"Warped" rotors come back?

[Canon20D]

The other week I swapped my tires and in doing so sanded my pads in an effort to stop my wheel from shaking under medium load braking (it was getting pretty serious!)

I figured it was something that got on them (paint?) or a little bit o' pad that was stuck on there. I tried the 80->20 stops and that helped but never stopped it

So I sanded them and it was great. But in the last week I noticed it was coming back, today, particually so!

Is there something else that might be wrong and it was just a coincidence that the tire change / pad sanding helped? I only sanded the fronts cause i figured that was the only way the wheel would shake is if the front pads were effected..

Help?!

[SunburnNYC]

your rotors are warped /obv

 

get them turned at a brake shop or get new ones

[Canon20D]

So why would they be Perfect for the past 2 weeks and suddenly come back

I've been told you cant actully WARP rotors, only leave deposits which cause the pads to press back on the system as it passes over the deposit, which is why it wobbles.. but its not actully mis-shapen..

True?

[NSFW]

I posted about shuddering during braking a few weeks ago, it seems to me that it's deposits, not warping. As you noted, it comes and goes. It doesn't surprise me that sanding helped.

 

Last weekend I had the brakes heated up real good, had the shudder minimized (but not gone) hit a hump in the road while braking hard, felt ABS grab for an instant, and the shudder got much worse at the next corner.

 

I've kinda given up on it for now, but I'm hoping that new pads will help.

[SunburnNYC]

I posted about shuddering during braking a few weeks ago, it seems to me that it's deposits, not warping. As you noted, it comes and goes. It doesn't surprise me that sanding helped.

 

Last weekend I had the brakes heated up real good, had the shudder minimized (but not gone) hit a hump in the road while braking hard, felt ABS grab for an instant, and the shudder got much worse at the next corner.

 

I've kinda given up on it for now, but I'm hoping that new pads will help.

 

strange... never had such an issue...

[robinlsb]

So why would they be Perfect for the past 2 weeks and suddenly come back

I've been told you cant actully WARP rotors, only leave deposits which cause the pads to press back on the system as it passes over the deposit, which is why it wobbles.. but its not actully mis-shapen..

True?

 

Once pad transfer occurs, and there is even a tiny bit of pad material left on the rotors, pad transfer will re-occur. Check stoptech.com for a detailed explanation. It will also explain why warped rotors is a myth.

[Canon20D]

Yeah thats what I thought, but in the optics world a flat disc can warp under high stress (called the "potato chip effect" where one the top and bottom curl in the opposite direction than the sides. Think Pringles chips)

alright, ill have to try to work on em again

[unstablementaly]

warped rotors a myth? have you ever turned rotors before? trust me, it's not a myth. it's foolish to think it is.

[robinlsb]

warped rotors a myth? have you ever turned rotors before? trust me, it's not a myth. it's foolish to think it is.

Well, I will put it this way. 99% of the time the rotor is not warped. You can warp the rotors if they have been heated cherry red (it which case a crack is most likely) or somebody took a air wrench and drove the lug nuts/bolts on so tight of misaligned that the CARRIER hub is bent. Other than that, I stand by my original statement and those of trained engineers.:)And yeah, I have machined brakes... back in the sixties though!

[unstablementaly]

i'll take experience over a trained engineer that's never held a rotor in his hand or machined one before. thanks.

[fweasel]

The rotors are likely not warped, as rarely they ever are (see tech faqs on any reputable aftermarket brake manufacturer website: Stop Tech, Hawk, ect...). The pad deposits causing your shaking are on your rotors, not the pads. Sanding the rotors would have likely yielded better results, but is not the recommended method.

 

If a re-bedding process did not eliminate your deposits, its likely they're too far gone (too hard) and cannot be removed with the pad material you're currently using. At this stage, you'll need to have the front rotors turned (to remove the deposits, not because they're warped) or switch to a significantly more aggressive front pad. Because you're not switching out pads on a regular basis for track reasons, the first suggestion is obviously your better bet.

[SunburnNYC]

I have seen so many warped rotors... to say they are a myth is ridiculous. maybe with a BB kit -but not stockers, it is a common problem... and yes I have turned many rotors.

[f1anatic]

At almsot 43k miles, i am on the original rotors. No warping...changed the brake pads to softer compound at about 28k miles though.

[robinlsb]

i'll take experience over a trained engineer that's never held a rotor in his hand or machined one before. thanks.

 

And what do you do with some one who has done both???????:lol:

[mccorry]

I've seen both warped rotors and pad deposits.

 

My LGT had a pad deposit / tranfer issue when I first got the car.

I have also turned rotors (MYSELF on a brake lathe) and have seen them warped.

 

My wife's car has undersided rotors for its weight (MHO) and it is really tough on rotors.

[KartRacerBoy]

The rotors are likely not warped, as rarely they ever are (see tech faqs on any reputable aftermarket brake manufacturer website: Stop Tech, Hawk, ect...). The pad deposits causing your shaking are on your rotors, not the pads. Sanding the rotors would have likely yielded better results, but is not the recommended method.

 

If a re-bedding process did not eliminate your deposits, its likely they're too far gone (too hard) and cannot be removed with the pad material you're currently using. At this stage, you'll need to have the front rotors turned (to remove the deposits, not because they're warped) or switch to a significantly more aggressive front pad. Because you're not switching out pads on a regular basis for track reasons, the first suggestion is obviously your better bet.

 

I'd suggest that the problem is the OP's braking habits. Lightly braking for long periods rather than harder braking later? If the problem is reoccurring after two weeks after sanding, examine what you are doing with the brakes and change those habits.

[lgtsoon]

i was having the same problem. get the rotors turned and get rid of the stock pads. i put on hawk hps pads and i'm very happy with this set up.

[G.T.Subie]

I'd suggest that the problem is the OP's braking habits. Lightly braking for long periods rather than harder braking later? If the problem is reoccurring after two weeks after sanding, examine what you are doing with the brakes and change those habits.

That's funny my Dealer's Service Mgr told me the exact opposite.

 

They told me I was too hard on the brakes and the deposits were my fault.

 

I changed the pads , it hasn't come back in 30k miles.

[KartRacerBoy]

^ Yea, I'm not sure which is the problem (light or hard braking but I suspect the former), but given what the OP said, I do believe it's a driving habit issue. But if better pads solve the issue, so be it.

[mccorry]

My stock pads did it. I re-bedded them and the issue went away. The pad's made it another 65K miles with no issues or re-occurances.

[Vimy101]

Once pad transfer occurs, and there is even a tiny bit of pad material left on the rotors, pad transfer will re-occur. Check stoptech.com for a detailed explanation. It will also explain why warped rotors is a myth.

The early Infiniti Q45s suffered from actual rotor warp. The rotors were not nearly robust enough to handle the weight of the Q combined with the grabbing power of the calipers. A few medium hard stops and the rotor was warped and often required replacement.

 

I don't know if it helps, but after a hard stop when I know the brakes are quite hot, I won't sit there with stopped with my foot on the brake pedal. Instead, I'll roll the wheels even a quarter rotation just to make sure that the rotor cools evenly minimizng slower heat dissipation at the caliper contact area which could cook the pad leaving deposits and/or heat warp the rotor.

 

People forget the power of the brakes. They have a stopping power equivalent of 1000 hp which generates some ferocious heat in those relatively small steel disks.

[mccorry]

^^^^^^^^^^^^^

 

All valid points and good suggestions, IMHO. I do some of the same things.

[Vimy101]

^^^^^^^^^^^^^

 

All valid points and good suggestions, IMHO. I do some of the same things.

They always are.