Deluxe seat woes

[youngengineer]

I recently took the plunge and upgraded to deluxe seats. So far with mixed results.

I'm running a 109 with a truckcab. 

Ok the seats look great and are firmer and more comfortable to sit in, but at a cost.

The combination of the thicker and firmer foam as well as taller backrests mean you sit further forwards. Me knees are in agony after an hours stop start traffic.

The top of the backrest now fouls just under the truckcab glass meaning that the seat is not able to rest onto the backrest support. 

I know that the truck-cab limits my adjustment possibilities but I would really like to keep it. Other then having custom seats made im not really sure what else I could do to improve the situation.

 

I appreciate this might be a frequently covered topic but from the few posts I've seen it looks like removal of rear bulkhead is the only option.

Edited December 17, 2019 by youngengineer

[Bowie69]

Raising the seat rails can help too. 

[Snagger]

Yep, raise the seat tracks 1-1.5” and move them back about 2” and you should have better results.

I had deluxe seats for years, and they were an improvement, but fitting Defender seats was a leap forward.  My next step is to get seat extension rails to do as above and to buy the lower seat cushions from Exmoor Trim that have increased thigh support.  I think they should be pretty comfy, while retaining the easy access underneath and not needing any creative mountings or mods to install.  Given that late SIIIs had what became known as Defender seats as standard (County models), they shouldn’t constitute a mod that insurers get uppity about, either.

[youngengineer]

2 hours ago, Bowie69 said:

Raising the seat rails can help too. 

I will try lifting the tracks first see how I get on. But in all honesty I'm, not keen on the idea as feel like im already very close to the top of the windscreen and looking down onto the road instead of ahead. I feel annoyed about not having forked out on defender seats when I had the chance.. Are Rx8 seats going to create more problems or a step in the right direction in terms of improving leg space?

 

The seat riser kits seem to be pretty simple. I think I could fabricate something out of some heavy duty Unistrut I have in the yard.

Edited December 17, 2019 by youngengineer

[David Sparkes]

The standard arrangement, as others have said, is to put risers between the seat box and the seat rails. This allows you to set the rails further back on the risers so the standard adjustment in the rails pushes the seat base over the flange at the back of the seat box.

Depending how much slope you put in the seat back, this can give you up to 5" of extra leg room compared to a fixed centre seat.
I realise you have thrown your centre seat away, but when judging the change, that is how you make the comparison.
Note that the foam resting on top of the back rest was inside the cover, at the very point it touches the window frame. The foam isn't doing anything now.
Note also the absence of the upper back rest support bracket behind the drivers seat, the one you can see is for the centre seat.

Note the comparison between the back rest pivots on the frame for the centre seat and the one on the drivers seat (which a PO has unwisely used as the seat buckle mounting point).

Possibly to give you an impression of greater space I feel you have the backrest sloping back too much; this is also why 'the seat (back) is not able to rest onto the backrest support '.
With the seat base moving further back, and the back rest more upright, (and possibly removing the upper back rest support) the back rest will rest against the window frame, not underneath it as it does now.

An alternative way to gain more legroom is to increase height of the brackets containing the pivot for the backrest. You make new pivot hole holes and lift the backrest 2 or 3 inches. This leaves an unsightly gap between the rear edge of the seat cushion and the lower edge of the back rest cushion. It is into this space your pelvis goes; put another way, this space needs to be big enough for the belt of your trousers to go into, although this measurement criteria doesn't work if you wear trousers so low slung the crack in your backside is visible to others when you bend over.

This modification works because as the pelvis moves backwards, so does the hip joint, which is the start point when it comes to measuring leg length while sitting down. The other advantages are that the standard seat base cushion effectively extends further forward under your thighs, and the back rest cushion effectively extends higher, giving more support to your shoulders.

From another vehicle, the raised back rest pivot. The first is an overview, showing the size of the gap between the two cushions; also compare the heights of the tops of the backrests, the drivers seat raised against the standard centre and passenger seats.

The second picture shows in clearer detail both the old and new pivot points in the modified seat base. Note that in this case the pivot point is both lifted AND moved back, and that NO risers are fitted underneath the seat rails, thus addressing your point about not wanting to raise the seat height.

This information is from an old thread on the forum of the Series 2 Club.

Regards.

[youngengineer]

14 minutes ago, David Sparkes said:

The standard arrangement, as others have said, is to put risers between the seat box and the seat rails. This allows you to set the rails further back on the risers so the standard adjustment in the rails pushes the seat base over the flange at the back of the seat box.

Depending how much slope you put in the seat back, this can give you up to 5" of extra leg room compared to a fixed centre seat. I realise you have thrown yours away, but when judging the change, that is how you make the comparison. Note that the foam resting on top of the back rest was inside the cover, at the very point it touches the window frame.
Note also the absence of the upper back rest support bracket behind the drivers seat, the one you can see is for the centre seat.

Note the comparison between the back rest pivots on the frame for the centre seat and the one on the drivers seat (which a PO has unwisely used as the seat buckle mounting point).

Possibly to give you an impression of greater space I feel you have the backrest sloping back too much; this is also why 'the seat (back) is not able to rest onto the backrest support '.
With the seat base moving further back, and the back rest more upright, (and possibly removing the upper back rest support) the back rest will rest against the window frame, not underneath it as it does now.

A way to gain more legroom is to increase height of the brackets containing the pivot for the backrest. You make new pivot hole holes and lift the backrest 2 or 3 inches. This leaves an unsightly gap between the rear edge of the seat cushion and the lower edge of the back rest cushion. It is into this space your pelvis goes; put another way, this space needs to be big enough for the belt of your trousers to go into (this measurement criteria doesn't work if you wear trousers so low slung the crack in your backside is visible to others when you bend over).

This modification works because as the pelvis moves backwards, so does the hip joint, which is the start point when it comes to measuring leg length while sitting down. The other advantages are that the standard seat base cushion extends further forward under your thighs, and the back rest cushion extends higher, giving more support to your shoulders.

From another vehicle, the raised back rest pivot. The first is an overview, showing the size of the gap between the two cushions; also compare the heights of the tops of the backrests, drivers seat raised against standard centre and passenger seats.

The second picture shows in clearer detail both the old and new pivot points in the modified seat base. Note that in this case the pivot point is both lifted AND moved back, and that NO risers are fitted underneath the seat rails, thus addressing your point abot not wanting to raise the seat height.

This information is from an old thread on the forum of the Series 2 Club.

Regards.

Great write-up thank you. It certainly makes allot more sense. Btw my seats are as far back as they will go. Maybe not on the picture though.

Edited December 17, 2019 by youngengineer

[Snagger]

You may be able to mount the seat tracks further aft without raising them if you cut notches in the raised mating flanges joining the seat base to the tub shelf.  Obviously, in addition to joining the two parts, this flange also gives the back of the seat box rigidity to support the weight of the seats and occupants, so you’d need to replace its strength by robustly attaching some sturdy angle or box section along the underside of either the tub or (better) the seat base.