brake pad deposition at high temps, not warping?

[the great him]

so this topic came up in another thread... and was wondering what you guys think of this, i have read both sides of this before and still am left with out conclusive evidence one way or the other... while yes i understand the pad deposition and transfer onto the rotor can cause variances in thickness and then the pulsing feeling you get under braking ect. but i also know that getting rotors hot as in when they start to change color will physically change their size and shape, especially with the pad clamping down at such high temps. persoanly i think its a combination of both but im curious as to what others on here think and or if anyone has any ideas or evidence that i or others have not seen or heard...

 

[Jungoes]

i was just about to post about this, recently i started to get a slight pulsing/ shimmy when i brake , doesn't happen at low speeds, i took down the front wheels yesterday and inspected for any shakes or looseness, and nothing budges. checked the rotors which seem fine and pads have alot of life left. Any ideas whats causing this slight vibration when braking welcomed

 

[the great him]

i was just about to post about this, recently i started to get a slight pulsing/ shimmy when i brake , doesn't happen at low speeds, i took down the front wheels yesterday and inspected for any shakes or looseness, and nothing budges. checked the rotors which seem fine and pads have alot of life left. Any ideas whats causing this slight vibration when braking welcomed

just do the tundra brake upgrade... search for it on here. its basically just swapping out your rotors and calipers for a front brake set up off of a 2000-2006 toyota tundra and it works wonders no more problems...

 

[Mr. Leary]

When the warping is not permenant, its commonly called "heat fade." While I have no evidence to present to prove that this is what is happening, I believe it beyond a doubt. The tolerances are very tight when a brake pad is clamped, so even variations in thickness measureable in microns will be noticeable. I would bet that the driver can feel even a 10 micron variation, which is pretty small. For example, that diameter of human hair ranges from 17 microns to 181 microns.

Variations in steel caused by heat are an extremely well documented subject. In fact we count on this effect to manufacture steel in the first place, as it allows carbon ingress. I'm sure there is a chemist who can give a better explanation, but my understanding is that the heat causes the structure to spread out, which will not cause a problem unless this happens unevenly. The thinner the metal, the more uneven the heat distribution will be... and that means more "heat fade."

Tundra rotors and calipers are much thicker, so something the weight of a 4Runner will be unlikely to cause them to build up enough heat to warp.

I would argue that heat buildup in the pads is not the root cause, since this problem does not go away with full ceramic pads.

 

[raidernation]

i was just about to post about this, recently i started to get a slight pulsing/ shimmy when i brake , doesn't happen at low speeds, i took down the front wheels yesterday and inspected for any shakes or looseness, and nothing budges. checked the rotors which seem fine and pads have alot of life left. Any ideas whats causing this slight vibration when braking welcomed

Your rotors are slightly warped/ warn unevenly. Its natural and this occurs often. Most of the time, it is not noticable to the naked eye. Take your rotors down to a brake shop and have them "turned." It should only cost about $15 per rotor. That should solve your problem.

 

[binhsterbinh]

so this topic came up in another thread... and was wondering what you guys think of this, i have read both sides of this before and still am left with out conclusive evidence one way or the other... while yes i understand the pad deposition and transfer onto the rotor can cause variances in thickness and then the pulsing feeling you get under braking ect. but i also know that getting rotors hot as in when they start to change color will physically change their size and shape, especially with the pad clamping down at such high temps. persoanly i think its a combination of both but im curious as to what others on here think and or if anyone has any ideas or evidence that i or others have not seen or heard...

I've learned a lot of through reading these articles/ramblings from Marcus at HeeltoeAuto:

HT-Spec Brake Pad Bed-in Procedure, recommended by Heeltoe on all HT-Spec braking systems. « HeelToeAuto.com's Pit Board
Tech Info: Is it ok to use new pads on used rotors, and vice-versa? « HeelToeAuto.com's Pit Board

While its entirely possible that 4Runner rotors are warping due to excessive heat, but I think shaking often times comes from not bedding them in with the new pads. Without bedding brakes in, they never experience the full potential of their high performance brake setups. I understand it's tough for people to go find a wide open, empty road to perform a bunch of 60-5mph stops until they have smoke fumes coming off the new pads/rotors. I'll admit, I've yet to do this process on my 4runner 231mm brake setup living in Seattle. I plan to do it soon though.

