Template for drilling disc

Crashedkiwi

XS650 Enthusiast
Messages
58
Reaction score
110
Points
33
Location
New Zealand
Hi there all; Could someone kindly post or direct me to where I might find a template for drilling my front disc please?
After all, why not?

Cheers
 
Here ya go. https://www.xs650.com/threads/how-to-cross-drill-rotor-w-patterns.12671/

The pic links are broken but the PDF files still work. I used one of 'em to drill the rotors on my SG. Don't recall which but I do remember having to resize the drawings. The guy who made 'em put a convenient scale on there to help with that.

Also... if I recall correctly, he didn't include the outermost holes. Those need to be there to cover the entire swept area. It was pretty easy to add those in.

Here's where I did mine. https://www.xs650.com/threads/jims-1980-sg-miss-september.50545/post-604386


1674702314038.png


1674702425817.png


1674702128710.png
 
There is also a 5 Hole version. This one is a bit more tricky to cut and paste to size though as you have to be creative with cutting the pattern to line the holes up.

1674743408286.png
 
I started out years back on my 1st disc with a 7 hole swirl and 6 swirls .....


Old Disc.jpg


This worked OK but I wanted more holes. I also didn't like the way the outer hole was so close to the edge of the disc. It's held up OK so far but I figured the disc may eventually crack out there. For my next disc, I acquired a 5mm thick SR500 one. I laid the above pattern out on it twice to get more holes, and I made them smaller (3/16"), but with only 7 holes in a swirl, the smaller hole size didn't cover the whole swept area. I compensated by making the first and last hole in the swirls larger. I alternated them, making the 1st hole larger in one, the last hole larger in the next .....

SR Disc.jpg


But really, I needed a new pattern, so I drew one up. This one uses 15 swirls of 8 holes each and was set up to use 3/16" or 5mm holes .....

normal_650-500_disc_drill_pattern_jpeg.jpg


But next came a new dilemma, lol. After researching the ideal hole size, I found that you get the biggest benefit (most additional surface area created for better cooling) if you use holes the same size as the disc is thick. So, while my new pattern was perfect for 5mm thick discs, it wasn't so good for 7mm thick ones like the stock 650 has. Now, I couldn't enlarge the outer hole much as it was already pretty close to the edge, and the inner hole was already part way off the pad's swept area, so I didn't see the point of enlarging it. So, I settled on just enlarging the 6 middle holes in each swirl. This worked out well and gained me lots more surface area, very close to what all 7mm holes would give .....

NewWheel.jpg


NewWheelMounted6.jpg


I've attached a PDF of my pattern if anyone would like it.
 

Attachments

  • 650 Disc Drill.pdf
    28.8 KB · Views: 86
Did anyone have to rebalance the tire afterwards? Do shops in general do high speed balance on motorcycle tires? Is that something that you would have to find the right motorcycle shop for? I might do this, drill disk, and static balance it as per this site and internet. Just curious about high speed balancing.
 
Now let me talk about hole sizes for a minute. Being that I'm dealing with used discs that may be worn a bit thinner, I decided to use a 6.9mm drill size. But where does one get them? Well, this eBay seller has a ton of them and they're cheap .....

https://www.ebay.com/itm/165398315144

And to help you with figuring out what size to use, what works best and gains you the most surface area, I made up this chart. The ideal hole sizes for 5 and 7mm thick discs are listed in red .....

DiscHoleSize.jpg


As you can see, using 6.9mm holes only loses me .04mm of surface area per hole as compared to 7mm holes, and that's if the discs are still a full 7mm thick, which they probably aren't.
 
Interesting thread. Am curious how easily are these stainless discs drilled.
While there is lost surface area for braking I assume benefits are derived through improved cooling to reduce brake fade and the ability of the holes sweeping by the pads to clean the pads of debris and give water a place to go when wet.
 
They're pretty easy to drill. I do all the holes first with the smaller 3/16" bit, that goes through pretty easy. Then I go back and enlarge the ones I want to, and that's pretty easy too, seeing as I'm just reaming out holes that are already there. But they do wear bits out. You might get one disc done with one bit but several may need more bits (or resharpening them).

