Trailer Brakes

[kingfishbig]

Does anyone know why my trailer brake calipers don't move from side to like they should (and a possible fix)? This is on one side only. I have removed the pins they sit on and regreased them but they don't budge when the bolts are tightened up.

[zmk1962]

Hi @kingfishbig  I presume you checked all the obvious things at the caliper/rotor assembly - like nothing was bent or out of alignment, no gunk / rust behind the brake pads etc. 

Also if your brakes are hydraulic - check that the cylinder piston is retracting - ie if you get rust behind the piston seal or in cylinder bore it may be jammed out. The cylinder may also be jammed in the out position if you have a pinched or blocked hydraulic line preventing fluid return or even possibly air in the line (expanding when hot) .

If all that has checked out, then perhaps you are where I was a few years back. I had similar issues and working with an experienced mechanic this is what we found:

1. My disc rotors were slightly oversized. Turns out some trailer manufacturers make boat trailer rotors slightly oversized to compensate for the extra rust encountered by dunking in salt... they expect you will have the discs machined more often and try to give you better longevity.

2. The brake pad thickness varies between manufacturers. Putting on a thicker pad combined with the oversized rotor took up all the tolerance or in my case reduced it to the point when the brakes warmed up the brakes would drag and the caliper would lock. 

The mechanic didn't have thinner pads on hand, so he fixed this by putting on a few thousand km's of wear on the fat pads (angle grinder and dust mask!) to create the clearance we needed.  

BTW, although I don't think its related to your immediate problem, I have absolutely stopped putting grease on the slide tubes. No matter what grease I used I found that eventually it hardened after 8-12mths and caused my brakes to drag. I now exclusively use Silicon spray - short spray using the tube nozzle directly into each slide tube and another squirt behind the brake pad where the hydraulic cylinder is does the job.  It takes 40 seconds to run around the trailer with a can of spray  just after the boat is launched.  I have had no brake issues for 5+ years using this technique.

PS - I do not spray the brake pads.

Cheers

Zoran

[kingfishbig]

Thanks for that. The brakes are mechanical override. The pads are well worn too - getting near replacement. So I am still scratching my head!

 

[zmk1962]

HA ! ... knew I  should have asked.... 

There aren't that many moving parts to mechanical overrides - did they ever work properly? Was it serviced recently? Perhaps someone may have fitted incorrect slides... 

I had a case once where a mechanic (apprentice?) fitted two piston O-ring seals and we kept wondering why that caliper always jammed until we pulled it apart.   

Best of luck.

Z

 

[Fab1]

19 hours ago, zmk1962 said:

HA ! ... knew I  should have asked.... 

There aren't that many moving parts to mechanical overrides - did they ever work properly? Was it serviced recently? Perhaps someone may have fitted incorrect slides... 

I had a case once where a mechanic (apprentice?) fitted two piston O-ring seals and we kept wondering why that caliper always jammed until we pulled it apart.   

Best of luck.

Z

 

Poor apprentices get blamed for everything.Maybe the Op can put up a few photos so your not going in blind to help him.Good advice thus far mate.