High quality rotors generally don't warp when you heat them up enough to turn them glowing red hot. I've done this to my RL 4-piston caliper/EBC yellowstuff pads/Racing Brake 350Z slotted rotors on my TL and had no issues with warping - of course I drove it for 10 minutes to cool them off before coming to a complete stop first though to avoid pad deposits. I got to this stage by trying to bed in the rear brakes, but ended up causing the front setup to fade first. If I were using a cheapo low grade rotor, I would have for sure probably ruined them as cheaper rotors aren't heat treated and are made of inferior metals.

 

[kball]

This guy says brakes almost never warp. Material build up makes sense. I've seen the image of a pad on the rotor before.

StopTech : Balanced Brake Upgrades

From what I know (which isn't anything more than what I've read) brake fade is when the brakes are used hard and over and over that the fluid boils at the caliper and then compresses so you get a mushy pedal and what feels like fade.

 

[THEREALTOR1]

Weren't there some threads on here from a member named "mom" about this?

 

[kball]

Yeah I think we need moms input on this.... lol

 

[THEREALTOR1]

Yeah I think we need moms input on this.... lol

Cool, i'm not losing my mind:

http://www.toyota-4runner.org/3rd-gen-t4rs/72097-solved-my-3rd-generation-4runner-severe-brake-pedal-pulsation-highway-speeds.html

 

[the great him]

Cool, i'm not losing my mind:

http://www.toyota-4runner.org/3rd-gen-t4rs/72097-solved-my-3rd-generation-4runner-severe-brake-pedal-pulsation-highway-speeds.html

that is some good info thanks for posting that!

 

[THEREALTOR1]

that is some good info thanks for posting that!

Yeah I don't know how I came across that, but I thought it was alot of information to think about. Also being I just got my brakes done thursday I should probably go back and read that and test out maybe tomorrow morning on some back road somewhere.

 

[the great him]

i bed my brakes in just as soon as i put them on... although i did my from about 60mph down about 10-15 let them cool for about 10min just driving around then redid everything again from 90mph. its how ive always done my bakes and most the i have worked on. even when i was working on ambulances -now that can get kinda scary when you get brake fade on a 20,000lb screaming brick at 50mph lol

 

[the great him]

Your rotors are slightly warped/ warn unevenly. Its natural and this occurs often. Most of the time, it is not noticable to the naked eye. Take your rotors down to a brake shop and have them "turned." It should only cost about $15 per rotor. That should solve your problem.

turning rotors imo has always been a bad idea, forst off you lose pad material there fore your ability to dissipate heat and actually increasing the chances of actually warping the rotor or damaging it other means is cracking, grooving, glazing ect. and secondly new rotors dont cost that much i dont really think its worth it to take it off and have them "turned" just to have them get the pusling feeling back again (probably even faster now that you have less actual material in the rotor now that its been "turned"/shaved) so may as well just buy new rotors can bed them in properly and be done with it

 

[TheDurk]

Weren't there some threads on here from a member named "mom" about this?

Aww...I was planning to post: "Hey Kid, ask Mom...."

(with a link, of course.)

 

[the great him]

Aww...I was planning to post: "Hey Kid, ask Mom...."

(with a link, of course.)

smart a$$ lol :bigok: i posted this thread not only for myself but also for anyone else who might be interested in this issue weather or not they have heard these theory's before or not. it seams every time i read something of this nature i learn something new... the more and more i read i tend to lean towards the theory that rotors rarely warp but more of the pad deposition. but i have seen a "warped" rotor, it was warped to the naked eye(cause by a seized caliper on a early 90s f250 7.3 will a full load that had just gone down a long steep grade with a stop sign about half way down the hill(about a mile long) we drove the truck for about another mile or so on level ground and yeah, it started pulling really hard to the right and as soon as we pulled over and that front right tire left the pavement i locked in the dirt... we had to put the truck in 4wd to keep the pad from welding to the rotor, it was a yellowish white color and ended up destroying the bushing on the shock(from the extream heat -melted) and the brake line was blistered ect. anyhow just for sh!ts and giggles we put the rotor on a lath and spun it and it was most defiantly out of round and not true plus cracked like you wouldnt believe