Brake Vibration

[mrmorrisminor]

Hi,
been having a few issues with vibrations when braking in my standard 1098 saloon. All is fine when driving along, apart from a slight wobble felt through the wheel over 60mph (must get the wheels re-balanced) but when the brake is pressed there is a VERY noticable vibration, the wheel shakes and you can feel it through the pedal too.

Having experienced this with a previous minor, I decided to treat her to a new pair of front brake drums. (purchased from a well known supplier)

After my first run I can report that the vibration has changed in frequency, feels faster and if anything it is slightly worse!

So.... has anyone had any issues with new drums recently? could there be anything else? 99% confident it's nothing to do with the rear, a slight pull of the handbrake (carefully of course) and no vibration evident anywhere.

[mike.perry]

Check the tie bars and rubbers and track rod ends, more likely to be a suspension fault than brakes

[mrmorrisminor]

Hi, thank you

In the last 1000 miles she's had:

-all new trunions

- new track ends

- new front shocks

- all new rubbers

- driver's side wheel bearing

The car can be jacked up from the bottom of the suspension arm and no play can be detected horizontally or vertically ..... I was assuming the problem was due to ovalated drums....
So all is a bit of a mystery

[mike.perry]

You should be able to detect oval drums by adjusting the brakes and spinning the drums. Push the brake pedal firmly to centralise the shoes then spin the drums, you will see if they catch on the shoes

[mrmorrisminor]

Positive on this one......... the old ones had a 'tight spot' when adjusted up... so I took them back 1 click so they were clear. This is what steered me towards buying new drums....... When I fitted the new ones I was not expecting the same but there was a noticeable point at which the shoes rubbed each revolution.....

[bmcecosse]

I agree with earlier posts - something is loose in the suspension. I've never know a drum to be 'ovalised' - is that a word??

[mike.perry]

One or two clicks will not affect the braking. If you think about it, the fact that the shoes are rubbing on the rotating drums should wear the drums circular

[daveyl]

Are the wheel bearings shot?

[dalebrignall]

could it be steering rack mine vibrates a bit .

[minor65]

My minor used to do the same, vibration through steering wheel when brake pressure applied. And recently a friends minor done exactly the same. 2 new brake drums fitted to both minors cured the problem straight away.

[mrmorrisminor]

Thanks for the responses. I found an article on brake drums the covers warped or oval drums

http://www.juratek.com/support-drums.php

When the car is slowing to a stop you can feel the brakes 'bite' in time with the vibration, the frequency of which is directly related to the speed of the car. At a walking pace with the brake lightly pressed you can feel the car slow and then the brakes slightly release in time with the vibration, which is what has led me to the brakes.

Suspension would not affect the power of braking in this way?

At the weekend I will swap the drums to my 2 door, that is A OK and see if the vibration is transferred to that car.

[mrmorrisminor]

Eureka!


I changed the new brake drums I purchased that I suspected were causing a vibration for a good spare pair my brother had from when he went over to disks. The vibration has completely disappeared I have completed a 100 mile round trip this weekend on A roads and have been braking from 60mph, which previously would almost have shook the wheel from my hand..... and all is completely smooth! The ONLY thing I have done is to change the drums over, nothing else has been touched.

I put each of the new ones I purchased in the lathe to check them over. one runs very true and smooth as one would expect. One of them seemed to not run as true, when I (carefully) rubbed my thumb inside as it was rotating I could feel a distinct variation in the internal surface of the drum, which caused my thumb to vibrate quite violently when I applied pressure (as the shoes would do I assume). On closer inspection this drum has some very strange machining marks that are not evident on the other one of the pair, as if it has not been finished correctly. They are more evident from the centre of the drum towards the outer edge which is where the surface feels very uneven.

I am in communication with the supplier and am sending them back for inspection.......

[bmcecosse]

When you set it up in the lathe - how did you mount it? The centre hole is not necessarily true to the rubbing surface - remember the drum is mounted on a hub - located by the 4 bolt holes, not by the centre hole. But there is n o doubt that if substitution immediately removes the vibration - there must be something wrong with that drum.

[mrmorrisminor]

Very true, I only used the 3 jaw chuck through the centre hole, I should have mounted it on a spare hub. However I feel that there is something strange with it as the machining marks are very different, almost as is it was not finished off. The other of the pair is smooth ans well finished where as the one I have suspicions about is coarse and has almost spiral machining marks which are VERY evident in comparison. Maybe a Friday afternoon job . . . .

[bmcecosse]

Can only suggest you try each drum back on the car - one at a time - to confirm it is the source of the problem,