chicane

No such thing exists. Rotors dont warp.... only your mind becomes this from being misinformed....

Let us first nix the phrase "warped rotors" from your vocabulary. "Warped rotors" are not physically warped at all, in nearly every case. The common misconception is that the rotors get hot enough to distort and then, upon cooling, they end up looking like a pretzel ? Contrary to popular belief, rotors dont warp in this fashion.

The vibration that is felt in the steering wheel, floorboard and pedal, is almost always caused by a rotor thickness variation, aka 'TV' and the physical pulsing in the pedal is nearly always a direct result of the caliper piston extending and retracting as it tries to follow a rotor of varying surface thickness.

Maybe we should start a thread talking about 'adhearent' and 'abrasive' friction and how it relates to braking systems ?? OR maybe we all need to read the Grassroots Motorsports article, "Bad Vibrations" in their June 2005 issue... to help shed the light on the subject ??

The basics still state, that the primary responsibility is to convert the kenetic energy of the chassis in motion into thermal energy, also known as heat. If there is available tire friction, the car will decelerate.... however the brakes do not stop the chassis. That's the tires job. No tire, no friction, no deceleration.

Now when you understand the pad and rotor interface, you will then understand this is where the energy conversion takes place. When you consider a cross drilled rotor, it is quite evident that it will have less mass and thats a bad thing.... when it needs to be a heat sink. Less mass, less absorbtion, other induced issues with fluid and this is right where adhearent friction starts to shed some light onto this 'bigger picture'.

Adhearent friction is where pressure and temperature collaborate to deposite a thin layer of pad material, or transfer layer, onto the rotor surface. Subsequently, the caliper squeezes the the pads against the rotor and the pads contact the transfer layer and not the rotor itself.

Back to what I stated earlier, the thickness variation from an improperly 'bedded' rotor and/or pads is the culprit. An overheated pad generates an uneven transfer layer as the pad material breaksdown. This creates an uneven layer and this can be viewed as spots of high and low friciton within the peaks and valleys of the transfer layer. Apply pressure to that condition and you will have a pulse......

But none the less, I recommend the article for those who have the interest.



Yes. As created from the stress risers during the 'drilling' process. It cuts through the grain structure and leaves fragmented grain structure, which is where a tare (or a crack, for lack of better terms) begins.

JasonWW

iTrader: (2)

Rotors can be warped. If the lug nuts are not tightened properly, the rotor face itself will not be true. It's usually fixed by loosening the lugs and then retightening properly.

It's pretty well known that uneven transfer film can cause the feeling that the rotor is warped, but you can usually eliminate it with a few good hard stops to even things out. Some people do that and it still doesn't change anything.

Also, I thought the transfer material was held in the pores of the cast iron, not completely on the surface.

PrototypE

Gentlemen, this info is all fine and good, but lets say, for those who don't flog their cars at the track constantly, I'm sure many people would like to know, how do we PREVENT or reduce brake pulsation? What combination of pads, rotors, fluids, etc will reduce this effect?

Not everyone can afford to spend $3000 on some extreme brake system, and may be overkill for many people who drive their cars mostly on the street. (not to mention the fact most won't fit under a stock wheel) Is there no affordable, direct bolt on combination of parts that will at least improve this?
Cryo-rotors? any particular pad, or fluid?

I don't pretend I have a race car, but I do enjoy my T/A, and sometimes driving aggressively means I need to stop aggressively.

I'd like to improve feel and fade resistance but WITHOUT causing TV, or at least dramatically reducing it. Is there no middle ground?

I'm more concerned about performance, than looks.
If this wasn't the case, I would've bought a V6.

Judd

iTrader: (1)

Yes, there is a middle ground and it has been discussed I think. If you simply want better braking at a lower cost you have a couple of choices. First choice is the cheapest and it consist of a "good" aftermarket stock replacement rotors {Nappa, whatever} and good pads. Make sure that you do not over tighten the lug nuts.

I had the stock rotors warp with-in 10K miles but I really think that that was due to over tightened lug nuts. I had the stock rotors turned and threw some HPS pads for around 40K miles and had no more warping but I made sure I checked the torque on the lug nuts. I did quite a few AutoXs and I play a good deal in the mountains, in other words, I gave them every opportunity to warp on the street. I also had some home-brew brake ducting at the same time but I really think that the HPS or HP plus pads on good rotors are fine for 90% of street driving.

