Quick drum to disc question

I talked to my friend a while back and he said he got a Wilwood conversion for his Mustang and he used his stock master cylinder because it was already a dual bowl setup. I was wondering if I could do the same since mine is a dual bowl setup, too.

Anything to save money, you know? :p

Also, would the hardlines for the drums be good enough for the discs? Maybe even the flex lines? Or would those not even match up?

Thanks,
Matt

this is MP Brake's tech site... check out page 49. talks about differences in disc/drum masters vs drum/drum masters... and disc/disc master cylinders...

ya may wanna browse through a few of the pages... may be of use to ya... this link is posted in the Web-Link Library, pg 2 in the brakes section ;)

http://www.mpbrakes.com/uploads/content/2006%20catalog.pdf


as far as hard lines go, i'm thinking yer stockers'll be fine... brake hoses maybe ya wanna upgrade to a braided hose (front & rear)



hope i helped :D


edit... yer brake hoses aren't the same. drum ta discs... you'll need the proper hoses to attach hardlines to the calipers... they'd prolly be supplied in whatever kit yer thinkin' of getting...


be Good :D

The disc brakes require more pressure than drum brakes. The piston size in the master cylinder is different from drum to disc. The hard lines will work, but we have found changing from 1/4 hard lines to 3/16 line incresaes brake frimness. The smaller hard line allows more pressure.

How does a smaller line allow more pressure?

You can also cut your drum spindles to except disc brakes to save some ****.If you use original 69 master for disc you'll need the metering valve assembly as well.


Paul

How does a smaller line allow more pressure?

the 1/4" line allows more volume but less pressure, the 3/16" allows less volume but more pressure. the same is true for master cylinders, a 1.250" master cylinder will provide a large amount of volume, ( hard pedal) while a 7/8" bore master cylinder will provide a much higher pressure. (soft pedal)

the reason is the amount of fluid volume available. Its all in the mechinal piviot of the brake pedal, with a (manual brake) with a 6.5:1 ratio with 100 lbs of pedal force applied the reusult is 650 lbs of force seen by the cylinder. I have links for all the math if you want them, I had to do a lot of research when converting from power 2whl disk to manual 4whl disk to get it right and safe.

the 1/4" line allows more volume but less pressure, the 3/16" allows less volume but more pressure. the same is true for master cylinders, a 1.250" master cylinder will provide a large amount of volume, ( hard pedal) while a 7/8" bore master cylinder will provide a much higher pressure. (soft pedal)

the reason is the amount of fluid volume available. Its all in the mechinal piviot of the brake pedal, with a (manual brake) with a 6.5:1 ratio with 100 lbs of pedal force applied the reusult is 650 lbs of force seen by the cylinder. I have links for all the math if you want them, I had to do a lot of research when converting from power 2whl disk to manual 4whl disk to get it right and safe.

I'd like to see the links to the math. I understand the ratio of areas between cylinders, but fail to understand what the size of the connecting line has to do with pressure. If you're moving a large amount of fluid you might have a transient restriction, but once the brakes are pressurized and the flow stops, the size of the connecting line is unimportant.

Let's say I have a 7/8" master cylinder and I am pressing on the 6.5:1 pedal with 100#. I have 3 pressure gauges in the system, one at the master, one at the midway point of the brake line, and one at the slave cylinder. What does each gauge read with a 3/16" line? What does each gauge read with a 1/4" line? Why?

I put the wilwood set up on my 71. I bought the Wilwood brake kit to go from calipers to the frame. They are steel braided. Her are some pics of my set up thats done so far
http://img168.imageshack.us/img168/2821/nova3hu7.th.jpg (http://img168.imageshack.us/my.php?image=nova3hu7.jpg)
http://img145.imageshack.us/img145/1710/nova6qq0.th.jpg (http://img145.imageshack.us/my.php?image=nova6qq0.jpg)
http://img176.imageshack.us/img176/3070/nova4vc3.th.jpg (http://img176.imageshack.us/my.php?image=nova4vc3.jpg)

When I first did the disc install on my 69, I ran the stock drum master for quite a while. No proportioning valve at all and the car stopped just fine. I now run an aluminum Mopar piece(same as what Strange/Wilwood/etc. sell)
Still no prop valve; once in awhile when making hard stops(100+) the fronts feel like they want to lock a little earlier than the rears, but it's easy to modulate and it's never been a problem even on short shut-off tracks.

