When I press the brakes to slow down, my car jerks or stutters forward. Not sure if it’s the brakes or something else. It’s kind of like when you ride a bike and keep pressing and releasing the brakes and it jerks you. Any ideas?
Warped brake rotors.
Tester
That won’t show up on a diagnostic scanner will it?
No.
Tester
Ok, last question, how do I know if it’s the front or back rotors? Thanks for your help
What kind of vehicle?
Tester
2001 Porsche boxster s
Nine times out of ten the front rotors cause this problem.
But to find out for sure, a dial indicator is used to check the run-out of the rotors.
Tester
I’ll just buy new rotors and replace them, Thank you for all your help
Buy new brake pads, too.
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If you have a parking brake that you can apply and release with one hand - like the between the seats lever with a release button on its end - that works only the rear brakes. You can apply/release it while driving and see if the rear brakes are working smoothly or not.
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It is typical with modern cars that they have disc brakes all around, but that they have a tiny set of brake shoes (i.e. drum brakes) inside a hat-shaped mechanism attached to the rear rotor. If this Porsche has rear discs with a separate drum brake mechanism inside a “hat”, your suggestion will not produce any valuable results.
Does the OP know whether his Porsche uses the disc brake mechanism for the parking brake function, or if it uses a separate set of brake shoes for the parking/e-brake function?
Yeah, you’re right. I was thinking of the rear drum brakes on my Honda and even older cars.