MGB pulsing brake pedal

[Sopwith_Camel]

the disks and the pads and the wheel bearings are new.
but down hill I get a pulsing on brake pedal.

steve

 

[YakkoWarner]

New discs and pads should mean your front brakes are OK. There is always a chance that one of your brand new rotor discs is warped....manufacturing defects do occur. Its much less common, but possible that an out of round or badly worn rear drum could cause the same type of symptom. Other possibility is related to vacuum if you have a vacuum boosted master cylinder.

 

[XJtom]

Rear drum brakes most likely, if the drums are still within the limit you can have them skimmed, if the shoes are still in good condition or need replacing - make sure the shoes are radius ground to suit the machined drums.....however as mentioned it's not impossible for new rotors to have a small high spot.

 

[Joe Reed]

It's also somewhat possible that, if the pads weren't properly bedded in, some pad material could have transferred to the discs in a couple of spots. I've never had that occur, so I don't know how pronounced any pulsation would be in that circumstance....

 

[Sopwith_Camel]

ahh i have recently adjusted the parking brake so i will look at the drums
thanks

 

[bobhustead]

Was the pulsing the same before you did the front brakes? If no, its the front brakes. If yes, its the rears. You could just take the drums and rotors to a machinist for turning.
Bob

 

[Sopwith_Camel]

nope defietly a high spot on the disk.

 

[bobhustead]

On the subject of radiusing brake shoes, one end of a set of shoes stays very still and the end on which you find the wheel cylinder moves. It is only toward the wheel cylinder end that contact is made between the shoe and drum (unless some added mechanical or hydraulic system makes both ends of the shoes move equally). The end that makes contact will radius itself in short order.
Bob

 

[maynard]

Did you clean the mating surfaces of the front hubs before installing the rotors?

 

[Sopwith_Camel]

I had the shop do it and the wheel bearings at the same time.

 

[billspohn]

I always take new rotors and have them set up on a brake lathe and use a dial indicator to check them for true. Much of the time they aren't and you need to take light cut to true them up so they won't do exactly what yours are doing. Never used to be an issue in the 70s but with parts now coming from who knows where, it just isn't worth throwing them on without checking them.