Cross drilling rotors at home?

[LonesomeSTX]

I sure would like to do this mod to all of my trucks. However, is it really that simple? I know if go through with it I have to avoid drilling into the center supports that are between the two friction surfaces. But is there more to it than that. And what about the rotors that do not have that void? Are cross drilled rotors designed from scratch, or are they a standard rotor with hole drilled in it? How many holse are too many and how many are not enough? What kind of input do you all have in this matter?

 

[RonD]

First, why do you want holes in the rotors, there is no mechanical benefits, no better heat transfer, water shedding or any real benefit along those lines, racers found that out years ago.
If you are doing it for less weight then may be a benefit there, but on a truck...weight??.
Looks are the reason for holes in rotors now-a-days, and if that is your goal then drill away.

Yes, do not drill through supports only in the cavities.
How many holes?
Well the rotors will crack at the holes eventually, so the more holes the faster you will see the cracks starting.
I would use a drill press not a hand drill, and lots and lots of oil.
Now just as a thought, if it's "the look" you want you might try drilling the holes just on the outside facing surface and not all the way through, then black out the holes, so they "look" like holes, wouldn't need much of a hole, the pads wear not the rotor.


Rotors manufactured with holes are usually strengthened so less likely to crack, but......there is also no weight loss because of the added support, so they are just for looks.

Most racing cars now use ceramic pads and solid rotors, holes and slots were used prior to ceramic because of pad gassing(bit of a myth), which is no longer an issue with the newer pad materials.

Slotted or holed rotors should also be a bigger diameter because of the lost surface area, lost surface area = lost braking power

 

[LonesomeSTX]

I was under the impression it helps with heat.

 

[PlumCrazy]

Bro. Holes help, dont listen to what people tell you. I used a 1" hole saw and put 6 holes in each rotor, stops like a dream now.

It acts like cheese grator on the pads, so they always have a fresh wear surface to grip the rotors.

Sent from my XT907 using Tapatalk 2

 

[LonesomeSTX]

Makes sense to me.

 

[RonD]

I was under the impression it helps with heat.

It does, less surface area, less heat and less braking, lol.

The braking power needed is the heat generated, laws of physics, so that doesn't change, it's now a matter of how to get rid of that heat.

The extra surface area of the holes in the rotor to allow more air contact for cooling is so minimal I doubt it could be measured.
And to get the same stopping power, same surface area, the holed rotor needs to be larger diameter, so it will have a larger surface area to dissipate heat.

So smaller solid rotor or larger holed rotor = same stopping power

Larger rotor, solid or holed = better heat dissipation

Drilling a smaller rotor would give less stopping power so less heat, but not less heat because of air circulation.

 

[wizkid00104]

Bro. Holes help, dont listen to what people tell you. I used a 1" hole saw and put 6 holes in each rotor, stops like a dream now.

It acts like cheese grator on the pads, so they always have a fresh wear surface to grip the rotors.

Sent from my XT907 using Tapatalk 2

I thought about doing this to my flywheel, don't forget the holes save weight

 

[LonesomeSTX]

Then I would say this is a nogo.

 

[James86]

DON'T do it yourself - buy some reputable rotors that COME drilled/slotted. If you do it yourself, it'll look like shit, and probably throw it off balance.

As for whether it makes a difference? It certainly does. Mine stops noticeably better now than it ever has in the 7 years I've had my truck. I can vouch for it because I do in fact have drilled rotors:

I had to replace my rotors and these were comparable in price and had high ratings wherever I looked. So there's my opinion based on experience, and take it as you will.

They DO help, they DO make a difference, but even then, don't do it yourself, and don't waste money on drilled and slotted rotors unless your rotors are already in need of replacing like mine were. I can definitely feel less brake fade on long stretches, and when hauling with my truck. It also seems to help in the rain.

 

[James86]

I thought about doing this to my flywheel, don't forget the holes save weight

On a side note, flexplates (flywheels for automatics) DO have holes in them sometimes:

We replaced the one in our Contour because that's where it failed

 

[Twister]

Disregard

 

[LonesomeSTX]

So that is one for cross drilled working better.

 

[James86]

It works better than the warped rotors I already had at the time I replaced them... I can't promise you anything more concrete than that to be perfectly honest. Are your current rotors bad?