Next option that is fairly cheap is a set of brake caliper relocation brackets {I bought a set of used LG Motorsports brackets} and used the stock calipers with C5 rotors. The rotors cost me a whopping 25 bucks a piece at Nappa. I've done more AutoXing, a HPDE that consisted of three 20 minute sessions and I won a 0-60-0 event at the Year One Experience. I had a 100 foot stop on a set of brakes that cost a whopping 250-300 bucks or so {includes rotors, pads and the relocation brackets}. The second place guy was a modded Viper and the third place guy was a modded Mitsubishi Evo so that will tell you that my car is braking pretty well especially considering that the Viper had me by something like a full second in the 0-60 part of the event.

PrototypE

Indeed, congratulations on your win! What would YOU consider good pads, Judd? Please, be specific. The pads you mention are made by Hawk, right? whats the difference between the two? The rotors on the front are brand new, and the pads are GM, (if i remember right). I machined the rears, also with GM pads (80% or so remaining.)

My beautiful T/A is very very rarely abused, but I do occasionally need to make it clear on the street a Trans Am is not to be confused with a base Firebird. Know what I mean? I'm sure there a few people on this board who fall into my driving catagory.

If the fuzz should be waiting for me around the corner, i need to be able to slow accordingly. Stock pads seem to be insufficent, and race pads are overkill, I would think.

Judd

iTrader: (1)

I hate to cop-out on your question but what might be a good pad to me, might be too noisy and dusty for another. On the other hand, there are some that might think my choice isn't good enough for them.

Saying that, I've used Hawk HPS pads {they had very little to no noise and minimal dust}. They worked well on the street and AutoX but I was afraid they would not be up to a track day {it's pretty well known they are not up to track days}. When I changed to the C5 rotors, I swapped to a set of Hawk HP Plus pads. I had decent luck with them, they are the pads I used to win the 0-60-0 contest and do the HPDE. They are pretty noisy at times {they do not have a noise reduction pad and I did not use any of the noise abatement glue stuff}. They dust a good bit more than the HPSs and they seem to be eating the rotors up at a fairly good rate. They also seem to be wearing a good bit faster than the HPSs. If you used some of the anti noise glue {for a lack of a better term}, the noise might be helped. Nothing you can do about the dust though. BTW, I've been using the stock rear pads. They work fine as there is very little braking done back there and if you get too much braking back there you can open a big can of worms {brake hop}.

BUT,,, there are all kinds of different pads and compounds out there. I have had the chance to only try three kinds {stock, HPS and HP Plus}. I will be trying a new pad in the future as I think I am out growing the HP Plus pads but as I go further into the extreme side of braking, I will be getting pads that just won't work as well on the street.

Here is link to a forum that might be of use to you {a little towards the racy side though}.

http://frrax.com/rrforum/index.php?act=SF&f=2

pimpmaro

I completely agree with Judd... it's EXTREMELY hard to recommend pads for someone else, especially if you don't know what their preferences/driving styles are. For rotors, the AutoZone Duralast rotors were recommended by mitchntx. I haven't used them yet, but I will be going that way in the VERY near future. On pads, however, I am currently on Hawk HPS pads and I haven't been overly impressed, specifically with more compounds I've been exposed to. Now they seem to be just as most other street pads to me. My next pads will most likely be Carbotech Panther+ pads... which I seriously think will be WAY too noisey and dusty for your usage. It's just a hard preference to judge.

JasonWW

iTrader: (2)

I'm running the Panther+ pads all around and once they are bedded in, they make little to no noise. Sometimes they are completely quiet and sometimes they may squeek a little. Honestly, I rarely notice it anymore.

For the job they do there isn't a down side. When cold they stop better than the stock pads and when warmed up they stop like you wouldn't believe. The initial bite is great, they grab as soon as you touch the pedal. The faster you go the better they feel.

The bottom line is that they feel good, real good. You can modulate them real well at the limit.

The only real down side is the initial cost ($285 all around) and the dust. The dust seems to clean up pretty easy on my polished rims. If you wipe them down about once a week, they seem to stay pretty clean.

PrototypE

Excellent info, dudes; I wish there was an easy way to compare pads to one another. However, my thinking is if one was to upgrade to a pad with more bite, would the additional grip not cause additional heat build up?

