disk vs drum pedal effort

[jocko]

Gents, basic disk vs drum brake question - how does the pedal effort for a MANUAL disk brake setup compare to a MANUAL drum brake setup? I've only ever had power disks or manual drums, so I'm missing the middle of the road for comparison. Gonna (eventually) do a front disk install, and am contemplating whether or not to include a power booster in the process.

My current manual drum setup (all stock) really doesn't require too much pedal effort - it's actually a very solid drum/drum original system, but I do want to convert here in the next 6 months or so.
Thanks guys.

[markeb01]

In my opinion, manual disc brakes require a lot more pedal pressure than manual drum brakes. This is because bendix drum brakes are self-energizing. Design features in the shoe attachments cause the rotation of the drum to dramatically increase the clamping force against the drums beyond what is applied at the pedal. Earlier style Huck brakes and disc brakes do not provide this self-energizing benefit. To multiply clamping force in these systems a comparable increase in pedal pressure is required.

A person without back problems may find manual disc brakes acceptable, but for someone like me with chronic back pain a booster in the disc brake system eventually became mandatory.

[onequickchevy]

I agree with that. I used manual due to my engine ( big cam and very little vacuum ) and it stops great. The harder I push the pedal the faster I stop. I don't have back issues so it doesn't bother me, but I can see where it could take the joy out of driving if you did.
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[geezer#99]

I ran manual disc's once. Found out they work best if you use a master cylinder with a smaller bore. I went from a 1 1/8" bore down to a 1" and it made a world of difference.
I think wilwood has some in even smaller bores.

[MikeN]

I put manual disc brakes on a Chevy Nova once, years ago. Honestly, I hated it. The pedal effort required to stop was way too high. If you're going to disc brakes, do it right and get a booster, IMHO.

[jocko]

thanks guys, that's what I was looking for. I've read/heard some claims (by mfgrs, of course) that manual disks will reduce pedal effort compared to the original drums, but found that odd - primarily because of what markeb01 mentioned, the self-energizing design of some manual brakes. (thanks markeb01, that's the bit of info I was trying to remember as to why these claims didn't make sense to me) - so figured I'd ask a few folks who may have done this conversion.

To be honest, the MAIN reason I was even considering manual disks was to keep the firewall a little cleaner - I do think manual brakes only (i.e. no booster) looks a little better/cleaner - but in the end, I will be going with the power booster. Thanks for your help, much appreciated!

Now, if I get really ambitious, I've been wondering about a kugel under-dash 90 deg power set-up and leaving the ol crusty stock single master cylinder under the hood for "show" only... I'm not all about original looking, I just like to be "innovative" I guess. Probablyu MUCH more trouble than it's worth - and I'm about 99% sure that I'll just go with the normal swap in the original master cylinder location. But it sure would be cool.

[MikeN]

Have you considered a hydra-boost?

[72BlckButy]

Running manual discs on my '69 and I haven't noticed much of a difference; if any it requires slight more pressure.

Now... I used to be able to lock up the manual drum brakes and I can't do that with the manual discs, but that didn't bother me much.

Still stops on a dime. I wanted to keep mine as stock as possible so I went with the disc brake upgrade (with lowering my truck 4.5/6") from ECE. No regrets.

[Hottrucks]

not the same but I addded the booster to my 70 thats a drum truck and the change was rediculious!!! had I known how much diff it was going to make I would have ponied up long before this...It stopps my 500 caddy long bed really well...I still plan on a disc set up but only because I have them and I want more drop at ride hieght

[61_FL_Apache]

I have tossed this idea around in my head too. Im planning to keep my 4 wheel manual drum. It stops good and straight....

On a side note: At my companies mechanic shop, a tool vendor stopped by. He shows us a tool to detect moisture in the brake fluid. It has a scale from 1-4. Im not sure if that is a %. Apparently, brake fluid can attract moisture and has to be changed more than you think. Water and hyd. fluid are going to compress at different rates making the effort different I would think.

[protrash64]

I have 2 trucks with manual disc brakes and I recommend grade 8 fasteners on your seats. They do require more pressure in my experience.

Many vehicles ran them from the factory so there are probably a few tricks to getting them working the most efficiently.

[likaroc13]

this is the same thing i was questioning not long ago...currently doing a disc brake swap on the front of my '66...haven't decided yet whether i will use a booster or not, but i will most likely use a booster...is any one particular booster better than another?

[markeb01]

Originally Posted by likaroc13

...is any one particular booster better than another?

I’m using the Master Power Brakes 9” slimline booster because it was the only option offered as a kit back when I did the swap:

http://www.mpbrakes.com/products/pro...product_id=194

It makes the pedal effort “comfortable”, but is on the light side regarding boost. For real “power” brakes the 8” dual diaphragm version or a larger factory unit would probably provide a great deal more power assist. Here’s the 8” design:

http://www.mpbrakes.com/products/pro...product_id=631

[greg64]

Any of you guys that ARE running a booster also have a hydraulic clutch? I'd like to have both, but the space seems awfully tight.

Thanks for any thoughts.

[jocko]

MikeN, I have considered a hydro-boost - but since my goal was to be "less" futuristic looking if I decided to go with power brakes, the hydro-boost stuff (although smaller, which I like) kinda looked like "laser beams" next to my simple dual master if ya know what I mean. So I think that when I do the upgrade, I will go with a vac pwr booster. Thanks for posting - that is a great question and one I've been considering for some time.

Markeb01, thanks for the links, this brings up a BIG follow-up question I've had in the back of my mind (and part of the reason I asked this in the first place). If you look at both of the boosters you posted links to, I notice they have a significant standoff bracket from the firewall. It seems that most kits have this set-up. What I'd really like to do is have the least amount of standoff as humanly possible and get the booster very close to the firewall. I've seen the Capt's brackets and they do a nice job of that - but then I'm not sure how long to make the brake push rod from the pedal to the master, other than trial and error.

