Why are my rotors warping? - Subaru WRX Forum
Reply
 
LinkBack Thread Tools Display Modes
post #1 of 34 Old 03-19-2008, 09:39 PM Thread Starter
WRXtuners Member
 
Nose Nuggets's Avatar
 
Join Date: Jun 2005
Location: California
Posts: 2,157
Nose Nuggets is known to be trustworthy and helpful Nose Nuggets is known to be trustworthy and helpful
Why are my rotors warping?

Sirtex PM'd me about warping rotors and i thought the discussion would be better suited in a thread for everyone to see. Mike agreed to my request for a full thread, the following is his original question with some non relevant portions removed (greetings and what have you);

Originally Posted by Sirtex
My name's Mike and I have some questions on brakes. You keep telling us that the stock brakes are fine for the regular driver. I keep warping my rotors. I have replaced the rotors several times in the 30K miles I've put on the car. 4 times to be exact. I've been to the dealer and they say there is nothing wrong with braking system itself. I don't ride my brakes, I don't use them to control my speed (that's why I bought a manual tranny) , I rarely hit them at highway speeds. I do drive spiritedly on the roads, but not abusively. I have limited knowledge so I don't really know what to tell you. I'm sure you will be able ask the questions that will help me solve my dilemma.

Thanks,

Mike
Nose Nuggets is offline  
Sponsored Links
Advertisement
 
post #2 of 34 Old 03-19-2008, 09:39 PM Thread Starter
WRXtuners Member
 
Nose Nuggets's Avatar
 
Join Date: Jun 2005
Location: California
Posts: 2,157
Nose Nuggets is known to be trustworthy and helpful Nose Nuggets is known to be trustworthy and helpful
Mike,

There are not many things that will quickly warp rotors. In your particular scenario, it sounds like you are warping then extremely quickly. 4 sets of rotors in 30K miles borders on ridiculous. Hell, every single aspect of my breaking system (including the pads) is what came with my car 34K miles ago. I do have a few follow up questions for you;

1) Did you get all 4 rotors replaced each of the 4 times? If not, please specify which rotors where replaced each time.

2) What mods do you have? Suspension power and esthetic mods, please.

3) Are the replacement rotors you received OEM replacements or 3rd party?

4) What pads do you use. If you have moved between manufacturers please list all of them.


Ill be honest with you right off the bat, there are few things that consistently and quickly warp rotors. The fastest way to warp rotors is to get them super duper hot then drive through standing water. Doing this once is probable, twice is plausible but three or even four times in 30K miles is inconceivable. Unless your driveway consists of a 5 mile downhill grade with a river at the bottom. The most common way people warp there rotors is prolonged light braking. This is incredibly easy to do subconsciously, especially if you drive on the freeway a lot. Many drivers will transition directly from the throttle to the brake to reduce or maintain speed instead of only lifting off the throttle and letting the drag of the drive line and wind/road resistance slow them down. Most people who are on a decline for prolonged periods of time will use the break to maintain speed, which is usually prolonged but light break application.

However, you state quite specifically that you don’t do these common things. You don’t use the break to maintain speed and you rarely apply the brakes on the freeway. That leaves only your spirited driving. What kind of roads do you drive? Is it mainly turns? If so are they slow sharp turns like you would find in the hills or is it longer sweeping turns? Is there much elevation change where you do your spirited driving?

If I had to make a guess based only on the information you have provided, and assuming that you are completely truthful about your daily ‘average’ driving habits (im not suggesting you’re a liar, but as I said before its commonly a subconscious habit) then I would say your breaking way too early for turns when driving in a spirited fashion and/or break early in general. To make a racing comparison, the proper application of the brakes requires you to start with the highest amount of force and then reduce that as you approach the turn, then transition smoothly from the brake to the throttle. Most drivers do the opposite, they gradually increase break pressure as the car slows down and then hold firm break pressure until its time to start moving again. Now, during your daily driving this might not be optimal nor advisable being that most of the people following you will get rather upset at the random WRX driver performing full fledged break test style stops as he approaches traffic lights. So when you’re on the road, just keep that theory and idea in mind. However, when your doing your spirited driving it could be beneficial to put it into practice. Before you get out on the road you should get familiar with what you car does and how it feels under full braking. Go someplace open, safe and dry, do 45mph and stand on the brake. The abs will kick in and you will chirp chirp chirp to a stop. Do this a couple times until you can maintain the maximum level of breaking before the abs starts to modulate for you. be aware that the point the abs starts to take control will differ widely based on the driving surface and the traction it provides. Then go back and do it at 55, then 65. Then just drive around for a while cool off those shoes. Try doing your spirited driving on the same road if possible and point out some braking markers for yourself. Remember where you start braking in relation to those markers, maybe it’s a half car length before/after maybe its two car lengths. Then, over time, VERY VERY VERY GRADUALLY reduce those distances. This will get you familiar with the cars ability to slow down and allow you to more effectively use your available stopping power. if i had to guess, you just dont know the full stopping capabilities of the car and are over compensating.

