Well, I agree that the pillion seat as installed by the factory is very uncomfortable. However, that is all I am able to agree to.
The factory pillion seat is rather narrow (about 150mm) with a length of 310mm. However, we should remember that it is mounted on an Indian bike. In Indian it is required to have a saree guard installed on the left side beside of the back wheel and a handgrip for the pillion on the right side. The background is that most Indian pillions, especially the ladies, do not sit in riding direction, but diagonally to it. In this sitting position, the pillion seat dimensions fits much better to the pillion’s butt, even European ones. For the export models, RE omitted the saree guard and the handgrip, but did not adapt the pillion seat. However, that is only one problem.
The seat upholstery has a height of about 70mm what should be sufficient for a comfortable ride. The shape of the upholstery prevent it. The seat is not flat on the top side, but convex. It is like sitting on a stubborn horse without a saddle fitted. The pillion will not find a comfortable position and the thickness and low stiffness of the upholstery leads to a steady sliding around of the pillion who will not find a comfortable position. Needless to say that such an ongoing movement will bring some disturbance in the whole bike and make the driver’s life no easier – especially as he also has seat related problems. We will see later what is wrong with the driver’s seat.
For the pillion seat modification the stock frame is a good base, plywood more likely not. Wood is sensitive for humidity and tends to crack when loaded. We should not forget that a seat is a safety-related part of the bike that has to carry the pillions weight, as well as withstand vibrations and blows from uneven roadways. (The stock bumpers will do it more or less, but more often less). For the pillion seat base I would prefer metal over wood.
You choose a piece of 120 mm thick high-density foam for the seat pad. Why such a thickness? Thickness is no guaranty for a comfortable ride. Such a thick peace of foam will not have a good lateral stability and has the tendency to tilt sideways when loaded. The pillion sitting position is much higher over ground than with the stock seat and more wavering, even when the seat is wider. Additional, you added some height by the welded frame.
Your replacement seat looks convex at it’s top side as the stock seat was. The pillion will not find a stable sitting position. The lack of a handle grip should make it more difficult do find a stable position on a jello.
When I got my C5 my wife complaint after the first ride that the pillion seat was not useful. Therefore, a modification was necessary. My first attempt was to replace it with a second driver seat. I made an adapter plate and brackets to mount the seat on the stock frame. (I did not allow myself any modifications to the seat or the frame.) The seat nicely fitted and my wife was happy, but I recognized that she was squirming to find a good position – as I did on the driver’s seat. Even the padding is sufficient, you will sit on top of the bike instead of “inside” as it should be when this seats are installed. Therefore, a different solution was desirable.
Above, I already hinted at driver seat problems. Even the seat may look comfortable, it is not. You will not find a good sitting position and as the rear shock absorbers are not really do what the name implies; bad roads are a pain for the back. Well, there are springs below the seat giving the impression of a swing seat and some comfort. In reality this springs are a pure fake. You could replace them by massive metal hardware and nothing would change.
The swivel point of the seat lays inside the bracket below the seat’s front end. There is an axle that holds the seat and allows it to turn around it when the springs are compressed. However, this in a wrong impression. The axle has a square shape as well as the hole in the frame’s mounting bracket. The seat-mounted bracket has a square hole, too, where the square shaped axle fits. No movement is possible. It acts as a sturdy connection and no seat swiveling is possible. When replacing the seats this problem should be fixed also.
When realizing that the form of the seats was the problem more than a lack of padding I decided to mount some older RE factory seat. I don’t know on what model they were installed originally, but as they are marked with the old factory logo and the old name Madras instead of Chennai they may be from the late 70’s. A very similar type is still available in India today and offered by auction houses.
The main difference to the stock seat is the shape. A pronounced seat recess prevents the passenger from slipping back and forth. You sit down and stay in place. As the upholstery is much thinner, you will sit in a deeper position – “inside” the bike instead of “on the top”. A thinner upholstery does not mean a lack of comfort – it is just the opposite situation.
I machined a new swivel axle for the driver’s seat to convert it to a real swing seat. The rest of the mounting hardware was unaltered and the factory springs were reused. The sitting position is very comfortable, especially the suspension.
For the pillion seat adapter brackets were machined from aluminum, so no modifications to the seat itself or the stock frame were necessary. The factory pillion handle grip was reinstalled in it’s original position. No springs were placed below the pillion seat to keep it low on the frame and allowing a sturdy mounting for more stability. For the sake of pillion’s comfort the doubtful factory rear shock absorbers were replaced by Hagons what dramatically improved the overall behavior of the bike.
All modifications were made with the classic appearance of the bike in mind, but satisfying the intention to make some essential improvements.