Here's a pic of one that looks like it was done using factory (i.e. chev from later years) and has minimal/no standoff from the firewall - I really like the looks of it and was wondering if I might be able to replicate this setup - I imagine it would be a "piece it together" affair since all kits I've ever seen have a pretty big standoff bracket.

Anyone know why most kits have this big standoff from the firewall? Is it just to avoid other stuff on the firewall (like ballast resistor, etc)??

Thanks for all the posts, this is helpful.
jocko

[jocko]

Originally Posted by greg64

Any of you guys that ARE running a booster also have a hydraulic clutch? I'd like to have both, but the space seems awfully tight.

Thanks for any thoughts.

Are you talking hyd throwout or hyd slave?

I think Capt Fab makes a nice bracket that allows this (slave, maybe would work for throwout also?). I've also seen them from Novak - I think they use a wilwood reservoir.

Here's a great thread by TR65 - you'll note he has the whole enchilada, hyd clutch, power booster, dual reservoir, etc. GREAT thread. http://67-72chevytrucks.com/vboard/s...d.php?t=300087

Here's the Novak Link for Hyd Slave retrofit (this doesn't really answer your question, this is the bell housing part though if interested): http://www.novak-adapt.com/catalog/kit_hcrc.htm

Keisler also offers some options if you're looking for Hyd throwout stuff: http://www.keislerauto.com/index.php...-or-truck.html (note - I had some trouble with this link, apologize if it doesn't work)

hope that helps. I think TR65's thread is probably the best info you can find anywhere.

[jocko]

here's a follow-up to my previous post about booster-to-firewall distance. Attaching another member's engine compartment - I really like the look of his brake set-up, he mentioned to me it only has about a 1.5" distance from back of the booster to the firewall and I think it looks really good. So this is an exception to what I mentioned above - this was a CPP kit 6366BB2 with a 9" booster for reference.

[Captainfab]

The hydroboost units can be rotated 180* to position the hoses on the bottom of the unit as opposed to the factory position on the top.

Determining the correct length of the booster pushrod is really quite simple. There's a couple ways to go about it depending on what means you have to accomplish the job.

The brake booster and bracket shown in that pic is an original factory assembly. There was one of those for sale in the classifieds not long ago.

Originally Posted by jocko

MikeN, I have considered a hydro-boost - but since my goal was to be "less" futuristic looking if I decided to go with power brakes, the hydro-boost stuff (although smaller, which I like) kinda looked like "laser beams" next to my simple dual master if ya know what I mean. So I think that when I do the upgrade, I will go with a vac pwr booster. Thanks for posting - that is a great question and one I've been considering for some time.

Markeb01, thanks for the links, this brings up a BIG follow-up question I've had in the back of my mind (and part of the reason I asked this in the first place). If you look at both of the boosters you posted links to, I notice they have a significant standoff bracket from the firewall. It seems that most kits have this set-up. What I'd really like to do is have the least amount of standoff as humanly possible and get the booster very close to the firewall. I've seen the Capt's brackets and they do a nice job of that - but then I'm not sure how long to make the brake push rod from the pedal to the master, other than trial and error.

Here's a pic of one that looks like it was done using factory (i.e. chev from later years) and has minimal/no standoff from the firewall - I really like the looks of it and was wondering if I might be able to replicate this setup - I imagine it would be a "piece it together" affair since all kits I've ever seen have a pretty big standoff bracket.

Anyone know why most kits have this big standoff from the firewall? Is it just to avoid other stuff on the firewall (like ballast resistor, etc)??

Thanks for all the posts, this is helpful.
jocko

[markeb01]

Originally Posted by greg64

Any of you guys that ARE running a booster also have a hydraulic clutch? I'd like to have both, but the space seems awfully tight.

Thanks for any thoughts.

Post #2 on the following thread shows how I did mine:

http://67-72chevytrucks.com/vboard/s...draulic+clutch

[jocko]

Thanks Capt! Can you post a link to determining the correct rod length or explain? I agree it would/should be straightforward, but wanted to make sure I wasn't missing something.

[michaudracing]

My experience seems to be a little different. Maybe my original drum brakes weren't up to spec. I have factory '76 half ton calipers and manual master cylinder. I still have the original '63 rear drums. After installing carbon/metallic pads and drilled rotors, I need less pedal effort to stop as compared to the drum/drum setup. I have worked on several cars with mismatched custom combinations, and it's always been difficult to dial the system in. M/C bore and stroke, brake pedal geometry, rear brake type, booster type, and the brakes themselves (rotor type/diameter, caliper volume, pad compound and surface area) will all affect pedal effort. I believe it's possible to get a manual disc system with drum-like pedal effort. It may take a lot of tinkering. I've used brake pressure guages to actually get numbers on what the changes do.

-Steve


-Steve

[Captainfab]

Once you have the new booster bolted to the firewall, crawl under the dash. Then hold the original pushrod in position on the pedal, and parallel to the new pushrod. Then make a mark on both pushrods in a convenient place to cut them both. An area where they are close to the same diameter would be helpful. Then remove the booster and cut both pushrods. Now connect the two pieces by either welding, sleeving and cross pinning, or threading and screwing together with a coupling nut. Just be sure the original pushrod is in the middle of it's adjustment. This way you can still adjust the pushrod after the lengthening.

I hope that makes sense.

Originally Posted by jocko

Thanks Capt! Can you post a link to determining the correct rod length or explain? I agree it would/should be straightforward, but wanted to make sure I wasn't missing something.