Need some help from someone with knowledge of rotors.

[wibblersnatch]

I have badly warped rotors and I've been looking for some online. I've heard someone say stay away from drilled rotors. Why?
Can someone take a look at these rotors for me and tell me what you think.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2920742341&category=1468

I appreciate anyones help.

 

[ArcticTsi]

Most tuners will tell you to stay away from cross drilled rotors cause they have the tendency to crack with age. I have had some crack myself. that is why now alot of places offer dimpled rotors. the holes do not go all the way through, thus not prone to cracking. Lots will recommend slotted or vained rotors. If you are set on cross-drilled go with a slotted/vained and drilled rotor. the best of both worlds and the thicker the better. thick in my exeperience tends mean strength.

 

[boostle]

You can get Brembo full-face rotors from TireRack for $58 each. I'd reccomend that over those Arospeeds anyday.

 

[Turbo Guru]

I have always used cross-drilled Brembo blanks from KVR Performance in Canada. (They have good prices and now have U.S. dealers and distribution channels.) I prefer Cross-drilled over any other combination (slotted, drilled/ slotted, dimpled, etc.) and I have had no problems.

Before I ordered my first set I spoke at length with their lead engineer (Terry) about the differences in design and their diferences in function (not to mention his recommendation.) I will give a short explanation of what they say about this subject. (Can be seen on their website.)

Cross-drilled rotors
"Cross Drilled Discs offer an enhanced initial bite (more responsive, especially in wet weather) and greater heat dissipation (reduction in heat induced fade - "brake fade") as compared to O.E.M. They also will last up to twice as long as O.E.M. rotors (depending on your braking style), with 40% Better Cooling, 20% better stopping, improved wet braking, reduces rotor warpage, less brake fade and longer life."

*important note*
I asked about the tendency of cross-drilled rotors to crack between the holes and this is what I was told; Due to rapid expansion and contraction of the materials it is quite common if the rotors are not tempered correctly when they are installed. (Not verbatim)

*Correct tempering Process*
(After installing new rotors, pads, and bleeding the braking system.) This tempering process must be performed before first use for greatest durability and reliability of your new cross-drilled rotors.
1) Check for proper operation
2) Find a Safe area that you will not impede traffic.
3) Accelerate to 25MPH
4) Brake as firmly as possible without locking up tires or engaging ABS system.
5) Repeat steps 3 and 4 five times (one after the other, with minimal time in between.)
6) Park vehicle and let rotors completely cool to ambient temperature.
7) Have fun

Gas-slotted rotors
"Slotted discs offer cleaning of the friction material (brake pads), but do little in terms of additional heat dissipation. Slotted brake discs do not cool better than cross-drilled discs or even standard discs. The face grooves will slice the brake pad material allowing the pad to bite harder into the disc, therefore causing an increase in disc temperatures. This is recommended for competition vehicles to bring pads and disc temperatures up to optimal operating ranges. (Race cars warm-up engines, tires and brakes for the best possible performance)."

*Important note*
"Proper slotting of a brake disc does not run off the outer diameter of the brake surface. This method can promote cracking as all brake discs expand with their release of thermal energy."

Hope this helps,
Joe

 

[Defiant]

Hooey. Slots/holes/dimples prevent effects of "gassing" of the pads, where the binders and/or dust raised under braking will create a layer of vapor that'll float the pads over the disk surface. Any method over stock smooth, consistent-thickness disks will create stress risers, where you have less beef to take up mechanical force and by that, uneven heating and dissipation. "40% Better Cooling, 20% better stopping" are guessitmates pulled from a hat. (I think where he says "slotted", he's referring to "grooved".)
In real-life road use, modified disks may work more quickly when wet, but they will not be as durable nor economical as stock. Cooling benefits on an already vented rotor will be slight. Where were holed rotors applied to the consumer market? On motorcycles, where you have an otherwise solid disk- in this application, you're as much as doubling the surface area which carries away brake heat to the air.

 

[Rx3]

Originally posted by Defiant
Hooey.

Definitely the new word of the day :laugh:

 

[Turbo Guru]

And your opinion on this subject is based on what?

Originally posted by Defiant
Hooey. Slots/holes/dimples prevent effects of "gassing" of the pads, where the binders and/or dust raised under braking will create a layer of vapor that'll float the pads over the disk surface.

Yes, they do prevent gassing, which is a good thing. So, what you are trying to tell us is that it is better if the pads don't come in contact with the rotors? Hmm, I was always under the impression that you want friction when it comes to brakes.

Any method over stock smooth, consistent-thickness disks will create stress risers, where you have less beef to take up mechanical force and by that, uneven heating and dissipation. "40% Better Cooling, 20% better stopping" are guessitmates pulled from a hat. (I think where he says "slotted", he's referring to "grooved".)

Who said anything about them not being smooth or of consistent thickness? Heating a will still be even and dissipation will be more rapid due to the effective increase in surface area created when a rotor is cross-drilled, (which you so interestingly pointed out below in your motorcycle reference.) The words that I copied are directly from their website and are near exactly what he told me when I discussed it with him several years before his website existed.

I don't think that the "40% better cooling and 20% better stopping are guessitmates [sic] pulled from a hat." And no, I am quite positive he doesn't mean grooved where he says slotted. (Besides, I have no idea what you are refering to when you say "grooved," but I have a funny feeling that you are refering to the same design as a Gas-slotted rotor.)

In real-life road use, modified disks may work more quickly when wet, but they will not be as durable nor economical as stock. Cooling benefits on an already vented rotor will be slight. Where were holed rotors applied to the consumer market? On motorcycles, where you have an otherwise solid disk- in this application, you're as much as doubling the surface area which carries away brake heat to the air.

In real-life road use I can attest to the effectiveness, (in dry conditions,) of cross-drilled rotors. The price of a set of Cross-drilled Brembo blanks (stock-sized, cadmium plated) is within a few dollars of a set of stock rotors from the dealer, which speaks for economy. As far as durability is concerned, after tempering my new sets of cross-drilled rotors I have only had one rotor (from several sets on several cars) show signs of cracking (from extreme heat caused by a sticky caliper.) Otherwise, I had put near 60,000 miles on a set before selling one of the cars that were equipped with them and they were still in great condidtion.

Cooling benefits on an already vented rotor will still be significant, (up to 40% in fact,) because you are still increasing surface area to dissipate heat from the rotor.

In closing
Everyone is entitled to their opinion, but before you attempt to debunk the words of someone that has extensive credibility in his field, namely Terry the lead engineer from KVR Performance (who incidentally [sp?] is a manufacturer for many reputable braking companies,) you may want to show some data or proven theory to back up your opinions. This reply was not meant to be a flame but was meant to point out the flaws in your logic.

My $.02
Joe

(I hope this contains decent grammar/ spelling I have been awake for far too many hours at the time I wrote this.)

 

[dano]

without getting into the blank / slotted / drilled argument, as far as sheer rotor longevity goes, i'd get a cryorotor. frozenrotors.com has 'em... they're a little pricey, but they last a *wicked* long time. they'll also do custom slotting and drilling (i'm not sure what brand of rotors they use pre-treatment... could be the brembo OEM ones, but i'm not sure). i have a set of full-face cryo-treated ones on my civic, and they've never done me wrong. rallycrossing, wintercrossing, and autocrossing and they're doing fine. =)

 

[Turbo Guru]

These people can Cryo-treat anything. FFWD