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Hi, I'm sure someone here has replaced their stock front caliper with a drilled one, what size or kind did you use that fits the stock GL500 caliper.I would basically be doing it for looks. I understand that going dual disk would be the best option for improvement in braking power but am basically going for looks on that one, with some improved pads of course. I am searching ebay but can't find one that says.. "this drilled rotor fits a 1981 Honda GL500". Can anyone help me out.
 

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Hi, I'm sure someone here has replaced their stock front caliper with a drilled one, what size or kind did you use that fits the stock GL500 caliper.I would basically be doing it for looks. I understand that going dual disk would be the best option for improvement in braking power but am basically going for looks on that one, with some improved pads of course. I am searching ebay but can't find one that says.. "this drilled rotor fits a 1981 Honda GL500". Can anyone help me out.
where is gary50....he knows
 

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I wonder what a local machine shop would charge to drill a rotor. I think I will check into it, if I can remember that is.
 

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That's not bad at all. I'm sure this has been asked before, but, how much of an advantage is there with the drilled rotors? I just wonder if it is enough to make the effort and have it done.
 

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Not sure what advantage you are looking for. Holes could give a somewhat better performance in the wet, the brakes should bite a fraction earlier. Although sintered metal pads will have a very similar effect.



Also note that small holes will make the rotor run cooler, large holes will make it run hotter. This can be determined by the surface area removed in the drilling process; if area removed is larger than the area of the cylinder in the hole (large hole) it will run hotter. If area removed is smaller than he area of the cylinder in the hole (small hole) it will run cooler. Hope this is understandable
. I had a formula for this, but cannot find it right now.



Michael
 

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That's not bad at all. I'm sure this has been asked before, but, how much of an advantage is there with the drilled rotors? I just wonder if it is enough to make the effort and have it done.




There are many benefits to cross drilled rotors. I would use a pattern that does have over lapping holes, why, because the holes with no over lapping will likely leave grooves. The factories use holed rotors, race teams (cars as well) do it because it works. Lighter rotating mass = better braking because of less flywheel effect, better initial bite, better out-gassing (between the pads and rotor surface) Less flywheel effect = better turn in as well. I've seen some home drilled jobs that are more like Swiss cheese and leaves little mass left to sink the heat away caused by the friction. The way brakes work is by turning kinetic energy into thermal energy and dissipating the heat. There will be an optimum mass/surface area that an engineer could figure out but just copy a factory set up and how far off can you be?. My GSX-R front rotors have 7mm holes. If you do your own drilling don't chamfer the holes, de-burr only. I wish "In welding We trust" was still around he would straighten me out on any mistakes, he's sharp guy with a racing background. Plus it looks cool.

Cheers, 50gary
 

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If you can find someone with a good drill press and a rotary table/indexer, then it is a piece of cake. As has been already mentioned, be mindful about taking too much meat away.







Milling Machine





Rotary Table



If you do end up drilling a rotor (or having it done), be sure to degrease it thoroughly before putting it into service. Acetone, MEK, or something comparable would work well. Most people will use a cutting oil or coolant to aid in the drilling process. The machining oils and coolants do not lend themselves to stopping efficiently!
 

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Measure disk braking surface. Using compass make circles representing the outside diameter and inside diameter with as many diameters of rows of holes desired. Use a protractor to locate the location of holes. Cut out the inside diameter and the outside diameter. Tape the template to the disk and center punch the points where the holes are desired. Buy a drill press and start drilling. If you screw up disks are cheap. I have at least one set in the garage. If you have access to a design program design the patern and print out 1:1 then transfer patern to disk. Milling machine and rotary table is great but not necessary for this operation
 

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In addition to what was just mentioned you should also get a few clamps to hold it down so in case it decides it has the dream to be a Frisbee that it stays put.
 

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In addition to what was just mentioned you should also get a few clamps to hold it down so in case it decides it has the dream to be a Frisbee that it stays put.
Don't tell 'em that. Everyone needs to learn like I did when that piece of sheet metal I was drilling got bound and started spinning at 1,000 rpm taking chunks out of my fingers. I learned real quick.
 

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Not sure what advantage you are looking for. Holes could give a somewhat better performance in the wet, the brakes should bite a fraction earlier. Although sintered metal pads will have a very similar effect.



