Brake size 11" or 13 ?

[Wolverine]

1987 V20 with 14 bolt semi float rear, what specifically do I measure to determine if 11" or 13" brakes ?

 

[Radiohead]

Drum diameter

 

[nvrenuf]

1987 V20 with 14 bolt semi float rear, what specifically do I measure to determine if 11" or 13" brakes ?

If 13” is a choice I’d bet you or the parts guy is looking at a full floater. I could be wrong but I don’t believe 13” was available on the semi floater.

 

[Blue Ox]

Inside diameter.

Re: above I have a semi floater with 13" drums.

 

[Grit dog]

Same here. Semi floater with big back brakes. Stops well!
Probably the same since same color and all…lol.
Nice looking truck!

 

[fast 99]

If 13” is a choice I’d bet you or the parts guy is looking at a full floater. I could be wrong but I don’t believe 13” was available on the semi floater.

FYI both of my K20 4x4's were 13" and not floaters. I converted one to floater for safety reasons and wider shoe.

 

[Ontheboulder]

my 87 has the 11" brakes,full float 14 bolt

 

[Wolverine]

Same here. Semi floater with big back brakes. Stops well!
Probably the same since same color and all…lol.
Nice looking truck!

Thank you ! Not nearly as pretty as yours, but a work in progress !!

 

[sickchev]

The inner diameter on the drum. My 1979 C20 has a 14 bolt FF with 11" rear and JB6 up front.

 

[oldretiredafguy]

FWIW: This chart will decipher what your brake system is by the RPO code on your build decal.

You must be registered for see images attach

 

[Blue Ox]

C6P would be the RPO for the heavy-duty 8600 GVW package that would include the JD7 brakes.

 

[oldretiredafguy]

Just looked at my 1986 3/4 ton build sheet. It has the C6P option, but no listing for brakes. I'm going to assume that the C6P package included the HD brake package.