Seat mountings

[peejay4A]

I'll soon be offering up my MX-5 seats to the shell so I thought I'd check out the captive nuts on the floor panels. All the captives except the inboard rear ones are effectively blinded by the chassis. So I won't be able to follow the Technicalities instructions for marking the MX-5 brackets for drilling and I'll have to find another way.

 

This is an early TR4 tub on a 4A chassis, is that the problem? I'm thinking of using studs rather than bolts as I'd prefer not to drill the floor.

[Alec Pringle]

Seat mounting rails for Type 1 and 2 TR4 seats are quite different from the later Type 3 and TR4A seats, and that is presumably the problem ?

 

Cheers

 

Alec

[RogerH]

Hi Pete,

I was working on the 4A today (in the pouring rain). Had to take the seats out. The passenger side rear inner rivnut is loose but is accessible.

However the front inner rivnut started spinning. It sits over a chassis rail.

Drilled the head off and the shank completed with rivnut disappeared into the chassis - me thinks I have a hole in the top of the chassis.

 

Roger

Edited October 19, 2012 by RogerH

[shuggie159]

I just put in MK1 MX5 seats. High back with integral headrests. (leather)

I didn't use any technicalities crib.

Bought about a 2m length of 40x3 poss 4mm strip (which was only just enough).

I cut the strip into approximately 470mm lengths and bolted them into the TR with the original bolts.

I positioned the new seats and established where the new mounting points would be, which is easier said than done. The new seats need to go as cenralised as possible.

 

I then drilled the strip and welded in captive bolts. (I did one and then marked up the remaining three)

 

It is fairly critical to ensure the new seat is able to pass the rear wheel arch. I was supprised, the headrest only just fits into the Surrey top.

The transverse alighnment of the inboard bolts has to be very similar to the existing TR ones, but they are about 25mm longer centres than the originals.

The outer centres are about 50mm further inboard than the TR holes, so I had to weld extension brackets to the new strip to accommodate the new captive bolt locations.

 

The final driving position is slightly higher than the original, but perhaps that is because my old seats are tired. And I'm relatively short 5'8" but the new seat position doesn't go that far back.

It's good enough for me.

 

Cost me a tenner. No harm in just going for it.

 

Crikey I hope you can make sense of that.... sounds like jibberish to me. And I've just written it.

[stuart]

The floors that have been available for years are the same for 4/4a (You have to work out for yourself where the hole for the handbrake goes) so if they have been replaced at anytime then the holes will be the same as later cars anyway.

Its not too difficult to measure up where the holes are and then fit the seats on the two bolts that you can get to and then work out the other holes accordingly. It is useful to drill the holes in the new brackets slightly larger than the bolts to give yourself a bit of wriggle room and use some table 4 washers.

Stuart.

[peejay4A]

Thanks for the info folks. When I was prepping the chassis ages ago I noticed some holes in the top of the chassis rails which I grommeted. I bet these are where the seat bolts would go. I have the Technicalities design adaptor plates already on the seats so I'm going with those and studs in the floor at first I think.

[stuart]

Its a bit difficult doing it with studs as you do need careful placement of the seats to avoid fouling of the reclining mechanism on the "B" post trim and getting them so they will also slide right forward for access behind especially on a Surrey topped car.

Stuart

FWIW on my 4a and on a couple of other cars when I fitted the seats using those brackets I only had to guess the front inner hole as all the rest were accessible from underneath.

[peejay4A]

Thanks Stuart. Fore and aft there's not much scope for variation with the Technicalities brackets, so hopefully not much room for error either. Laterally is where I'll have to be careful. Nothing ventured etc.

[MikeF]

FWIW I offer the following experience from a non engineer type.

On my early 4 I was easily able to use the existing floor holes.

I read and re-read the technicalities CD and ended up informed and slightly confused! (I’m more used to thinking in microns than inches/thou). Now I have installed the seats I think I would say the first thing is to get the front cross bar in place as that only has one place to go.

Then place the back plate in roughly the right place.

Move the seat right back on its runners and offer it so it goes back as far as it can clearing the wheel arch which it just does. Make sure you have the front of the seat runners centrally placed on the fixed in cross bar and the runners are at true 90 and not making a parallelogram shape.

Mark the front bar, drill and lightly fix seat. Now you can slide seat forward and do the same on the back plate, sliding it around as needed

Lift seat back out, Fix plate to floor, then replace seat, mark and drill the back plate to bolt to runners.

You may need to do a little more in and outing than this ,can't remember the entire sequence, but this is the essence.

Naturally being a TR nothing fits as marked so the floor holes in the plate at least need to be oversize with big washers as suggested by Stuart so you get a wiggle factor for fine adjustment.

Getting the seats centralized allows them full travel on the runners. I’m about 5’ 11” and with them fully back can’t comfortably reach and depress the pedals completely. Conversely they will go far enough forward that you can lay them back to go under your tonneau.

I find the new seating position a little high and have retained an old post about removing some of the stuffing from the MX5 seats to lower squab height.

First I will see if I can drop the front of seat a little by using some square section tube from B&Q. I think that will give me an inch, concern is may lose some fore/aft adjust.

The MX5 seats are a real pleasure and transform using the car. Forty years ago bucket seats were all the rage, but now? 60s back and sixties seat are not a good combo

Good Luck

 

 

Mike