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Who woulda thunk...there's Metric on my car!

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TR6BILL

Luke Skywalker
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I have the brake booster out (along with the master) to send off to Apple for a rebuild and decided to clean up the rusty thread of the 4 studs that hold the booster to the firewall.
And, they ain't 5/16" either. Turns out they are 8 mm Metric! And this was an OE replacement that I had bought from TRF some 6 years ago. Shoulda been suspicious because all the 4 nuts, locks and flat washers are all red in color, Metric red. Was this the way they were built, back in the day? Prolly used the same booster for other European cars back then.

Found an 8 mm die to chase the threads (thank goodness for NAPA).

Any other suggestions besides Apple for quality rebuilds? They redid my clutch master last year and there is a very slight weeping of fluid (resleeved and everything, yet).
 
I sent my booster to Brake Materials and Parts, in Ft. Wayne, IN. I installed a new M/C.
 
TR6BILL said:
I have the brake booster out (along with the master) to send off to Apple for a rebuild and decided to clean up the rusty thread of the 4 studs that hold the booster to the firewall.
And, they ain't 5/16" either. Turns out they are 8 mm Metric! And this was an OE replacement that I had bought from TRF some 6 years ago. Shoulda been suspicious because all the 4 nuts, locks and flat washers are all red in color, Metric red. Was this the way they were built, back in the day? Prolly used the same booster for other European cars back then.
Click to expand...

Thats the difference between OE "Replacement" and OEM. They were not metric from the factory. It means whoever remanufactured it couldn't be bothered to re-tool from metric when threading the studs. Cheaper to supply the correct metric hardware instead.
 
Here's a post I saved from Paul:

You can have it completely rebuilt, sandblasted and powder coated by these guys. They do great work with a very quick turnaround if you need it.

The price is great too. $125 for everything, done complete. That price may include shipping as well, unless UPS raised the rates a lot since I had mine done last year.

brake materials and parts
800 sherman blvd
ft wayne in 46808

260-426-3331
 
A lot of the parts that are now OEM replacement are metric. Awhile back I bought two of the round transmission mounts, and yes they were metric. I told TRF, it would have been nice if they told me or at least provided the hardware.

I do not know why we are not on the metric system. Should have done it a couple of decades ago...
 
Bill: Not sure if you use Dot 3 or silicone. When I got my master from TRF after it was on backorder for 3 months, this warning was on the box. if you want to use silicone, tell whoever rebuilds the unit to use compatible seals.
 

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TR6BILL said:
...decided to clean up the rusty thread of the 4 studs that hold the booster to the firewall.
And, they ain't 5/16" either. Turns out they are 8 mm Metric! And this was an OE replacement that I had bought from TRF some 6 years ago....
Click to expand...
Anyone who has bought a wheel cylinder in recent years has likely noticed that the bleed screw, which always used to take a 7/16" wrench, now takes a metric (forget the size, but ISTR it's a bit smaller than 7/16") wrench. Thankfully, the threads still seem to be SAE!?
 
The only metric nut on my tr3, is the knurled nuts that hold the guage brackets on! They are 5mm.
I believe that Jaeger is a French company.
DPO used two American sized knurled nuts-they won't fit!
Emmett
 
Even my TR3A has metric - i.e. after TRF sent me some replacement Taiwanese made ball joints. I am still stewing about that one. I should probably hang tags on them to warn the next owner about them.
 
emmett1010 said:
The only metric nut on my tr3, is the knurled nuts that hold the guage brackets on! They are 5mm.
I believe that Jaeger is a French company.
DPO used two American sized knurled nuts-they won't fit!
Emmett
Click to expand...

I don't know about that. I just went and measured the threads on a spare Jaeger speedo I have, and they measured 10-32. I took a 10-32 screw out of my bin, and it threaded right on. However, they may be British association threads, as a 2BA size is really close to 10-32...it measures as a #10 size screw, with 31.4 tpi. Maybe that's the problem you ran into. My 10-32 nuts are pretty loosey-goosey and go on OK. See below for the the BA link.

The British Association threads in sizes smaller then 1/4". The only two I ran across were 2BA and 4BA. I now have taps and dies in those two sizes. Of course, I'm not including the SU carbs, because I think there are some Whitworth sizes there.

BTW, a bit of googleing came up with a Swiss Jaeger Co. that supplied dash instruments for mostly French cars, and a British Jaeger Co. that was somehow associated with Smiths. So, who knows?? :thirsty:
 
My TR3 speedo & tach have metric (not BA or Whitworth) threads, as do the smaller instruments (but not the same metric thread). Learned that the hard way, many years ago, after I started running a 10-32 tap down a stud, to "clean it up". They aren't even common metric threads, at least I couldn't find them listed in any of the modern metric standards. But I think they did change to SAE, later on.

The overdrive lockout switches also have metric threads.

The studs on the starter solenoid and starter are British threads, although I don't recall offhand if they are BS or BA. ISTR the screw terminals on the control box, fuse block, headlight switch, ignition switch, etc. are as well. And you're right, the H6 carbs are almost totally British threads. Even the hex plug that carries the damper takes a Whitworth wrench.

Don't know where they came from, but my parts bin had some bolts with chrome heads that look very similar to the bolts used to blank off the racing screen mounting holes. Had the proper 5/16NF threads, but the heads are closer to 12MM than 7/16".
 
Actually, about half way through the 1973 run on the TR6, BL changed the small rigid piece of front brake pipe that runs from the caliper to the flex hose to Metric. Mine is not. I have a set of brand new, OE Metric pipes if anyone needs them. And they are not aftermarket. I only want $1000.00 for them, seeing as how Girling stuff is NA now. Or, I will take postage only if you don't want to pay the grand. Say, 2 bucks?
 
Not that I like to disagree with you Randall, but I think Art is correct here. But not that I'm an expert. I retooled mine to except 10-32 nuts.
 
I honestly never thought this would come out, but it happened I was in the garage with the camera in hand and there was a speedo laying on the bench in front of the tap & die drawer ...

Note how the teeth of the gauge line up with the threads in the middle, but not at either end. It's definitely not 32 tpi.
 
That we made clear with Art's note. It some sort of Weird British thread, I had heard or read or something.
 
My apologies Art, misread your post.

I guess they might be 1BA threads, as 1BA has a pitch of 28.22 tpi which converts to 0.900mm and my 0.9mm gauge fits perfectly. But I measured the diameter at 0.194" which seems a bit small for 1BA (nominal 0.2087") so I still think they are 5mm (nominal 0.1969") x 0.9mm.

But my 10-32 nuts won't begin to go on these studs, so I still suspect they are different than the ones Art is looking at.

BTW, Maryland Metrics has a great chart for identifying threads.
 
I think what we have here is some of the gauges came with different thread styles. I know when I put my "32" gauge on the threads of the speedo, it fit just about perfectly, and Randalls isn't even close.

Edit: Just remembered...I have a 2BA tap. Why not match that up with the threads on my speedo and see how they fit?? Well, they matched prefectly. The threads on MY speedo is definetly 2BA. Since they are 31.4 tpi, that would explain why my "32" thread gauge seemed to fit pretty good, and why the loosey-goosey 10-32 nuts went on fairly easily.
 
I've seen those smaller ones, and mistook them for 10-32. Was on a post-60K car that I parted out, so I assumed (there's that word again) that it was a change for later cars. As I recall, there were several other slightly different details as well, including the calibration number.
 
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