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What is the reason the braking surface of a disc has so many holes?

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What is the reason the braking surface of a disc has so many holes?

Old 04-28-19, 03:35 PM
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Obeast
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What is the reason the braking surface of a disc has so many holes?

I notice on the more high end bikes the discs have a ton of holes on them. Is this to save weight or what? Would the cheaper discs with less holes provide more braking power since there´s more friction due to more material rubbing against each other?
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Old 04-28-19, 04:53 PM
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Originally Posted by Obeast View Post
I notice on the more high end bikes the discs have a ton of holes on them. Is this to save weight or what? Would the cheaper discs with less holes provide more braking power since there´s more friction due to more material rubbing against each other?
Heat management. Disc rotors are rather small and the braking force on such a small surface area generates a lot of heat. The holes increase the surface area of the rotors and let them shed heat better.
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Old 04-28-19, 05:06 PM
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As stated, increased surface area for heat managment.
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Old 04-28-19, 05:14 PM
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Originally Posted by Obeast View Post
I notice on the more high end bikes the discs have a ton of holes on them. Is this to save weight or what? Would the cheaper discs with less holes provide more braking power since there´s more friction due to more material rubbing against each other?
Honest question: have you ever heard of google?
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Old 04-28-19, 05:17 PM
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Originally Posted by Koyote View Post
Honest question: have you ever heard of google?
Sometimes it is better to check with your mates and get a conversation going. Google is not always the final, or most accurate, authority.
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Old 04-28-19, 05:19 PM
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Originally Posted by eja_ bottecchia View Post
Sometimes it is better to check with your mates and get a conversation going. Google is not always the final, or most accurate, authority.
On this topic, google works just fine.

My point is that many questions have already been asked and answered about a thousand times. And I wouldn't go with this response if the OP didn't already have a history of this sort of thing.

We're talking about an OP who recently started a thread asking for advice on how to take a crap in the woods...Apparently he keeps falling into his own s**t:
Any advice on taking a crap in the wild or dense forest?
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Old 04-28-19, 05:40 PM
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Originally Posted by Koyote View Post
On this topic, google works just fine.

My point is that many questions have already been asked and answered about a thousand times. And I wouldn't go with this response if the OP didn't already have a history of this sort of thing.

We're talking about an OP who recently started a thread asking for advice on how to take a crap in the woods...Apparently he keeps falling into his own s**t:
Any advice on taking a crap in the wild or dense forest?
That’s funny.

I have a friend like that, he is a serial-asker (is that even a term?). He is a nice guy, just likes to ask questions, like a little kid.

I just shrug my shoulders and answer him. He is otherwise a good guy.
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Old 04-28-19, 05:42 PM
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Originally Posted by eja_ bottecchia View Post
That’s funny.

I have a friend like that, he is a serial-asker (is that even a term?). He is a nice guy, just likes to ask questions, like a little kid.

I just shrug my shoulders and answer him. He is otherwise a good guy.
I suppose I am intolerant, since I mastered defecation long before acquiring my first personal computer.
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Old 04-28-19, 05:46 PM
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Originally Posted by Koyote View Post
I suppose I am intolerant, since I mastered defecation long before acquiring my first personal computer.
I am 63 yo. The older I get the more tolerant I become. I guess I just want people to be patient and tolerant with me when I finally become a blathering and dithering old fool...
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Old 04-28-19, 06:18 PM
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They are drilled to shed heat and water.
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Old 04-28-19, 06:39 PM
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heat, water dissipation, weight reduction, & add a touch of sportiness to the cycle.
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Old 04-28-19, 07:13 PM
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Originally Posted by Troul View Post
heat, water dissipation, weight reduction, & add a touch of sportiness to the cycle.
Honda passed on the weight reduction and cool factor on my 1969 750. Lots of after market stuff to rectify both.
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Old 04-28-19, 07:26 PM
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Originally Posted by bobwysiwyg View Post
Honda passed on the weight reduction and cool factor on my 1969 750. Lots of after market stuff to rectify both.
Honda does tend to leave something left for tinkering around with.
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Old 04-28-19, 07:55 PM
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The obvious answer is because it's made of Swiss cheese!
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Old 04-28-19, 09:43 PM
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Originally Posted by Koyote View Post
Honest question: have you ever heard of google?
Honest question: is it that hard to just not reply?
Surely you're not original in this either?
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Old 04-29-19, 12:14 AM
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Originally Posted by Doctor Morbius View Post
The obvious answer is because it's made of Swiss cheese!
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Old 04-29-19, 04:31 AM
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One thing that is never discussed on BF: Are disc brakes superior to rim brakes?
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Old 04-29-19, 05:43 AM
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Originally Posted by Koyote View Post
On this topic, google works just fine.

