BRAKE FAQ - Suspension and Brake Forum

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BRAKE FAQ
Friday, June 11, 2004 10:29 PM
As the resident Brake Vendor and gearhead...I thought I'd answer some questions that I see asked in here as well as those that I answer over the phone all day. All you computer guys out there, feel free to reorganize this thread as you see fit, because I'm putting it all on one page.

Here we go:

#1 Slotted or Crossdrilled rotors.

These rotors both accomplish the same basic things. Contrary to popular belief, slots and drill holes DO NOT help cool the rotor. They simply allow the brakes to operate properly at a much higher temperature. When pads get hot, the resins and binders that hold the friction material together with do 2 things, either melt or "gas". If they melt, this will act as a lubricant and the brakes won't work, if they gas, the gas will tend to float the pad off the surface of the rotor, so all your pedal pressure goes into compressing this gas rather than forcing the pads against the rotor. Slotted and Crossdrilled rotors allow an escape route for these things. Crossdrilled rotors are mainly beneficial for high end racing where there is a lot of concern for the reduction of unsprung weight. Aside from that and the cosmetic aspect (face it...they look good) there is no reason to go with crossdrilled rotors. Slotted rotor maintain about 95% of the friction surface that the original rotor had while crossdrilling removes much more material leaving only about 70-80% of the original friction surface. A crossdrilled rotor also does not have holes passing evenly over the entire pad as do most slotted rotors, leading to uneven pad and rotor wear because the pad is contacting the rotor for a full 360 degrees at certain points and much less than that at others. Crossdrilled rotors generally wear out pads faster than slotted rotors as well. Another problem with crossdrilled rotors is that they sometimes develop stress cracks around the holes. When the drilling takes place, stress risers are formed because the "web" of the casting is disturbed. Slotted rotors do not have this problem....especially if the slots do not extend past the outer edge of the friction surface. Slotted rotors are better for the street.....Crossdrilled for the track if you are changing rotors after every race and they are not repeatedly heat cycled, which will most likely promote cracking.

#2 Everything you need to know about brake fluid.

DOT 3 and 4 fluids are classified as Hygroscopic..this means that they absorb water. This is a good thing. DOT 5 fluid is silicon based and does not absorb water. NEVER use DOT 5 fluid in an ABS system. The reason for this is that because is does not absorb water, the moisture that is introduced to the system ends up collecting in corner of the hydraulic system and corroding the hell out of whatever it touches. Hygroscopic fluids will absorb the moisture so that it is in very low concentration everywhere in the hydraulic system and will not cause any considerable corrosion if the system is properly maintained. Brake fluid does need to be changed at a minimum of every two years. As water is absorbed into the system....the boiling point of the fluid is decreased. When brake fluid boils, you get brake fade because it develops a gas in the hydraulic system. Gas is compressable while liquids are not. If gas exists in the system, your pedal pressure will go into compressing that rather than forcing the pads against the rotors and stopping the car. Additionaly, as water is absorbed into the system, the chances of component corrosion is greatly increased. I recommend that brake fluid be flushed once a year, or if the vehicle is race (not drag racing, but road racing) in an environment where the brakes are pushed past there limits, the system should be flushed after every race. For racing or high performance use, a performance brake fluid like MOTUL or ATE super blue is recommended.

#3 How do I change my own brakes?

Buy a repair manual....it will prove to be indispensable one day and they only cost about $12

#4 All about Stainless Braided Lines

Stainless lines are by no means a necessity for a brake system. They offer a slightly stiffer pedal, more wear resistance, and better bragging rights than standard rubber lines. Most quality stainless braided lines have a teflon liner inside a rubber hose with a stainless jacket over the top.....some DOT approved lines also have a clear vinyl cover over the stainless jacket. This is to prevent the stainless from cutting holes in whatever it might rub up against in the course of its duty. For a high performance brake system, stainless lines are a great addition to complete the performance package.