Yes to all you said but drilling also gives a slight improvement in normal dry weather braking too. With my first disc, I never ran the bike without it drilled so had no comparison. On the '83 I got recently, I did run it for a while with the stock undrilled disc, and when I finally did swap a drilled one on, I noticed it did brake a little better. It might be because pads off-gas as they heat up and the holes give that gas somewhere to go.
 
Am curious how easily are these stainless discs drilled.
I drilled 2 discs... 84 holes per disc... with a single 1/4" drill bit. No pilot holes, just marked with a center punch and drilled.

...and that bit is still in my box and in regular use.
 
Here ya go. https://www.xs650.com/threads/how-to-cross-drill-rotor-w-patterns.12671/

The pic links are broken but the PDF files still work. I used one of 'em to drill the rotors on my SG. Don't recall which but I do remember having to resize the drawings. The guy who made 'em put a convenient scale on there to help with that.

Also... if I recall correctly, he didn't include the outermost holes. Those need to be there to cover the entire swept area. It was pretty easy to add those in.

Here's where I did mine. https://www.xs650.com/threads/jims-1980-sg-miss-september.50545/post-604386


View attachment 234388

View attachment 234389

View attachment 234387
Cheers Jim; that looks perfect & a great job done also!
 
I started out years back on my 1st disc with a 7 hole swirl and 6 swirls .....


View attachment 234414

This worked OK but I wanted more holes. I also didn't like the way the outer hole was so close to the edge of the disc. It's held up OK so far but I figured the disc may eventually crack out there. For my next disc, I acquired a 5mm thick SR500 one. I laid the above pattern out on it twice to get more holes, and I made them smaller (3/16"), but with only 7 holes in a swirl, the smaller hole size didn't cover the whole swept area. I compensated by making the first and last hole in the swirls larger. I alternated them, making the 1st hole larger in one, the last hole larger in the next .....

View attachment 234415

But really, I needed a new pattern, so I drew one up. This one uses 15 swirls of 8 holes each and was set up to use 3/16" or 5mm holes .....

View attachment 234416

But next came a new dilemma, lol. After researching the ideal hole size, I found that you get the biggest benefit (most additional surface area created for better cooling) if you use holes the same size as the disc is thick. So, while my new pattern was perfect for 5mm thick discs, it wasn't so good for 7mm thick ones like the stock 650 has. Now, I couldn't enlarge the outer hole much as it was already pretty close to the edge, and the inner hole was already part way off the pad's swept area, so I didn't see the point of enlarging it. So, I settled on just enlarging the 6 middle holes in each swirl. This worked out well and gained me lots more surface area, very close to what all 7mm holes would give .....

View attachment 234418

View attachment 234419

I've attached a PDF of my pattern if anyone would like it.
As ever 5twins, sensational! Thanks for the insight and patterns! 3B!
 
Thanks to all for the great assistance and commentary here; I really appreciate it! The project is getting closer to being complete & once I've drilled the disc as above ( on the fence about twin discs; I've the potential to do this but I'm having an asthetic debate with myself on this) and the tank and side plates are back from the paint shop, I'll throw some progress pics up. Been great to have the support here; thanks again, all.
 
You have
Nice! Hmm.... My build is a custom cafe look so I'll go imagine this against my mental image of the bike.
You have to set a priority as to what is more important to you. That nice balanced two brake appearance comes at the expense of almost 10 lbs of unsprung weight. For some, that’s meaningless. For others, it’s a deal breaker.
 
Yes, the stock disc is a real porker, lol, at almost 7 pounds. The SR500 5mm thick version is about 1.5 pounds lighter but honestly, I don't notice any difference in handling. Maybe that small of a weight difference isn't enough to make a difference, but adding near 10 pounds might, lol. The only difference I notice on the 5mm disc is it heats up more and faster. It's never been an issue, never gotten so hot that the brake faded. So I guess the thicker 7mm disc is better at dissipating heat.
 
I don`t need a template anymore, I just drill the rotors (and wheels and side cases and chain guards and heads and battery boxes and frame gussets) from memory.:thumbsup::jk:
 
Last edited:
If you do the swirl pattern, just be sure the swirls spin in the right direction. I’ve seen some done backwards and always sticks out like a sore thumb to me.
 
Back
Top