My point is that many questions have already been asked and answered about a thousand times. And I wouldn't go with this response if the OP didn't already have a history of this sort of thing.

We're talking about an OP who recently started a thread asking for advice on how to take a crap in the woods...Apparently he keeps falling into his own s**t:
Any advice on taking a crap in the wild or dense forest?
Love it ... I just read the other thread .... virtually had tears rolling down my face I was laughing so much

Personally I try and make sure I've been to the loo before going out so I don't get caught short and I could never seriously ask something like that in a forum.

One poster did suggest practicing squatting, and whilst personally I never plan on taking a dump in the woods, I may start practicing this in the garden just to see the look on the other halves face when she asks me what I'm doing
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Old 04-29-19, 07:03 AM
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Originally Posted by Witterings View Post
Love it ... I just read the other thread .... virtually had tears rolling down my face I was laughing so much :lol
That thread wasn't even original. I have been around long enough to have seen at least one other thread about "making" in the woods. Wasn't all that long ago either. Maybe within the last couple of years.

BTW...I really doesn't take much practice. During my last two two-week tours I had to use the woods a total of three times. I wear bibs, so I try to travel with full-zip jerseys. Makes things easier.
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Old 04-29-19, 07:06 AM
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Originally Posted by bobwysiwyg View Post
Honda passed on the weight reduction and cool factor on my 1969 750. Lots of after market stuff to rectify both.
1960s tech 4-finger disc brakes without holes sure seemed better than drum brakes with a diameter of the wheel itself.

I had a 1978 CB750F, with 2 front discs with no holes. Still needed 4 fingers compared to later versions. Engineers of the time didn't want us to lock the front wheel, I guess.

Last edited by FiftySix; 04-29-19 at 07:13 AM.
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Old 04-29-19, 07:08 AM
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One of the OP's questions was is a solid rotor would give better stopping power

The answer is yes. It would create more friction with a solid surface and would give better stopping power.....

...until it got too hot.
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Old 04-29-19, 07:14 AM
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Originally Posted by Skipjacks View Post
One of the OP's questions was is a solid rotor would give better stopping power

The answer is yes. It would create more friction with a solid surface and would give better stopping power.....

...until it got too hot.
So, for non-racers that don't use their brakes hard, solid discs would be fine. Except they'd weigh more and have no style.
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Old 04-29-19, 07:49 AM
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Originally Posted by FiftySix View Post
So, for non-racers that don't use their brakes hard, solid discs would be fine. Except they'd weigh more and have no style.
I don't think so.

It's not a matter of using the brakes hard. It's a matter of using them.

You might be able to get away with a solid rotor in an ultra flat place where you're barely using them.

But any kind of normal riding where you need to slow a decent down a hill and the drilled rotors will get hot enough that touching them will involve needing burn ointment at the least. No joke. They get pretty hot during normal usage.

You won't make them glow red like you see on the 'brake cam' in NASCAR. But you'll make them dangerously hot to touch with anything other than a steady ride without using the brakes at all.
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Old 04-29-19, 08:12 AM
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How thick are bicycle discs?

If we assume that the holes are circular, for the surface area of a drilled disc to be larger than that of a solid disc, the following would need to be true:

surface area of exposed material due to hole > surface area of the material that would be there if there was no hole

2*pi*r*th > 2*pi*r*r

th > r

Is that usually the case? What am I doing wrong?
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Old 04-29-19, 08:23 AM
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How do those guys at Moto GP manage to not die while using discs without holes all over them?

Behind the brakes: stopping power in MotoGP? | MotoGP?
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