Do cross drilled/slotted rotors cause vibration?
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Captain
Joined: Aug 2009
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From: abington,ma
Do cross drilled/slotted rotors cause vibration?
I have a ram 1500 with stock 20" rims and I had my rotors replaced with new cross drilled slotted rotors (all 4) and cmax brake pads (all 4) and now i notice that everytime i slow down i feel a vibration in the brake pedal. If im going fast and slow to a quick stop i dont always feel it but if im goin 30 then slow to a stop i feel it near the end before i stop. Is this just because of the cross drilled/slotted rotors or something else? a few years back i also put these type of rotors on my old car and the same thing happened.
Rookie
Joined: Aug 2012
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The slots in the rotors sometimes can cause a pulsating sound and slight pedal feedback. Ive seen this on several sports cars with slotted rotors.
Slotted and drilled rotors are however more likely to warp and crack than their solid counterparts. After repeated heat cycling the very nature of the holes and slots creates stress fractures and possibly even warping.
I really dont think they belong on a truck, let alone on track/sports cars (which is where ive been involved in this debate originally). Brakes job is to convert rotational force into heat via friction, you want the most mass you can get to be able to cope with this heat buildup. The only real reason for drilled/slotted rotors was when pads tended to outgass which has been solved via modern pad compound technology. But hey, they LOOK sporty right.
You are getting absolutely no benefit other than increased pad wear, probably this pulsating, and less thermal capacity from your drilled slotted rotors. Next time just get high quality solid rotors...my .02
Oh one thing you might try is to re-bed the pads...sometimes this solves the problem because on green pads/rotors they can leave deposits in one spot if you heat them and park the vehicle. First get then brakes to operating temp, then do a few repeated hard stops from about 50-0 (until you smell the brakes), then drive around without stopping to let them cool for about 15 minutes. The cooling step is important, so find a good place with no traffic or stop signs/lights. You should see a grey film on the rotors which will let you know you did the job right.
Slotted and drilled rotors are however more likely to warp and crack than their solid counterparts. After repeated heat cycling the very nature of the holes and slots creates stress fractures and possibly even warping.
I really dont think they belong on a truck, let alone on track/sports cars (which is where ive been involved in this debate originally). Brakes job is to convert rotational force into heat via friction, you want the most mass you can get to be able to cope with this heat buildup. The only real reason for drilled/slotted rotors was when pads tended to outgass which has been solved via modern pad compound technology. But hey, they LOOK sporty right.
You are getting absolutely no benefit other than increased pad wear, probably this pulsating, and less thermal capacity from your drilled slotted rotors. Next time just get high quality solid rotors...my .02
Oh one thing you might try is to re-bed the pads...sometimes this solves the problem because on green pads/rotors they can leave deposits in one spot if you heat them and park the vehicle. First get then brakes to operating temp, then do a few repeated hard stops from about 50-0 (until you smell the brakes), then drive around without stopping to let them cool for about 15 minutes. The cooling step is important, so find a good place with no traffic or stop signs/lights. You should see a grey film on the rotors which will let you know you did the job right.
Last edited by guitman32; Jun 21, 2013 at 01:25 PM.
Champion
Joined: Nov 2005
Posts: 2,875
Likes: 1
From: North Eastern England
The slots in the rotors sometimes can cause a pulsating sound and slight pedal feedback. Ive seen this on several sports cars with slotted rotors.
Slotted and drilled rotors are however more likely to warp and crack than their solid counterparts. After repeated heat cycling the very nature of the holes and slots creates stress fractures and possibly even warping.
I really dont think they belong on a truck, let alone on track/sports cars (which is where ive been involved in this debate originally). Brakes job is to convert rotational force into heat via friction, you want the most mass you can get to be able to cope with this heat buildup. The only real reason for drilled/slotted rotors was when pads tended to outgass which has been solved via modern pad compound technology. But hey, they LOOK sporty right.
You are getting absolutely no benefit other than increased pad wear, probably this pulsating, and less thermal capacity from your drilled slotted rotors. Next time just get high quality solid rotors...my .02
Oh one thing you might try is to re-bed the pads...sometimes this solves the problem because on green pads/rotors they can leave deposits in one spot if you heat them and park the vehicle. First get then brakes to operating temp, then do a few repeated hard stops from about 50-0 (until you smell the brakes), then drive around without stopping to let them cool for about 15 minutes. The cooling step is important, so find a good place with no traffic or stop signs/lights. You should see a grey film on the rotors which will let you know you did the job right.
Slotted and drilled rotors are however more likely to warp and crack than their solid counterparts. After repeated heat cycling the very nature of the holes and slots creates stress fractures and possibly even warping.
I really dont think they belong on a truck, let alone on track/sports cars (which is where ive been involved in this debate originally). Brakes job is to convert rotational force into heat via friction, you want the most mass you can get to be able to cope with this heat buildup. The only real reason for drilled/slotted rotors was when pads tended to outgass which has been solved via modern pad compound technology. But hey, they LOOK sporty right.
