Next, get a set of aggressive pads and shoes on it. Long story short, all pads and shoes sold in the US have a two letter DOT friction code on them somewhere. The letters indicate the coefficient of friction both cold and hot. Basically the closer the letters are to Z, the more aggressive the friction material is. The most aggressive pads I'm aware of that will fit JB6 trucks are the Raybestos EHT369H, they're HH code. Unfortunately FF code shoes are the most aggressive I've been able to find, but the bias still feels good to me even with the Raybestos pads on the front.
A follow-up comment on this: The buyer can't (generally) tell beforehand what friction code they'll get when shopping for pads; it's not as though the DOT friction code is listed on RockAuto along with the part numbers. Rather, if you first
buy a set of pads and then
look at them, you'll find the code on the back.
@df2x4, did I get that right?
Now,
@nick7269, regarding the NBS MC you said you've already bought. It's designed to be used with calipers that are
not the "low-drag" type. AFAIK the GMT400 calipers having the larger bores (3.15 aka 80mm and 3.38 aka 86mm, typically deployed on 2500/3500s with JB7/JB8 brakes), are not the "low-drag" type... so the NBS MC will work well with them (as will an MC designated for JB7/JB8, as it is not a “quick-take-up” MC).
The 3" aka 76mm bore calipers are AFAIK "low-drag" type and were used on JB5/JB6 equipped vehicles. These "low-drag" calipers require a corresponding "quick take-up" MC designated for JB5/JB6.
(edit:
See @Schurkey ’s remarks in the subsequent post.)
See the attached .pdf regarding “low-drag” calipers and “quick take-up” MCs, and be enlightened.
Somebody correct any mis-statements I've made above; there's probably at least one.
This thread (link below) is reasonably coherent IIRC on the topic of front wheel brakes, but it does disclose a
lot of different combinations of front equipment, possibly to the point of confusion (including front brake combinations which came on single or double rear wheel 3500s). It touches on the rear brakes a bit too.
Hi I am new to the forum. I Looking to upgrade my brakes. I have a 88 GMC K2500 with 6 lug wheels..(7200lbs). I have front calipers with the 2.94 diameter piston. Has anyone upgraded to the 3.15 calipers from the 8 lug (8600lbs) calipers. Is this a direct bolt on caliper. The only difference...
www.gmt400.com
I modified my K1500's JB6 brakes years ago using the NBS (for a 2001 Silverado w/ vacuum boost) and 3.15" bore calipers in front, with K2500 pads in the calipers and SS lines. I've made minor changes to the rears too (SS lines and bigger cylinders).
I'm very pleased with the performance of my brakes, which BTW use OE vacuum boost. Others here will tell you hydroboost is notably better. While I believe they're correct, I'm so darn pleased with how mine work now, esp. compared to how they once worked, that I'm staying-put. I DO have the hydroboost valve body NIB on a shelf, and the requisite PS cooler I have already installed; all I need AFAIK are the brake pedals, hoses and motivation.
Knowing what I know now, I probably would have used a JB7/JB8 vacuum boost MC instead of the vacuum boost NBS MC, as AFAIK NBS has a larger piston diameter 1.34" aka 34mm vs. the JB7/JB8 1.125" (vacuum boost) or 1.25" (hydroboost) bore MC. The larger bore of the NBS MC offers less hydraulic advantage ("leverage") over the slave cylinders, by a factor of the ratio of the bore area, e.g., for a 1.125" bore (vacuum) to a 1.34" bore it's 70%, and for 1.25" bore (hydroboost) it's 87%. All that said, I don't feel like my NBS MC brakes are underboosted.
For the record, I believe the hydroboost NBS bore is 1.46" aka 37mm, at least for some 2001 GMT800s.
The NBS MC
is suitable for rear disc brakes by virtue of its larger reservoir, which may be useful for others but that doesn’t apply to me (tho maybe someday I’ll graft on a GMT800 disc brake rear).