Rear brake unbalance

Took my 1990 Ninety for MOT today and passed Yeha.
However do have a brake unbalance issue on the rear axle [ drum] with OS not performing as well as NS. This is a ongoing issue.
For last year's mot new shoes and drums were fitted and the rear brakes were unbalanced then. Tester put it down to new bits needing bedding in. But this year have the same issue, not enough to fail test but borderline.
Slave pistons are free and operate as normal. No oil or fluid leaks.
Just asking any ideas why? as both tester and I are stumped

Increase the power to one side by adjusting it to work harder, Ballance them up that way

Just wondering if you fitted genuine or OEM drums or maybe some cheaper ones which may be slightly out in terms of thickness?

Toyota Twonk said:

Increase the power to one side by adjusting it to work harder, Ballance them up that way

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Wow, you know a lot ....
How do you do that then ?

miktdish said:

Wow, you know a lot ....
How do you do that then ?

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I think he winds one adjuster until that side binds making it ‘more powerful’

If you can't Ballance drum brakes and your MOT tester is also none the wiser perhaps you could seek professional help

I had that on last years mot on front brakes , I recently cleaned up shoes , bought new cam adjusters as the old bearmach ones had rounded off got some old moprod ones off eBay quality a lot better so adjusted up and the imbalance is lot better but braking not as good as before, so I need to play around a bit more on mine.

it’s worth checking how all the shoes compare to see if all areas actually touch the drums, can do this by removing them side at a time after cleaning up shoe place it inside drum and see where it runs , use feeler gauges to check and gaps and sand down any to get a better fit around the circumference. This assumes the shoes sit square onto drum , then onto next but

when fitted check the steady post is correct in keeping shoes square to drum by set square on the axle stub end , then fit proper and go for a test drive and see if shoes marked all way round across the width

have you any air in one side could contribute towards the imbalance

Def90man said:

I think he winds one adjuster until that side binds making it ‘more powerful’

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A drop of oil on one side will make the other side more powerful

Knappster said:

Just wondering if you fitted genuine or OEM drums or maybe some cheaper ones which may be slightly out in terms of thickness?

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After having bought a pair that were not even round, did not need to measure you could see it. I sent them back and for not much more got OEM that checked out fine.

steve2286w said:

it’s worth checking how all the shoes compare to see if all areas actually touch the drums, can do this by removing them side at a time after cleaning up shoe place it inside drum and see where it runs , use feeler gauges to check and gaps and sand down any to get a better fit around the circumference. This assumes the shoes sit square onto drum , then onto next but

when fitted check the steady post is correct in keeping shoes square to drum by set square on the axle stub end , then fit proper and go for a test drive and see if shoes marked all way round across the width

have you any air in one side could contribute towards the imbalance

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Did have a look inside before mot, everything dry and shoes looked to be wearing much the same.
However will look again and measure as you suggest. Shoes been in a year so are bedded in [ or should be]
No air in system. Cheers.

Swap shoes side to side, and see if fault moves with the shoes.
If fault the same swap slaves.
Or do as I would do and ignore it!

Keep an eye out for a disc rear axle.

lynall said:

Or do as I would do and ignore it!

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Nice.
So you openly admit you would operate a defective vehicle....

It would have to pretty severe, but a crushed/kinked pipe could do it.

Toyota Twonk said:

Nice.
So you openly admit you would operate a defective vehicle....

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This is how you can tell a pro mechanic from a bar stool mechanic.

Nothing a matter with pipes, we checked. Had a look again and have different make slaves each side, although why it would make any difference I can not think. Still will swap out.

Are they both the same size? You haven't got a front one on the back have you?

tottot said:

Nothing a matter with pipes, we checked. Had a look again and have different make slaves each side, although why it would make any difference I can not think. Still will swap out.

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Same slaves as series Iirc, in which case I reckon @kermit_rr has hit the nail on the head.

I have a series three as well and not had this issue with it or 2a's I have owned.
I better check did not pull a series front from the spares box.