Simple question.

I have replaced the vac pump, rotors, drums, shoes, and pads on my truck a bit ago. Vac pump originally went out and went ahead and did the rest, even though they had a few miles left in them. That being said, I am still not happy with them. I have driven a few other OBS trucks recently and the front brakes are much more responsive, and the pedal a bit softer than mine. My pedal feels the same as before with the OE pump. I can not lock my fronts up for the life of me if I tried on dry asphalt. I have had to step on it hard and swerve out of traffic towing 12k+ a few times when the village idiot is on the road, even standing on the pedal I can’t get them to lock. I’m not trying to lock them by any means, but they sure as hell do on other trucks if I apply that much force.

Pads, rotors, drums, and shoes were all oe equipment. Pump was not, but there isn’t a difference in feel over the old OE pump that finally went out. I replaced the new one with a second pump without noticing a change. Calipers are not dragging, but are dried out a bit, wondering if they need to be cleaned out and rebuilt, or just replaced. The entire system was bled when I did the brakes as well. Drums are always kept adjusted.
Masters failing typically give a soft pedal feel, and it is harder than any other OBS I have recent driven. My old OBS 460 gasser brakes much harder than the 7.3.

Any opinions?

 

If you have a hard pedal, it may be time for a new brake booster. There is a thread in the stickys about installing a zero loss booster.

 

I bought a 0 loss booster last spring. It has made a world of difference. For inspection I replaced the front brakes, calipers and rotors

 

From what I read, the 97's were the first to get the zero loss. Might be time for a new one though.

 

When changing your master cylinder, order a master for an F SUPERDUTY of the same year. it is a larger bore master and easily modified to fit, the mounting bolt holes need to be reamed closer to the center. it is amazing the stopping power you will get.

As for sliding the tires, a lot of that depends on how aggressive the pads are, I am currently running fleet pads from Oreilly's and when cold they are not at all aggressive, once they get hot they get real aggressive and don't fade.

 

A larger bore master will reduce the hydraulic pressure at the calipers vs the same applied foot pressure. The pedal travel will be reduced due to the larger displacement.

But I agree that the biggest improvement for getting more stopping ability is to use friction material with a higher coefficient of friction.

 

I have read a couple dozen threads regarding it. I however do not have the issue with a floating pedal, so I'm not sure if that is the case. I however think I may go along with it anyways.

I have replaced all but the booster/master.

Good to know. I however don't feel as if the master needs to be replaced, I could be wrong though. The pedal holds good pressure, and even get pretty hard towards the bottom as it should and does on all of my OBS trucks. The simple fact is the truck doesn't stop as it should. I agree the bite of the pads will make a big difference, but that being said I am running the same pad on 3 trucks, the other two are night and day different in stopping.

Larger bore simply increases volume, and won't reduce pressure at the calipers if one is held constant. More volume behind the same size pot will increase your pressure. is my thinking correct? Simple hydraulics. Either way its the best option and will be what I go with if I can not get this resolved.

 

No, back to hydraulics 101.

IF YOU INCREASE MASTER CYLINDER BORE DIAMETER:

Increase Pedal Effort
Decreases Total Pedal Travel
Reduced Push-rod Stroke to Master Cylinder
Decreases Line Pressure for a Given Pedal Force


IF YOU DECREASE MASTER CYLINDER BORE DIAMETER:

Decrease Pedal Effort
Increases Total Pedal Travel
Increases Push-rod Stroke to Master Cylinder
Increases Line Pressure for a Given Pedal Force

More volume behind a piston without an increase in pressure does not increase any force, but will increase the actuation speed ( movement).

 

I stand corrected! Must have been the whiskey clouding my thoughts the other night. Thank you!

 

Sounds to me like the booster is the issue, that or the check valve on them can leak.

 

well I will let you all know when I put a new one in...

 

Glad if it helped. Many make the same mistake and then think about it a little more. It gets more confusing when you start to work with hydraulic cylinder push and pull forces when many don't realize on the one side you have to decrease the piston area by the area of the rod. Many homemade log splitters end up with lower force then expected.