TR4/4A Tr4a - 3 point seat belts with Miata seats

[Tr4aJim]

Folks, I am putting Miata seats in my Tr4a. I also want to install 3 point seat belts. I see that several sites offer 3 point belt kits, but are these kits designed to only work with the stock seats? Since the Miata seats have higher backs, would the shoulder strap sit too low?

thanks

Jim

 

[tdskip]

Hi Jim - had Miata seats in my TR6 and it was not an issue. Expect the same to be true in TR4a.

 

[Foura]

I have Miata seats in the 4A with 3 point inertia reels. They work fine. The ones I bought have a short extension strap which mounts to the upper bolt and the shoulder strap runs up from the reel through that to give the correct angle.

The only problem is that using the lower bolt hole to mount the reel mechanism restricts the rearward travel of the seats. My youngest son, who is closer to 6', can not drive the car. The rest of the short asses in the family have no problem. One of the guys in the local club made up a bracket which mounts to the bolt on top of the wheel well to hold the reel. If you mount them to the inner face of the wheel well, as on some TR6s, it restricts your luggage capacity and the bags can interfere with the belt.

 

[Tr4aJim]

Rocky,

I'm not sure I understand how your belts are attached.

I thought that the fixed end, and the reel end, would attach to the existing loop bolts on the floor. Then the shoulder belt loop would attach somewhere on top of the rear wheel arch, requiring a new hole to be drilled.

Could you take a few pics of your belts so I can see how yours are installed?

BTW - I'm looking at the Securon belts. What belts did you use?

thanks

Jim

 

[Foura]

Hi Jim

It took till the weekend to get some shots and now I am having trouble uploading them. BCF keeps rotating them, so you may have to download and turn them around.

 

[Tr4aJim]

Hi Rocky.

i only see one picture, but it does show something I didn't realize. I thought the reel mounted to the floor using the seatbelt eyebolt attachment point, but you have yours mounted in the back. Was that your choice or a requirement of the belt kit?

Also, after going through the guide loop the belt is going up. Do you have some sort of belt guide on the seat, where belt passes through?

Finally, did you have to reinforce the mounting points for the reel and belt guide attacment points, or did you just use large washers?

thanks

Jim

 

[Rut]

Jim,
Ive not installed 3 pt belts in my TR4a yet, but I have in the MGB and Bugeye Sprite and the retractor can go on the wheel well or floor. The most important aspects of mounting belts is security of those mounting points and never having the shoulder belt below parallel to the floor. In case of a forward impact accident the shoulder belt will crush the wearers shoulder and possibly do spinal damage. You can research seat belt geometry and it will help with mounting points.
HTH, Rut

 

[Foura]

Jim, you have to rotate the picture through 90 degrees anti clockwise (or your head!). I tried loading pictures about 6 times and it kept rotating them, so I gave up. The reel is mounted to the original side mounting point just up from floor level, and the belt runs straight up, through the loop that is attached to the extension piece which mounts to the bolt on top of the wheel well, and then forward to your shoulder. This keeps it pretty much parallel to the floor as Rut mentions, and keeps the reel vertical.

I now recall that the wheel wells were partially replaced when the body was rebuilt to cut out some minor rust. Some parts came from a TR6 that came to grief on the racetrack when a rear stub axle broke so I may have TR6 top mountings. The car was advertised as a California car when I bought it, but the last registration was Denver Colorado. I hear that they occasionally get snow there.

I'll try one more time with the photos.

 

[Tr4aJim]

Rocky,

ok now I see what you mean!

Where the top loop extension is attached, did you have to strengthen the wheel arch at the mounting point, or did you just use a big fender washer?

thanks

jim