Rear brake nipples

[Jon_Dodson]

Are they all a standard thread size across all cars (modern and old)? I’ve always struggled to bleed my Mk2 because the back plate gets in the way. The hex bits are now quite mangled. I’ve seen extra long nipples advertised on Amazon but the advert doesn’t describe the thread so I’m hoping they’re all standard? Kinda doubt it for an AF car in a metric world, but thought I’d ask here anyway in case anyone knows for sure. Thanks, Jon.

[wild bill]

I think you'll find that the ones advertised are metrics when I was working,I used to fit them.I did take one and re-thread it UNF to suit the prop shaft and other grease nipples, but I certainly would not trust putting modified ones into the brake cylinders.

[johnnydog]

I have a good number of new rear wheel cylinders, both nos and new aftermarket. The thread size of the bleed nipples does vary, as some aftermarket cylinders have larger sized bleed nipples. The length of them varies too. I try to fit replacement cylinders with longer bleed nipples for the exact same reason as you have found.
I would be tempted to remove one, go to a good hardware supplier that can check and establish the thread type / size and then locate longer bleed nipples based on the thread size which should make the job a lot easier.

[Jon_Dodson]

Thanks both. Good idea about getting it measured (they are actually aftermarket cylinders/nipples). I think there’s more air than fluid in the system at the moment anyway so I shouldn’t lose much.

[johnnydog]

If you put a hose clamp or even carefully placed molegrips on the the flexi pipe, then you shouldn't loose too much before doing a full brake fluid change and bleed when you get longer bleed nipples.