JDC_747 Posted November 24, 2021 Report Share Posted November 24, 2021 (edited) Hi all I'm fitting mk2 MX5 seats using the TRTrader brackets. The captive nuts on my 1965 TR4 have what seems to be somewhat unusual spacings - see pics. Should be 36cm outboard measurements apparently. Carl has very kindly offered to reverse engineer the brackets, free of charge, rather than have me drill new holes in the tinfoil floorpan. Still, I'm wondering what is different on mine, having checked underneath I can see no sign of nuts or plates being moved/replaced on my floor. Can anyone shed some light please? thanks Jeremy P.S. seats were originally sh*te brown, so I sprayed them with poly leather dye and added the fabric Triumph badge. Really pleased with the result. Edited November 24, 2021 by JDC_747 Added a belated thankyou Quote Link to post Share on other sites
Malbaby Posted November 24, 2021 Report Share Posted November 24, 2021 (edited) What is achieved by the "reverse engineer the brackets". Couple of the captive nut holes on my 4A chassis are different to your TR4. Your holes are in a perfect rectangle, whereas mine are not. My outside [near door] spacing is less at 360...Front holes are at right angles to the sill. Rears are not. The difference being the outside rear captive nut locations on your car. Also my factory MX5 RHD seat runners are different from right seat compared to left, so you will need to check your seats to see if they are identical. Seems to me that the TR trader brackets have not been made correctly. Those brackets may have been made to have the seats offset slightly which is OK, so as to ensure that there is sufficient clearance of the seat to the B pillar. If the intention was to have the offset, then the design is still problematic. I cannot explain why you have the 33.5 and 34.5 measurements, as these should be exactly the same. The 41 to 43.5 can be partially explained by having the outside rear captive nuts moved to the TR4A location, but then there is still the offset problem Hopefully the 41 and 33.5 measurements are correct for your MX5 seats. Edited November 25, 2021 by Malbaby Quote Link to post Share on other sites
JDC_747 Posted November 25, 2021 Author Report Share Posted November 25, 2021 (edited) A detailed reply, thanks Malbaby. Yes, Carl's view was that outside spacing should be 360mm as you say. I believe this would then align bracket studs with runner holes. I have 4mm spreader plates and appropriate bolts etc, so I suspect I'll drill the floor to match. Ta, JDC. Edited November 25, 2021 by JDC_747 Spelling!!! Quote Link to post Share on other sites
TR4ffic Posted November 25, 2021 Report Share Posted November 25, 2021 Hi Jeremy I had a similar problem when fitting Carl's brackets/MX5 seats in to my 3a... I went down the route of positioning the bracket/seat where it needed to go, marked out bracket position on to the floorpan and drilled new holes in the brackets. I also took the seatbelt bracket off the MX seat frame to give me a bit more room against the transmission/propshaft tunnel. Regards Nick Quote Link to post Share on other sites
stuart Posted November 25, 2021 Report Share Posted November 25, 2021 25 minutes ago, TR4ffic said: I also took the seatbelt bracket off the MX seat frame to give me a bit more room against the transmission/propshaft tunnel. Regards Nick That bracket and belt mechanism should always be removed, its not safe to use when these seats are fitted to a TR. Stuart. Quote Link to post Share on other sites
JDC_747 Posted November 25, 2021 Author Report Share Posted November 25, 2021 Hi Nick Thanks for the reply, yes that's what I'll be doing. Can use the rear 2 captive nuts thankfully. Hi Stuart Yes, agreed, massively unsafe to use them so already off, also gives a better fit re: tunnel. Thanks chaps. Jeremy Quote Link to post Share on other sites
rcreweread Posted November 25, 2021 Report Share Posted November 25, 2021 Jeremy - drill the brackets to match your floor mountings, not the other way round - just better in my view and the floor remains intact if you decide to change again - there should be enough width of metal on the brackets to safely achieve this. Cheers Rich Quote Link to post Share on other sites
Hamish Posted November 25, 2021 Report Share Posted November 25, 2021 When I fitted my rigard seat to my 3a a drilled the floor to suit the seat frame runners where the bolts were welded to the runner. I also fitted long metal flat bar under the floor for the front and rear bolts to pass through as reinforcements for each runner with washers and nyloc nuts. Makes for simple removal of the seats from underneath. Quote Link to post Share on other sites
