Rebuilding seats

If you hate the seats in your car, take a long look at this. In this article we show you how you can start with seats that are not great in comfort and support – and end up with something that feels better than a Recaro. Exaggeration? Nope – these seats are now superb.

So if your car has poor seats, why not simply fit aftermarket seats – or some really good seats from another car? Trouble is, changing your car seats for new ones can be a real hassle – there are the legal and insurance implications, not to mention the problems of fabricating brackets. In the case of the Honda shown here, there was another obstacle – the seatbelt (both sides of it, not just one) attaches to the seats. That means that any replacement seat needed to have this feature – and that’s quite rare.

Note that you’ll need a fair amount of home workshop equipment to modify the seats in the way shown here – a MIG welder, small tube bender, angle grinder and assorted hand tools were used. And a final note: after rebuilding your seats you’ll need to get them re-trimmed, so that cost also needs to be taken into account.

Airbags If your car seats have airbags within them, we do not recommend that you make seat modifications. But if you chose to do so, at minimum you must have the factory procedure for disabling and handling airbags, and any seat padding changes that are made must not affect the placement or support of the airbags.

Starting point

The seats were in a 2001 Honda Insight. They might look the right shape but in fact they lack side and lumbar support. In a previous iteration, we stripped the seats and added just new foam bits that fitted under the standard seat trim – see Reshaping Factory Seats. This worked fairly well, but we figured that since the seats were also going to be re-trimmed this time, we may as well go for broke in terms of changing seat shape.

The seats were removed from the car – this is the driver’s seat. Be careful when removing seats – it’s easy to damage door panels or scratch sill trims.

The upholstery trim on these seats unzips and unclips. Other seats might require just unclipping.

Carefully peel off the original upholstery. You don’t want to rip this - even if it’s not being reused, the trimmer will want it as a partial template for the new trim.

You can cut the C-clips with a pair of strong side-cutters.

The stripped seat. Inspect the foam carefully to ensure it hasn’t split or degraded. If it is in poor condition, source another factory seat or, if you can, just a replacement foam. If the foam has only a few minor splits, these can be glued back together.

The foam removed from the frame. Don’t be devastated if the frame is rusty – most car manufacturers don’t paint or coat the steel of the frame. In the case of this Honda, just the lower part of the frame was painted. If the frame is rusty and you want to fix it, get the frame blasted and then paint it.

Making decisions

So now the seat is in pieces – what next? The next step is to explore changes in seat shape to give it the comfort and support that you want.

Place the foam back on the seat and then, working with the help of another person, sit in the seat and then get the other person to change the seat shape. For example, if they hold pieces of foam firmly against each side of your back (like side bolsters), is the seat improved? If so, how high can these bolsters go before they become uncomfortable under your arms? Or, if the seat already has side foam bolsters, and these are pushed inwards, is the seat better?

You can explore in this way side support (upper), side support (lower), lumbar support, under-bum cushioning – and so on.

At this stage you don’t need to have precise measurements of the required changes, just an indication of where the seat shape needs to be altered.

Unless you’re the only person who is ever in the car, it’s important that you get a variety of people to sit in the seats. People are different shapes and sizes and what is just perfect for you might be very uncomfortable for a woman with wide hips, or for a child.

When I previously changed just the foam of these seats, I added foam extensions to both the lower and upper bolsters. These extensions worked well, but their support could have been much improved if the shape of the underlying steel frame had stopped them splaying with body weight. In other words, the bolsters were the right shape until someone sat in the seat, whereupon they tended to fall away.

So in the case of the seats shown here, the next step was to start trialling changes to the steel frame itself, aiming at improving support of the side bolsters.

Using bits of steel tube or similar, tack weld them in place and then fit the foam back over them. You need to do this slowly and carefully – at this stage you don’t want to start cutting up the foam and so the foam will need to fit around, and on top of, the steel additions.

Modifying the upper frame

After lots of trialling, measuring and assessing with different body shapes, we decided to add four new steel pieces to the frame. Each of these was designed to internally support a side bolster – two on the bottom part of the seat and two on the back.

