Brakes Update

[DeuceKustoms]

ok, so as a few of you already know, its way PAST time to update the brakes in my 59 Pontiac.

Here is my 2 options:

1) buy disc coversion brackets that bolt onto stock spindles, using 77 Bonneville wagon 12" rotors and 68-72 GTO calipers, thusly forcing me to switch to 15" (or larger) 5x4-3/4" front wheels, (stock is 14" 5x5"), which would in turn force me to run 15" 5x5" rear wheels, and buy tires for these new wheels, (which I need new tires anyways, i guess).

the conversion brackets alone are $165, then I would be looking at off the shelf parts prices for  rotors, calipers, pads, hoses, bearings etc. probably be around $300-400, not including new wheels/tires/booster/master cylinder. but this would also convert me to roller bearings instead of ball bearings ($265 to replace both sides on the front) so this option could potentially save me money down the road...

-or-

2) Rebuild my front drum brakes (rears were completely redone last year), icluding new booster and dual-chamber master cyl (single has screwed me twice now), wheel cylinders, hoses, etc.
Re-doing and retaining the front drums to me is plenty easy enough, but the only question I have is about plumbing the brakes after replacing the booster/master cylinder. was looking at getting a universal GM style setup, but speedway says its setup for disc/disc, or disc/drum. and they say that you need to use Residual pressure valves in each circuit (psi depending on what style of brakes) and to use an adjustable pressure valve in the rear circuit.  

can I just use a stock-style GM proportioning valve right off the master cylinder, and then plumb the lines from there using the RPV's in both circuits, or can I forgo the RPV's since I am going drum/drum? this is where it gets tricky for me, as I really don't want to screw up my brakes... i know that My 70 pickup has a non-adjustable proportioning block right off of the master cylinder and then straight lines to front and rear, with no adjustments, to a drum/drum setup.

I guess if anyone has already done either of these types of setups, as I am sure some have, I just would like to hear some feedback of pros and cons of either way before I start ordering parts.

Thanks for all of your help!

[tracywiedrich]

Are you sure front rotors off a 77 Bonny dont have the same bolt patttern as your originals. I just hauled a 77 Bonneville to the srapper and it came from the factory with the five spoke ralleyes and they were 5on5 not 5 on 4,3/4...

[31Rodder]

I used option 1 on my old 55 chev.  I did not have any better braking after switching over.  the thing that was nice as you said you get the roller bearings instead of ball bearings.  I too had to switch rims.

I too had brake failure with the single resivoir as a rear brake line gave way to too much heat from the exhaust.  Long story.  Luckily I just went up the Ayr exit and back down the Ayr exit without incident.

So that being said, I would go for option 2 and switch to the dual master cylinder.  I think if you check out the classical pontiac site they have alot of good info on that and which master cylinder to use.  I just don't remember anymore.  starting to lose what I once knew.

[Serious]

What i have read is that Drums need 2psi RPV and discs need 10PSI.  But i have also read you dont need them if the master cylinder is higher than the rest of the system.  All they are there for is to keep all the fluid from backfiling the master cylinder.

if i were you id rebuild your stock stuff.  those drums are great for one stop, the only time i think they have issues is having to stop multiple times in short succession then you have pretty serious brakefade.  i run all the stock stuff on the edsel, and they work great.

[Tom]

I like the idea of you thinking of going to 15" wheels. It's easier to find used tires ( well it used to be ) and in most cases I think it fills the wheel opening better.

[Kustom Dallas]

I think some GMs had pwr drum brakes with dual master.

[DeuceKustoms]

Are you sure front rotors off a 77 Bonny dont have the same bolt patttern as your originals. I just hauled a 77 Bonneville to the srapper and it came from the factory with the five spoke ralleyes and they were 5on5 not 5 on 4,3/4...

I guess you are right. I got ahead of myself in assuming they were 4-3/4". my mistake. fact is though, I still cannot use my stock 14's with the disc brakes.

