DIY Drilling Rear Rotor

[one_civic]

Hey guys,

So I upgraded my single disc front caliper and rotor to the later model 83 850g dual front caliper's, bracket's and slotted rotors. Rebuilt the new front calipers, replaced piston's and seals and rebuilt the rear caliper as well. I have new Ferodo pads to use as well.

I want to drill my rear rotor to match the front's and for the obvious benefits,
My question is,

what size hole to drill, how many holes / pattern and should I countersink the slotted holes?

I've heard to stagger the holes but is there an optimal pattern to use?

Cheer's

Darren

 

[DohcBikes]

The optimal hole size and pattern is a matter of aspect, depending on the rotor.

You want a pattern that overlaps the path of the holes evenly so that the entire pad gets cleaned. Manufacturers spend a lot of time and $ on R&D so to study and imitate a stock type patern is the best approach imho.

Don't chamfer the holes. This is a common mistake on motorcycle rotor drilling. Pad material will collect in the holes if you do. The reason they chamfer holes on cars when they do drill them is to reduce the chance of cracking in the cast rotors.

Use a high quality cobalt drill bit.

Don't drill too close to the outer edge.

Watch how you handle the cuttings, they will be extremely sharp.

This one here, I recently drilled with a cordless drill. It was bolted to a wooden workbench while drilling. It didn't come out perfect, mostly due to me not taking the project very seriously, but I think it came out pretty good. The rotor was grooved a lot worse before and I should have done the light surfacing before I drilled it, because the grooves caused my drill to walk on a couple holes. Obviously when using a drill press this will be a non issue. I'm showing this one because it is a GS rotor and to illustrate the pattern and the fact that it can be done with a hand drill if that's all you have. The pattern is just a copy of an EBC replacement rotor, and since the rear rotor was smaller i just sized the holes down a bit to where they looked right. Not sure of the bit size but i can check later if you are interested.

 

[DohcBikes]

Next to the EBC

 

[GS1150Pilot]

On a rear rotor, the "obvious" benefits aren't particularly obvious.

 

[one_civic]

thanks dohc, I'll be using a drill press, I'm more curious to whether the rotor has the potential for warping if drilling too many holes too fast, if anything I would rotate the the rotor 180 degrees after every few holes, I'm also using dual compound pads, I'm not home right now to take a picture of them as I bought them NOS ferodo but without the packaging, their literally 2 different colors,

 

[one_civic]

but they have to match the front for the "Bling" factor, lol

 

[one_civic]

Could you check the hole size for me dohc? This will give me something to do while I wait for parts coming in the mail

 

[DohcBikes]

Affix an air nozzle on a flexible stand near the rotor so you can blow air on the bit while drilling. I will check the hole size tommorrow. It obviously makes sense to allow the rotor to cool between holes if you have the time. However remember that rotors are engineered to get very very hot over and over and not warp.

Weight savings is weight savings, and in addition a properly drilled rotor will always reduce brake fade. I am a very heavy rear braker and can tell you that it does without a doubt improve the braking performance.

 

[one_civic]

I completely agree, 'I'll upload a pic of the NOS ferodo rear brake pads, never seen that type before, I am also a heavy rear braker but I think that will change this summer with the new dual disc swap

 

[one_civic]

Anyone know what these are made up of, aside abestos? Half Sintered, Half Organic maybe?

 

[one_civic]

Back side

 

[one_civic]

And have to show these really old NOS ferodo front gs850 pads, lol

 

[GS1150Pilot]

A heavy rear braker? Uh, OK.

 

[one_civic]

I had to, that old warped single front disc wasn't sometime's always enough. Anyone with a 78 750b know's what I'm talking about

 

[GS1150Pilot]

Why aren't you looking into the Salty Monk brake upgrade?

 

[DohcBikes]

Why aren't you looking into the Salty Monk brake upgrade?

Well who knows maybe he hadn't heard of it, maybe he doesn't care. Maybe some people don't want mismatched parts on their bikes. Maybe some people think that brake upgrade is overkill or doesn't look right. Who knows.

Maybe because not everyone is exactly the same or wants to do what you want them to do.

He already went another route that will improve his braking performance.

Yes, i'm a heavy rear braker.



Do you have a problem with that?

I will outride you any day of the week.

So far your entire involvement here has been negative.

Is this how you and the rest of the site normally operate? Or is it just you.

Do you have anything to contribute to the original post other than your skepticsim and negative opinion?

Or are you just here to try to rile up a new guy that intimidates you? Just curious.

 

[tkent02]

Yes, i'm a heavy rear braker.

Do you have a problem with that?

I will outride you any day of the week.

Oh, this is going to get interesting.

 

[DohcBikes]

He is attempting to get somebody twisted up, just wanted to return the favor.

His reaction to exactly what you quoted is going to be entertaining for me as well. The rest will likely be ignored but the response to any will be interesting and will tell me even more about him.

My positive contribution here is complete. Happy drilling.

 

[tkent02]

I have never seen a GS that needed more rear braking, except for one with a brake problem. They all need more front brake, the older ones need it more than the later ones, but every one I have ever ridden had more than enough rear braking to lock the rear wheel effortlessly. They were designed for the tires of the late 70s and early 80s, tires in that day only had so much traction, only so much weight could transfer to the front tire. Now with better tires more weight shifts, even less rear braking is needed.

It is so easy to double or triple the braking ability on any GS by improving the front brakes, which will actually do something to improve the ability to stop.

Drill the rear? I guess if you think it looks cool.

 

[Sandy]

Good luck with the conversion. I'm doing my 1000 this winter with stock parts to keep it close to stock. Did you get instructions with those pads regarding the proper break in procedure?