Drilled Rotors = Warped Rotors

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tunaboy
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Drilled Rotors = Warped Rotors

#1

Post by tunaboy »

Decades ago drilling rotors was common. I have a 1980 1100 and some say that after drilling the rotors they have had warping problems. I have never heard of this. Anyone here have the warping problem?
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Re: Drilled Rotors = Warped Rotors

#2

Post by gregforesi »

I'm not a metalurgist...
There are internal stresses in steel. When a piece is machined and material is removed, those stresses can cause a piece to change shape. Parts with thin cross-sections (a rotor) are more susceptible Heating a part can do it as well.
So in answer to the question "Can they warp?" I would answer "yes - but not always".
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Re: Drilled Rotors = Warped Rotors

#3

Post by Track T 2411 »

There are plenty of members here who have drilled their rotors, and I think there was one instance just recently concerning warping. Even then, it was not entirely clear that being drilled was the only cause... I'll be drilling mine before the bike hits the road this year, to compliment the rest of the brake system renewal and upgrade. My 2 cents...

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Re: Drilled Rotors = Warped Rotors

#4

Post by WShie »

I have drilled mine with no warping problems. I do believe that you need to use your head when drilling. Make sure your holes are not too big, too numerous, or too close to the edge. Also make sure not to overheat your rotors when drilling; use a sharp drill and slow speed with coolant. Lastly torque your rotors with a torque wrench in a star pattern to the proper values when re installing.
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Re: Drilled Rotors = Warped Rotors

#5

Post by Greg »

I think there is a very good chance those that claim the rotor/s warped after they were drilled never bothered to check before drilling that the rotors were not warped. Can they warp during drilling? of course they can if you spend too much time drilling the hole with a Dal drill.
If you drill as Whsie said you should not have a problem one, especially if you drill and continue to drill on the opposite side of the last hole drilled.
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Re: Drilled Rotors = Warped Rotors

#6

Post by sunnbobb »

I think the vastly improved stopping when wet is worth the small risk of drilling them. You can always have them turned after drilling too.
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Re: Drilled Rotors = Warped Rotors

#7

Post by mcgovern61 »

sunnbobb wrote:I think the vastly improved stopping when wet is worth the small risk of drilling them. You can always have them turned after drilling too.
I didn't think these rotors could be turned, only ground down?
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Re: Drilled Rotors = Warped Rotors

#8

Post by Placerville »

I believe that knowledge is a good thing, especially when considering the modification of something that (potentially) saves lives. Asking questions here is a very good place to start but, don't make a decision based soly on what you read here or any other forum. Do your homework. If you decide to move forward with this, I'd suggest that you contact at least 3 different professionals who do this type of work and get their opinions. One place to contact would be http://www.truedisk.net/Home.php. Call them (don't email) to discuss the job and follow up with photos and specs. of your discs so they'll have a true understanding of what they'll be working with. Ask everyone you speak to the same questions so you can accurately compare responses.
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Re: Drilled Rotors = Warped Rotors

#9

Post by sunnbobb »

Semantics. Yes, ground is correct term.

Bradshaw Bikes provides a grinding service. I have ground many disks that have been drilled, and none of them have shown warp-age prior to grinding. Well, actually one did, but I knew it was warped before being drilled.
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Re: Drilled Rotors = Warped Rotors

#10

Post by heraldhamster »

another +1 on what WShie said.

I use a new bit on every set of rotors and lots of cutting oil. drilling properly is an art. unfortunately, many have never learned the skills needed to do it effectively with the least amount of effort & wear/tear.

best I can offer w/o getting seriously in-depth is; the bit should carefully carve out a curly sliver and you never want that sliver to get too long. ease off on the press handle to "break" the sliver before it gets more than, say, 3/4" long, then continue onto the next sliver. slow is always better. actually most drill presses I've found run way too fast (even when geared all the way down) for proper cross drilling but they can be used is you're patient. best thing to use, if you can afford it is a mill. that's what the machine shop will use...

if the rotor starts to sing or "ring" your bit is dull and not cutting properly.
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Re: Drilled Rotors = Warped Rotors

#11

Post by Motowalt »

+2 on Wshie post...

I drilled mine and have thousands of miles with no warpage...they actually stop way better now dry or wet and they look the part too (not to mention the weight savings lolol ). It takes a while to do...slow and steady...sharp bits a must...I figured something like 600 passes with the drill press were required...first pilot holes, then full size holes, then chamfer the holes, then flip over and chamfer the insides...but I love the smell of cutting oil in the morning :mrgreen:

Randaak's master cylinder and stainless braided lines and new pads helped alot too.

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http://www.ngwclub.com/forum/viewtopic. ... 9&start=45
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Re: Drilled Rotors = Warped Rotors

#12

Post by Don R »

Good cutting oil makes the job easier and the drills last longer. I have drilled a couple with the same bit. I always punch the start and begin the cut with a centering bit.
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Re: Drilled Rotors = Warped Rotors

#13

Post by desertrefugee »

This is the job I farm out. The margin for error is just too slim. And I don’t have a drill press.
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Re: Drilled Rotors = Warped Rotors

#14

Post by Old Fogey »

Over the ten years I have drilling doing them for customers, I have not had a single (known) instance of warping because of it.
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Re: Drilled Rotors = Warped Rotors

#15

Post by tlbranth »

OK I'm ignorant but I'll chuck this out there as a mere observation anyway: I drilled my rotors and saw no warping. I also saw no improvement in braking. Once when I was caught in the rain 2-up and had to make a quick stop, it felt like I was luging. Sticking my feet down would've done a better job I reckon. I think drilling is mostly done for cosmetic reasons.
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