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 Post subject: drum brakes
PostPosted: Thu Mar 29, 2012 9:30 pm 
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848cc
848cc

Joined: Fri Jun 11, 2010 4:31 am
Posts: 211
Location: Perth
just drove my mini for the first time ... i bought it with the clutch not working.

Anyways these brakes are terrible. It is the first time ive driven a mini with drum brakes... but i did adjust them and bleed them. They seem to work fine MOST of the time... but then occasionally, the brake pedal will go to the floor :( It seems really random when it does it. Sometimes i will be stopped at the lights, foot on the brake, and it will just go to the floor.

This is not normal (brake fade) is it? I was not even driving hard.

I still have plenty of brake fluid in the canister...


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PostPosted: Thu Mar 29, 2012 9:33 pm 
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848cc
848cc
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Joined: Mon May 22, 2006 9:01 pm
Posts: 51
Location: Perf. Western Australia
Sounds like your master cylinder has gone

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PostPosted: Thu Mar 29, 2012 9:34 pm 
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848cc
848cc

Joined: Sun Nov 18, 2007 10:57 am
Posts: 181
Location: Adelaide SA
Sounds like you have a master cylinder fault . The fluid is bleeding past the cups. You will need to take it of and overhaul it or replace it as necessary

Regards


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 Post subject:
PostPosted: Thu Mar 29, 2012 10:39 pm 
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1275cc
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Joined: Mon Sep 19, 2005 4:57 pm
Posts: 3635
Location: Gulgong
Yeah hydraulics some where.

Brake fade is quite different . its where everything feels right pedal pressure etc but the brakes just dont have the braking efficiancy they should have - in otherwords your just not stopping.

Mostly its because the linings and drums have got very hot due to repeated braking and have lost their friction co-efficient as a result. They then cool down after a period on non heavy braking and normal braking resumes.

The same thing happens if you drive a drum braked car through reasonably deep water and the drums fill with water that acts as a "lubricant" between the linings ad the drums.

Disc braked cars also develop brake fade under continous heavy braking But generally they disapate heat faster and return to normal braking more quickly. Because of their open nature they also shed water more quickly and dry faster.

Race cars (mostly in earlier years) could also boil the brake fluid which gave a different problem where the boiling brake fluid would cause a loss of pedal pressure.

However, none of the above is what your describing. You have hydraulic problem somewhere and it does need to be looked at.

Mike


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 Post subject:
PostPosted: Thu Mar 29, 2012 11:42 pm 
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848cc
848cc

Joined: Fri Jun 11, 2010 4:31 am
Posts: 211
Location: Perth
thanks again guys - mike, a great explanation of brake fade, thankyou :)

I've ordered another master cylinder from minisport :)


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 Post subject:
PostPosted: Fri Mar 30, 2012 8:08 am 
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1098cc
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Joined: Mon Apr 06, 2009 9:02 am
Posts: 1233
Location: Sandy Bay, Tasmania
Drums will never be as good as discs, but I've learned that if you fix them up properly and keep them well tuned, they can pull up well.

I had issues with pedal height, and I ended up getting a new maser cylinder
(a rover split bore tandem) and reconditioning the bias valve, and the brakes are now great.

And yes, I'd say it's your master cylinder. If you haven't bought a new one already, you can use a reco kit which is much cheaper, provided the bore is alright.


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 Post subject:
PostPosted: Fri Mar 30, 2012 9:45 am 
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Location: Wodonga - Vic/NSW border
my mate has drums on his motorkhana car - people often comment on how well it stops...

theres a huge amount of friction material in there, so long as they're properly adjusted and don't get hot, nothing wrong with drums


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 Post subject:
PostPosted: Fri Mar 30, 2012 10:04 am 
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1275cc
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Joined: Sun Jan 21, 2007 9:16 pm
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Location: North of the Harbour planning my next mini project
It may alos be a good idea to check each of the wheel cylinders as I find they currently only last about 18 months before they start to leak and at about $20 each it is much easier to replace at the first signs of any leakage.
More hassle and frequent maintenance than disks but they do work well when all bits are nice and fresh.

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 Post subject:
PostPosted: Fri Mar 30, 2012 2:13 pm 
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1098cc
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Joined: Mon Apr 06, 2009 9:02 am
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Location: Sandy Bay, Tasmania
simon k wrote:
my mate has drums on his motorkhana car - people often comment on how well it stops...

theres a huge amount of friction material in there, so long as they're properly adjusted and don't get hot, nothing wrong with drums


Yeah, for low-speed stops I find my drums great. It's only if I've been driving a while and I suddenly need to go from 100 back to 0 that I really feel the difference.


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 Post subject:
PostPosted: Fri Mar 30, 2012 10:50 pm 
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1275cc
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Joined: Sat May 02, 2009 4:53 pm
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Location: Port Stephens, a little north of Newcastle, Australia
The other problem with drums is that they will pull sharply to one side unless you pay a lot of attention to adjustment. And just for a little bit of extra excitement add a booster.


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