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YOUR RESEARCHVibration when braking
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Replace brake rotors as cross drilled rotors can't be turned
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Suggestion
Vibration only under braking is normally a warped brake rotor issue which mean to replace the brake rotors as cross drilled rotors can't be turned.
Leading evidence: 'Replace brake rotors as cross drilled rotors can't be turned' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Replace brake rotors as cross drilled rotors can't be turned' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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In the last day I have noticed a vibration sort of thumping that only happens when I apply the brakes. I have not had the car long enough to have changed the brakes so I don't know if this is a normal sign of them needing replacement or possibly a bigger issue. Seems to be coming from the rear. Any advice is welcomed.
Thump is really not good. Vibration only under braking is normally a warped brake rotor issue which mean to replace the brake rotors as cross drilled rotors can't be turned. A thump could be something more severe.
Thanks 10!!...I'm thinking the thump is probably my interpretation of the "sound" associated with the feeling. Would it be "normal" for a rotor to warp? I'm used to rotors more of less wearing pretty evenly.
What year, how many miles, always helps with diagnosis. Could also be tire related. Bulge, flat spot, delamination, cracked wheel or brake rotor, etc...
Hard to diagnose based on your description, but it could also be some deposits baked into the rotor or glazing. I had this happen awhile back on my front rotors. If this is the case, the fix is easy: just pull the wheels off, remove the pads from the calipers and give the rotors and pads a light sanding with 200-400 grit sandpaper. Put everything back together and then give the pads a quick heat cycle to re-bed them.
Thanks Capt. I'm going to pull the wheels (unfortunately not this weekend) and take a look. I figured it would be hard to diagnose over the net, but like I said, I don't know if there is any difference in how the 996 reacts to worn pads vs any other car.
Thanks fpb... I was thinking that if it was tire related as you mentioned, wouldn't I likely notice it something when driving and not just when braking? I don't feel any vibration at any speed, it only shows up when braking and it doesn't seem to matter whether I'm braking at 80 mph or 10 mph.
Thanks again for the responses.
You won't be able really "see" anything wrong with the rotors or pads. It only takes about 5 minutes to load/unload the calipers, so I'd just sand them down while the wheels are off. Don't forget to do the back side of the rotors as well. You don't need to remove the rotors, either.
Does the frequency change with speed? If so clean up the rotor as Capt suggests. If not?? Need more info to help. Put a dial indicator on the rotor and see what the run-out is. where in NJ?
Are warped rotors a "common" thing? It just seems strange to me that it happened literally from one day to the next.
fpb....I'm in Lopatcong outside of Phillipsburg...I-78 west right on the PA border. There doesn't seem to be any difference regarding speed. Again, there is no sound or anything when driving only when applying the brakes.
Did you put the car away wet? My money is on caliper rust from having wet pads stuck to them overnight.
If this is the case, the problem will resolve with a bit of driving.
Do you have drilled rotors? Spend the 30 seconds to eyeball them, since cracks can connect up the holes and this can definitely result in a bad experience if left unresolved.
5CHN3LL...I do put the car away wet sometimes (not by choice lately) and typically when I start it the next time I can feel the rust (I assume) breaking away when I back up and grind off when I get to the end of the driveway. But as you say, it usually goes away by the time I'm at the corner. Will be washing her again tonight so I'll spend some time checking out the rotors and see if there is anything obvious.
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