#5 Why do rotors "warp"

They don't. The vibration you feel in the pedal that everyone explains to you is a "warped" rotor is actually a thickness variation in the rotor. If a rotor was warped, it would simply wobble slightly side to side and the caliper (which SHOULD slide freely) will follow it back and forth and no problem will ever be noticed. Most brake vibration problems are caused by rust or dirt build up or a slight runout in the hub. The outside diameter of the hub is maybe 2 or 2.5 inches from the centerline whereas the outside diameter of the rotor is between 5 and 7 inches from the centerline, depending on the car, and possibly more or less, depending on the brake system. This means that .001" or .002" of runout at the hub will translate into .006" or more of runout at the OD of the rotor. This indicates a slight rotor friction surface "wobble". As the rotor wobbles, it will touch the pads slightly at one point on the inboard surface and at another point on the outboard surface. The pads will eventually wear the rotor slightly at these two points causing a thickness variation in the rotor. Instead of floating the caliper back and forth, a thickness variation will force the piston back into the caliper and then let it back out slightly, multiple times throughout one revolution of the rotor. As the piston moves into and out of its bore in the caliper, it moves the fluid into and out of the master cylinder, which is mechanically connected to the brake pedal. This is why a vibration is felt in the pedal. There is also another reason for the cause of brake vibrations...but for this one, I will have to give credit to the rocket scientist STEVE RUIZ of STOPTECH, our sister company for his exemplery explanation..check out this page

http://www.stoptech.com/whitepapers/warped_rotors_myth.htm

I'm tired...but I'm not finished yet....please post all questions and I will answer them to the best of my ability with the best resources I have. Moderators....please make this a sticky.
<br>

rubbin' is racin'

Re: BRAKE FAQ
Friday, June 11, 2004 11:18 PM
STICKY!!!!

thanks pat for your hard work and letting us non-know-it-alls be more informed

<br>


Re: BRAKE FAQ
Sunday, June 13, 2004 8:48 PM
damn good info pat, like i said in another post i wish i knew this stuff earlier before i bought my rotors. some one needs to make this sticky <br>

Visit High Rev Motorsports for all your High Performance needs.
Re: BRAKE FAQ
Sunday, June 13, 2004 11:10 PM
Sticky Sticky Sticky!!!!!!!!! Thank you man, beautiful, keep it up! Later,
Clay
Re: BRAKE FAQ
Sunday, June 13, 2004 11:13 PM

Make this a sticky....I will add to it....any questions...please post...I will answer all of them <br>

rubbin' is racin'
Re: BRAKE FAQ
Monday, June 14, 2004 6:10 AM
I've got a buddy that turns all my rotors and drums for me. He has a bench brake lathe and an on-car brake lathe. He says the on-car lathe, even though more of a pain to setup, is way better to use. Is this because rotating the rotor while it's still on the car it follows the path it will while driving, so it will eliminate the variations in thickness and wear due to runout in the hub?
Re: BRAKE FAQ
Monday, June 14, 2004 8:11 AM
Turns out i do not have warped rotors after all. It just needed cleaning with brake cleaner. I felt alot of vibration when braking, it was more like sliding then a vibration so I took the tire off and used the brake cleaner and BOOM i am back to normal...THOUGHT this might help...

Great info dude. STICKY <br>

---------------------------------------------------------
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View the website and read the Novel.
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Re: BRAKE FAQ
Monday, June 14, 2004 8:21 AM
jonnyonwheels wrote:

I've got a buddy that turns all my rotors and drums for me. He has a bench brake lathe and an on-car brake lathe. He says the on-car lathe, even though more of a pain to setup, is way better to use. Is this because rotating the rotor while it's still on the car it follows the path it will while driving, so it will eliminate the variations in thickness and wear due to runout in the hub?


