Got a day off and the sun is shining, figured it's time to tackle the T-top. It has a water leak, so I've been trying to remove the carpets... which is when I discovered, someone's removed all the factory seatbelt hardware and replaced it with generic locally obtained replacements.

Problem is, they replaced the fasteners too... and the new ones weren't a good fit. Water has got in from beneath the car, and rusted the bolts into the frame. I've managed to drill the heads off them, and get the carpets out. But now's the time to drill out the remains and clean up the mounting points, put it back to stock. Trouble is, I have no freaking idea what the standard bolts should have as far as thread and pitch!

Can someone help a brother out? The one causing problems is the bolt that holds the belt receiver to the tunnel.

You might have trouble finding replacement bolts unless you buy them from GM. As I'm sure you're aware, they are a specialized bolt with a portion of the shank that's unthreaded and which is larger in diameter than the shorter threaded tip. They're also pretty hard (grade 10.9 or 12.9 if I recall correctly). I have a few kicking around the shop that I can measure for you tomorrow, if no one else has done so by then.

I have a couple of those in my garage I'll take a look ... maybe I can ship them out to ya ... let me look first I'll post pics tomorrow.

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My build Thread
http://www.tylerstoy.com
My LED marker kit

Thanks guys. The last guy made a real mess... he's used what appeared to be Grade 10.9 bolts, but they were smaller and he put nuts on from behind. Add to that damage from what appears to be lifting the car by the floorpan, and it's all just a lot of grief. One step at a time though. seatbelts are a pretty important aspect, so I'll sort that, then straighten up the floor, seal it, clean the carpets, make sure the seat mounting points are all square and level so the seats sit up straight instead of on a lean... the joys of used cars, eh?

wonder if you get FASTENAL to make you one? might cost a pretty penny, but having a batch of them made and selling them would net you the spent money plus some.

Here's the scoop: I dug up my seat belt bolts and found that there were three different lengths. I'm not entirely sure which ones go where, but I'm sure someone here can find out if you're not sure yourself.

The longest one is an M12 X 1.75 X 45 where only 20 mm are threaded. The rest of the shank is unthreaded and is 14 mm dia.
The middle one is an M12 X 1.75 X 35 where only 18 mm are threaded. The rest of the shank is as above.
The shortest bolt is an M12 X 1.75 X 25 that is threaded for it's whole length.

All the bolts are Torx T-50's and have markings on the heads but they aren't standard grade markings (a triangle, a "C", and two separate "2"s).

Also, the two longer bolts come with sleeves to allow the seat belt anchors to rotate freely even after the bolts have been torqued to specs. The sleeves are 17 mm OD have a 25 mm dia integral top washer. They're a total of 20 mm long. Here's a pic of the parts described above:

i wanna say ive seen those markings before. i think they could be the manufacturers mark as they dont designate strength.

From what I can tell comparing with what I have out of the car:
The longest ones are for the belt anchors.
The middle-size will be the receiver - the corrosion on the end gives away that it's been poking out of the frame toward the underbody.
The short ones hold the retractor mechanism to the frame.

Those specs help a lot, I'll have to do a sortie down to the local bolt shop and see what they can find in those threads. I know, I know... they are a critical safety item and shouldn't be substituted, but having at least bolts of the right thread means I can have the frame back to factory spec and swap the bolts for the correct parts when the time comes. Will probably involve having to import a set of real belts, the locally made ones in the car just look plain flimsy when sat side-by-side with the real ones.

Thanks so much Bloozberry!

is this something i should start picking from fieros when i go to pull a part? i like to grab the unique fiero-only stuff that there is no reproduction for.

Not sure what safety inspections you guys have, but inspectors here are a bit aardvark about things like seatbelts. If the orange tag that lists the safety standards they are made to is missing, they must be replaced. If they're faded, they must be replaced. Yet at the same time, they're more than happy to let sub-standard seatbelts that don't correctly fit the vehicle replace the originals...

I'm equally not sure what other vehicles the Fiero's seatbelt system was used in, or if its bolts were used in any other applications. Locally, most vehicles are JDM and use very different belt setups with M12x1.5 bolts throughout. If you do find some tidy grey belts at the pick-a-part though, I'm needing both receivers, both belts and all the bolts to fix my '86.

something that's been bugging me all day (almost) since removing the upper belt anchor bolt and putting it back in and noticing that there was quite a bit of steel dust on the bolt (I've had the upper and lower bolts out earlier, maybe I mixed them up the first time?): what do you do if the threads in the frame are damaged?

Run a tap through them. Had to do that on mine. Don't forget to use some sort of lubricant/cutting oil.

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Anything I might say is probably worth what you paid for it, so treat it accordingly!

Dave

www.ltlfrari.com

I just changed my interior--I have both sets of grey belts and latches, and some of the bolts--if you need them pm me

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Pat Jones

[This message has been edited by 88FieroGT TTops (edited 07-06-2012).]

quote Originally posted by Bloozberry: The longest one is an M12 X 1.75 X 45 where only 20 mm are threaded. The rest of the shank is unthreaded and is 14 mm dia. The middle one is an M12 X 1.75 X 35 where only 18 mm are threaded. The rest of the shank is as above. The shortest bolt is an M12 X 1.75 X 25 that is threaded for it's whole length.

I tried fitting M12 x 1.75 nuts on the bolts and they didn't fit. DOT regulations and SAE standards apparently require that seatbelt hardware be 7/16-20 grade 8. If you check the diameter of those bolts they are almost down to 11 mm (7/16 in = 11.11 mm). 14 TPI is the same as a 1.81 mm metric thread pitch -- very close to 1.75. So it seems they're close to 7/16-14... but I'm not sure if that's an allowed size.

[This message has been edited by Steven Snyder (edited 06-19-2013).]

Interesting. When I measured them two years ago with a thread gauge I was pretty certain they were metric as I stated. Perhaps they are made slightly off-size to ensure an interference fit, or perhaps the threaded holes in the frame are purposefully deformed to lock the bolts in place like prevailing torque nuts. That might explain the metal filings that PerKr found earlier (I have noticed filings too in the past).

The bolt threads are some unique size, larger than 12x1.75 and smaller than 1/2-13. I tried Fastenall for a replacement and the shoulder size (5/8") is also unusually large for the length. No luck. If you can use the stock bolt and threads, that's certainly best and easiest. I had one of the tunnel nuts strip and ended up using a 1/2-13 grade 8, with a homemade steel sleeve to increase the shoulder of the bolt to 5/8". I found an old brake caliper bolt had a sleeve that just needed to be drilled out to 1/2"" to fit the bolt and cut to length. I tapped the hole to 1/2" and also used a nut on the underside. The sleeve length is tricky, too long and the bolt head hits the seat track. Too short and it makes the buckle fit tight. It was an iterative process that tries your patience!

Figure it was probably worth updating this post since I've sorted the seatbelt situation.

The damage to the anchors in the floorpan was so severe I had to get quite drastic, I ended up having to cut openings in the floor to access the anchors, drill the spotwelds out and remove the anchors, repeat the procedure on my '84 wreck for some donors, weld the donor anchors back to the floor then weld the openings back shut, seal the lot and paint it all. With the carpets over the top now, you'd never know.

Big thanks to npdimonte for hooking me up with a complete pair of grey belts, all looks and feels OEM now. Let's just see if it'll pass inspection when the time comes