Drewmotty Posted November 25, 2021 Report Share Posted November 25, 2021 I don’t have much trust in the captive nuts holding the seats on TRs and removed them when I had standard seats in my TR3 in favour of Nylocs and penny washers. Regardless of the seats ( Corbeau Classic in TR3 and MX5 in the TR4) I drill in the best position to suit the seat/seat positioning and use Nylocs with large washers under the floor to spread the load. Quote Link to post Share on other sites
JDC_747 Posted November 25, 2021 Author Report Share Posted November 25, 2021 Hi all Thankyou for all the help and advice, it's invaluable, shows what a brilliant forum this is. After some more trial fitting and finger-crushing, I now have a plan, involving the 2 rear original fittings and some nylocs and 4mm spreader plates. The big thing for me was to have the driver's seat as 'square' to the steering wheel as possible, to minimise the left-hand offset. A slight realignment of the rachets on the runners has allowed this, keeping the seat squab nicely against the tunnel. Spacers on the front and none on the back give an ideal rake and just keep the top of my head below the windscreen trim level. Just need to trim the rear bracket studs to allow a bit more rear movement of the runners, which I need despite having stumpy legs. I'm starting to ramble now so I'll end with a final thankyou. Jeremy Quote Link to post Share on other sites
Malbaby Posted November 25, 2021 Report Share Posted November 25, 2021 5 hours ago, JDC_747 said: A detailed reply, thanks Malbaby. Yes, Carl's view was that outside spacing should be 360mm as you say. I believe this would then align bracket studs with runner holes. I have 4mm spreader plates and appropriate bolts etc, so I suspect I'll drill the floor to match. Ta, JDC. Jeremy.....There will still be a problem because there is a parallelogram created not a rectangle. Your existing holes are a perfect rectangle. The trader brackets geometry is wrong...eg your 41 line is not at right angles to your 33.5 line. If we accept that the brackets were originally designed to fit the MX5 seats in an offset position to ensure clearance to the B pillar, then the runner bolt in the bracket for the front outside has to be moved backwards to create a right angle. Therefore the new hole for the outside rear bracket mount has to be carefully measured and drilled as it will not be parallel to the sill. Bottom line....check the mounting hole measurements of your MX5 seat runners, both right and left. Place the seats on the floor pans in their optimum position and see how the runners align with the trader brackets. Also as others have mentioned, captive nuts alone are not the ideal fixing method. Quote Link to post Share on other sites
Ian Vincent Posted November 26, 2021 Report Share Posted November 26, 2021 FWIW when I fitted MX5 seats in my TR3a I ended up bolting the TR Trader type brackets to the seat and placing it where it needed to go and then marking the position of the holes in the floor from underneath. Then redrilled the brackets to suit. Rgds Ian Quote Link to post Share on other sites
stuart Posted November 26, 2021 Report Share Posted November 26, 2021 This is why I use the brackets as described in the Technicalities CD. To my mind they are much stronger and are an easy fit. Stuart. Quote Link to post Share on other sites
JDC_747 Posted November 26, 2021 Author Report Share Posted November 26, 2021 Hi Malbaby If you consider the rear fixings as exactly that - fixed - then by adjusting the point at which the seat rail ratchets engage, it is possible to realign whilst remaining with the rear fixed, crabbing the seat sideways for want of a better phrase. This essentially shifts the front squab be closer to the tunnel, but still allows the seat to clear the B pillar when moved rearwards. It's not a great amount of lateral movement but enough for me to get the position relative to the steering wheel that I wanted, and the seat is flat and moves smoothly back & forth. Does require new holes drilling however, as mentioned by others. The geometry of both brackets and seats is not ideal but I have a pragmatic solution. thanks Jeremy Quote Link to post Share on other sites
Malbaby Posted November 26, 2021 Report Share Posted November 26, 2021 Hello again Jeremy...if you have the time, would you care to post a revised pic of your solution....new holes etc. Quote Link to post Share on other sites
JDC_747 Posted November 28, 2021 Author Report Share Posted November 28, 2021 Hi Malbaby Yes, of course I will, when the weather calms down enough for me to go out finish the job. It might even be of some use to someone with a similar problem. Cheers Jeremy Quote Link to post Share on other sites
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