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Old 12 July 2010, 14:23   #1
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Knott brake adjustment

Hi,

Just replaced the brakes in my trailer (Knott 200X50) and am currently trying to adjust the drums.

I've seen various strategies on this

http://www.knottuk.com/fileadmin/Kno...ver_Brakes.pdf talks above tigtening the adjuster until the brakes start to lock then backing it off until they "just" run free in forward direction.

I also saw another website http://myreader.co.uk/msg/127539041.aspx talking about turning the adjuster till the brakes lock with moderate pressure then backing them off about 1/2 turn.

In my case, I tightened the adjuster till the wheel was pretty much locked (hard to turn by hand in forward motion) then backed it off. If I back it off about 3/4 turn, then there is pretty much no rubbing noise.

My question is - when the instructions talk about the wheel "just turning freely" does that mean with no rubbing atall or just slight rubbing and how critical is this?

I realise I will probably have to adjust the brakes soon again anyway as they are new but would like to know what I should be adjusting to!


Edit (further info)

The next step in the instructions talks about applying the handrake and then turing the wheels in reverse where they should apparently turn a bit then lock (and handbrake should move slightly back). In my case, with the drums adjusted as above, I can't turn the wheels backwards with brake applied!

I tried this with one wheel that I hadn't yet adjusted (had the adjuster way too slack) and with the handbrake applied the wheel would turn backwards (after initial effort to get it to release) but not forwards (and the handbrake did indeed move back in reverse). However I then adjusted this wheel the same as the other side (as per description above) and it's now solid in both forward and reverse with handbrake applied.

The shoes were fitted the same as the ones that came off and the direction of rotation arrow on the shoes is correct!

Help!



Thanks!
Al
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Old 12 July 2010, 15:57   #2
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its all very well adjusting nice dry car brakes like that but I prefer seawater dunked trailer brakes to have some travel to ensure, as far as I can, that the return springs pull them well away from the drums when the boat is left(with h/brake off of course) so they dont grow rust between the surfaces. Also a bit of travel makes the shoes travel to do some work instead of barely moving and again just rusting in situ. Adjust them too tight and you can also have the trailer wheels lock up every time you touch the car brakes. and when you come back to the trailer after a few days they have seized up! Horrible things drum brakes on boat trailers. When the brake shoes get nice and rusty they have a habit of popping the bonded linings off and then everything locks up. happy adjusting eh
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Old 12 July 2010, 17:46   #3
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Yeah that does make some sense!

So how slack are you talking here ? 1/4 turn slacker than when they stop making any rubbing noise?

The bowdens have a reasonable bit of travel with H/B on so the expander is at least moving a fair bit but I do take your point about exercising the mechanism.

Are there any implications if the brakes are adjusted loose at the drum? does this cause any issues with the brakes snatching (due to fact there is some more slack in the system)
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Old 12 July 2010, 18:11   #4
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I have Alko brakes so can't say whether this will work for you however I was told the following by one of the Alko engineers.

Each cable should extend about 10mm when the brakes are applied. So wrap a piece of wire around the wire where it exits the brake cable tube so that as you pull on the brakes you can see the wire move and measure it. Tighten or loosen each drum to get the same amount of movement at the cable ends. Once this is done tighten up the threaded bar that runs to the hand break until you take up the tension.

Works really well for me.
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Old 13 July 2010, 05:37   #5
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I just contacted Knott UK and they were very helpfull. so for reference:


Adjust the brakes on the drum such that they are "just" rubbing and no more.

In terms of turning the wheel back with the handbrake on - he said is was really hard to turn but if the trailer crabs backwards when you have the handbrake on and move the hitch side to side then everything is working as it should.

I do take on board the earlier comments about things ceasing on so may back the adjuster off till there is no rubbing but will drive a bit 1st to bed the brakes in a bit.

Thanks.
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Old 13 July 2010, 10:57   #6
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Adjusting drums is kind of a guessing game - too many variables to come up with a technique that works every time.

I use the "adjust until the wheel is noticeably dragging, then back off the adjuster 12 clicks" method. I use "noticeably dragging", as just hearing rubbing may be rust on the drum surfaces or similar. Similarly, "Locked" means different adjustments depending on how gorilla-like you happen to be.


jky
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