swap/upgrades to front calipers

[borahshadow]

Id just put the 3/4T M/C on it.

With all this talk of the master cylinder not matching the bigger brakes I'm a bit confused. I can see the reasoning and the engineering logic behind saying that they have to match (and I don't necessarily disagree with it) but what about the hydroboost? The same master cylinder is listed for all models with hydroboost. Be it a 1500, 2500, or 3500. So if the master cylinder is the same for all the calipers that goes against all the explanations saying how important it is for them to match...

 

[scoob8000]

Id just put the 3/4T M/C on it.

You'd need to change the booster for that master. Changing the booster, might as well do hydroboost.

I'm gonna drive it a few more miles and finish bedding the pads and bleed it one more time. If it doesn't get better, I'm putting the proper 1/2 ton calipers back on it.

 

[TylerZ281500]

are your bleeders on top or bottom?

 

[scoob8000]

are your bleeders on top or bottom?

Top. I'm confident they were bled down good. Pedal feel didn't change when pumping them up.

Don't get me wrong, the truck stopped. Just with the pedal on the floor. And couldn't engage ABS on dry road.


Just put the 1/2t calipers back on and bled them, night and day better. I can also now make ABS kick in on a dry road panic stop.

 

[Coveman]

Just catching up... are you still running the 3/4 ton calipers? Any chance you'd consider swapping the MC?

 

[Coveman]

Well got it all buttoned up last night. Going to the 3/4 ton calipers was a major mistake.

Sparg93/Nakk,
I'm as sceptical with the NBS master cylinder. Wouldn't the porportiong valve/combi valve handle the residual pressure to the rears? Or do our trucks not have an external one, I don't have the truck with me and don't recall seeing it.

The combo/proportioning valves are under the haynes ABS module on my truck. In addition to the work you've done up front, I wonder if your rears are operating optimally. Have you adjusted the drums? That can contribute to the long pedal travel. Can you lock those up / trigger the abs?

 

[Neb15]

Am I sol with a 5 bolt 1/2 ton for better brake parts (short of hydroboost)?

 

[ccreddell]

No, but I havent finished building it yet. Hopefully soon.

 

[Ironhead]

A very interesting and educational thread. Particularly appreciate NAKKs look at the total system.

What I think is missing here is some sort of valid comparison between the braking performance of a GMT 400 and GMT 800 truck. If they had similar tires, and options, I'd like to know if the 800 stops appreciably shorter than the 400. I'd also like to know the fade resistance of both systems.

If the 800 brakes really do perform much better than the 400, then the swap of the total system (calipers, rotors, MC, proportioning valve, etc) would seem to be worthwhile, especially if you have to do a brake job anyway.

 

[evolocomotive]

If the 800 brakes really do perform much better than the 400, then the swap of the total system (calipers, rotors, MC, proportioning valve, etc) would seem to be worthwhile, especially if you have to do a brake job anyway.

But a full on swap is astronomical, your better off doing a OBS 3/4 ton MC swap, SS Brake Lines, pads, rotors and calipers. I just did that on my son's 97 k1500 F44 code truck and braking is 1000 times better than before, and did the rear drums as well . Total cost was around 700 with labor. Shop didn't even take the whole day, dropped off in the morning and they were done before he got out of school at 3.