Sizes of?.....

[Pinger]

I have to replace corroded rear brake lines on my 1999 Suburban C2500 and the bleed nipples (that's what we call them in the UK but maybe you call them valves) are looking a bit ratty. Does anyone know the thread size. All I can find in the GM manual is 'GM SPO Group Number 4.666' and when I Googled that found that it was fitted to Chevrolet's in the 1950s - which I'm guessing wasn't metric then.
I have some new nipps here that look about right but if I knew the correct thread I could better check that they are - or get hold of new ones before I get started.

Ditto the fittings that fix the rigid pipes to the slave cylinders and the connection with the rubber hoses. The sizes of the nipps are more pressing though - if anyone knows them?....

 

[SUBURBAN5]

When it comes to wheel cylinders I order the oem ones. 2nd if your also talking about the plungers I clean them off with a wire brush and reuse them. 3rd normally the bleeder valves/ nips come with the new ones. So never needed to replace that unless I needed I new cylinder. I never rebuilt the cylinders for piece of mind. On your new ones maybe find the rubber caps that cover the nips /bleeder... helps protect them from gunk. I'll send a pic of mine later

 

[Nad_Yvalhosert]

The inverted flare 3/16" steel brake lines use a 3/8 x 24 fitting.
Here in the states, a set of wheel cylinders only cost about 5 bucks each. Pretty darn cheap just to replace them... Comes with brand new bleeders.
As for the lines, universal replacements come in multiple lengths. And if you're proficient with a cutter, bender, and flare tool, buy ones longer than you need, and cut & flare 'em for an OE look.

 

[96-2D-Hoe]

I have to replace corroded rear brake lines on my 1999 Suburban C2500 and the bleed nipples (that's what we call them in the UK but maybe you call them valves) are looking a bit ratty. Does anyone know the thread size. All I can find in the GM manual is 'GM SPO Group Number 4.666' and when I Googled that found that it was fitted to Chevrolet's in the 1950s - which I'm guessing wasn't metric then.
I have some new nipps here that look about right but if I knew the correct thread I could better check that they are - or get hold of new ones before I get started.

Ditto the fittings that fix the rigid pipes to the slave cylinders and the connection with the rubber hoses. The sizes of the nipps are more pressing though - if anyone knows them?....

You should be able to find all those parts pretty cheap on rockauto.com. You may also be able to find the sizing info you need. I'm pretty sure they ship internationally. There's also a 5% discount code.

 

[Pinger]

You should be able to find all those parts pretty cheap on rockauto.com. You may also be able to find the sizing info you need. I'm pretty sure they ship internationally. There's also a 5% discount code.

Trying to source in UK as need to get this done by next week - Rock Auto shipping takes 2-3 weeks.

 

[Pinger]

The inverted flare 5/16" steel brake lines use a 3/8 x 24 fitting.
Here in the states, a set of wheel cylinders only cost about 5 bucks each. Pretty darn cheap just to replace them... Comes with brand new bleeders.
As for the lines, universal replacements come in multiple lengths. And if you're proficient with a cutter, bender, and flare tool, buy ones longer than you need, and cut & flare 'em for an OE look.

Definitely 5/16'' OD?

 

[east302]

This site may help as they show the GM part numbers/diagrams and usually have information in the part descriptions. I don’t think that you can order from them, though.


https://nemigaparts.com/cat_spares/epc/chevrolet/

For example,

You must be registered for see images attach

You must be registered for see images attach

The model codes are in the center column and are a three digit number followed by two numbers in parentheses. GM part number is in blue on the far right.

The first digit is the load capacity (1, 2 or 3 for 1/2 through 1-tons) and the next two are the wheelbase.

07 - short wheelbase
09 - long wheelbase

So your 2500 Suburban would be 209, the number prefaced by C or K for drive type.

The numbers in parentheses define the cab type:

(03) two door cab
(06) four door utility [Suburban or Tahoe]
(16) two door utility
(43) four door cab
(53) two door extended cab

The complete number for yours would be C209(06).

In the second image above and first row, it says that the bleeder is used for CK1,2(06-16). So that’s any 1/2 or 3/4 ton two or four door utility. Applicable RPO codes for each system are then listed. Note that the GM part number is actually the same despite the separate line items for each part.

Regardless, it’s showing an m8x1.25 bleeder in the part description.

 

[454cid]

Metric threads are different.....threads don't crossover. The tubing should work with either.

Our trucks use sae threaded double flare fittings.

I've noticed that Rockauto specs can be off in this area or at least in constant. Edit: speaking of things like wheel cylinders here. You'll often see both SAE and metric measurements, so unless you know its not always obvious what the designed size is.... one will be a conversion and sometimes not accurate.

 

[east302]

Metric threads are different.....threads dont crossover.

Good to know, thanks for clarifying.

 

[454cid]

Good to know, thanks for clarifying.

Just in general, Metric and SAE threads are speced differently. SAE is tpi (threads per inch) and metric is pitch, which if I recall correctly has to do with angles between threads.

Here's something I learned/observed when doing my Saturn's lines.... looking at straight sections of lines with fittings.

SAE, with double flare is labled as American or US or something
metric with double flare fittings is labeled Japanese
metric with bubble flare fittings is labeled European

My Saturn as with some other GM vehicles actually uses the European. I had never used bubble flare but it's kinda nice, as it only uses one press, with the flaring tool. I don't have a lot of experience doing brake lines, so maybe there is something about double flares that I'm missing, as I've only done one or two of them.