check the harness shoulder slots again after you add anything under or behind you
First, how much too big is it?
Everything else in this guide hangs off that question, so it is worth ten minutes with a tape measure before you spend anything.
Sit in the seat in the clothes you drive in, belts done up properly. Then put your hand flat between your hip and the side of the seat. A finger or two of space is a padding job. A whole hand is a different seat.
Garreth is firm on this one. A bucket seat holds you by being close to you, and a shell that is a full size too big cannot do that however much you stuff into it. Motorsport UK make the same point in their own seat guidance: a seat that is too big lets you come out of it, and too much foam takes away from what the seat was designed to do.
Cameron is a bit more relaxed about the in between. Plenty of people buy the XL because they are right on the line between sizes, and on those, a little padding in the right place is exactly what the fix should be. Where they meet is that padding sorts out the last inch. Past that, you want the next shell size down.
The Revenge XL, and why the standard one might be the answer
The Revenge comes in two widths and they are sized by waist. The standard shell suits a 32 to 36 inch waist, and the XL suits 36 to 40. The XL is the same deep shell with lateral head support, cut wider through the hips. If your waist is 36 or 37 inches, you are at the bottom of the XL range, it is going to feel roomy, and that is the seat doing what it was built for.
Before anything else, Cameron would want your waist measurement. If it puts you in the standard shell, the tidy answer is the standard Revenge, and a Revenge XL in good condition is an easy seat to sell on to somebody it does fit. If you are genuinely in the XL band and just on the slim side of it, read on, because a pair of side cushions will sort you out.
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What you are allowed to add to an FIA seat
If the seat has an FIA label and the car gets scrutineered, the padding question has a rulebook answer. The FIA’s own seat rules, Appendix J article 253-16, say the seat itself must not be modified. Padding that goes between you and the seat is allowed, within limits.
| Seat standard | Padding between you and the seat | Anything added to the seat |
|---|---|---|
| FIA 8855-1999 | A cushion up to 50mm thick | Must meet ISO 3795 flammability |
| FIA 8855-2021 | A foam insert is allowed, as long as the seat still gives the minimum support at your head, shoulders and hips | Must meet ISO 3795 flammability |
| Road and track day seats | Whatever keeps you held in place | Nothing formal, but the same sense applies |
On an 8855-1999 seat, which is most of what we sell, 50mm is the most a cushion can be. That is plenty to take up a finger or two of space and nowhere near enough to turn an XL into a standard. And anything you add has to meet the ISO 3795 flammability test, so check that whatever you fit says it does. The Totim and Schroth insert kits both state it.
Plenty of championships write their own padding rule too. Castle Combe’s Hot Hatch regulations, for one, allow extra seat padding up to 50mm and ask for it to be fire retardant. Read your own series regulations, because they are what the scrutineer will have in front of them.
A road car or track day seatNone of the FIA rules apply to a seat that never goes near a scrutineer. The sense of them still does, so we would still use a proper cushion over a bit of foam from the shed.
The quick fixes for a seat that is only just too big
This is what the caller was after, and for a seat that is only a little out, it is usually all you need.
Which one you want depends on where you move about. Loose at the waist and ribs is the cushions, a seat that has gone soft is a new cushion set, and one empty area is the Totim padding.
Side kidney support cushions
The Endurance Motorsport pair clip into the side bolsters of a fixed back bucket seat and bring them in against your waist and ribs. They are made for exactly the seat that fits your height and legs and is just too wide through the middle, and at £30 they are the first thing Cameron reaches for on a road or track day car. They carry no fire rating, so they are for cars that do not get scrutineered. On a competition car, the Totim padding below does the same job and meets the flammability standard.
A fresh cushion set
This one catches people out. Seat cushions flatten with use, and a tired set makes the whole seat feel a size bigger than it is. If the Revenge has done a few seasons or came to you second hand, a new Revenge XL cushion set at £109.80 might be all it needed. Check the label under the seat first, because the standard and XL sets do not swap.
Totim insert padding
The smallest size Totim make, 60 x 50cm, is sized for filling part of a seat. It is the same moulding foam as their full kits, so you can take up the space in one area, such as the hips or behind your back, without doing the whole seat.