Also note that small holes will make the rotor run cooler, large holes will make it run hotter. This can be determined by the surface area removed in the drilling process; if area removed is larger than the area of the cylinder in the hole (large hole) it will run hotter. If area removed is smaller than he area of the cylinder in the hole (small hole) it will run cooler. Hope this is understandable
. I had a formula for this, but cannot find it right now.



Michael


The stock rotors on the CX are a waste of time to modify as they were not designed to be drilled. Take the rotor of an R1, they run a LARGE diameter rotor, thin drilled and light...it all works together with the caliper type you use, if you comparing to a Superbike.



Holed rotors are not done for weight savings, that you can do easily enough in rotor thickness, size and material composition, it's done for heat dissipation. At one track I had to brake from over 280km/h to 40km/h to make a 90deg turn in around 100m with the rear wheel fish tailing to make it...now HERE you generate HUGE amounts of heat....
....the CX will never generate this kinda heat..



You want better brakes, dump the WHOLE CX system and fit a complete system from say, RVF400, just an example, it has all you want already from mutiple pots to race rotors...




I do agree thou, even thou I have just rebuild the whole braking system and even fitted S/S braided lines, the CX500 brake setup is really poor and reflects the time it was build in.
 

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Trev. here's my '78 CX project with new front end and old style Comstar 2.15" X 18" also converted rear drum to disc. Does the job. I think Rooben just wants to improve the performance a bit not up to Superbike standards. I'd drill in a factory type overlapping pattern and 7 or 8mm diameter don't go crazy and remove too much and don't chamfer the holes. It'll be fine. If I were to do a single caliper CX set up I'd use the GL 650 caliper and bracket, S/S line, HH pads and drill the rotor. No major surgery and basically stock parts.

Cheers, 50gary























 

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Trev. here's my '78 CX project with new front end and old style Comstar 2.15" X 18" also converted rear drum to disc. Does the job. I think Rooben just wants to improve the performance a bit not up to Superbike standards. I'd drill in a factory type overlapping pattern and 7 or 8mm diameter don't go crazy and remove too much and don't chamfer the holes. It'll be fine. If I were to do a single caliper CX set up I'd use the GL 650 caliper and bracket, S/S line, HH pads and drill the rotor. No major surgery and basically stock parts.

Cheers, 50gary



do you have a build thread on this bike? i'd love to read up on the details and see all you did.
 

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PFFT. Cross-Drilled brake rotors? Get real man. The best and newest development in the braking world is Cross-Drilled brake lines. Install them on your race bike and the bystanders will be begging for you to stop!
 
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Just recently finished cross drilling my rotors. turned out pretty well. I made my template using adobe illustrator. Had them template cut out on vinyl, stuck it on, and drilled out the the holes i created on a mill (much faster and easier than a drill press) .



there are 108 holes, so it is very time consuming. One thing to do if you are planning on resurfacing the rotor surface on a lathe, do that first before drilling the holes. I didn't. The holes cause the cutter on the lathe to "jump" and produce an uneven surface. You can see this in the 1st picture I posted. the second photo is the other side not run on the lathe. I will have to clean this up with some light, even sanding.



From my understanding, the holes ARE drilled to lighten the rotors, and not much else. Cross drilled rotors were initially made to release gases created by early generation brake pads . These gases, if not released, would create a buffer between the rotor and pad, greatly increasing braking distances. New brake pads don't generally create these gases anymore.
 

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Drilling the rotors reduces unsprung weight, which helps somewhat with handling, steering and braking. It will improve wet-weather braking, especially on stainless steel rotors. It will also improve heat dissipation.



All this presumes that the drilling is done properly, both in terms on size and pattern. From what I have been able to learn, I would recommend sticking with 6mm or 7mm holes. 8mm s/b okay, but that would be max diameter. Do not go up to 3/8" holes. I would recommend against chamfering the holes. Deburring is good, chamfering is bad. The distance between the holes (edge-to-edge) should be no less than the diameter of the holes. The distance from the edge of the disk to the edge of the closest holes s/b no less that the diameter of the holes. Stainless rotors should be surface ground, and not turned on a lathe. IMHO, it is also better to surface grind any drilled rotors, rather than using a lathe.



This thread on the NGW forum has a couple of links to people who drill bike rotors.

http://ngwclub.com/forum/viewtopic.php?f=1&t=37474&hilit=drilled+rotors&start=0



It looks like the sohc forum gentleman does good work at a fair price, but the last time I looked, he was chamfering the holes after drilling. This reduces some of the benefits of drilling the rotors.
 
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