Note: I use the terms “many drivers” and “most people” a lot. Im not stating you do this specifically, just playing the numbers.
Nose Nuggets is offline  
post #3 of 34 Old 03-21-2008, 01:32 PM
WRXtuners Member
 
MilesFox's Avatar
 
Join Date: Jan 2008
Location: Wisconsin
Posts: 106
Images: 1
MilesFox is an unknown
the #1 cause for warped rotors is overtorqued lug nuts. what did this guy have for wheels? was he doing the work himself or having the work done? i guess he would have used an impact on the lugnuts
MilesFox is offline  
post #4 of 34 Old 03-21-2008, 01:43 PM Thread Starter
WRXtuners Member
 
Nose Nuggets's Avatar
 
Join Date: Jun 2005
Location: California
Posts: 2,157
Nose Nuggets is known to be trustworthy and helpful Nose Nuggets is known to be trustworthy and helpful
how long does it take for over torqued lug nuts to warp the rotors?
Nose Nuggets is offline  
post #5 of 34 Old 03-21-2008, 08:37 PM
WRXtuners Member
 
IH8PVMNT's Avatar
 
Join Date: Oct 2007
Location: New York
Posts: 341
Images: 5
IH8PVMNT is an unknown
over torqed lugnuts will almost instantly warp the rotors !! saying this from experince... if the rotors were cut to thin thy warp faster and riding and or beating on them will warp them.. long braking... i warped my front rotors at 8k but i was doing really heavy stopping.
put some stoptech cross slot rotors on and ive been fine with the same abuse sine for about 30k-ish
IH8PVMNT is offline  
post #6 of 34 Old 03-21-2008, 09:08 PM
WRXtuners Member
 
oldfartracer's Avatar
 
Join Date: Jun 2006
Location: Maryland
Posts: 344
oldfartracer is more helpful than not
I have used stock rotors for track days with Hawks pads and didn't warp them. He is either using cheap rotors or pads that are in heat range that is to high. I would say he needs to go a batter rotor, I like DBA 4000.
oldfartracer is offline  
post #7 of 34 Old 03-22-2008, 07:56 PM
WRXtuners Member
 
Join Date: Jul 2007
Location: Connecticut
Posts: 17
Sirtex is an unknown
Lots of input from ya'll and I greatly appreciate it.
Sirtex is offline  
post #8 of 34 Old 03-22-2008, 08:20 PM
WRXtuners Member
 
Join Date: Jul 2007
Location: Connecticut
Posts: 17
Sirtex is an unknown
So first things first, I only replaced the fronts. I looked at the rear pads, they looked fine. There was no noise or vibration from the rear. I checked them each time.

#2. No mods. That I know of anyway. Nothing under the hood looks aftermarket. Only thing different from stock as I know it are the tires. They are Nokians. I don't really like them. Because of this recurring brake problem and difficulty find real employment (no more though) I haven't done anything. I started a thread a while back asking if I should go suspension or power first.

#3. If you mean Napa etc.. as a third party then yes. One set from Advanced Auto, One from Napa, and one from Autozone. Also one set from Subaru. That would be brakes and pads. I read up on how to bed them, and bedded each set.

Unfortunately, I have neither a 5 mile driveway or a river to drive thru. However I do live in CT. and we do get snow. However I am not sure how I would get my brakes super duper hot, I honestly do not drive that abusively. I do drive alot though. 30k since I bought my car last February.

I am very aware of my braking habits, mostly because of this problem. I don't do any long light braking, that's what downshifting, lift throttle etc... is for. There aren't really too many times in my daily drive that situation might come up. To me though that might be the most likely possibility.

As far as what type of wheels I have the stock wheels. I use a hand powered torque wrench to put my wheels back on. 95 pounds. Is that too high?

What do you mean by pads that are in a heat range that is high?

Nuggets, what you are suggesting is that I might try braking later? I'm not sure if I'm doing what you are talking about with the pressure on the brakes, but I do notice that I lift my foot off the brake pedal as I come to a stop. I thought I read somewhere, maybe here, that I shouldn't keep my brake depressed for more than ten seconds. True or not, that is how I drive. Less than 10 seconds on the brake. Otherwise hit the clutch, blip the throttle, downshift.

