steel brake tweaking technique

[Truglodite]

i'm sure many of you already know this, but some steel brake disks are not made as precise as they should be. i found that lapping my Ofna stamped steel brake disks made a dramatic difference in both the smoothness & strength of my brakes. lapping is basically a way to sand the surface of an object to a smooth/mirror-like finish. if i'm not making any sense, read on:

lapping a brake disk usually takes a few minutes each side, depending on how warped your disk is & how shiny you want it to be. you start with fine grit wet-sandpaper on a mirror. i usually start with 600grit, but 320 is sometimes needed to take down high spots on very warped disks. keeping the sandpaper damp, rub the disk's flat side using a random circular motion until the low spots disappear. water keeps the paper clean & the disk cool, while the random motion ensures you get an even finish, so use both. when the surface is smooth, move on to very fine grit (i end with 1500grit). continue lapping until the surface is shiny, then do the same process to the other side of the disk.

after i lapped all the disks on my Worlds they not only looked really sharp, but they operated way smoother than before & required far less servo torque to stop effectively. i know some ppl will probably say it isn't worth it, but i plan on lapping my disks at least every other race.

btw, thanks to jason at my lhs, who turned on the lightbulb in my head after suggesting i sand the ball diff plates on my t3 before i rebuild them. that works great too!!!

let me know if you tried lapping your disks & how it worked for you.

 

[Çh®i§tiªñ]

GREAT info!

Thanks for the tip!

 

[Truglodite]

thanks & welcome!

btw, sunday i ran through about 8 tanks practicing with freshly lapped disks on my local track (which requires lots of hard braking at high speeds). my disks retained the mirror finish with only a few minor grooves (2 or 3 per side). the brake response has not changed at all. i may not need to redo them as often as i thought.

 

[Çh®i§tiªñ]

Well I just had the LHS put aside the heavy duty metal disc for my Savage and will be certain to try it out. Ill let you know how it goes.

Also, I'm going to be pulling my TC3 apart to put in some hop-ups and Ill sand those down as well.

 

[FastEddy]

Nice Tip.

 

[Truglodite]

Çh®i§tiªñ, i used to think carbon disks were the way to go, but after last sunday i'll be sticking with lapped steel. i hope it works well for you too.

thanks FastEddy.

btw, i guess sanding diff disks is more common than i thought. i found a similar suggestion in the good ole setup guide at Competition X under "diff adjustment". they say to use only 600grit, which i suppose is OK since the 600 will wear down a bit as you lap.

from my experiences i think it is good to have 1500grit (or more). it will ensure a mirror finish, & it makes refinishing a slightly worn disk easy (since you don't have to take down high spots low grit isn't needed, you just need to polish the surface).

 

[mjime714]

Great tip! Thanks for sharing. Time to wrench!

 

[Çh®i§tiªñ]

Ok I got the new disc by hot bodies tonight. Do I put the disc on the mirror for a reason or can I just put it on a trued flat surface?

Also, do you use a sanding block on top of the paper?

 

[mjime714]

I think the mirror is just so you could watch yourself while you work. "Damn I look good when I'm sanding!" or maybe you could sniff up the fine powder when you're done.....

Yeah what is the mirror for. What Çh®i§tiªñ said makes sense, but is that why?

 

[John Clark]

Excellent tip, that's usin your mellon! I'm not sure how well it would work with a steel brake disk, but this is what I use to lap automotive valves when rebuilding heads. I couldn't get the lapper to suction to my fiber Maxx disk, but with some down pressure it still worked pretty well. The compound is like a paste, and comes in different grits. Should be available at any decent automotive parts store for a few bucks each.