OzVMX Forum

Clubroom => Tech Talk => Topic started by: Husabergpete on August 24, 2009, 12:23:55 pm

Title: Rear drum brake backing plate failure?
Post by: Husabergpete on August 24, 2009, 12:23:55 pm

Guys,
        Looking for possible causes for a floating rear backing plate to fail. ie the anchor section for the brake stay rod to snap off.

Not sure if I should be looking at alignment, bearing etc. Any starting point would be appreciated.

Pete

Title: Re: Rear drum brake backing plate failure?
Post by: lms6201 on August 26, 2009, 08:55:41 pm

floating bush / bearing seized can do it

Title: Re: Rear drum brake backing plate failure?
Post by: Rosco400 on August 26, 2009, 09:12:14 pm

Quote from: Husabergpete on August 24, 2009, 12:23:55 pm

Guys,
        Looking for possible causes for a floating rear backing plate to fail. ie the anchor section for the brake stay rod to snap off.

Not sure if I should be looking at alignment, bearing etc. Any starting point would be appreciated.

Pete

I would guess you are talking about Dean Burts bike Pete, Dean rides hard so guess theres a lot of heat generated into alloy, does he ride  with the brakes nipped up tight with little brake pedal movement, that would only lock up rear wheel if that was the case if pads expaned,never heard of a 400 backing plate letting go until now ???

Title: Re: Rear drum brake backing plate failure?
Post by: Nathan S on August 26, 2009, 09:19:18 pm

Pics of broken bits will help.

Title: Re: Rear drum brake backing plate failure?
Post by: holeshot buddy on August 26, 2009, 09:26:15 pm

sounds like its not floating freely
to snap off stay mount ;)

Title: Re: Rear drum brake backing plate failure?
Post by: Husabergpete on August 27, 2009, 07:44:11 am

Gents,

        Thanks for the input so far.

Most of the bits are lost but there is a small section left attached to the rear brake arm. I need to have a good look at that bit. I can discount the brake being wound up too tight and most likely a bearing failure. More CSI needed.

Title: Re: Rear drum brake backing plate failure?
Post by: BultacoMacca on August 28, 2009, 12:03:35 am

Not that its specifically relevant, but back in the day I had to replace my Rm400N hub after it disintegrated at the old Canberra Karma Gutza track. I put it down to the thin metal aroung the bearing on the sprocket side. Never had any problem with a backing plate failure.
Is the backing plate magnesium?

Title: Re: Rear drum brake backing plate failure?
Post by: Husabergpete on August 28, 2009, 12:17:11 pm

Macca,

          Yep they are magnesium. Someone has suggested that magnesium goes brittle with age. If so a few of us are in trouble.

pete

Title: Re: Rear drum brake backing plate failure?
Post by: oldfart on August 28, 2009, 04:01:15 pm

Check to see if bush that goes thru N /R bearing on brake hub is installed the right way round . As It will grab on wheel bearing when nipped up and rotate with hub - installed wrong  ;)

Title: Re: Rear drum brake backing plate failure?
Post by: Husabergpete on August 29, 2009, 06:56:51 am

Oldfart,

         Do you mean the bush/bearing in the centre  of the backing plate or the bush the torque arm bolts onto?

And thanks for your thoughts.

Pete

Title: Re: Rear drum brake backing plate failure?
Post by: oldfart on August 29, 2009, 07:33:54 am

bush / bearing  that axle passes thru

Title: Re: Rear drum brake backing plate failure?
Post by: Husabergpete on August 29, 2009, 05:34:12 pm

Oldfart,

          Your assumption is looking like it has some cred. Early days yet and we need to do some more digging, but.... It appears the manual which was used to put the bike together says to put the bush in one way and the exploded parts view shows the opposite. I'll keep you posted.

Pete

Title: Re: Rear drum brake backing plate failure?
Post by: Husabergpete on September 07, 2009, 07:15:47 pm

The answer has been found!!!

I haven't checked this out myself but this is what I have been told. The Suzuki hub runs 2 bearings. A certain amount of sideways float was occurring. This allowed the protruding pins of the actual brake backing plate to come into contact with the internal webs of the hub. Resulting in the wheel catching the backing plate and rotating it somewhat. Enough `somewhat' to tear the plate to bits. Simple fix really.

Thanks for the imput.

Pete

Title: Re: Rear drum brake backing plate failure?
Post by: oldfart on September 07, 2009, 08:59:37 pm

To find a new rear brake plate may take a while  ::) If you come across a spare brake spacer hub
part # 64213 - 40300 and rear brake lever  # 64451 -40301   I'll buy them off you  :)