Morris Minor Owners Club

Having searched high and low for nearly 24 months for original BMC upper seatbelt mounting brackets for my MM convertible, I made some myself and am quite pleased with the results. I had seatbelts fitted soon after acquiring the car, but the mechanic that fitted them, put the upper mounting bolt into the B post as he felt this was a stronger position. However, it was too far forward and too close to the shoulder, so the belt kept slipping off in use. The Workshop Manual (Sections R34 and R35) show the correct top mounting point (2 doors and convertibles) to be 8” back from the door aperture under the rear window sill and figure R.53 shows the small triangular plate in the fitting kit ADA3896. I also made up some reinforcing plates to go inside the sill above the bracket and drilled holes through for the 2 securing bolts each side.
The position is now much safer, more comfortable and secure and I now need to decide whether to fill the old holes in or put a rubber grommet in and paint them over.

I am not aware of any data or performance figures produced/published for the crash/impact/passenger survivability for these after factory fitted seat belts without the later factory incorporated mountings. I am not aware of any data for even the later seat belts with incorporated mountings.
Whilst they are better than nothing I would suggest that they are nowhere as efficient in keeping the passengers safe as current or later Minor installations with the incorporated mountings.
Having back in the day fitted many after factory Minor seat belts when the regulations regarding seat belts came into play I would suggest that the fitting instructions and locations were more of a nod to the regulations than safety of the passengers.

Thanks for that observation Phil. I am not aware of any 'current or later Minor installations with the incorporated mountings' or know how they would significantly differ from those shown in the workshop manual. My brackets follow the factory recommended position but also have a 4mm thick plate to spread the load on top. As you say, they are better than nothing, in my view a significant safety improvement, but unlikely to pull away unless in a very high impact crash, which would be bad news anyway in a Morris Minor. Neither of my cars (1952 & 1960) had belts fitted from new or any mounting points. If there are any improved or safer setups available, I would be interested in details.

The incorporated mounting points are described in BMC wksp manual Section R35 (Minor 1000 convertible and 2 door saloon) for the window sill fixing point as "inner reinforcement in the body". The applicable body numbers are quoted in section R35. Previously the window sill fixing did not have the inner reinforcement in the body but a strip of metal with suitably threaded mounting holes was supplied to reinforce the window sill. The incorporated sill mounting point had a captive nut where previously a floor mounted 'U' bolts was used. The transmission tunnel incorporated fixing point was two factory drilled holes in the transmission tunnel blocked by rubber plugs. When fitting the transmission tunnel belt mount the rubber plugs were removed and the two mounting bolts fitted through the tunnel into the threaded mounting plate. The transmission tunnel is quite strong in the area of the mount and is more than adequate for seat belt retention.
There is very little difference between the fitting instructions in wksp man Pt No: AKD530 L and the latest edition 14.
I do think that BMC towards the end of production did try to improve and strengthen the factory seat belt mountings but was limited by the body design which hindered the mounting of properly designed seat belt mounts which would transmit the shock loading through the body and not just point loading which the factory mounts were. Latterly the Minor was on its way out so BMC I would suggest were not going to invest in radical body modifications just to install what would be considered today as proper seat belt mounting points.
Phil

philthehill wrote: ↑Thu Jan 29, 2026 9:54 pm The incorporated mounting points are described in BMC wksp manual Section R35 (Minor 1000 convertible and 2 door saloon) for the window sill fixing point as "inner reinforcement in the body". The applicable body numbers are quoted in section R35.

I own a 1966 2 door saloon with these factory mounting points. Does anyone know what bolt size fits these mountings?
As I am in Europe, used to metric, bolt sizes in a MM can be challenging.

Mart&Daisy wrote: ↑Sun Mar 01, 2026 4:41 pm

philthehill wrote: ↑Thu Jan 29, 2026 9:54 pm The incorporated mounting points are described in BMC wksp manual Section R35 (Minor 1000 convertible and 2 door saloon) for the window sill fixing point as "inner reinforcement in the body". The applicable body numbers are quoted in section R35.

I own a 1966 2 door saloon with these factory mounting points. Does anyone know what bolt size fits these mountings?
As I am in Europe, used to metric, bolt sizes in a MM can be challenging.

https://board.mmoc.org.uk/viewtopic.php?t=79707
See this post, I posted size and rating of seatbelt bolts.
They are not metric' they are 7/16 UNF

Thank Bill! Much appreciated!

I don't reckon the B pillar on a convertible to ever be suitable as a mounting point. It's little more than part of a fragile window frame, catastrophic forward movement being constrained mostly by the door (if it stays closed!).

Mart&Daisy wrote: ↑Mon Mar 02, 2026 11:57 am Thank Bill! Much appreciated!

Thank you well

[quote="Mr Spigot" post_id=716215 time=1769699976 user_id=49284]
The position is now much safer, more comfortable and secure and I now need to decide whether to fill the old holes in or put a rubber grommet in and paint them over.
[/quote]

I own a 1964 2 door saloon. Seat belts were not originally fitted but added by the last owner. I have changed them to inertia reel but they rub my shoulder. Would it be possible to weld this bracket to the frame? What are the dimensions of the bracket please?

