Matt RX8

I have a new 2004 6 speed model. It's a 5/03 build so it has been sitting for a while.

I have a question regarding braking and I want to see if my car is the same as everyone else.

When I brake, I pick up a slight vibration. If I press the brake lightly I can feel the vibration and then it goes away as I press the brake harder. It's sort of like I can squeeze into the brakes nicely the harder I press. It actually doesn't feel that bad and the vibration sort of lets my know when I've got the pads to the rotors.

I was wondering if anyone else gets this vibration under light braking.

It's possible that my car has something that has built up on rotors since it has been sitting so long. I don't want to bed the pads because it says to not do hard braking during break-in. Is it possible that the rotors are warped? Although I read once that most rotor warping can be cured by bedding the brakepads into the rotors.

Visual inspection of the rotors doesn't show anything. I have put 100 miles on the car in the past few days so that has cleared the rotors of any residual rust.

Go48

First, check the tire pressure. Should be 32psi with tires cold. That will eliminate a possible simple problem. However, it does sounds like your rotors need to be turned. What you describe is typical of rotors that are a little "warped". That is, they are not within spec for runout and when you apply the brakes the tiny bit of wobble in the rotors translates to a vibration in the brake pedal. Take it back to the dealer and ask them to turn the rotors, and while you're at it, ask them to replace the front pads with the new pads that are mentioned in a Mazda Service Bulletin.

Check the tech section of this forum for a Sticky link to the Service Bulletins and print out the one on the brakes to take with you.

EDIT: Here's the link to the new brake pad TSB.
http://www.finishlineperformance.com...cs/04-006.html

Matt RX8

I'm not so sure they are warped. Usually with warping you'd feel the vibration even further down.

The service advisor said the vibration was caused because as you lightly brake, the front brake grabs first and then the back grabs. It's that small moment until the rear brakes grab that is causing the slight vibration and that's why it occurs only during light braking and stops as you apply more braking force.

If there was a factory defect on the rotors, than it will be covered for 12 months so I'll probably break the car in, then bed the brake pads and see how it feels.

Q-chan

iTrader: (1)

When a car sits without movement for a long time, rust is likely to build up on the rotors. This is not necessarily a problem, but may cause vibrations due to the initially uneven surface. You are adviced to avoid any excessive braking until the surface has been smoothened out. If the vibrations persist, ask for a rotor and pad replacement. Of course your rotors could be reworked, but this would mean a reduction in thickness, which means a reduction of their lifetime (you can rework rotors only down to a minimum thickness). I wouldn't accept the rework option on a brand new car.

Mr M

New car? Warped discs? Not likely.

Try bedding the brake pads in properly. This is how I do it:
Drive along at about 40mph in 3rd gear, then push the brakes hard, but not suddenly (i.e. gradually increase the pedal pressure). Brake as hard as you can without the ABS cutting in. When you are down to 10 mph take your foot off the brake and speed up again. Repeat 3 or 4 times after driving 1/2 a mile between each attempt.

Oh, and make sure nobody is behind you!!!!!!

As long as you don't brake so hard and so often to make smoke come from your brakes you won't do any harm to your new car.

Good luck!

Matt RX8

Thanks guys, I've been bedding the brakes and I think everything is much smoother now.

StewC625

Just a bit of lot rot ... further use will fully resolve.

G8rboy

Agreed- that poor thing has been unloved for over a year and a half... it just wanted some attention