Lowering early type Cerbera seats -solved!

Lowering early type Cerbera seats -solved!

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black_350i

Original Poster:

49 posts

187 months

Sunday 29th March 2015
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After driving around in quite a funny position for some time I posted asking for recommendations to lower the early type Cerbera seats.
http://www.pistonheads.com/gassing/topic.asp?h=0&a...

Now I found a way that solved the problem for me and here is what I did:
(Sorry, I have not taken any pictures so I have to make a lot of words to say the same.)
First I asked a professional what he would do. I used his services before and was entirely happy with it, only with this job I just could not specify how much he should lower it -so I started on my own to be able to test and redo it as often as necessary and probably let him do it properly if I was not happy with the result.
I found the seat bolster to be attached only at the back and at the front. The perforated back part of the seat cushion is one peace of leather that goes up to the backrest as well. To the front there is a second part of leather stitched to that in a curvy line, which is not perforated. This front part of leather is attached to the metal frame and the grp on the front/underside of the seat. The sides of the cushion are not attached to the frame, but only to the foam inside -you can actually stick your hand in to the sides of it and under it.
I peeled the leather off the front/lower edge of the seat. It came away easily, so I did not have to use any tools let alone cut anything away. Now the whole cushion could be folded back against the backrest and gave easy access to it's underside. The front part of the leather is flapping around freely, only the perforated back part is attached to the foam -the sides are folded around and glued to it's lower face. These came of even easier. Now I had the leather of the cushion separated from the one-piece foam element, as opposed to many different pieces I would not be able to get back into position again. So far all of the work was completely reversible, you would just need some glue to undo it perfectly.
Having a close look the whole construction did not look very sophisticated to me so I was confident to proceed. The foam element must have been formed in a mould, so it's shape defines the form of the cushion. Where you can see the curved stitching in the leather there is a recess in the foam as well. After some testing I found my backend to rest on the perforated part only (not on all of it). So to lower my position I used the recess in the foam as a guide to cut with a sharp knife. Some clever hot wire thing would be better, but it worked fine without too many small bits of the foam coming off. This got me two pieces of foam, the rear part you could now adjust to the height you want. I removed it completely and replaced it with another piece of foam that is only a few millimeters thin. This is the perfect height for me and I still have the part I cut off to put back in later should this be necessary.
To reassemble I glued the long sides of the perforated part to the lower face of my newly added foam and the front of the other part back to the front/lower edge and lower face of the seat as per original. The remaining front part of the foam does not move backwards too much (if there is any movement you can barely notice it) as it is wider than the missing rear part, so the side bolsters stop it.
Now I have a nice deep hole to place my backend in and quite a high front part of the cushion so I will never ever slide forward under braking. (It feels like I could hit a wall without sliding.) It remains to be seen if this will be comfortable in the long run, but the situation is quite similar to the later style seat without the removable cushion. In any case I could lower the front part as well.
The cushion now looks rather empty -well it actually is, so I think of putting in some foam that will collapse completely once I sit on it just to make the empty seat look nicer. Aside from aesthetics I will have a close look at the leather if it is stretched further than before and if it might show signs of stress at some point. There is some slack now though, so I am not too worried.

The cost of the modification was next to nothing and the result is perfectly fine for me.
Starting from a removed seat it took me about an hour with a lot of hesitating and looking for the glue. Would I do it again I guess it would take 30 minutes maximum.
Worst part of the job was to see how filthy the inside of a seat gets over the course of 17 years;-)

MPoxon

5,329 posts

172 months

Sunday 29th March 2015
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That is very useful to know. Most of the time the seats are fine but for taller people on trackdays where a helmet is required headroom can be a bit tight.

MPoxon

5,329 posts

172 months

Sunday 20th December 2015
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Juts done this mod to mine, driving position is not much better. How did you get on with yours long term with regards to the comfort?


black_350i

Original Poster:

49 posts

187 months

Sunday 20th December 2015
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Hi MPoxon,

I'm sorry you're still not happy with the seating position. That is really spot on for me now. I basically sit on the grp of the seat which gives me the necessary headroom at the cost of harder seating. I might put a little foam back in to help that. Still this is way more comfortable than not sitting upright all the time. So I'm happy.
What's worse is the lower edge of the backrest: There seems to be some solid part in there. Leaning against that for longer periods of time is not too nice. All in all this mod made the car enjoyable for me, but still might not be the final solution.

The thing is I was not in the car as often as under it: Two weeks after the mod the gearbox went bang.
So I don't have real long term experience.

H.


MPoxon

5,329 posts

172 months

Sunday 20th December 2015
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Hello Henning,

Many thanks for the reply. Sorry I meant to write the the driving position is now better. Phone and fat fingers!

I found that a small layer of foam gave a very similar height as sitting straight on the GRP as the foam collapses. It is a bit cold sat straight on GRP as well.

It is booked in for a retrim in Feb so will get it done properly, maybe with a thin layer of memory foam.

Thanks for the sharing the idea and good luck with the gearbox.

Matthew