You are getting absolutely no benefit other than increased pad wear, probably this pulsating, and less thermal capacity from your drilled slotted rotors. Next time just get high quality solid rotors...my .02
Oh one thing you might try is to re-bed the pads...sometimes this solves the problem because on green pads/rotors they can leave deposits in one spot if you heat them and park the vehicle. First get then brakes to operating temp, then do a few repeated hard stops from about 50-0 (until you smell the brakes), then drive around without stopping to let them cool for about 15 minutes. The cooling step is important, so find a good place with no traffic or stop signs/lights. You should see a grey film on the rotors which will let you know you did the job right.
Like a lot of things these days, a lot of BS PR on stuff, makes people believe that it "must be true".
Everyone then jumps on the band wagon, so statistics say it must be true that performance increases because 9 out of 10 people use them.
Ill say one thing.....do F1 cars use them??
Al.
Champion
Joined: Nov 2005
Posts: 2,875
Likes: 1
From: North Eastern England
I wonder if routing some large bore conduit type flexi tube from the front of the truck diverting cool air through an ever reducing diameter over the brakes, would be a better upgrade for braking performance and a lot cheaper??
It's probably very much overkill for a truck though.
It would help when towing down long hills.
Al.
It's probably very much overkill for a truck though.
It would help when towing down long hills.
Al.
Veteran
Joined: Dec 2006
Posts: 295
Likes: 5
From: Wheatley Ontario, Canada.
Depending on how severe the vibration is. My guess is one of your new rotors is warped? I agree on the EBC rotors/ green pads. Not really happy with them as well. Specially for $$$ they charge. I am running Brakemotives on my Dodge Ram and for under $200.00 including shipping (cashed in on DF specially when it was on) they work great! No cracking and good pad wear so far! Even put the Brakemotives on my Olds and Cavalier and no trouble there as well.
For the vibration I'd check the new rotors that were installed. My bet is one maybe two are warped. Happened to me before.
Good Luck.
For the vibration I'd check the new rotors that were installed. My bet is one maybe two are warped. Happened to me before.
Good Luck.
Professional
Joined: Aug 2012
Posts: 138
Likes: 0
From: Mobile, AL
It is not uncommon for drilled or slotted rotors to cause a noise or light pulsation until they are worn in a little.
As for the argument for the drilled/slotted rotors being of no gain, its not entirely true. No they dont "stop the truck faster", thats 100% bandwagon of everyone using their butt dyno to think the truck now stops faster in addition to going faster from the K&N stickers they put on the window...
As for the heat, you are partially correct. Braking is the transfer of energy, not just converting it into heat. Large mass is needed to absorb the heat, but the mass of the rotor can only hold so much heat, which is why it needs to dissipate heat as quickly as possible. This is why rotors have vents in the center, to dissipate heat quicker than a solid rotor. The mass of a rotor as well as its ability to dissipate heat determines its efficiency.
Slotted rotors are about moving gases out from the pads, this can be argued whether it does any good with modern pad compostions, but it makes no noticeable change that can be felt. Drilled rotors walk the line between reducing mass and improving heat dissapation, where the rotor is removing heat fast enough that it no longer requires the large mass to absorb more. These will also not cause any quicker stopping, because you will not generate more heat than the rotor can absorb in one stop. But they do prevent brake fade, which happens when the rotor has absorbed as much heat as it can.
As for the argument for the drilled/slotted rotors being of no gain, its not entirely true. No they dont "stop the truck faster", thats 100% bandwagon of everyone using their butt dyno to think the truck now stops faster in addition to going faster from the K&N stickers they put on the window...
As for the heat, you are partially correct. Braking is the transfer of energy, not just converting it into heat. Large mass is needed to absorb the heat, but the mass of the rotor can only hold so much heat, which is why it needs to dissipate heat as quickly as possible. This is why rotors have vents in the center, to dissipate heat quicker than a solid rotor. The mass of a rotor as well as its ability to dissipate heat determines its efficiency.
Slotted rotors are about moving gases out from the pads, this can be argued whether it does any good with modern pad compostions, but it makes no noticeable change that can be felt. Drilled rotors walk the line between reducing mass and improving heat dissapation, where the rotor is removing heat fast enough that it no longer requires the large mass to absorb more. These will also not cause any quicker stopping, because you will not generate more heat than the rotor can absorb in one stop. But they do prevent brake fade, which happens when the rotor has absorbed as much heat as it can.
Man, I just put these on and I have no vibration, and a truck that stops a lot quicker than it did before. Who woulda guessed
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Rookie
Joined: Aug 2012
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The slots in the rotors sometimes can cause a pulsating sound and slight pedal feedback. Ive seen this on several sports cars with slotted rotors.
Slotted and drilled rotors are however more likely to warp and crack than their solid counterparts. After repeated heat cycling the very nature of the holes and slots creates stress fractures and possibly even warping.
