need help, brake conversion problems..

[tommie]

i have a 70' 1/2 ton swb. i converted the front to disc (6 lug) using a kit from GMC paul. i have replaced the master cylinder with one for a 71' chevy truck, non power, and a new proportioning valve for a 71' i bought all new steel ines from inline tube, and replaced the rear drums, shoes, wheel cylinders, springs. basicalyeverything is new...

the pedal has always felt very hard, i know, i don't have power brakes, but when the truck had 4 drums and now power the pedal effort was less.

i drove a friends truck tonight after aligning it, he converted his brakes to disc up front no power, and his pedal effort was much less, he is using a newer aluminum master cylinder though..

what kind of problems do you think i could have?

i was thinking it could be the master cylinder mabey? or could it be something with the kit i got from GMC paul? the kit was to put rotors on using 73-87 spindles for 1.25" think rotors. mabey the bore size is different on the calipers since they are for a 73-87?

any ideas?

thanks for the replies
tommie

[tommie]

ttt any suggestions? ideas? anything?

[krue]

No clue, have you pm'ed or contacted GMC Pauls for their input?

[tommie]

no, i didn't. i bought the basic kit from them, front rotors, bearings seals, front hoses, calipers and brake pads. i was just wondering if anyone else had come across this problem. i just haven't driven many vehicles with maunal brakes, and don't know if this is a normal characteristic or actualy a problem. was hoping some other people could chime in also...

[wibilly]

sorry i don't have an answer foryou but personaly i think it would be the perfect time to upgrade to power disk brakes

[tommie]

i would like to have power disc brakes, but i don't like the way the brake booster, and brackets look on these trucks, i would want a booster that would mount closer to the firewall.

[ChevLoRay]

I have power brakes, with an ECE disc brake conversion. My pedal pressure is the same as it was when it had drum brakes.

You really oughta talk to GMCPaul.

[Longhorn Man]

Drums use lower line pressure to activate the brakes than discs do.
Can you stop the truck?
Can you lock up the tires?
Does it stop better than before?
Is it really THAT important that you don't have the "ugly booster" on there?

[wibilly]

i'm pretty sure you could modify a later model mc and booster to fit closer to the firewall. i would be more concerned with stopping the truck than what the boster looked like

[tommie]

Originally Posted by Longhorn Man

Drums use lower line pressure to activate the brakes than discs do.
Can you stop the truck?
Can you lock up the tires?
Does it stop better than before?
Is it really THAT important that you don't have the "ugly booster" on there?

yes i can stop the truck, yes i can panic stop the truck, i have never tried to lock up the tires, it stops better than before(one of the front drums mas broken in 2 pieces before) but with the amount of pedal effort required, i would be leary of my wife ever having to drive my truck. (even if i was crazy enough to let her ....

no its not that important about the ugly booster. i would rater find a booster that looked better, if i have to use a brake booster.

the main reason that i started this thread was to see if anyone with manual disc/drum brakes, had an experience with a stiff pedal?

when i drove my friend's truck with manual brakes disc/drum his brake pedal felt completly different, it was almost twice as easy to press as my pedal, it seemed to stop very well also, form the 5 miles that i drove it.

i don't have any other trucks aroud here to compare with. no one else actually has theirs on the road.

has anyone else used a brake booster set up other than factory 67-72
that is actually closer to the firewall?

[neonlarry]

Like Andy said manual discs require more effort than drums (pressure wise about twice as much). If you don't like the big vacuum booster try a hydra-boost. A little more effort but worth it.