heatherly

I have had my Cobalt for one year (August) and it has apx 20k miles on it - its a stock car literally, no power anything, just your basic car. (its a 2009)

Lately when I put on my brakes my car (the brakes) pulsate/vibrate - lightly - and not every time I do it - I have read a lot about it possibly being worn/warped rotors but my BF has a GMC cargo van (a 2008) that he bought at the same time as me (it was new although it was a 2008) and he is noticing the same problem (altho he has about 45k miles) and when I mentioned rotors he was almost positive it was not that (since "his rotors are the size of my tires" apparently )

Just wondering if anyone could help me out - Mine is still under warranty but his is not

I am thinking of sending mine into service to see whats wrong but the problem is so intermittent that I know the dealership will say theres nothing wrong.

Also what about the recall that started in March? I havent heard anything from Chevy about this - has anyone else gotten a letter or had their car fixed?

And just wanted to say I do love my car - I really havent had a single problem with it since Ive bought it and it really is the coolest little thing Ive ever owned once i got the windows tinted

MyOtherSS

iTrader: (1)

I would bet it's more than likely your rotors. The Van is likely to need rotors too, the size is all relavant they're bigger because they are stopping more weight so they are likely to be warped just the same. All it takes is one panic stop to warp rotors at a good rate of speed.

ecot3c inside

iTrader: (11)

how hard are you pressing your brakes? Might just be the abs, or you need your rotors resurfaced.

insylem

Ill go with rotors. Mine are warped too, but im going to wait till my pads wear down and to them all at once.
Oh, besides a panic stop warping rotors, also overtorqueing your lugnuts can warp them too.
Some people smoke them on with "Gorilla Torque" or use an impact to install them.

The proper torque for them is 100 ft lbs. (1200 Inch lbs)
If you don't have a torque wrench, use a 24" Braker bar and apply 50 lbs of tightning force. (use a fish scale if you have one) or you can use "Calibrated Elbow" Torque (going by feel)

Malaclypse

iTrader: (1)

OP: Your rotors are warped. So are the rotors on your BF's van. I'd bet a paycheck on it.

08SSTCRD

First off rotors don't "warp". Anyone who says that knows nothing about automotive brake system repair. Which includes almost everyone these days.

Rotors develop two possible conditions. The first is runout, second is out of parallel.

Runout means that the rotor is not "true". In other words, looking at it from the side it would "wobble". The rotor is out of spec, but you will generally not feel this condition in the brake pedal or steering wheel unless it is extremely bad. Most manufacturers allow for no more than .001" (one thousanth) or rotor runout. Rotor runout typically leads to thickness variation, because the rotor is not running true as it passes through the caliper.

The second is out of parallel. This can best be described as thickness variation. If you took a brake micrometer and measured various thickness points in the rotor (like the face of a clock) you would get a different number at each point. Most manufacturers allow for no more than .0005" (thats half-a-thousanth) in thickness variation between any two points on the rotor. This is the issue that causes pedal and steering wheel pulsation. It is typically caused by uneven deposits of brake pad material on the rotor, or too much runout due to poor quality rotors or hub runout issues (rust buildup, ect). This can only be corrected by machining the rotors or replacing them.

The best practices to ensure you have minimal runout and no out of paralellism issues is to use high quality OEM spec rotors, ensure the hubs are 100% clean of any rust of buildup, properly torque lug nuts in sequence, always replace or refinish rotors when changing pads, and properly burnish (bed-in) each new set of pads and rotors installed on the vehicle.

Nacademus

iTrader: (2)

warp (wôrp)
v. warped, warpˇing, warps
v.tr.
1. To turn or twist (wood, for example) out of shape.
2. To turn from a correct or proper course; deflect.





...dick.



"warp" doesn't include variations in thickness and planar equidistance?

Watch what you say when you assume the intelligence of others is lower than your own, Mr. GM Goodwrench.
Pulsation in the pedal typically means one thing, a warped rotor (warped however you want to describe it-as in NOT true and proper).
My cousin is a UTI graduate too, and he thinks his **** doesn't stink either.

More than likely your rotor became hot during a stop and caused them to reach a temperature that is near enough to the material's melting point to cause it to become malleable and warp. When it hardened, the imperfections in the shape of the rotor remained. What you feel now is the pad and caliper piston riding the undulations of the rotor's surface forcing the brake fluid back in the through the line rhythmically with the rotation of the disc. This in turn pushes back through the pedal and to your foot where you feel it.
Replace them.

08SSTCRD

No, richard, theres just too many uneducated people in here such as yourself that have no concept of whats actually going on with their brake systems, yet they think they know it all.

Lateral runout (or "warping" as you maintain) does not typically cause pedal pulsation. Parallelism does.

insylem

Does it matter wich defect they have? Or what we call it?
Bottom line: Rotors are F$*#ed, Change them.

ronn

iTrader: (3)

I think your *lecture* is really like spitin' in the wind here....it's gonna go nowhere. Why?
The term *warped* is the vernacular and really adequately describes what's going on here for 99.99999% of people that live on this planet. It's UNIVERSALLY used by layman and professionals alike.
It's much easier to say *warped* when describing this condition than it is to talk about *RUN OUT* and *PARALLELISM*.... 99.9999% of the time, that is.

D_sean257

THis^

also this^lol