curious about drilled rotors

[fullercameron]

I was thinking of drilling my rotors while the bike is in the shop for the next few weeks and I was looking to get some feedback regarding people's experience.

I am wondering if anyone has had especially good or bad luck with particular patterns, etc. I've seen car rotors that have cracked and didn't know if anyone has had any issues with cracking or other problems.

In reading it looks like I don't want to exceed the thickness of the disc in hole diameter, and that the holes should be left un-chamfered for best results, but I haven't found any information on whether a 4, 5 or 7 hole pattern does a better job of cleaning pads, etc.
The 4 and 5 hole patterns don't appear to completely cover the pad area since the holes are far enough apart that they never overlap. I have also seen issues with uneven pad cleaning eventually causing grooving and wondered if this problem had been experienced.

I am also curious if anyone has noticed significant differences in pad life and braking ability.

Thanks for any info.

 

[hotdog]

Holes are there for water dispersion in wet weather riding. I don't think pattern will matter much - just remember the more hole the less surface area for the brakes to apply the pads to.

 

[weekendrider]

If you want to search it out Retiredgentleman did a write up about drilling rotors.
Also there are printable patterns available if you can find the thread they are in.

 

[5twins]

I can't say I notice a night and day difference in my brake since drilling the rotor but I feel it does help and besides, it looks trick. Also, it's basically a free mod. I did my original disc with a pattern off the internet. It came out fine and I liked the look .....

Once I found out about the hole sizes, I needed to re-work the pattern a bit. I also wanted more holes so I added an additional swirl line between each of the originals. This disc is a 2mm thinner SR500 one, hence the smaller hole diameters .....

This pattern was based on the original 7 hole swirl I found on the internet. I needed to make the 1st and last hole in each swirl slightly larger to increase pad coverage. I eventually drew up a new pattern using 8 holes per swirl all of the same size.

 

[rusty rocket]

When I drilled mine I drew a line thru the 6 mounting bolts then I took my deviders and measured in between the 6 lines and drew 6 more lines. I alternated 3 hole and then 2 holes. I hope this make sense, sort of hard to explain but real easy to do.

 

[Dakota_Lew]

5 twins you don't happen to have another PDF for a rear?

 

[5twins]

Sorry, no. I have a drum rear so had no need for that pattern.

 

[Square Circle]

http://www.xs650.com/forum/showthread.php?t=12671
I just drilled mine a couple weeks ago using the 7 hole pattern on front rotor. I think the pattern was a little big for my 79 rotor, so i used the top of the circle where it intersects the line as opposed to dead center . I did to get it balanced between useable edge to edge in the rotor. I used 3/16 holes to get the most holes (12 sets of 7).

 

[aldo5468]

You can see there are lots of ways to do it that all should work out well. If reducing unsprung weight is an objective, start with a 5mm OEM Yamaha rotor that bolts right up - depending on model, there are solid ones that you could drill using whatever pattern you like and slotted ones that wouldn't need drilling.

 

[fullercameron]

Thanks for all the input. I was mainly concerned about braking power, pad life and if anyone had had any issues with cracking rotors.

My main reason for drilling has to do with the trick look. I just want to make sure I am not sacrificing safety or performance for looks.

As far as the different patterns go, I was really wondering about the area or the holes that sweep the pads. It looked like the 4 and 5 hole designs wouldn't end up sweeping the entire pad area - looks like there would be areas between the holes that be missed. Just didn't know if this caused any problems with uneven pad or disc wear.

 

[5twins]

You want the holes in one row to overlap the ones in the other rows. That's how you'd get full pad sweep. Honestly, the patterns out there that don't do this are just plain crap and shouldn't be used. Don't get your outermost holes too close to the disc edge and you shouldn't have to worry about it cracking.

 

[hotdog]

+1 agree - even though I did say pattern would not matter much, I was meaning a pattern with full coverage - not randomly drilled...

You want the holes in one row to overlap the ones in the other rows. That's how you'd get full pad sweep. Honestly, the patterns out there that don't do this are just plain crap and shouldn't be used. Don't get your outermost holes too close to the disc edge and you shouldn't have to worry about it cracking.

 

[XSLeo]

Drilling the rotor has several things going for it. One is cooling. adding holes up to but not bigger than the thickness of the rotor adds surface are and promotes cooling. Holes larger than the thickness decreases surfsace area and can over heat.
As the brakes are used the pads heat up and create gases on the surface of the pad. If enough gas builds up it can lift the pad off the rotor. Holes bleed off this gas. As well as any water as mentioned by hotdog.
He also mentioned that too many holes can decrease the amount of pad contact.
Look at most new bikes with holes in the rotors. some have a lot others not so much. the sport bikes yse lots of holes for cooling and use calipers with tremendous grip. So don't over do it.
As you use the brakes the pads and rotior wear. The pads abraid metal off the rotors. This metal embeds into the pads and can decrease the grip of the pad on the rotor. leaving the edge of the holes sharp helps clean the metal off the pads.
Drilling has many advantages, the bit of extra wear on the rotor and pads is a minor thing compared to the increase in braking.
You might not see this extra braking improvment in normal riding, it's more noticable under hard riding. Like racing.
But the extra margin of safety is well worth it.
Leo