The shape of the steel addition matches the shape of the final foam bolster. This addition was made from round tube, 19mm diameter x 1.6mm wall. Tube is good in this application because it has strength but does not present any sharp edges. Ensure that no sharp edges could slice through the foam (and maybe you) in an accident. This tube was bent in a bench-mounted, small hand-bender.

The side rail was MIG welded into place. Note that the steel from which seat frames are made is quite thin – it’s easy to blow holes in it when welding.

The two new side rails in place. Before fully welding them like this, ensure that they are the right shape!

So that the foam could fit back over the modified frame, two longitudinal slits were made in the foam. Depending on the foam type, a long sharp knife or even a hacksaw blade can be used to make this incision. You can see from this pic how the steel tube addition strongly supports the foam bolster.

The next step is to shape some foam to suit the revised side bolster. Note that you must use high density foam – it needs to maintain its shape under pressure.

This bent wire guide shows the shape in the foam addition that is being aimed for. The guide can be used to ensure that the bolsters each side of the seat are the same shape.

The foam is shaped using a variety of techniques. An electric carving knife, sharp knife and scissors can be used to rough shape it. Fine tuning can then be carried out with a belt sander and a sanding disc in an angle grinder or similar. Be careful that the sanders don’t yank the foam from your hands. You don’t need to get the external shape perfect at this stage.

Using contact adhesive, the new foam can then be glued to the original. Note how this is being done with the steel frame in place – the shape needs to be held correctly before you add the new foam. Try not to glue the new foam to the steel frame – you want to be able to still remove the foam from the frame. Follow the glue instructions exactly – this bond needs to be good!

Use bulldog clips or similar top hold the foam edges together as the glue dries. Note how the clips here are being used to hold the edges of the incision (made in the original foam) together as well. Let the glue thoroughly dry before undertaking the next step, which is to shape the foam to its final dimensions. I found the use of a sanding disc in an angle grinder best for this - be very careful as it’s possible to easily remove too much material.

Modifying the lower frame

The lower frame was modified with the addition of these curved steel tubes. Again, they were bent in a hand bender.

Initially, these bits were just butt-welded to the top of the seat frame but when they were trialled on the workshop floor, I found that people bent the pieces as they pushed down on them with their hands as they were getting out of the seat. This meant that they steel hoops needed to be remade, with strong welds that connected them to the side of the seat frame as well as the top.

To allow the lower side hoops to support the foam, the seat base needed to be cut in this way.

This shows how the hoop (now painted black to match the rest of the seat’s lower frame) fits through the modified seat foam.

The outer section of original foam could then be glued back into place – again, be careful not to glue it to the steel frame! With this piece back into place, new foam can be added over the top.

Here is the seat with the steel extensions and new foam in place. At this stage the foam needs to be tidied a little and given a final sand to shape.

Trialling

The next step is to place the seat back in the car, covering it with an old sheet or similar. Then drive the car – leaving the seat in the car in this form for a week or two.

This step is vital – you must find out what the seat is like in normal service. Do you get a numb bum – or legs? Is what felt nicely snug when trialling the seat on the workshop floor claustrophobically enclosing when you’re in the seat for hours at a time?

In the seats pictured here the greatest concern with they were fitted to the car was easily getting in and out. The side bolsters – especially on the seat back – make it much harder to slide in and out of the seat. Basically, you cannot in fact slide in and out; instead you need to fit your body past the bolster before sitting back in the seat. Furthermore, the bare foam of the seat bolster wore very quickly – with the seat in its final trimmed form, this will also be a high wear area.

Trimming

The final step is to take the modified seat to a trimmer for re-trimming – and that’s beyond the scope of this story.

Conclusion

Very few people seem to make wholesale modifications to their seats but as this story shows, it can be straightforward and the results outstanding. The modified seat has proved to be brilliantly comfortable. In fact, at a car show I was able to take advantage of the availability of a range of Recaro seats to sit in. Both my wife and I are convinced that my modified seat is better than any of the Recaros we sat in – better for us, anyway…