Joined: Tue Nov 07 2006, 11:35AM
Location: There, not here
Posts: 111
It's been so long for me I don't remember what's really what but. I have a 4 wheel set up and due to the cam I have I had to go with a dual vac booster. The only real problem I can see is with tranny linkage is that if it's held together with a screw tightened clamp. With the connection on the bottom, it will not go through all the gears. Just loosen the band clamp and twist the band around till you have clearance. Good Luck
Joined: Wed Dec 21 2005, 07:34AM
Location: indiana
Posts: 791
jazzandmoparguy wrote ...
I STRONGLY recommend not using the drum brake booster - yes it will work fine in most situations, but the reality is that it simply does NOT have enough boost to fully energize the disc brakes.
How will you feel when, because you couldn't stop/slow down just that bit more quickly enough to avoid a collision... or worse yet the child that runs out in front of you, that you could have prevented disaster for the sake of a few bucks?
You always find out you don't have enough brakes when you need them the most - when it's too late.
Get the right booster.
This! ^^^ All of it.
flj wrote ...
If I had the choice of front disc brakes set up using the drum brake booster or front drum brakes I would take the disc brakes every time. These cars were designed to work (maybe not great) if the booster had failed. I had a 66 Newport with disc brakes with no booster at all and the pressure to apply the brakes was very similar to the un-boosted drum brakes
For normal operation, with a panic stop after multiple heavy stops, the mismatched combo might have a performance edge if the drums would be fading. But on a panic stop on ‘cold’ brakes, I think the discs would be worse due to reduced boost.
Then, if there is no vacuum, that combination will have the worst available braking of anything because you have reduced leverage from your feet thru the PB pedal setup. In addition, drum brakes have a characteristic called ‘servo action’ where the shoes are drawn into the drums during operation, whereas discs do not have that characteristic, so another disadvantage (extent unknown, though).
flj wrote ...
Bad disc brakes are better than good drum brakes. Usually not enough brakes comes from shortcomings in the brakes themselves and not because the driver has not been able to apply enough force.
For brakes in poor condition, you may be right. But this is a retrofit, which should not include a questionable compromise from the onset. The fact that the factory used different boosters makes it questionable (not internet discussion). Yes, there are lots of areas where we modify our cars because the factory diluted some aspect of performance to suit the masses, but I don’t think this booster is one of those things. The factory did far more testing than we could ever dream of.
GranTorino -
Your combination needs to be correct from pedal to wheels, some variations of our backyard engineering fall within the realm of reasonably safe, some may not. You have several folks in this thread giving reasons to not use a drum booster (and Chrysler also, if you think about it), so you should take that to heart. I have seen similar discussions on Moparts, and similar sentiment from non-C folks also, it’s not just Jazz and me that would tell you this.
The original drum booster should NEVER be considered an option simply because it seems good enough for most conditions or because it’s ‘good enough for my driving style because I’m a careful driver’. You need your braking performance to be sufficient in an emergency, so after any major brake work you should fully test them (under conditions that do not jeopardize other drivers/people, of course).
IMO there are really only 2 ways to go with discs –
a disc booster, appropriate-bore MC and PDB pedal setup,
or discs with a small-bore MC , no booster, and MB pedal setup.
I have owned C-bodies since around 1991 (not saying I’m superior to everyone, just that I’m no novice at them) and did my 1st disc conversion in 1991 by digging thru the NAPA catalog and determining the where-used info on all the brake and suspension components. I’m also not saying I’m the 1st guy that swapped to discs, just that I learned about it all the hard way, on my own, way back before the internet.
In doing that 1st conversion I put a disc booster and MC on a MB pedal setup, because I didn’t know the pedals were different. The pedal was super-soft and seemed to always need re-bled. None of the ‘experts’ I asked (incl several brake/repair shops) during my months of diagnosis questioned the pedals either. That car had phenomenal braking, better than my sister’s then-new 91 Camaro, but the parts were mismatched. Who knows what might’ve happened if the booster was over-traveled by the longer pedal throw???
The conversion I’ve liked the best has discs (’73 style, but 69-72 would be comparable), no booster, MDisc MC from a mid-70s Dodge truck (which was available as an MDisc setup) and the factory C-body MB pedal. Braking feel is similar to the MDrums, so it has good foot control due to longer pedal travel, and the increase in braking performance is amazing. I can stand on the pedal with both feet and it stops faster/more controlled than any PDB C-body I’ve ever had, with the rear tires just on the edge of slipping (although my rear tires are wide). To avoid rear-wheel lockup a slight flex of my ankles is all that is needed to keep the back tires doing their job. Modulating a power brake pedal is much more difficult due to the really short pedal travel. I practiced several panic stops on country roads after the conversion and the hardest part was keeping my chest off the steering wheel from 30mph on down. I will probably do any future factory disc conversion with an MB pedal/non-boosted as the core.
Joined: Wed Dec 21 2005, 07:34AM
Location: indiana
Posts: 791
stubs300 wrote ...
It's been so long for me I don't remember what's really what but. I have a 4 wheel set up and due to the cam I have I had to go with a dual vac booster. The only real problem I can see is with tranny linkage is that if it's held together with a screw tightened clamp. With the connection on the bottom, it will not go through all the gears. Just loosen the band clamp and twist the band around till you have clearance. Good Luck
Yeah, from what I've heard from guys that used the large-dia disc boosters on 68-older cars, is that the column shifter will not travel all the way down into 1st, but the car can still be driven as normal.
Joined: Sat Mar 29 2008, 03:36PM
Location: North eastern Wis.
Posts: 1638
Personally, I would go with a manual set-up. I like the feel of both manual brakes and manual steering. Can't say why but I do. It's just easier, and one less part to malfunction. We all know what opinions are worth though.