One task that looks dead easy - until you try to do it - is installing secondhand seats. But why'd you want to do that, anyway?
Nothing dates a car more than its seats. Get into a car out of the Sixties and Seventies and you just wonder what the designers were thinking - flat, formless and unsupportive seats abound. There's no such thing as holding you in place, nor for that matter supporting your lower back. And seat adjustment? Well, forwards and backwards will be there, but as for height height, or cushion tilt, or adjustable lumbar - forget it!
But help is as close to hand as your nearest wrecker. If you live in an area where an import wrecker does business, you'll be laughing. That's cos these seats are available for ludicrously low dollars - like, less than AUD$150 will get you a pair of good-looking, comfortable and supportive seats. And let me assure you, if your car has awful seats, that's a damn' cheap lift in safety, comfort and driving security. And even if you have to pay more from a conventional wrecker, it's still worth taking a long, hard look at what's around.
Starting
But before you head off breathlessly to the wreckers - a few things to do first. Have a look at the colour and trim used on the originals in your car. You're not going to be replacing all of the interior trim (well, you might be - I'll come back to that in a moment) and so the new seats are gonna stand out like a sore thumb if they're not of a like colour and style. Greys and blacks are common, but if you can get away with say a dark red or blue you'll probably be able to get a pair of seats a little cheaper. Why? Simply because these are less popular.
Grab a tape measure and very carefully get down a few dimensions. Most critical is the width of the seat cushion. Seats vary in width to a surprising degree - it's not hard to check out a pair of seats that look the goods only to find that they literally won't fit in between the handbrake and the closed doors.... So, measure cushion width, then seat back height, and lower cushion length.
Make sure that the original seats are roughly 'square' (eg the seat backs don't taper as they go upwards so that they'll clear the B pillar - or something silly like that) and look at the general features needed of the seats. For example, are there releases (eg for boot and fuel cap) that are jammed in between the seat and the door? If there are, your new seats will near to clear them. Are the seatbelt buckles cut into the sides of the lower cushions - or worse still, attached to the seats themselves? (If the seatbelts are in fact hung off the seat frames, we suggest that you don't proceed with changing the seats. If you do, you're basically re-engineering the restraint system of the car.)
Have a long look under the seats and see how they're mounted. You might even want to make a simple sketch of this - not that you'll have to match this perfectly in your new pews but some similarities in the mounting system will make things a lot easier. Is your car a two-seater where the front seats must be able to tilt forward to allow entrance to the back seats? If you buy seats that only recline, you won't be too popular...
Buying
When you get to the wrecker, pick on the basis of appearance, then size, then mounting system - in that order. Once you've found a seat that looks like it will satisfy these criteria, sit in the damn thing! Most seats out of cars will not sit well on the floor - the mounting lugs are often at uneven heights, twisting or skewing the seat to one side. So support the seat properly (some blocks of wood, or a few bricks - or something!) and then get comfortable. When you're sitting there, try each of the adjustments. Do they all work? Do they give the sort of adjustment that you actually want? For example, I always like a lot of lumbar support, but not a bulge that pushes out of the seat-back right down low. So is the seat comfortable and supportive? Incidentally, be careful when leaning back in the seat - most will over-balance backwards if they're not bolted to the ground...
When you've finalised your choice, run through a quick mental checklist - size, trim, mounting system, need for certain features (eg tip forward if they're going into a two-seater.) Once you've done that, do some bargaining and then carry 'em out!
Fitting
When you get home, pull out the driver's seat (don't do the passenger one yet). Put some blocks of wood on the floor of the car and then carefully manoeuvre the new seat into place. The height at which the seat is mounted, the distance back from the wheel, and the tilt of the seat cushion will all hugely affect how happy you are with the outcome. For this reason, make sure that all of the seat adjustments are positioned in the middle of their range - for example, the seat is at the mid-point on its fore-aft adjustment track. That way, if you can sit in the seat comfortably, someone who is smaller or larger will still have enough adjustment range left. (Of course, if you are a giant or a midget, take that into account with the seat positioning!)
You'll also soon realise that in small cars you can mount the front seats further back than factory - giving you better legroom, though of course cutting into the space of the person behind you. This flexibility also means that if you like a high seating position (or a low seating position) you can tailor the installation to your preferences.