I really dont think they belong on a truck, let alone on track/sports cars (which is where ive been involved in this debate originally). Brakes job is to convert rotational force into heat via friction, you want the most mass you can get to be able to cope with this heat buildup. The only real reason for drilled/slotted rotors was when pads tended to outgass which has been solved via modern pad compound technology. But hey, they LOOK sporty right.
You are getting absolutely no benefit other than increased pad wear, probably this pulsating, and less thermal capacity from your drilled slotted rotors. Next time just get high quality solid rotors...my .02
Oh one thing you might try is to re-bed the pads...sometimes this solves the problem because on green pads/rotors they can leave deposits in one spot if you heat them and park the vehicle. First get then brakes to operating temp, then do a few repeated hard stops from about 50-0 (until you smell the brakes), then drive around without stopping to let them cool for about 15 minutes. The cooling step is important, so find a good place with no traffic or stop signs/lights. You should see a grey film on the rotors which will let you know you did the job right.
Slotted and drilled rotors are however more likely to warp and crack than their solid counterparts. After repeated heat cycling the very nature of the holes and slots creates stress fractures and possibly even warping.
I really dont think they belong on a truck, let alone on track/sports cars (which is where ive been involved in this debate originally). Brakes job is to convert rotational force into heat via friction, you want the most mass you can get to be able to cope with this heat buildup. The only real reason for drilled/slotted rotors was when pads tended to outgass which has been solved via modern pad compound technology. But hey, they LOOK sporty right.
You are getting absolutely no benefit other than increased pad wear, probably this pulsating, and less thermal capacity from your drilled slotted rotors. Next time just get high quality solid rotors...my .02
Oh one thing you might try is to re-bed the pads...sometimes this solves the problem because on green pads/rotors they can leave deposits in one spot if you heat them and park the vehicle. First get then brakes to operating temp, then do a few repeated hard stops from about 50-0 (until you smell the brakes), then drive around without stopping to let them cool for about 15 minutes. The cooling step is important, so find a good place with no traffic or stop signs/lights. You should see a grey film on the rotors which will let you know you did the job right.
It is not uncommon for drilled or slotted rotors to cause a noise or light pulsation until they are worn in a little.
As for the argument for the drilled/slotted rotors being of no gain, its not entirely true. No they dont "stop the truck faster", thats 100% bandwagon of everyone using their butt dyno to think the truck now stops faster in addition to going faster from the K&N stickers they put on the window...
As for the heat, you are partially correct. Braking is the transfer of energy, not just converting it into heat. Large mass is needed to absorb the heat, but the mass of the rotor can only hold so much heat, which is why it needs to dissipate heat as quickly as possible. This is why rotors have vents in the center, to dissipate heat quicker than a solid rotor. The mass of a rotor as well as its ability to dissipate heat determines its efficiency.
Slotted rotors are about moving gases out from the pads, this can be argued whether it does any good with modern pad compostions, but it makes no noticeable change that can be felt. Drilled rotors walk the line between reducing mass and improving heat dissapation, where the rotor is removing heat fast enough that it no longer requires the large mass to absorb more. These will also not cause any quicker stopping, because you will not generate more heat than the rotor can absorb in one stop. But they do prevent brake fade, which happens when the rotor has absorbed as much heat as it can.
As for the argument for the drilled/slotted rotors being of no gain, its not entirely true. No they dont "stop the truck faster", thats 100% bandwagon of everyone using their butt dyno to think the truck now stops faster in addition to going faster from the K&N stickers they put on the window...
As for the heat, you are partially correct. Braking is the transfer of energy, not just converting it into heat. Large mass is needed to absorb the heat, but the mass of the rotor can only hold so much heat, which is why it needs to dissipate heat as quickly as possible. This is why rotors have vents in the center, to dissipate heat quicker than a solid rotor. The mass of a rotor as well as its ability to dissipate heat determines its efficiency.
Slotted rotors are about moving gases out from the pads, this can be argued whether it does any good with modern pad compostions, but it makes no noticeable change that can be felt. Drilled rotors walk the line between reducing mass and improving heat dissapation, where the rotor is removing heat fast enough that it no longer requires the large mass to absorb more. These will also not cause any quicker stopping, because you will not generate more heat than the rotor can absorb in one stop. But they do prevent brake fade, which happens when the rotor has absorbed as much heat as it can.
Slots, no benefit with modern pad compositions for any type of vehicle (feature not found on any modern race car that I have seen)
Crossdrilled, although does provide marginal additional cooling, is a tradeoff between longevity and performance. GT3 cup cars use crossdrilled rotors, however they are going through at least three sets of rotors per weekend per car. I have seen too many cracked "performance" crossdrilled rotors for anyone to convince me that the average price minded consumer grade crossdrilled rotor is worth its weight in salt (factoring metallurgy, desired longevity, etc)
On a sports car little to no benefit, on a truck, gimme a break.
Pic taken at Sebring, pile of used Porsche cup rotors...notice the crack emanating from the drilled hole in the upper right corner.
Last edited by guitman32; Jun 24, 2013 at 03:43 AM.