You want the front brakes to lock before the rear brakes. If you lock the rears the car will swap ends.

I'd like to see the links to the math. I understand the ratio of areas between cylinders, but fail to understand what the size of the connecting line has to do with pressure. If you're moving a large amount of fluid you might have a transient restriction, but once the brakes are pressurized and the flow stops, the size of the connecting line is unimportant.

Let's say I have a 7/8" master cylinder and I am pressing on the 6.5:1 pedal with 100#. I have 3 pressure gauges in the system, one at the master, one at the midway point of the brake line, and one at the slave cylinder. What does each gauge read with a 3/16" line? What does each gauge read with a 1/4" line? Why?

Mike, your thinking is CORRECT!!! The connecting line has absolutely nothing to do with pressure- this subject has been discussed many times before. I dont know where people get these preconceived notions about pressure changes from brake line sizes.

[QUOTE=NOGO;379015]Mike, your thinking is CORRECT!!! The connecting line has absolutely nothing to do with pressure- this subject has been discussed many times before. I dont know where people get these preconceived notions about pressure changes from brake line sizes.[/QUOTE

Mike I am at work, the links are at home,

and I guess I mis spoke when I said higher line pressure, its volume.

having to move greater amount volume of fluid makes for hard pedal in the case of the 1.25 MC.

the larger the line size the more volume and hence harder push or higher effort to achive the same pressure. the more fluid you have to push the greater the force need to move the volume over the same distance. having to move less fluid takes less effort therefore; can equate to higher line pressures when given the effort needed to achive the same pressure on a greater volume


This Too I can tell you, in my app. I had the stock .250 rear lines from rear calipers to the M/C. the brakes were mushie, (no air) when replaced with 3/16" line the firmness was astounding. I will get you the links for the brake stuff.

Yeah, I know Mike, I meant to say the fronts want to lock a little prematurely sometimes--depending on the surface conditions. I have a van at work that I drive sometimes, and the ABS light will come on now and then; in normal conditions the van stops like it hit a wall, but if you get on them hard when the ABS light is lit.....YEEHAW!! it will swap ends in a heartbeat!
But it's a F**D van

Mike I am at work, the links are at home,

and I guess I mis spoke when I said higher line pressure, its volume.

having to move greater amount volume of fluid makes for hard pedal in the case of the 1.25 MC.

the larger the line size the more volume and hence harder push or higher effort to achive the same pressure. the more fluid you have to push the greater the force need to move the volume over the same distance. having to move less fluid takes less effort therefore; can equate to higher line pressures when given the effort needed to achive the same pressure on a greater volume


This Too I can tell you, in my app. I had the stock .250 rear lines from rear calipers to the M/C. the brakes were mushie, (no air) when replaced with 3/16" line the firmness was astounding. I will get you the links for the brake stuff.

Once again I am going to have to disagree with you veno. The fluid volume moving depends on the ratio of the mc piston to the caliper piston(s) surface area and distance traveled. The line size will be a factor in determining how much static volume your brake system has- but not dynamic volume. This is a principle of basic fluid dynamics.

Your personal experience regarding pedal firmness may be an attribute to many different factors- but it is not an attribute of brake line size alone.

I maintain that a 1/4" line vs 3/16" line has the same effect as the affect of larger M/C vs smaller M/C. but that just my .02

http://www.hotrodheaven.com/tech/brakes/brakes1_index.htm

From inline tube: http://www.inlinetube.com/cartalk.htm

Typically, the smaller the tube, the more pressure it creates and the better the brake system will function. Disc brakes require about 1000 lbs. of pressure and the drums use about 300 lbs. Disc brake cars use 3/16” tubing and drum brake cars use ¼” tubing.