Thanks all, keep the ideas coming.
Sirtex is offline  
post #9 of 34 Old 03-22-2008, 08:46 PM
WRXtuners Member
 
MilesFox's Avatar
 
Join Date: Jan 2008
Location: Wisconsin
Posts: 106
Images: 1
MilesFox is an unknown
95 is not terribly high. i would think more like 75-80 but that would be for steel wheels, alloys need a little more so 95 sounds appropriate. torque wrench is the best way.

how do they vibrate" do you have vibration all the time or only in the brake pedal?
MilesFox is offline  
post #10 of 34 Old 03-22-2008, 09:41 PM
WRXtuners Member
 
oldfartracer's Avatar
 
Join Date: Jun 2006
Location: Maryland
Posts: 344
oldfartracer is more helpful than not
95 is too high, the WRX call for 80 stock. I think you have other problems, I have use stock rotor on the track for a weekend and didn't warp them. The stock rotors are very good quailty.
Are you checking the rotor for run out when you install them? Maybe you have a hub problem, or wheel bearings.
oldfartracer is offline  
post #11 of 34 Old 03-24-2008, 07:59 AM
WRXtuners Member
 
Longshot's Avatar
 
Join Date: Aug 2007
Location: Connecticut
Posts: 1,119
Images: 5
Longshot is a helpful contributing member
Send a message via AIM to Longshot
Quote:
Originally Posted by oldfartracer View Post
95 is too high, the WRX call for 80 stock. I think you have other problems, I have use stock rotor on the track for a weekend and didn't warp them.
+1 You overtorqued them. 80 ft lbs is what you should be tightening them to.

Mike
DTRacing Tuned
Longshot is offline  
post #12 of 34 Old 03-25-2008, 12:19 PM Thread Starter
WRXtuners Member
 
Nose Nuggets's Avatar
 
Join Date: Jun 2005
Location: California
Posts: 2,157
Nose Nuggets is known to be trustworthy and helpful Nose Nuggets is known to be trustworthy and helpful
95 isnt THAT high. you could go lower and be safe still but i would be surprised if 95 is warping them.

10 seconds per brake application is a good goal imho.
Nose Nuggets is offline  
post #13 of 34 Old 03-26-2008, 05:19 PM
WRXtuners Member
 
Join Date: Jul 2007
Location: Connecticut
Posts: 17
Sirtex is an unknown
I don't know what runout is. Please explain. As far as when they vibrate, that happens when I apply the brakes, no other time. I took it to the dealer I bought the car from the last time I changed the brakes. I told them my deal, they took the brakes off and checked them out. They told me that everything looked fine. They also checked them out for free. Plus I would assume that since the Suby techs did the work that it would be done right. Evidently that isn't a safe assumption then they have started warping again, only at highway speeds.

I have been trying to be more aware (if that's even possible) of how I brake, waiting longer to hit the brakes, trying do what Nuggets suggested bout how racers drive. Now a question bout that practice of braking hardest first and then reducing the amount of brake force I apply. That seems to throw whatever is not tied down to the floorboards. Not to mention anyone in the car gets a closer look at whatever is in front of them. Umm, that seems counter-intuitive. Maybe more detail or explanation?

Again guys and gals, thanks for taking the time to help me enjoy my baby to it's fullest.
Sirtex is offline  
post #14 of 34 Old 03-26-2008, 05:31 PM Thread Starter
WRXtuners Member
 
Nose Nuggets's Avatar
 
Join Date: Jun 2005
Location: California
Posts: 2,157
Nose Nuggets is known to be trustworthy and helpful Nose Nuggets is known to be trustworthy and helpful
if the rotors are warped you should feel the the inconsistancy at low speed. at high speed it will feel like a vibration. at low speed it will feel like a wobble. as you come to a stop it will feel like there is something under the tire.
Nose Nuggets is offline  
post #15 of 34 Old 03-27-2008, 02:27 AM
WRXtuners Member
 
MilesFox's Avatar
 
Join Date: Jan 2008
Location: Wisconsin
Posts: 106
Images: 1
MilesFox is an unknown
with warped rotors you will feel it in the pedal, a slight undulating feel similar to that of ABS function but more rythmic and not as chunky.

if your subaru techs looked at them for free they probably took off the tires and looked for grooves and what not, but didnt break out the runout gauge.

what is runout? imagine looking at a bent bicycle wheel head on as it spins. make sense? the rounout of the rotor is pressing on the brake pads/piston back at your foot as it rotates, thus the vibration in the pedal.

after re-reading these posts i will agree that 95 lbs is too much. my u-haul 8 bolt wheels torque down to 110 lbs torque, and that is an 8200 lb truck with a 11,000 lb gross
MilesFox is offline  
Sponsored Links
Advertisement
 
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome