Sizes of?.....

[Erik the Awful]

Metric is the distance between the threads. If the thread is 1.5 it means the threads are 1.5mm apart. In metric a higher number is coarser threads. In standard the opposite is true.

 

[454cid]

Metric is the distance between the threads. If the thread is 1.5 it means the threads are 1.5mm apart. In metric a higher number is coarser threads. In standard the opposite is true.

Ok, I thought it was more complicated than that. I know I've seen drawings with angles, though..... maybe it had to do with SAE/TPI, then.

 

[Armalite15]

If your truck has 10" shoes there is Dorman / MTM bleeder screw assortment #13949 that has 5 pairs of bleeders in it. Assuming your have stores there that carry Dorman, hope that might help.

 

[Pinger]

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,

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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.

Thanks for the link and info. I couldn't get the linked site to work for me - could only find C1500 not C2500 but we'll put that down to operator error (been a rough day).
And as you've done the heavy lifting for me....

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

But there's something not quite gelling here.

Firstly, the OD of the brake pipes on my truck is 3/16'' not 5/16'' as previously suggested. (Visually, they have a protective sort of wire wrap on them for most of their length but I forgot to check material (eg steel or copper) to help ascertain if genuine GM).

Secondly, the bleed valves on mine are very small. I have new unused bleed valves here that are no smaller than is fitted and they are M6 with 1.0mm pitch and the hex is 8mm across the flats. As I say, they do not look to be smaller than is on the truck currently. At a guess, they will fit.
Looking at the ones on the truck, I'm pretty sure they aren't M8. So that kind of implies mine has different slave cylinders.

The pipe fittings on the truck also look close to what I have here and they are described on the pack they came in as 10mm x 1.0mm for 3/16'' pipe.

It would be handy if the above is suitable because although the nut fittings look reusable the bleed valves are a bit tatty and I can't easily get out to buy more as I'm grounded after the door glass getting broken today - but need the brakes sorted ASAP for MOT (annual safety inspection).

Can anyone make sense of the above?

 

[Pinger]

If your truck has 10" shoes there is Dorman / MTM bleeder screw assortment #13949 that has 5 pairs of bleeders in it. Assuming your have stores there that carry Dorman, hope that might help.

The truck came with spare shoes and assuming they are correct - they measure 11&1/4'' across where the friction material ends and 12'' across where the steel ends (there's a part number on them but they aren't GM parts). The drums on mine are massive - fill out a 17'' rim. Must be a tight fit with a 16'' wheel.

 

[Armalite15]

OK that's definitely an 11" shoes set up which is normal for 3/4 ton although 10" is an option. I'd almost bet if you found that assortment locally one of those pairs would fit. If I can find an 11" specific listing I'll post it.

 

[Armalite15]

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As far as brake line is concerned I believe it will be 3/16 standard thread with an inverted flare.

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[Pinger]

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As far as brake line is concerned I believe it will be 3/16 standard thread with an inverted flare.

You must be registered for see images attach

Thank you kindly - most helpful. I was getting concerned that mine was some kind of bodged job with 3/16'' where it should have been 5/16''.

Re the Dorman kit - very likely I can get in the UK within the timeframe. I can very probably re-use the existing bleed valves for now - just not leave them in over a winter when I could have new with fresh hexes. My options are opening out.

 

[96-2D-Hoe]

If your truck has 10" shoes there is Dorman / MTM bleeder screw assortment #13949 that has 5 pairs of bleeders in it. Assuming your have stores there that carry Dorman, hope that might help.

This is how I changed them on my 96 Tahoe. I bought this selection and it had the sizes for the front and rear. IIRC the rear was metric and the front was imperial.


EDIT
The Dorman were not great quality and very soft. I used the kit to determine the sizes and then I bought some better quality ones. I have a pair ready to go on my fronts that I need to change as one is about to completely round off.

 

[HotWheelsBurban]

You might want to put a squirt of penetrating oil on the bleeder screws before you open them. Let it sit a while before you put the wrench on it. Those are easy to round off. There's special L shape wrenches for this purpose, that have a socket in one end, and they're hollowed out so any fluid can come out in a manner it can be controlled. There's also ones that are just box end wrenches that are bent 90 degrees. At lunch now so not close to the big toolbox at home, or l would post pictures. I used to read tool catalogs as a kid LOL.
Edit: a 2500 series should have at least 11" drums and shoes if not 13". My old 90 R2500 Burb had 13" and a semi floating axle. The drums were huge and heavy, but it would stop pretty well. Check on your truck build sheet or the option code list on the inside of the glove box door. The brake option code should be JB and a number like 6,7 or 8 for a 2500. You need this code to get the right parts, because this denotes the master cylinder, calipers, wheel cylinders and shoe and pad size and type.