Drums or disc 1/4 times

gt-351 · Dec 7, 2006

Just wondering if anyone has changed there setup from drum to disc and noticed a difference in 1/4 mile times. It seems the rotational mass by the drums would be slower, but I think the disc seem to put more drag on the wheel.

seijirou · Dec 7, 2006

I think the disc should actually reduce drag. Drums actually have a brake line pressure thingie that holds a little bit of line pressure to the shoes all the time. If I remember correctly, this is the link that is located under the passenger side hood hinge in the rear brake line that everybody replaces with teh brake bias dial when they do rear disc conversions

silverstangman · Dec 8, 2006

i do know that the aerospace drag brake kit takes 42 lbs off the front end when compared to the weight of stock brakes. and i also know that in some cases like my friend scotts, will cause the car to stand on the bumper lol. http://www.boyerracingmotorsports.com/ lol and i also know that alumastars weigh 7 lbs. lighter a piece than draglites. just thought i would throw that info in there for u.

stang8urimport · Dec 8, 2006

seijirou said:
I think the disc should actually reduce drag. Drums actually have a brake line pressure thingie that holds a little bit of line pressure to the shoes all the time. If I remember correctly, this is the link that is located under the passenger side hood hinge in the rear brake line that everybody replaces with teh brake bias dial when they do rear disc conversions

There is not constant line pressure at the rear drums. They are adjusted with an expanding rod to hold a slight amount of pressure, and if not adjusted properly, can chip and even break the shoes.

stang8urimport · Dec 8, 2006

triple post lol

stang8urimport · Dec 8, 2006

85_SS_302_Coupe · Dec 8, 2006

I'd say the biggest benefit is weight loss....i highly doubt you'd notice any ET gains just from a brake swap, even with Aerospace disks. It's the kind of thing that would add up with a few other mods and then maybe you'd pick up a couple tenths.

Mustang5L5 · Dec 8, 2006

There is a little more to figuring out which is quicker.

This question all depends on the weight of the individual disk and drum AND the diameter of the disk and drum.

The drums are more compact being only 9" on the Mustang, while some disk brakes are 10-11" in diameter in the rear. SO which matters more? Being closer to the center of rotation...or being lighter in weight??

The math is too complicated for an answer on a friday evening

85_SS_302_Coupe · Dec 8, 2006

Mustang5L5 said:
There is a little more to figuring out which is quicker.

This question all depends on the weight of the individual disk and drum AND the diameter of the disk and drum.

The drums are more compact being only 9" on the Mustang, while some disk brakes are 10-11" in diameter in the rear. SO which matters more? Being closer to the center of rotation...or being lighter in weight??

The math is too complicated for an answer on a friday evening

Yeah, the rotational mass of a 13 inch or even stock 10 inch rotor would be much more than a 9 inch drum and in all actuality the 13 inch rotor probably weighs more than the drum setup anyways. The Aerospace disks on the other hand are single disk wide like a motorcycle, but are not recommended for street use because of that reason so i wouldn't run one on the street even on a weekend cruiser.

silverstangman · Dec 11, 2006

they actually have a drag race kit and then a street kit for our cars.

seijirou · Dec 11, 2006

PoopDawg said:
There is not constant line pressure at the rear drums. They are adjusted with an expanding rod to hold a slight amount of pressure, and if not adjusted properly, can chip and even break the shoes.

I'm not sure you understood what I'm referring to.

It is known as a residual pressure check valve. It does not allow line pressure to the drum brakes to drop below a certain PSI. I can't remember what the psi is on the Mustang.

Here is a link to some that Wilwood sells. http://www.wilwood.com/Products/006-MasterCylinders/010-RPV/index.asp

If you google search the topic, you can find articles from Bendix on troubleshooting drum brakes that even mention checking the residual pressure check valve if your drum brakes are squishy.

After you take a look at the wilwood link. Take a look at your brake lines under the hood, on the passenger side right next to the hinge. What looks like a brake line connection is infact a residual pressure check valve. Note, no other brake lines throughout the car have any connections like this except for the line to the rear drums. Mustangs with 4 wheel disc factory do not have this connector. Most of them aren't doing their job anymore on our older foxes.

Drums or disc 1/4 times

gt-351

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