Using an ON-CAR lathe will give you a better result because it is referencing the centerpoint off of the actual hub on the car, rather than the hat on the rotor. This will compensate for any runout in the hub and eliminate the posibility of the hub being machined with runout due to improper mounting on a regular brake lathe. I go out to shops all the time when they have problems with our parts and redo the brake jobs for them (the right way) and I have found more than several brake lathes to have bent arbors or mounting hardware. So yes, if an on-car lathe is available, use that <br>

rubbin' is racin'
Re: BRAKE FAQ
Monday, June 14, 2004 11:19 PM
I can't do a rear disc setup on my ride because of class rules in solo2. Do you guys have or can you get better compounds for the rear shoes? I'm at my budget right now but in the future I wanted to know if I have the option.
Re: BRAKE FAQ
Tuesday, June 15, 2004 8:36 AM
I might me able to get you bigger wheel cylinders for the rear, but as far as shoe compound goes...there is only a couple compounds still in use in the aftermarket and the high performance shoe is a thing of the past <br>

rubbin' is racin'
Re: BRAKE FAQ
Tuesday, June 15, 2004 6:01 PM
Very interesting, friend. Excelent info.

Regards, <br>

___________________________
MAKING MY DREAMS A REALITY
Visit my cardomain site !!!

ELIOT. Now.....boosted.


Re: BRAKE FAQ
Wednesday, June 16, 2004 11:05 AM
what brakes to use with a slotted rotor?

we should cover that also.

<br>

207 hp cavy
18,000 so far

200 hp rsx type S
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I love my car
Re: BRAKE FAQ
Wednesday, June 16, 2004 7:29 PM
Keith wrote:

what brakes to use with a slotted rotor?

we should cover that also.


You will probably hear different things from everyone to whom this question is asked, and I too have heard many different responses. I will tell you what I have found in my experience.
Brake pad selection while using slotted rotors should be the same as if using standard rotors. There are no pads out there that "won't work" with slotted rotors. If you want race pads because they stop better and can handle a lot more heat, then get race pads, If you want crap pads because you just bought the slotted rotors so you look cool, then by crap pads. The scale of pad performance when using slotted rotors is very similar to the scale of performance when using standard rotors, the only difference is that the whole setup will be able to handle more heat up to the point where the friction material simply fails or the fluid boils in the caliper. <br>

rubbin' is racin'
Re: BRAKE FAQ
Sunday, June 20, 2004 5:50 PM
Awesome thread man. You just answered just about every question I had on brakes. <br>



When finess fails, use brute force.
Re: BRAKE FAQ
Wednesday, July 21, 2004 8:42 AM
Hey Pat, can you write something about brake pads? Different materials, how to bed them, etc?

Thanks!
Re: BRAKE FAQ
Thursday, July 22, 2004 10:51 AM
coming up tonight <br>

rubbin' is racin'
Re: BRAKE FAQ
Wednesday, July 28, 2004 11:16 AM
wow man thanks a lot for writing all this in your spare time.

I really appreciate you sharing all this knowledge.

I also was under the impression that rotors can warp
Thanks for setting me straight!

I will definitely have to get a Haynes manual and see what this
"hub" and "centerline" stuff is your talking about though.

I definitely want to learn how to do my own brakes so thanks again!

<br>


Re: BRAKE FAQ
Sunday, August 15, 2004 2:05 PM
Is there a good and or bad pad to use with crossdrilled rotors?

I have the brembo sport crossdrilled rotors and perfornamce friction carbon matalic pads with stainless hoses and the difference from the stock stuff that was on the car when i bought it is night and day, it stops so much quicker, straighter and alot less drama now, and i havent had any problems with the rotors cracking.

Basically im asking is there a better pad than the PFCM pads i have now, that will stop better and at least last as long. I have used these pads on my last 4 vehicles and my wifes 97 C1500 truck and they are my only choice when its time to replace the pads, but if there is a better product im interested.