If so, how does one combat that, knowing drilled or slotted rotors will be of no use for that purpose on the street? If standard rotors 'warp' with stock pads rather quickly, Logicially, wouldn't a better performing aftermarket pad aggravate this condtion?

pimpmaro

PrototypE, one of the major points about warped rotors is how they're bedded in and IMHO, the quality of the rotor. I wouldn't go and buy the OEM rotors, but I would be happy to buy the duralasts as I've heard great results from them. The additional heat build up is pretty much one of our points with slotted/cross drilled rotors. The rotors act as a heat sink to dissipate rotational energy into heat energy. The less mass your heat sink has, the less it's capability to absorb heat energy (I think that's right...). The lower mass of a slotted and cross drilled rotor doesn't allow it to absorb as much heat energy before becoming saturated, while the cross drills and slots don't help dissipate heat fast enough to make a major difference. Plus the cross drills are potential weak spots in the rotor, depending on the design of the holes. If the edges are chamfered, that helps prevent cracking... but how in the hell do you chamfer the inside of each hole between the two faces of the disk? For disk cooling, the rotor vanes in between each face of the disk are adequate for dissipating heat. Now mind you, this is all without hard numbers, but if you really absolutely positively need convincing, I'm sure that the numbers can be dug up somewhere.

camaro98z28

I agree. I also have a friend that has had them on his can for over a year and they still look great. I noticed a difference at the track with these rotors.

JasonWW

iTrader: (2)

Good point. Let me clearify some of the terms, though. "Initial Bite" is how much friction you get when the pad first contacts the rotor. Some pads grab immediatly and maintians that level of friction and some start out with low friction and then ramp up to higher levels. It depends on what the pad is for. There are all kinds of variations in between. The Cf or coefficient of friction is just that. How much friction the pad can produce overall and not necesarily when you first hit the pedal.
If you look at the chart below:
http://www.wilwood.com/BrakePads/003-DESC/index.asp

You will see see how the different Wilwood compounds react to heat. The coefficient of friction is on the left and it changes as it gets hotter. Now don't look at the Cf in relation to the pads, I just want you to look at the curves and how they change as the temperatures change.

The stock pads don't change at all as they get hotter. They start and end up with the same coefficient of friction, kind of like the "J" compound only flatter. That's good because it is very consistant, but the overall Cf is low so the performance is low.
The Panther+ is more like an "H". It is also consistant but gets grippier as the pads get hotter. It starts out at a Cf higher than the stock pads and then goes up to even higher levels.
The Williams S2 autocross pads I tried were like a "B" compound. When you first pressed the pedal they grabbed like stock and then ramped up to higher levels. It allows the nose of the car to come down more gently to prevent the rear from becoming too light for an instant. It would be great for autocross where you need to maintain maximum grip at all times, but I didn't like the way it felt.

Now to get back to your point, yes a higher Cf pad will generate more heat, but how much is too much for a drilled/slotted rotor? With my Williams pads I bedded them in pretty aggressivly with no problems, the Carbotechs were a bit trickier as they can handle much more heat and generate more friction as well. I did 6 stops from 60-10 with full pedal pressure back to back. My Rotorpros rotors held up fine, they turned a little blueish but no big deal. It didn't feel like they were bedded in so a couple of weeks later I bedded them again. I did 6 stops from 80-10 with full pedal pressure back to back. Now that was too much. I put 3 cracks in the front left and 3 in the front right through the outermost holes. I swapped the front to the Duralasts and then bedded them with 6 stops from 60-10 with about 60% pedal pressure back to back. That did the trick.

Overall, the Rotorpros held up to some pretty good abuse right until I cracked them. I mean street driving is never going to get them as hot as I did in my 60-10x6 procedure. So I think most street cars should be fine with the drilled/slotted rotors even with an aggressive pad as long as you don't get them super hot and if you are running a pad closer to stock it definately should be fine.

On my setup I have plans to make some brake ducts to channel cool air into the rotor hat area. I don't think I would really need it, but I'm going to do it anyway. Cooler brakes will last longer and there is no down side. More info and lots of pics of the ducts can be found here.
http://frrax.com/rrforum/index.php?act=ST&f=2&t=4902

PS. I can't comment on the warped rotors because I have yet to have that problem.

