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Holes in Disk Rotors

Old 02-21-17, 04:48 AM
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Holes in Disk Rotors

Does the number and size of holes in a disk rotor make a difference in braking power?

I know they're for mud clearing, but what about when riding dry?

in dry conditions, would a rotor with fewer/smaller holes (and thus more surface area) have stronger braking?

Dissatisifed with mine and have to wonder if that might be a factor to consider in replacing....
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Old 02-21-17, 07:07 AM
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Holes are more for heat dissipation than fluid clearance, but do accomplish both. It is a fine art
designing disk rotors that don't warp when hot, and heat is a more consistent problem than
water which is a more likely problem than mud. Holes do help clear the fluids (mud/water) as
well. I doubt you would notice much difference in braking power in reality but yes in theory
more rotor metal would assist braking. I would look elsewhere first before changing rotor just
for perforation amounts, such as pads or a bit larger rotor if possible on your frame.
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Old 02-21-17, 08:55 AM
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I would say the first step is to make sure your current rotors/pads aren't contaminated-- wipe the rotors down with some denatured alcohol, lightly re-surface the pads by sanding them on some 400 grit sandpaper laid on a piece of glass (or anything equally flat.) When cold, most any rotor/pad combo should provide adequate stopping power. Also, if your calipers are mechanical, make sure the gap between pad and rotor isn't too large, that will give the levers more travel and make the brakes feel unresponsive.
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Old 02-21-17, 09:05 AM
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Originally Posted by xenologer
Does the number and size of holes in a disk rotor make a difference in braking power?

I know they're for mud clearing, but what about when riding dry?

in dry conditions, would a rotor with fewer/smaller holes (and thus more surface area) have stronger braking?

Dissatisifed with mine and have to wonder if that might be a factor to consider in replacing....
There's more surface area for braking but less surface area for heat dissipation. If the rotor retains too much heat, the braking will start to fade and/or the rotor will start to change shape (i.e. warp) due to inconsistent cooling and heating.

Originally Posted by DrIsotope
When cold, most any rotor/pad combo should provide adequate stopping power.
I would agree that the rotor and the pad aren't going to be a problem. The caliper, on the other hand, could be. Not all calipers are equivalent and there are some out there that simple don't work that well no matter what pad or rotor you use.
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Old 02-21-17, 09:16 AM
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Originally Posted by xenologer
.... braking power? ..... Dissatisifed with mine and have to wonder if that might be a factor to consider in replacing....
Maybe... if we back-up and look at it this way. Your brakes aren't stopping you well? What brand, age, configuration are they?

(I am thinking selfishly with thoughts of my own brakes).
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Old 02-21-17, 09:29 AM
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Originally Posted by DrIsotope
I would say the first step is to make sure your current rotors/pads aren't contaminated-- wipe the rotors down with some denatured alcohol, lightly re-surface the pads by sanding them on some 400 grit sandpaper laid on a piece of glass (or anything equally flat.) When cold, most any rotor/pad combo should provide adequate stopping power. Also, if your calipers are mechanical, make sure the gap between pad and rotor isn't too large, that will give the levers more travel and make the brakes feel unresponsive.
+1 to all of this.

I'd like the OP to give more details about why they are not happy and the bike/set-up we're talking about.

I've logged 20,000+ miles over 13 years on three disc brake bikes. I've used these bikes in nearly every environment/conditions imaginable* and the only times I've found my disc brakes less than great is because of maintenance issues.

* I live in Minnesota, so I don't have long descents.
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Old 02-21-17, 12:11 PM
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Stopping power is mostly affected by the clamping force of the caliper. It doesnt matter if the rotor is full of holes or solid. Learned this years ago when drilling motorcycle rotors became all the rage.

Next in line is the rotor material. Some are great and some just suck, followed by brake pad material. Using rotors and pads of the same brand should bring a bigger smile over your braking abilities.

-SP
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Old 02-21-17, 01:49 PM
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Originally Posted by xenologer
Does the number and size of holes in a disk rotor make a difference in braking power?

I know they're for mud clearing, but what about when riding dry?

in dry conditions, would a rotor with fewer/smaller holes (and thus more surface area) have stronger braking?

Dissatisifed with mine and have to wonder if that might be a factor to consider in replacing....
Do we have to guess what kind? Photo is nice, rotor size, rider weight, type of brake system, conditions and age would be helpful. Did you bed the rotors/ pads in first?
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Old 02-21-17, 02:47 PM
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Louisville UCI Pro CX world championships , the riders , few that were running discs

Could not get the pads to last an Hour.. the elite race length..

So they got some made with out any holes.. flown in overnight..

the sand pit they had to cross every lap left enough sand in the holes

to wear thru the Pad Rapidly.. too Much abrasive Friction.



...
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Old 02-21-17, 06:51 PM
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Originally Posted by xenologer
Dissatisifed with mine and have to wonder if that might be a factor to consider in replacing....
Hydraulic or mechanical?

How much do you weigh?


-Tim-
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Old 02-22-17, 02:01 AM
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Originally Posted by speedy25
Stopping power is mostly affected by the clamping force of the caliper. It doesnt matter if the rotor is full of holes or solid. Learned this years ago when drilling motorcycle rotors became all the rage.
Yes quite. I remember back to when they invented drillium, It was all the rage all the rage.
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Old 02-22-17, 09:59 PM
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I'm using TRP Spkye mechanical calipers (mtb pull version of Spyre)
Clarke's organic pads
with Yokozuna Reaction compressionless housing
and an old Deore XT M739 series lever
The rotor is the big holey 180mm one from EBC found here

and I am aware of how to set up a lever to grab as my fingers wrap for ergonomics/hand strength

My dissatisfaction, is the inability to lock the front brake and endo.
I'm 190lbs

Reviews of the TRP Spyke/Spyre often claim great modulation, un-spectacular stopping power. Maybe I'm seeing that firsthand. A gradual grab that makes it more useful for bleeding momentum than doing an endo stoppie.

Thanks
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Old 02-23-17, 08:49 AM
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Originally Posted by xenologer
and I am aware of how to set up a lever to grab as my fingers wrap for ergonomics/hand strength
I'm not sure what you mean by this statement. I suspect that you have set up your levers so that the lever doesn't really engage until about half travel so that you appear to have better hand strength. If that is the case, I've never had brakes that worked well with that kind of lever travel...especially disc brakes.

I have Spykes on 3 bikes without any special cabling using 203mm rotors on the front and either 180mm or 160mm on the rear (or v-brake for one bike). My rotors are Avid or Magura Storm or Magura Storm SL. All of them have lots of holes and the Storm SL has more holes than the Storm. I haven't noticed any lack of braking ability and, in fact, the brakes judder now under heavy braking as the fork blades move back and forth. Never noticed any judder when I had Avid BB7s.

But all of my brakes...disc or rim...are run so that the levers are basically locked at about half travel to the handlebars. I think that is the key to having effective brakes. I tried the longer travel method in the past and it lasted exactly one very short ride.

Try pulling the pads in closer.
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Old 02-23-17, 06:17 PM
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Can you get a proper metallic brake pad for those things? Organic pads always feel horrible and soft to me.
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Old 02-23-17, 06:41 PM
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Rotors have holes in them to aid in cooling and reduce rotating mass, simple stuff but people often overlook at the pads as part of their braking package.
Good pads are as important as a good rotor because, together, they stop you faster with more control.
If you don't feel secure with your brakes, that might indicate some adjustments are needed but usually, parts need to be replaced or upgraded.
Brake bleeding, fluid levels, rust, "stiction" of the pads and more can really affect the braking performance of a bike.
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