<br>

Mike

1992 GMC Sonoma GT #492. Oh, Its just a stock V6!

1999 Cavalier Coupe, daily driver, 2200/M5. Mods and pics are in my registry.

Best 1/4 mile with all mods listed and a 50 shot N2O 15.54@85 w/a 2.20 60'
Best 1/8 mile with all mods listed and a 50 shot N2O 9.88@70
Re: BRAKE FAQ
Wednesday, August 18, 2004 12:07 PM
Axxis Ultimates, I've got them for $55 per set <br>

rubbin' is racin'
Re: BRAKE FAQ
Wednesday, September 08, 2004 9:51 PM
ok, here is one.

is it possible to warp a caliper? i let a person help me change my brakes and instead of using a c-clamp to force the piston in he used some home made tool that incorporated a flat metal plate with a nut welded into it and a long bolt through the nut. the plate rest on the thinner side of the caliper opposite of the piston and the bolt was turned to force the piston in. now i have only about 30% of the pad touching the rotor on the front face, but the rear side is fine. the other caliper seems to be fine even after sing this makeshift tool. so in short is the caliper warped if only about 30% of the pad is touching the rotor on one side?
<br>




Re: BRAKE FAQ
Thursday, September 09, 2004 7:16 PM
Home-made tool? What you're describing is a standard brake pad spreader. If he made it himself, props to him for the effort. I bought mine for under $20.

<img src="http://images.canadiantire.ca/media/images/Automotive/TestTune/BrakeTools/0256287_450_sc_189e0.jpg">

It shouldn't have done any damage to your caliper.

Forgetting about the tool, calipers CAN warp under certain circumstances, though I've never heard of people having issues on the j-body.

How did you determine that 30% of the pad is touching? Which 30% is making contact? Describe it in a bit more detail. Are you getting wedge shaped wear on the pads?
<br>




Re: BRAKE FAQ
Sunday, September 12, 2004 8:44 PM
well 70% of my rotor has rust on it and the other 30% has contact. could the pad i have now just have a defect, i mean they are new.
<br>




Re: BRAKE FAQ
Sunday, September 12, 2004 9:32 PM
Phlatcav wrote:

well 70% of my rotor has rust on it and the other 30% has contact. could the pad i have now just have a defect, i mean they are new.


If you take the wheel off & look at the pad, do you notice any uneven wear? I just replaced pads on mine last week and noticed some.

Re: BRAKE FAQ
Sunday, September 12, 2004 10:04 PM
most of the rotor isnt in the FIREPATH, aka the contact path of the pad to the rotor....

most untreated rotors will rust....around the hat and the other parts and the edges..

so basically thats why most rotors rust, but not in the firepath... <br>


Re: BRAKE FAQ
Tuesday, September 14, 2004 12:43 AM
Most likely what is happening, if in fact your pad is not making complete contact with the rotor, is that your caliper is not sliding or is sliding to much. There are two types of slide pins present on J-body calipers. There is a tube with a bolt going through the middle and also just a bolt with a larger OD that acts as a slide pin. If the caliper sliders are not moving freely, or the rubber bushings that isolate the slide pins from the caliper casting are worn out allowing too much movement, you will experience uneven pad wear. Like Muffins said, make sure that the rust you are seeing is on the surface of the rotor that is swept by the pad, if it is outside the swept area, you can easily fix it with a can of high temp paint. If you are seeing rust in an area of the rotor that is in the path swept by the pad, like JuiceZ said, pull the pads out and check the wear on the pads. If by looking at the pads you see uneven wear, pull both pads out of the caliper and bolt the caliper back on the car. Now grab the caliper and try to move it. It should slide freely and smoothly back and forth on the axis that the attachment bolts are on. If it does not, my recommendation would be to purchase a set of reman calipers. What happens is the caliper casting corrodes (especially in the salt belt states). When corrosion occurs in the Inside of the hole where the rubber bushings are installed, it will expand against the bushing, pinching it down on the slider thus hindering its ability to slide. Othertimes, the rubber bushings will simply degrade to the point where they are sloppy and the caliper flops all over the place. If the caliper is loose (meaning you can grab the caliper and flex the mounting bushings more than about 10 degrees in any direction) it will load the pads at the trailing edges when the brakes are applied, or it will torque out towards the wheel causing the inside edge of the outer pad to lift off the rotor. Check these things out and post your findings. <br>

rubbin' is racin'
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