JasonWW

iTrader: (2)

One thing I forgot to mention. The stock rotors are made from a poor mix of metals and once you replace them with a different brand, the constant warping should go away.

pimpmaro

I'll bet they do. I can't imagine a can that's heavy enough and moving fast enough to cause serious rotor wear.

PrototypE

All your input is great guys, and that chart was just what i was looking for, JasonWW!!

In that chart, though, why would anyone want a set of Wilwood's 'C' compound, as opposed to 'A' compound? Longevity, or dusting must play a role. I'll have to read their complete pad descriptions to find the set that best suits me.

And, as you guys were saying, there really is a difference in the quality of a set of rotors, i.e. Brembo blanks would be more resistant to warp, than, say, a set of o.e.m. from my parts department, at work, due to superior metallurgy, and whatever possible benefit from drilled or slotted rotors, is far overcome by the fact the 'blank' rotor can absorb more heat? Are cryo-rotors also a joke?

We know bedding of the pads is crucial to overall performance of a braking system, (I've had plenty of brake pull concerns on customer's cars related to improperly seated pads) but does it also affect resistance to warp, if done properly? What methods would work best for my '99?

PrototypE

Brake ducting might be a little much for street use, JasonWW, but not out of the question.

JasonWW

iTrader: (2)

The pad descriptions are only valid for Wilwoods pads. Most other pad makers don't give you that information. A lot of the time the pad makers will tell you the peak Cf to make it seem like a powerful pad, but that isn't really usefull because peak CF isn't reached very often on the street.
So when it comes to different brands you just have to go with what other people describe. If you want a pad that grabs hard as soon as you touch the pedal then that would be described as a pad with good "initial bite". Some pads have it and some don't to different degrees. The Hawk HP+ and the Carbotech Panther+ both have good "initial bite" and are streetable. Personally, I like that feel. When you are going really fast and you need to slow quickly, you don't want to wait half a second for the pads to grab because in that half a second you may have traveled 25-50 feet and that distance is added to your stopping distance. I like it when it grabs immediately.

As far as bedding, each pad manufacturer has there own recommendation for their own pads. If you can't find the info, you can call them and ask.
I think a blank rotor can absorb more heat "without cracking" compared to a drilled/slotted. The holes and slots do seem to cause weaknesses that are more susceptable to cracking under high temps.

I don't know anything about the cryo treated rotors.

PrototypE

A great deal of useful information here. I may not post much, but there's always plenty of reading material here. This thread, i'm sure, helped me avoid throwing money away on items that probably would have disappointed me.

I hope others read this, and gain knowledge from it, as I have.

Thanks for letting me interject, folks.

JasonWW

iTrader: (2)

One thing I forgot to mention. When you get some strong brakes they are a lot of fun, so you find yourself using them more aggressively. I haven't got my Carbotechs to fade yet, even when I got them hot enough to crack the drilled/slotted rotors. So they are amazing pads that can take some real heat (1250*F) and since I'm using them more, brake cooling ducts would let me utilize their full potential if the need should arise.

It's all cause and effect, one thing leads to another. Most folks don't need ducts, so no big deal. Then there are others who can benefit even on the street. I figure I could make some real trick ducts for less than 70 bucks, so why not?

Judd

iTrader: (1)

I fully agree with Jason on that point. You can whittle a set of brake ducts that will work AND can be completed for very little money. Here is a link to my cardomain page with a short write-up on my brake ducts-
http://www.cardomain.com/ride/296918/7

I have since replaced the lower air dam and the shop vac scoops with a new air dam {costs something like 40 bucks if I remember right} and purpose built scoops that were made for this use. I need to take some new pics as the air dam/ scoop assy. does not look nearly as cobbled up now. As I said in the write-up, I was experimenting at the time.

I've had those ducts under the car for quite a while now and the only problems I've had was back when my car was substantially lower {maybe a 2 inch drop, maybe a bit more} I scraped the air dam on everything. Nothing to do with the scoops though. I've since raised it back up a bit and I hardly ever hit the air dam. I also had a small amount of rubbing between the inner wheel lip and where the ducting was attached to the tie rod mount at full lock. I eventually fixed the rubbing issue and now I don't even notice the ducts are under there. BTW, the shop vac hose is still under there. It has held up very well to one HPDE event and around 2-3 years of mountain play. I was a bit worried that they would not be able to take the heat but apparently I have the hose mounted far enough away from the heat source.

I really recommend the ducting, cheap, easily reversible and no drawbacks on the street.