The Triumph Dolomite Club - Discussion Forum

Are the brake pipe fittings imperial 3/8"UNF or Metric M10?

I believe the tandem master cylinder has metric threads (two different ones to prevent the lines getting mixed!) but generally all the rest are imperial

xvivalve wrote: ↑Thu Dec 14, 2017 10:59 am I believe the tandem master cylinder has metric threads (two different ones to prevent the lines getting mixed!) but generally all the rest are imperial

Alun

Im gald you said that,as i have switched over from a single master cylinder,to a tandem master cylinder not made my brake pipes yet

Dave

Thanks guy, great info as normal

I've been dwelling on this all day, so just opened up a new tandem cylinder to check.

The smaller of the two unions is 3/8". The larger has a diameter that seems to be either slightly bigger than 7/16" or slightly smaller than 12 mm, but I've not been able to lay my hands on a bolt or union of either size to test. 7/16" seems the closer, but something niggles that there's something metric about the cylinder...

was the bore a metric size Alun? I have a twin cyl off a car and thought the threads looked imperial still?

Tony

xvivalve wrote: ↑Thu Dec 14, 2017 10:05 pm I've been dwelling on this all day, so just opened up a new tandem cylinder to check.

The smaller of the two unions is 3/8". The larger has a diameter that seems to be either slightly bigger than 7/16" or slightly smaller than 12 mm, but I've not been able to lay my hands on a bolt or union of either size to test. 7/16" seems the closer, but something niggles that there's something metric about the cylinder...

All the tandem cylinders i've had have metric at both outlet ports, I have unions in stock that fit the front (larger) port, they are the same as used in a number of Peugeot and Citroen rear wheel cylinders (which is how I buy them from the factors) I can't say exactly what the size is, i've never asked, but I can't imagine a French car company using imperial unions at ANY price! You can get a 3/8" UNF bolt into the rear port, but it will not tighten correctly if you use a 3/8" union on a brake pipe. The correct thread at the rear is 10x1.25, the standard metric male union.

Steve

Thanks Steve, good job I only lose tested 3/8” then!

Hi Guys I'm in the process of converting my Dolly to dual circuit and have obtained a tandem mastercylinder that definately has the primary outlet of 7/16" unf and the secondary of 3/8" unf as checked with thread gauge, micrometer and sample bolts just to make sure. I was told it was an early type so from previous replies it seems as though early ones are imperial and later ones are metric. Hope that helps.

Jim

pheaduk wrote: ↑Sat Dec 16, 2017 10:54 am Hi Guys I'm in the process of converting my Dolly to dual circuit and have obtained a tandem mastercylinder that definately has the primary outlet of 7/16" unf and the secondary of 3/8" unf as checked with thread gauge, micrometer and sample bolts just to make sure. I was told it was an early type so from previous replies it seems as though early ones are imperial and later ones are metric. Hope that helps.

Jim

There is an early dual circuit master cylinder that was only offered on certain export market cars which is different to the generally accepted tandem cylinder (Triumph part number519978) I've not seen one of these in many years, but this is presumably what you have and it may well be imperial. There are possibly even 2 different early ones as there is a LHD choice too (I have one of these, BOTH ports are 10mm)

Steve