If I recall, my rotors are "Stoptech" and most reviews online when I searched range 4-5 out of 5 stars on average, and people use them on everything from Evos to BMWs. They ARE likely overkill and a bit unnecessary, but as I stated, I had to replace them anyways, and on RockAuto, they were comparable in price to OEM style rotors. The pads are Raybestos semi-metallic if that means anything. Basically, decide what you need, and do your homework - that's why I bought what I bought.

 

[JoshT]

As you've already figured out don't do it. FYI "good" ( use that subjectively) cross drilled and slotted rotors aren't actually drilled or have holes machined. They are cast with the slots and holes at the factory, this makes the grain of the metal conform to the holes and slots rather than being interrupted by them. After casting they may work the surface a little to spiff them up. The "cheap" ones are drilled and do have the holes and slots machined into a plain rotor after casting. It weakens the structure of the metal and makes them a lot more susceptible to cracks and breakage.

First, why do you want holes in the rotors, there is no mechanical benefits, no better heat transfer, water shedding or any real benefit along those lines, racers found that out years ago.
If you are doing it for less weight then may be a benefit there, but on a truck...weight??.
Looks are the reason for holes in rotors now-a-days, and if that is your goal then drill away.

Most racing cars now use ceramic pads and solid rotors, holes and slots were used prior to ceramic because of pad gassing(bit of a myth), which is no longer an issue with the newer pad materials.

Partially correct. Most of your first sentence is correct, but I personally think you should have said "is big mechanical drawback" instead of "is no mechanical benefit". I call increased susceptibility to cracking a major drawback on a braking component. As for the racer bit, little off there. Racers are the ones who originally found benefit in the holes and slots. Back in the days of asbestos brake pads they had big benefits and were worth the trade off in strength of the rotor, but back then rotors weren't subjected to the forces that they are today. As racers got faster braking forces increased, a solution that improved braking without weakening the rotor drove manufacturers to develop better brake pad compounds. With the improved compounds rotor materials it was eventually phased out as being useful and actually determined to be quite the opposite in those conditions. As for weight savings, they are negligible. Racers can get much more weight savings by changing tires and/or wheels, many easier and cheaper places that that weight can be shaved from before touching the rotors. These days about the only people you will see at the track with drilled and slotted rotors are amateur weekend warriors that buy into the hype, or showy types that put more weight on looking good that performance and talent.

Slots and holes were never related to ceramic pads, it was asbestos pads that did out gas. They would build up a layer of gas between the pad and rotor and destroy braking. That's where the idea of drilling and slotting came from as mentioned above. The holes would allow the gas to escape, and the slots would clean the pads (not needed these days either). These days a slotted rotor is the only one with a benefit, and it is only to people that can't drive. On a slotted rotor with each pass of the slot a little bit of the pad material is removed. People how like to ride their breaks tend to glaze pads which messes up braking power. A slotted rotor will clean off this glaze with each pass, the trade off it that it eats a set of pads in a hurry. Much better and more cost effective to teach drive not to ride breaks or keep them from driving.

It does, less surface area, less heat and less braking, lol.

Actually less surface area = less heat transfer but it means more heat (higher temps)

Sorry RonD not picking on you just wanted to clarify the information and put it out there for people.

DON'T do it yourself - buy some reputable rotors that COME drilled/slotted.

As for whether it makes a difference? It certainly does. Mine stops noticeably better now than it ever has in the 7 years I've had my truck.

They DO help, they DO make a difference, but even then, don't do it yourself, and don't waste money on drilled and slotted rotors unless your rotors are already in need of replacing like mine were. I can definitely feel less brake fade on long stretches, and when hauling with my truck. It also seems to help in the rain.

That first sentence x10000000000000000... If you are going to do it buy a set from a reputable manufacturer, don't do it yourself and don't buy ebay specials.

Really, stops better now with new cross drilled & slotted rotors and new pads (you don't mention what pads) than it did 7 years ago with new plain rotors (same brand) and new set of the same pads. You can remember exactly what it felt like 7 years ago with all that new stuff then?

hmm...

It works better than the warped rotors I already had at the time I replaced them... I can't promise you anything more concrete than that to be perfectly honest.

That's more like it. In that hypothetical world where all trucks are equal and exactly the same with the exception of one having drilled and slotted rotors, I highly doubt that you would notice one bit of difference in braking power. Unfortunatly in the real world there are so many other components both inside and outside of the braking system that the average Joe could never effectively test that, much less be able to afford to.

 

[LonesomeSTX]

I will just turn them and let it go at that then.