Thanks

Rich

mike1864 wrote: ↑Mon Mar 02, 2026 3:09 pm I don't reckon the B pillar on a convertible to ever be suitable as a mounting point. It's little more than part of a fragile window frame, catastrophic forward movement being constrained mostly by the door (if it stays closed!).

It is totally unsuitable as you say!!!! If in any doubt, have a look at this photograph of my convertible from last week.You can see that the B-post would never be strong enough as a seatbelt mounting point.

Stephen

What a superb illustration about the wisdom (NOT!) of mounting seat belts to a convertible's B pillar.
And in a major collision the forward distortion of the B pillar (from the inertia of the occupants) would likely shatter all the side windows, showering the (already compromised) occupants in broken glass.
Waist rail mount every time!
Personally I have head rests too. Not original; but in the event of rear end shunt I'm more concerned with preserving the originality of my (and my passenger's) cervical vertebrae.

Mr Spigot wrote: ↑Thu Jan 29, 2026 3:19 pm Having searched high and low for nearly 24 months for original BMC upper seatbelt mounting brackets for my MM convertible, I made some myself and am quite pleased with the results. I had seatbelts fitted soon after acquiring the car, but the mechanic that fitted them, put the upper mounting bolt into the B post as he felt this was a stronger position. However, it was too far forward and too close to the shoulder, so the belt kept slipping off in use. The Workshop Manual (Sections R34 and R35) show the correct top mounting point (2 doors and convertibles) to be 8” back from the door aperture under the rear window sill and figure R.53 shows the small triangular plate in the fitting kit ADA3896. I also made up some reinforcing plates to go inside the sill above the bracket and drilled holes through for the 2 securing bolts each side.
The position is now much safer, more comfortable and secure and I now need to decide whether to fill the old holes in or put a rubber grommet in and paint them over.

Hi Mr Spigot
I’ve just seen your triangular brackets, looks excellent, would it be possible to have the dimensions please?

I know this is for the floor but will it work as above.

https://ebay.io/m/uFrAtM

Rich

No, as there is not enough width to spread the load along the sill.
The factory supplied ones had two bolts fixing the bracket to the window sill. I attach photos of one I scrapped with measurements which I hope will help. I traced the shape and took dimensions from the originals I had fitted to my other car.
I used 5mm steel, but 4mm or even 3mm should be enough. If you cannot make them, any good engineering company should be able to make some easily. It is important that you also make a reinforcing plate to go inside the sill for the two bolts to go through, before going through the sill, to spread the load, dimensions to match the top of the bracket or be slightly wider.

Thanks very much for the measurements, I shall have a go!!!

Hi
Did you fit static or inertia belts?

svenedin wrote: ↑Mon Mar 09, 2026 8:02 pm

mike1864 wrote: ↑Mon Mar 02, 2026 3:09 pm I don't reckon the B pillar on a convertible to ever be suitable as a mounting point. It's little more than part of a fragile window frame, catastrophic forward movement being constrained mostly by the door (if it stays closed!).

It is totally unsuitable as you say!!!! If in any doubt, have a look at this photograph of my convertible from last week.You can see that the B-post would never be strong enough as a seatbelt mounting point.

Stephen



IMG_4483.JPEG

I'm sure many will disagreee with me, but surely the 'mount' on the B-post is more of a guide than a mount. The montings on the transmission tunnel and the inner sill would take the bulk of the strian in the unfortunate event of the seatbelts being used in 'anger'. While I agree that the 'mount' on the B-post should be strong, I think it serves as more of a guide than a load bearing mount.

liammonty wrote: ↑Mon Jun 29, 2026 11:07 am

svenedin wrote: ↑Mon Mar 09, 2026 8:02 pm

mike1864 wrote: ↑Mon Mar 02, 2026 3:09 pm I don't reckon the B pillar on a convertible to ever be suitable as a mounting point. It's little more than part of a fragile window frame, catastrophic forward movement being constrained mostly by the door (if it stays closed!).

It is totally unsuitable as you say!!!! If in any doubt, have a look at this photograph of my convertible from last week.You can see that the B-post would never be strong enough as a seatbelt mounting point.

Stephen



IMG_4483.JPEG

I'm sure many will disagreee with me, but surely the 'mount' on the B-post is more of a guide than a mount. The montings on the transmission tunnel and the inner sill would take the bulk of the strian in the unfortunate event of the seatbelts being used in 'anger'. While I agree that the 'mount' on the B-post should be strong, I think it serves as more of a guide than a load bearing mount.

But if it tore loose in an impact, the inertia would already be locked, so creating a large amount of slack. This would render the belt useless!

Establishing the force on the upper mount is quite straight forward. The applied forces are the tension in the belt. For the upper mount there is the tension of the belt in two directions plus the offset of the belt to the fastening point. With the belt pulling downward but at different angles it will be the point with the most total load with an addition force component in the forward direction.