I understand the causes of them, but was wondering if my rotors are really warped or may have some other problem. On the street my brakes are fine, but after coming down a long mountain road when the brakes really heat up, I get the classic pulsing/shuddering under the brake pedal only upon application of the brakes. I assume my rotors are warped, but my question is, why do they not pulsate after the brakes cool down? if they are warped, shouldn't the deformed rotors be present all the time and not just when they heat up?

could someone explain what happens to the rotor when it heats up enough to "shimmy" versus why it is perfectly fine at cooler temps. doesn't quite make sense to me. in my mind, if they get hot enough to warp, why do they not stay warped at all temps? I figured you guys have had your share with overheated brakes and could best address the topic.

BTW, car is a stock 98 type R.

Thanks!


[Modified by kkim, 2:22 AM 1/19/2002]

 

i can't give you a really good explaination of why, but i've had the same issue:

i was running on my OEM rotors at roebling and going into turn 1 where you have to brake HARD (120 down to 65 for me) and after a few laps i got the classic 'bump -bump-bump' while braking. my instructor guessed i had warped them a bit at a previous track event where i did hard braking. i've since bought a set of brembos for the track and use the OEM rotors on the street where they give no feel of being warped at all. using the new rotors for hard braking and the originals on the street i don't get any pulsing/shuddering at all.

 

Interestingly, I have noticed that i get that warped rotor feeling when driving my wife's CRV but only sometimes. It doesn't seem to be when the brakes are getting used heavily - which is like never with this vehicle - so I am having trouble coming to any conclusions.

<SWAG mode>It is possible that when your rotors heat up, they change shape inconsistently, going vaguely potato chip shaped when expansion takes place. </SWAG mode>

Kirk

 

thanks. good to hear that this is a brake rotor issue and not anything more serious. I have the same symptoms, but in my case, my daily commute takes me from 13 miles of straight, flat, sea level road road to a 13 mile winding mountain road from sea level to 3800 ft. Coming back down the mountain is when I get the brake pulsing after I heat them up from over usage. if I am careful, I can get them to not pulse, but if I use them hard, they will start to pulse and continue to do so until they cool back down.

I don't think it's practical for me to be switching out rotors, in this case, but I appreciate the input so at least I know that this is something that doesn't happen to only me. sounds like it's time to start looking into some brembo blanks!

 

As an atlernative you can try to get your rotor temps down by using a brake ducting system. I rigged one to my car that I do track events with (non honda) and it helped tremedously on boiling brake fluid, glazing pads, etc.
Barry H.

 

I imagine the reaason you feel them warped more when heated is when anything is heated it expands and and thus making the warp feel worse. then when cooled it settles back down. mine are warped and I notice it when either braking slowly for a while or breaking hard. Althugh I just spent $350 on them only 2 months ago and they re cut them, I'm gonna deal with them now until i get some nice brembo rotors. A good setup for like $265 shipped. I imagine i can do the install myself, just the brake line????

 

One major contributing factor to rotors warping is pads. I have yet to warp a rotor using either Porterfield R4-S, R4, or Hawk Blue.

Pyro .. gotta get your entry speed up a bit!

 

okay, so my rotors are warped. but... if they only pulsate after they get hot, I assume they are okay(even) until they overheat. so, if I were to take these rotors to get turned(which I won't be) how can they even out the warped rotor when they turn them while cold? are there such things as rotor which get warped and are mis shapened when both hot AND cold? anyone ever seen this case?

 

Mine do the same thing, the rotors were tracked on stock pads one day, second time on R4S. They're bone straight most of the time, but when they get really hot they can vibrate. We'll see what happens on the Panther+ at VIR

 

One thing to check (which you probably already did) was make sure the lugs are all torqued evenly. I've found the warp or wobble tends to be less if you get the wheels torqued evenly.

 

I remebered one of CarbotechAndie post mentioning "hot warping" of rotors. Something about the warp that does not manifest itself until the rotors are hot.

Trent

 

I was going to suggest this, as well!
Finger tight til they seat, then maybe like two steps to 85 lb/ft.

 

You're talking about steering wheel shimmy, right? A warped rotor could conceivably cause the brake pedal to pulsate too (and, no, I don't mean ABS)?

 

thanks for the suggestion, but I always hand torque the lugs to 80ft/lbs., in a 2 step cross pattern.

 

Well now, that's interesting. I see you've edited your post to indicate shuddering of the brake pedal. I thought you had meant steering wheel vibration, which is the more common symptom of warped rotors (in my experience anyways). Since it's with your pedal, and only when hot, I'd like to propose that it may have something to do with the brake fluid getting superheated. When's the last time you purged your brake system and what fluid do you use?

 

I've not changed the brake fluid, yet. stock fluid. just got the car a few months ago and this has been on the to do list. good suggestion,though, as I've been looking at the hand pump type of power bleeder to change the fluid. but, what would old fluid have to do with warped rotors... or are you saying the pulsation is due to the super heated fluid? and if so, how does it make the pedal pulsate?

 

Probably nothing. If anything I'd think hot fluid and the easy-to-compress air trapped within it would reduce the feeling of any kickback from the calipers. I just threw it in there as another possible contributing factor. I myself have never felt anything through the pedal from warped rotors, just the steering wheel. Are you feeling anything through the wheel? If your rotors are warped, you certainly should. If your wheel feels rock solid all the time, I'd think it's improbable your rotors are warped.
No need to invest in a power bleeder, just use a buddy. I've installed Speedbleeders from http://www.speedbleeder.com, but have yet to form an opinion on them (with my first-and-only bleeding with them so far, I went through 2 liters of ATE Super Blue and there were still bubbles in the lines...).

 

pulsates through both the pedal and wheel when hot. I almost bought the speed bleeders but got some feedback that they leak after time and they also may allow air to be sucked in from the bleed screw thread area after they are used a few times. yeah, I know how to manually bleed brakes, but it's such a PITA to do so. I want something easy and foolproof so I can do all of my cars with the same tool. (just lazy, I guess) That's how I came to the pressure bleeder conclusion.

I do agree that it's time to flush and change my old fluid. was just looking for feedback on the hot rotor pulsing issue and if it's a common thing among those who push their brakes to the limits. thanks for the input. I'll be using ATE blue to flush the system soon.