I got a question about cross drilled and slotted rotors

Posted By: TX9H6E4CUDA

I got a question about cross drilled and slotted rotors - 05/17/08 02:17 PM

Ok i just purchased some cross drilled and slotted rotors. I figured they were a great price on the bay (cheaper then napa rotors). Well i installed them on my daily driver with some EBC green stuff pads. Well they do work great and i only have 250 miles on them, but when i hit the brakes i am getting a noise and vibration at lower speed that sounds like a wheel bearing. ITs a Vrrrrrrrrrrrrrr sound and i can feel it in the steering wheel. Are cross drilled and slotted rotors supposed to do this? Will they ever stop making this noise or will i be stuck with it forever. I was thinking of checking them out tommorrow but just wondering because this is my first set of these rotors.

Thanks moparts

Posted By: kab69440

Re: I got a question about cross drilled and slotted rotors - 05/17/08 04:06 PM

My guess is that until the pads and rotors "wear in" together, you'll have that noise and vibration. I've been seeking a matched pair of late-B drilled/slotted front rotors and Lincoln rears as specified for the Scarebird rear disc conversion. I can't get any one of those eBay sellers to respond to my queries regarding them.

Posted By: 73 SSP

Re: I got a question about cross drilled and slotted rotors - 05/17/08 05:18 PM

Quote:

My guess is that until the pads and rotors "wear in" together, you'll have that noise and vibration. I've been seeking a matched pair of late-B drilled/slotted front rotors and Lincoln rears as specified for the Scarebird rear disc conversion. I can't get any one of those eBay sellers to respond to my queries regarding them.

I learned when a they don't respond their not ones to do businuss with.

Posted By: 71sat440

Re: I got a question about cross drilled and slotted ro - 05/17/08 05:30 PM

You probably already know this but just in case, are they on the right sides.
I know the slotted I sell have a left and right side.
People have mixed them up before.

Posted By: GoodysGotaCuda

Re: I got a question about cross drilled and slotted rotors - 05/17/08 05:58 PM

i wouldnt expect much out of cheap, ebay drilled/slotted rotors myself.

I wouldn't think they would take much abuse before cracking/warping

Posted By: MNobody

Re: I got a question about cross drilled and slotted rotors - 05/17/08 06:02 PM

I've never used rotor's of this type but i would guess any rotor that was slotted and drilled would make a different sound than solid rotor's.

Posted By: 2Bad360sfromNC

Re: I got a question about cross drilled and slotted ro - 05/17/08 07:27 PM

I bought a cheap pair off the 'bay for my Dakota R/T. I think they were like 75 or 80 bucks for both. I put Raybestos QS pads on there--never had any noise or vibration at all. I did finally screw one of them up, because I had a caliper start sticking. I was a good ways from home, so I determined to drive it 'til it started smoking. I made it home, but the rotor was toast at that point. The next day I got some regular cheap rotors from work and another set of QS pads, which are still on there to this day. I will say it doesn't stop quite as well with the standard rotors--you don't realize how much difference the drilled/slotted ones make til they're gone.

Posted By: da50r

Re: I got a question about cross drilled and slotted ro - 05/17/08 10:53 PM

You do know drilled or slotted rotors don't work until they are very hot and the gas effect starts happening.

Posted By: jcc

Re: I got a question about cross drilled and slotted rotors - 05/18/08 04:04 AM

I assume the only change was the pads and rotor, and you bedded them in as per rotor pad manufacturer suggested, and you checked rotor runout, and the caliper mounting is correct, then I would say the noise is not a good sign, but a sign of what, I don't know. I would think the drilling would not be a source of your problem, and the slots if mounted wrong direction I don't know. I personally would never drive a car with drilled rotors, slots maybe. The Porsche High dollar rotors have cast holes. The little weight savings vs chance of a failed rotor does not make sense to me. And some pads do not like slots.

Posted By: Greentween

Re: I got a question about cross drilled and slotted rotors - 05/18/08 01:40 PM

I used rotorpros off ebag for mine, and there was too much runout. Had to have them turned at napa.

Posted By: TX9H6E4CUDA

Re: I got a question about cross drilled and slotted ro - 05/18/08 04:47 PM

Quote:

You probably already know this but just in case, are they on the right sides.
I know the slotted I sell have a left and right side.
People have mixed them up before.

really dang they were not marked side or anything on the box and they didnt come with directions at all for break in and neither did the pads. Im going to jack it up today and take a look.

Can these rotors be turned?

Posted By: Magnum

Re: I got a question about cross drilled and slotted ro - 05/18/08 05:34 PM

I had drilled and slotted on our LHS. It was a bit louder during hard braking.

I later went back to smooth rotors because the drilled/slotted rotors wore out my front brake pads in 9 months. We typically get 3 years out of the front brakes on the LHS.

Overkill for a daily driver but they do work. I tried seriously abusing the ABS one day and the brakes would not fade or vibrate.

Posted By: TX9H6E4CUDA

Re: I got a question about cross drilled and slotted ro - 05/18/08 05:52 PM

so how do i know if they are on backwards? the slots and holes are heading towards front of the car when top dead to the rotor. They are mirrored looking (i guess i hit the brakes a little hard a couple of times) Im gonna hit it with some sand paper and scuff them up again

Posted By: Chilort

Re: I got a question about cross drilled and slotted ro - 05/18/08 06:03 PM

Here is a drilled and slotted rotor. Granted, it is for a G-body (Daytona) but should be okay as a reference. Notice the sticker with the L and arrow.

These are Baer so they are good quality. It took a while to get used to them. There is some different vibration and whatnot than a regular disc. Now that my pads are set though, it isn't as bad (it took a bit though). I really don't care if they eat pads because I love the way the car stops. This car doesn't have ABS. The action is real linear. I can go in deep and still press harder if I feel I need to.

