Topic: drilled my cb550 rotor. PICS inside.

[karmasic]

i couldnt find one for a 550 rotor in the searches. so here is mine. enjoy. Came out good, and it made a difference in the braking for sure.

[turboguzzi]

looks like you chamfered the holes edges. if so, it's not a good idea. the sharp edge of the hole cleans the pads.

TG

[KingCustomCycles.com]

the burrs from the holes will really keep those pads clean... nice job, and sweet layout!

[karmasic]

i read in my research that some people think un-chamfered holes help crack the rotor. any thoughts, i am doing another one this weekend. seems like it wont clean the pad as well, but it still cleans it a hell of a lot better then i did.

[mystic_1]

I bought drilled rotors for my K0, all the holes are chamfered.  No idea who did the work, they were an eBay find.

mystic_1

[Soos]

I had mine drilled by a co-worker on a CNC horiz. mill, then I personally chamfered and rounded the edges as per a racers advice.

The racer I know(Tom Watanabe) said that un-chanfered holes will give you more "grab" than un-chamfered, it will also wear your pads out prematurely.

He also said the only rotors he has had a catastrophic failure with were the un-chamfered.
The 2 rotors fail in 10+ years of racing.(gone through countless bikes, all came drilled, or he had them done professionally... he's got a sponsor for his racing $$.)
One resulting in a SERIOUS crash(100+mph, lost a front rotor) and the other time in a corner at under 60mph.
He swears the cracks both times came from the unchanfered holes.
Now he makes sure all have a nice radius to the holes.(does this himself though)

Don't really know if they get less"grab" than un-chamfered holes....
But can it hurt to be cautious?

I even ran a flapper type hone to round them out even more, to remove ALL sharp edges, the way he does.
It's your face vs the asphalt... which one will win?




Nice looking rotor pattern there!




l8r

[Steve F]

It's common practice in the aircraft industry to chamfer holes to prevent the propagation of stress cracking and the like.  I personally have chamfered the holes on my rotors to keep the "cheese grating" of the pads to a minimum.  Better than a flat chamfer is a radius on the edges, but that's too tedious to undertake for something like this.

[karmasic]

here are a few more patterns if anyone is interested. they are for cb750 size rotors.

here is a hires pdf : http://unscience.files.wordpress.com/2008/09/rotor1.pdf




of course, use at your own risk.

[goon 1492]

DUUUUUUUUUUDE! YOU ARE THE SHIZZLE!  :-*Thanks for the hole pattern, I had plans to do just this but haven't had the time yet to draw it up on the computer. Now I can get right to business, and need to find the rest of the parts needed to get dual discs up front. Peace.

[karmasic]

i can make a 750 patter the same as mine. i will post it friday. 

[karmasic]

shhhhhh... did it today. dont tell my boss.

PDF: http://unscience.files.wordpress.com/2008/09/rotor-3.pdf

[goon 1492]

I wont tell your boss if you don't tell mine I'm drilling my rotors at work

He he he you stole my line
Hey what kinda drill bit did you use? I have titanium coated and wondered how many times I will have to use the ol' drill doctor to re sharpen, and on that note a helpfuyl tip: if you sharpen your own bits remember they bit size gets larger as you get closer to the shank when grinding a new tip on them.

[750fromhell]

Really cool.

[turboguzzi]

regarding the chamfer thing, Mike from Vintage Brakes recomended not to chamfer and I guess he knows a thing or two about brakes.... In all my modern bikes holes are un-chamfered too with no ill effect on wear. 

Regarding your patterns, I think you went way too close with the holes near the edge (mike warned me about that... ) and that could be a much bigger source for cracks. I discussed with him drilling patterns and he strongly rcomended the daisy style. One thing that is hard to see from your pics is if you have good overlap between the holes, with the daisy desings its easier to get good overlap between holes that promotes good pad sweep.

TG

[754]

The pattern shown is similar to the BMW pattern used in the late 70,s and 80,s.

Stock discs are often laser cut or punched, then ground, hence no need to chamfer.

This is what I used sometimes to break the edge without excessive chamfer. Get a bit and brace with a drill chuck, and mount the countersink in it. Clamp disc down the chamfer lightly 2 or 3 turns..per hole...simple..

[goon 1492]

Hey, is there some one that can upload a pdf for me, I made three drill pattern versions of the 750 rotor, because I was a goon and forgot that this one is for a 550, guess that's what I get for only getting to look here on break at work and moving too fast, well I started from scratch and made up three patterns and wanted to share. Here is a jpeg of it if I can get someones email who can upload it I would glagly send it to ya. thanks for any help maybe it can go in the faq.

[tank410]

Hey man could you make one like the botom right for a 500/550?

[SteveD CB500F]

Goon, you can email it to me and i'll put it up on the site (or get Glenn to!)

Steve

steve.dennis AT sohc4.net

[goon 1492]

Thank you for your help Steve I couldn't get your email to work from mine so I sent it to Glen and it worked, thank you guy's for your ehlp with this and I hope it makes it to the faq's for many to use. 

[Flying J]

OK so i rode my bike today for the first time since i drilled my rotors and the breaks feel a lot different. they used to grab real well, almost touchy but now i feel like i have to grab a lot of break now to get the same stopping action. Is this because i reduced my break surface are or is something wrong. Anybody experience this before?

[UnCrash]

Looks great!  I don't understand why this would diminish your stopping power...

[SteveD CB500F]

They do look good.

While you have reduced the brake swept area by drilling it won't be significant. Just remember how inefficient these old systems are. It's probably more to do with just removing and refitting them.

Do a brake caliper clean, reset and bleed and see if it makes any difference.

[Grumpol]

OK so i rode my bike today for the first time since i drilled my rotors and the breaks feel a lot different. they used to grab real well, almost touchy but now i feel like i have to grab a lot of break now to get the same stopping action. Is this because i reduced my break surface are or is something wrong. Anybody experience this before?

Did you replace the reservoir? you have twice the cylinders to push, you need twice the fluid "push"

[Flying J]

i rubbed my hands over the disks and they feel like there might be some residual oil from drilling. I'm going to do a good clean and see if that fixes it.

[Soos]

If just cleaning the disks doesn't help try sanding the rotor surfaces, and de-greased them.
(don't forget those holes!)
As well as sand the pads to get a new surface to mate with the disk.

I was thinking like a new cylinder hone, and new piston rings.

2 new mating surfaces allowed to "wear into" each other.

I did this, and mine stop me in a heartbeat.


l8r