Other brands make fill out pads for their own seats. Racetech do side cushion sets for smaller hips and thighs, and Bride do tuning pads for the head, sides, knees and lower back. We do not list those, but if you have one of those seats, ring us and we will find out what is available for it.
Seats that are built to be re-padded
If you are still choosing a seat, and you know you sit between sizes, it is worth knowing some shells are designed around this problem.
Cobra’s PRO-FIT system is the best example. One shell, and separate cushions for the back, the base and under your thighs that come in different thicknesses. Cobra put it at up to 18 combinations per seat. Swap the backrest for the thinner one and you sit further back; keep the standard one and you sit further forward. They fit the PRO-FIT seats named in the listing, the Suzuka and Imola among them, and nothing else.
Garreth likes these for anyone buying for more than one driver, because the seat can be set up for whoever is in it that weekend.
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The proper fix: a moulded insert
When the seat is further out than a pair of cushions can sort, or when you want the seat to fit you exactly, a moulded insert is what the professionals do. There are two ways of making one, and we sell both.
Foam in a bag
The Totim kits are polyurethane foam inside a flame retardant bag. You squeeze the bag to mix the two parts, sit in it while it expands around you, and about 20 minutes later it has set to your shape. An hour after that you can trim the edges. There is no pump or hose to buy with it, and the kit is certified to the 3795 flammability standard.
Beads and resin
The Schroth Profi Seat Kit and the Real Race kits work the other way round. The bag is full of small beads, resin goes in, you sit in it, and a vacuum pulls the lot down around you while the resin cures. Schroth quote a 30 minute set, and their kit is used across single seaters and touring car racing. Our guide to the Real Race kits goes through that side of it, fire standards included.
Cameron’s view is that either is a proper afternoon job and you want a second pair of hands, one to sit and one to hold the bag. Garreth’s is that if you are going to that trouble in a seat that was the wrong size, you may as well have bought the right seat. They have not agreed on that one yet.
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Once it is padded, check the harness again
Anything you add changes where you sit. A cushion under you lifts you, and a cushion behind you moves you forward. Both change how the harness shoulder straps meet your shoulders.
Motorsport UK’s seat guidance points out that when the shoulder slots end up below your shoulders, tightening the harness pulls down through your spine. So after the padding goes in, sit in the car, do the belts up, and look where the straps come through. If they now come from below your shoulders, there is too much under you. Take some out.
Common questions
Can I use memory foam or a camping mat?
In a road car, it is your call, though it compresses and moves about. In a seat that gets scrutineered, anything added has to meet the ISO 3795 flammability standard, and household foam and camping mats are not sold with that. Use a pad or insert that says it meets it.
How thick can a cushion be in an FIA seat?
On an FIA 8855-1999 seat, 50mm between you and the seat. On an 8855-2021 seat there is no thickness figure; instead the seat has to keep a minimum of support at your head, shoulders and hips with the insert in. Your championship may have its own rule too.
Does adding padding void the FIA homologation?
The FIA rule is that the seat itself must not be modified. A cushion that sits between you and the seat, within the thickness limit and to the fire standard, is allowed for. Cutting, drilling or gluing into the shell is a different matter.
Does Corbeau make thicker cushions for the Revenge?
Corbeau make replacement cushion sets for the Revenge, in standard and XL. They restore the seat to how it left the factory; they are not thicker than standard. For taking up space, side cushions or insert padding do that job.
Will side cushions work in any bucket seat?
The Endurance Motorsport cushions clip into the side bolsters of a fixed back bucket seat. Send us a photo of your seat and we will tell you if they will sit properly in it.
Is an insert kit a one person job?
Not really. Someone has to sit in it while it sets and someone has to hold the bag in place and, on the bead kits, work the vacuum. Plan it as an afternoon with a mate.
Should I just buy a smaller seat?
If you can fit a whole hand between your hip and the side of the seat, yes, that is what we would do. Send us your waist and height and we will tell you which size you are.
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Two measurements settle most of thisYour waist, and where you move about
Send us those with the seat you have, and we will tell you whether it is a £30 pair of cushions, a fresh cushion set, an insert kit or a different shell.
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