From CH TOPPING:
http://www.chtopping.com/streetrodbuild/
http://www.chtopping.com/StreetRodder4/
http://www.chtopping.com/mustang.html

From:WWW.MARKWILLIAMS.COM

Only stainless steel braided teflon hose, stainless or seamless steel tubing (3/16” x .028”) should be used for brake lines.

http://www.stoptech.com/tech_info/wp_brakesystems_upgradeselections.shtml


EARLS:

http://www.mpsracing.com/products/Earls/Speed-Flex.asp
Since brake actuation produces high pressure with very little fluid displacement, we recommend -2 & -3 Speed-Flex for brake systems. Clutch actuation, on the other hand, requires moderate pressure but considerable displacement of fluid. For hydraulic clutch systems we recommend the use of -4 Speed-Flex.

here a few more for good general brake systems
http://www.geocities.com/torkerscamaro/torker.html
http://www.camaros.net/techref/articles/brakes1.htm
http://www.pozziracing.com/first_gen_suspension.htm
http://www.teamscr.com/grmbrakes.htm

since it was much easier to search for first gen camaro then 3rd gen nova for info when I did my conversion from 2whl pw disk to for 4whl manual

From your link at Stoptech Vern:

[QUOTE]1) Line pressure can only be increased by either increasing the mechanical pedal ratio or by decreasing the master cylinder diameter. In either case the pedal travel will be increased.

2) Clamping force can only be increased either by increasing the line pressure or by increasing the diameter of the caliper piston(s). Increasing the size of the pads will not increase clamping force. Any increase in caliper piston area alone will be accompanied by an increase in pedal travel. The effectiveness of a caliper is also affected by the stiffness of the caliper body and its mountings. It is therefore possible to reduce piston size while increasing caliper stiffness and realize a net increase in clamping force applied. This would typically improve pedal feel.[QUOTE]

Notice there is nothing mentioned about pressure and brake line size.

Here is a good read for you:

http://auto.howstuffworks.com/brake.htm

Didn't want to start a huge debate here. :eek: :p

Looks like it's possible to run the stock master cylinder, but I think I'm just going to get the new one anyway, just to be on the safe side, ya know? I figure I can cut corners anywhere, but definitely not on brakes.

Matt

We aggree to disagree....

you over looked earls, inline tube, and mark williams. wilwood used to have a link on 1/4 vs 3/16 but it is longer available.

Didn't want to start a huge debate here. :eek: :p

Looks like it's possible to run the stock master cylinder, but I think I'm just going to get the new one anyway, just to be on the safe side, ya know? I figure I can cut corners anywhere, but definitely not on brakes.

Matt


I am sorry SuperNova69 lost the reason I replied. buy a disk M/C you should replace front lines. the flex lines from the drums will not fit. If it were me I would buy some goodrich SS braided lines from your local cicrle track speed shop for the fronts and get the earls adapters for the conversion. the ss braided will come out cheaper than the stock flex lines.

I understand your math. And you are correct the pressure on a gauge will most likely be close to the same. But with the 3/16 line you are not having to move as much vol. of fluid as with a 1/4 line to get the same results. Thus resulting in better feel in the pedal, frimer not as spongy.

I talked to my friend a while back and he said he got a Wilwood conversion for his Mustang and he used his stock master cylinder because it was already a dual bowl setup. I was wondering if I could do the same since mine is a dual bowl setup, too.

Anything to save money, you know? :p

Also, would the hardlines for the drums be good enough for the discs? Maybe even the flex lines? Or would those not even match up?

Thanks,
Matt

Matt, all drum M/C since 1968 in all domestic cars has had a built in 10psi residual pressure valve, if you use the stock M/C your cailpers will not release fully and result in premature failure. get a disk M/C. same year as yours

I understand your math. And you are correct the pressure on a gauge will most likely be close to the same. But with the 3/16 line you are not having to move as much vol. of fluid as with a 1/4 line to get the same results. Thus resulting in better feel in the pedal, frimer not as spongy.

The fluid foes not compress, so according to the law of physics your pedal feel should not change from the larger line size and volume the system holds.

I hate to sound like a friggin hard-headed engineer on here debating about fluid dynamics, but I am 100% confident in my knowledge of brake systems and principles. I understand others may disagree with me, but all I can do is try to relay proper information to others. What other people do with the information is up to them.

I have a 70 and it was a 4 wheel drum brake car and I switch from drum to factory disk brakes in the front.The only thing I had to change was the brake hoses.I just got the disk brake lines from chevy2only.Used the same proporstion valve same brake lines and master cylinder.I changed from manule drum to manule disk and they worked great.If you are getting factory disk brakes I would go to your local parts store and order calipers,rotars,wheel berings,seals,and the bolt that the calipers bolt to the spindel.Get the brake hoses and the bolt that holds the brake hoses to the caliper.As for the spindels try to find some at a junk yard it you can or buy them new.I saved alot of money this way.