[tracywiedrich]

The nice thing is that 5x5 steel wheels are easy to find. Chevy pickups, large GM cars and some Ford large cars all had em....good luck

[DeuceKustoms]

What i have read is that Drums need 2psi RPV and discs need 10PSI.  But i have also read you dont need them if the master cylinder is higher than the rest of the system.  All they are there for is to keep all the fluid from backfiling the master cylinder.

if i were you id rebuild your stock stuff.  those drums are great for one stop, the only time i think they have issues is having to stop multiple times in short succession then you have pretty serious brakefade.  i run all the stock stuff on the edsel, and they work great.

that makes sense aaron about the M/C being mounted higher than the rest of the system, since the typical street rod M/C would be mounted on the frame rail, thusly requiring the RPVs. So if i was to just use a stock GM proportioning valve from a drum/drum car, i should be fine just re-plumbing the lines from the new dual master cylinder.

[DeuceKustoms]

so I guess right now I can get by with just putting a new booster/dual master cylinder, and re-plumbing the entire brake system, without messing with my front brakes. they work fine as of right now, and last summer when I inspected them they looked alright, at least like they had been gone through quite a bit more recently than the rears. they should get me thru for now, and at least if I blow a wheel cylinder (again) I won't lose all of my brakes. then in the meantime I will probably start acquiring the necessary parts to convert over to disc brakes. I have no problem with my drums, but I really want roller bearings, as I have a feeling that my one wheel bearing is going out again (or already may be) and to replace just the front wheel bearings on that is $256.00 (yikes!) so It will probably save me alot of money down the road to convert to discs, as well as probably being cheaper up front too. i dont know if I can get my drums turned another time or not and new ones are $120 each (double yikes!) right there that is $500.00 just for wheel bearings and brake drums. I don't really see that as being "worth it". just a thought...

[racerjohnson]

What i have read is that Drums need 2psi RPV and discs need 10PSI.  But i have also read you dont need them if the master cylinder is higher than the rest of the system.  All they are there for is to keep all the fluid from backfiling the master cylinder.

if i were you id rebuild your stock stuff.  those drums are great for one stop, the only time i think they have issues is having to stop multiple times in short succession then you have pretty serious brakefade.  i run all the stock stuff on the edsel, and they work great.

that makes sense aaron about the M/C being mounted higher than the rest of the system, since the typical street rod M/C would be mounted on the frame rail, thusly requiring the RPVs. So if i was to just use a stock GM proportioning valve from a drum/drum car, i should be fine just re-plumbing the lines from the new dual master cylinder.

A little background/correction on the M/C being higher than the wheel cylinders. The residual pressure valve is required with drum brakes because the springs on the shoes are constantly trying to pull the shoes back away from the drum, forcing the pistons back in and the fluid back into the M/C. That also means if you didn't have a RPV the shoes would pull away from the drums too far and you'd have to pump the brakes everytime you wanted to stop to make up the increased distance between shoe and drum. Yes, a 2psi RPV is good for that. For disks with the M/C higher than the wheel cylinder, no RPV is needed. No spring or anything else involved in a disc caliper to pull brake pads back. The piston backs off on its own (and with a little help from the rotor knocking it back).

I agree that you need RPV's at all corners with the M/C lower than the wheel cylinders to avoid filling the M/C, but I don't know what psi is needed. I'd research the stock proportioning valve personally and use it. Hope this helps.

Come to think of it, I can't remember if I put RPV's in my roadster. DOH!

[Serious]

i believe that most OEM Master cylinders have the RPVs in them factory. either that or the Poportioning valve.  i m not sure witch.

[Eyeball]

It's true that most OEM masters have the RPV's but you will not find them in most remam units. The remans use to have them but the last few years they are no longer puting them in but I don't know why. The master I used on the 32 was suppose to have them in from the factory and the reman unit does not so I added them and fixed my brakes.

[DeuceKustoms]

It's true that most OEM masters have the RPV's but you will not find them in most remam units. The remans use to have them but the last few years they are no longer puting them in but I don't know why. The master I used on the 32 was suppose to have them in from the factory and the reman unit does not so I added them and fixed my brakes.

thats good to know... sounds like cheap insurance anyways, since I will be re-plumbing the whole works anyways.  

and also, after doing all my math, it looks like its going to be a bit cheaper to convert to disc brake fronts, plus it will save me a lot of money down the road... esp. wheel bearings ($30/set vs. $260/set), rotors ($50/ea vs. $120/each) etc... plus I guess I will have a slight bit more peace of mind running new stuff. Plus I realized I already have a set of 5on5 15" rims at my house (DOH!) so I just need a set of skins.

oh yeah... and the wife is apparently ok with me spending money on my car... weird...