It is my daily driver in terrible ATL traffic, so stopping frequently and hard is a regular event.

Posted By: Stanton

Re: I got a question about cross drilled and slotted rotors - 05/19/08 01:49 AM

Quote:

The little weight savings vs chance of a failed rotor does not make sense to me. And some pads do not like slots.

a) rotors are not drilled or slotted to save weight - they are drilled for cooling, they are slotted to get rid of moisture and dirt

b) pads don't know the difference whether there are slots, holes or nothing at all - as long as the rotor has been turned after the drilling or slotting process. When properly done, the holes and/or slots should both be chamfered.

c) runout would be a b*tch to check on a slotted rotor but you'd usually notice a pulsing if they weren't true as opposed to a noise.

I'd take them off and check pad wear and maybe get them turned to make sure they're true. Then chamfer all the holes and slots if they aren't already done. I'd also check the hub mounting face and make sure there's nothing like rust buildup or anything that would affect the rotor runout.

Posted By: jcc

Re: I got a question about cross drilled and slotted rotors - 05/19/08 10:49 AM

Quote:

Quote:

The little weight savings vs chance of a failed rotor does not make sense to me. And some pads do not like slots.

a) rotors are not drilled or slotted to save weight - they are drilled for cooling, they are slotted to get rid of moisture and dirt

b) pads don't know the difference whether there are slots, holes or nothing at all - as long as the rotor has been turned after the drilling or slotting process. When properly done, the holes and/or slots should both be chamfered.

c) runout would be a b*tch to check on a slotted rotor but you'd usually notice a pulsing if they weren't true as opposed to a noise.

I'd take them off and check pad wear and maybe get them turned to make sure they're true. Then chamfer all the holes and slots if they aren't already done. I'd also check the hub mounting face and make sure there's nothing like rust buildup or anything that would affect the rotor runout.

A. There are people who would disagree with you on why rotors are drilled. The MAIN reason seems to be it looks cool. Drilling rotors lowers their weight, that is not in dispute, which also lowers the amount of heat that can be absorbed because of less mass. We can also assume that anything solid with a hole in it, when suddenly heated drastically, has higher stress concentrations then someting without a hole in it, and therefore more prone to heat cracking.

B. by normal design a slot is almost always chamfered, a hole maybe, and some pad manufactureres care very much whether the rotors are holed or slotted

Posted By: Kam*Kuda

Re: I got a question about cross drilled and slotted ro - 05/19/08 03:16 PM

Quote:

Quote:

Quote:

The little weight savings vs chance of a failed rotor does not make sense to me. And some pads do not like slots.

a) rotors are not drilled or slotted to save weight - they are drilled for cooling, they are slotted to get rid of moisture and dirt

b) pads don't know the difference whether there are slots, holes or nothing at all - as long as the rotor has been turned after the drilling or slotting process. When properly done, the holes and/or slots should both be chamfered.

c) runout would be a b*tch to check on a slotted rotor but you'd usually notice a pulsing if they weren't true as opposed to a noise.

I'd take them off and check pad wear and maybe get them turned to make sure they're true. Then chamfer all the holes and slots if they aren't already done. I'd also check the hub mounting face and make sure there's nothing like rust buildup or anything that would affect the rotor runout.

A. There are people who would disagree with you on why rotors are drilled. The MAIN reason seems to be it looks cool. Drilling rotors lowers their weight, that is not in dispute, which also lowers the amount of heat that can be absorbed because of less mass. We can also assume that anything solid with a hole in it, when suddenly heated drastically, has higher stress concentrations then someting without a hole in it, and therefore more prone to heat cracking.

B. by normal design a slot is almost always chamfered, a hole maybe, and some pad manufactureres care very much whether the rotors are holed or slotted

My understanding here.
Braking produces gasses. Cross drilling the rotors give the
gasses a way to escape. This will increase the ability to apply pressure.

Posted By: JeffC

Re: I got a question about cross drilled and slotted ro - 05/19/08 03:31 PM

Quote:

Quote:

Quote:

Quote:

The little weight savings vs chance of a failed rotor does not make sense to me. And some pads do not like slots.

a) rotors are not drilled or slotted to save weight - they are drilled for cooling, they are slotted to get rid of moisture and dirt

b) pads don't know the difference whether there are slots, holes or nothing at all - as long as the rotor has been turned after the drilling or slotting process. When properly done, the holes and/or slots should both be chamfered.

c) runout would be a b*tch to check on a slotted rotor but you'd usually notice a pulsing if they weren't true as opposed to a noise.

I'd take them off and check pad wear and maybe get them turned to make sure they're true. Then chamfer all the holes and slots if they aren't already done. I'd also check the hub mounting face and make sure there's nothing like rust buildup or anything that would affect the rotor runout.

A. There are people who would disagree with you on why rotors are drilled. The MAIN reason seems to be it looks cool. Drilling rotors lowers their weight, that is not in dispute, which also lowers the amount of heat that can be absorbed because of less mass. We can also assume that anything solid with a hole in it, when suddenly heated drastically, has higher stress concentrations then someting without a hole in it, and therefore more prone to heat cracking.

B. by normal design a slot is almost always chamfered, a hole maybe, and some pad manufactureres care very much whether the rotors are holed or slotted

My understanding here.
Braking produces gasses. Cross drilling the rotors give the
gasses a way to escape. This will increase the ability to apply pressure.

Gassing out was a problem back in the day of organic brake pads. but not any more, modern brake pads don't gas out like the old ones did.

Posted By: Chilort

Re: I got a question about cross drilled and slotted ro - 05/19/08 07:06 PM

http://en.wikipedia.org/wiki/Disc_brake