Once you are happy with the seat's position, get the other drivers of the car to sit in it. Can everyone adjust the seat so that they are comfortable? So that they have adequate vision? So that they can reach the controls? So that they can see the instruments? It's important spending the time now so that the seat is in the right position...
When everything looks jake, place a spirit level on the seat base to check that you're actually sitting on a horizontal surface. Even if the seat is angled by 10mm or more it can be hard to pick by feel alone, although sitting like this is likely to give back or muscle pain after a long drive.
OK, so finally the seat is in the right position.
If possible, leave the lumps of wood in place so that the seat can go back in at just the right height - and you might like to mark exactly where the seat is sitting on the blocks so that it will in fact go back in the same location. Once you've done that, take the new seat out and place it upside-down, with the original seat placed in the same orientation next to it. This is so you can compare the seat mounts.
It's almost never worthwhile trying to swap the adjusting mechanism from one seat to the other. Most seat tracks use rivets with very shallow heads - drill those out and replace them with bolts and the seat will jam as it tries to slide back over them. Instead, look at the mounting points of the old and new runners. With a bit of luck they'll be in similar positions and/or heights. (Of course, if you can, it makes sense to select new seats from an upgrade version of the car you already have - that way the new seats will just bolt into place and you'll wonder what the hell I'm on about when I go through all this stuff about selecting heights, making mounts and so on. And then you can also grab all of the interior update trim, and then...)
But it's much more likely that you're going to have to make new brackets to hold the new seat in place. So here's a critical question - can you still use the original seat mounting points in the car's floor? That's damned important because the factory has already strengthened those mounting points - they're designed to expect 120kg of human jumping in and out of the seat, day after day. In fact, if you look closely, you'll see how these mounts are well braced, and often adjoin (or are part of) a pressing in the floor designed to give rigidity and strength. And safety too - if someone rear-ends you, you don't want the seat breaking off.
Making the Mounts
Now there are probably design rules and legal implications and local by-laws and environmental regulations and rules of Monopoly that deal with mounting seats. And this article ignores them all. But what is does state is that you need to make your seat mounts super strong, and - as mentioned above - you don't want to change the mounts if the seatbelts are to be hung off the seats.
It's a common preconception that seat mounts only have to support the weight of you and the seat - not so. They also have to withstand acceleration forces - forwards, backwards, sideways and vertically - and have to absorb the punishment of people getting in and out. Furthermore, when you push on the brake or clutch pedals you're trying to force the seat backward - and you don't want it moving under these forces. So, make those seat mounts strong!
The easiest material to work at home is mild steel flat bar, with 40 x 5mm or similar being super-strong. However, it's not too stiff that it can't be bent with the help of a hefty vice and a big hammer. If you want to go lighter, reduce the width rather than the gauge. But a lot of what's right depends on the length of the brackets needed. If the brackets will only by 25mm long, they're much less likely to buckle than those which are 60mm long. So use common sense - but remember, these supports normally need to be stronger than it first appears. If you are using aluminium, go well up in thickness over mild steel, and be very conservative in the amount of bending of the material that you do to make the bracket. Better with aluminium to cut and then have the final brackets TIG-welded together - like the seat mount shown at the beginning of this article. But most of us don't have TIG alloy welders at home, so we're back to mild steel which can be bent in the shed and then welded by any old exhaust shop.
If you need to bolt directly to the floor away from the factory mounts, you must place a strengthening plate or strip in the floor. Don't do that and you'll see that part of the floor moving up and down as the weight comes on and off the seat. Not only does that feel bad, but over time you'd expect the floor to develop cracks in the flex zone. The plate needs to be bolted into place and then the seat bracket bolted to that strengthened point.
And talking about bolts, forget your normal hardware store items. Instead you must use high tensile nuts and bolts, suitably equipped with spring (or star) and flat washers. Good automotive accessory shops usually have a range of high-tensile hardware - it's expensive but these are bolts that you can torque up without fear of thread stripping - or worry that they'll later fall apart. Spread the load wherever possible with thick, flat washers, so that brackets or holes in seat tracks can't elongate and let the bolt head pull through in times of severe stress.
Actually making the brackets is up to you - it's a case of looking, cutting, judicious bending and drilling. Then trying, discarding, making, fitting - and then, finally, finding that it works!
Actually, it's not really that hard, but you do want to make 'em strong - have I said that before...?
