New Trailer Brake Pads Rubbing.

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MikeAqua

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#303307 31-Jan-2023 10:53

I just rebuilt the brakes on my boat trailer. New seals and boots, rods greased, new fluid, bled. The brakes are working well including the hand-brake.

But ..... the pads are rubbing the rotor (just). I can turn the wheel by hand easily but it won't spin freely. This means the trailer would fail a WOF inspection (which it is due for).

This is the second time I've rebuilt these brakes (saltwater sucks), and I didn't have this issue last time.

There is no adjustment for the brake calipers and the pistons are fully retracted. It's like the pads are a little too thick, but they only come in one thickness. I did a brief test tow and there was no heat build-up.

My conclusion is that the rotors have a little rust build up and if I tow the trailer say 20kms (stopping regularly to check for heat build-up) and gently engage the brakes a few times, the rotors and brakes will flatten each other out.

Any advice appreciated, as I haven't hit this problem before.

Mike

gzt

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#3029927 31-Jan-2023 12:38

I think you're in the normal range. Give it a short run and see how it feels.

johno1234

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#3029938 31-Jan-2023 12:52

How far has it been towed with the new pads? It might resolve itself after towing for 10min or so.

MikeAqua

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#3029945 31-Jan-2023 13:43

johno1234:

How far has it been towed with the new pads? It might resolve itself after towing for 10min or so.

0 km. It's still in the shed.

I think I'll do a wee tow today and see how I get on.

Then WOF inspection Thursday.

Mike

MikeB4

MikeB4
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#3029947 31-Jan-2023 13:58

A long shot. We had similar after changing the pads on the Stabi's trailer. It turned out to be the wheels bearings. Don't ask me how, the mechanic changed the bearings and the issue went away.

Here is a crazy notion, lets give peace a chance.

tweake

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#3029954 31-Jan-2023 14:27

if the pads are loose on the piston, check the pads are sliding properly. thats in the grooves at the ends, some don't have shims so they slide in the rough casting. bit of anti-seize in there. also the sliders, quite often find the sliders will stick and cause one pad to rub.

wheel bearing, i havn't seen it but i'm told wheels bearings want to be a tad loose so the wobble knocks the pads back (only talking tiny amounts).

one thing i've had is squished brake line causing a restriction. that makes it hard for the fluid to go back to the master cylinder. the coupling usually only pushes the pads out, its the flex of the seal which pushes the fluid all the way back.

reminds me make sure the piston seals are tight and grabby, not slick and sliding smooth. you want the seal to stick to the side wall.

MikeAqua

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#3029973 31-Jan-2023 15:28

MikeB4:

A long shot. We had similar after changing the pads on the Stabi's trailer. It turned out to be the wheels bearings. Don't ask me how, the mechanic changed the bearings and the issue went away.

The bearings are all good. Just changed them and the wheels were spinning freely, before I reinstalled the brakes.

It's definitely the pads.

Mike

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MikeAqua

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#3029974 31-Jan-2023 15:35

tweake:

if the pads are loose on the piston, check the pads are sliding properly. thats in the grooves at the ends, some don't have shims so they slide in the rough casting. bit of anti-seize in there. also the sliders, quite often find the sliders will stick and cause one pad to rub.

wheel bearing, i havn't seen it but i'm told wheels bearings want to be a tad loose so the wobble knocks the pads back (only talking tiny amounts).

one thing i've had is squished brake line causing a restriction. that makes it hard for the fluid to go back to the master cylinder. the coupling usually only pushes the pads out, its the flex of the seal which pushes the fluid all the way back.

reminds me make sure the piston seals are tight and grabby, not slick and sliding smooth. you want the seal to stick to the side wall.

All those thigs are OK. I'm more and more convinced that I just need to run them in. I'll try that and report back.

Mike

Mehrts

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#3031032 2-Feb-2023 18:07

Correct trailer brake bedding procedure:

1. Overload trailer with everything you can find. At least 4000kg should do. Tyres must be very flat on bottom at normal pressure.
2. Apply trailer brakes firmly.
3. Drive as fast as possible for a few km.
4. Don't stop until you see smoke and/or fire from brakes.
5. Park at home.
6. Crack open a cold one and admire your skills.
7. Don't take advice from stangers on the internet.

Daynger

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#3031038 2-Feb-2023 18:33

Take it for a drive, self clearancing.