Cobra trailer loose backing plate

[Nelson Howe]

While maneuvering my trailer by my shop yesterday I discovered the right brake suddenly got stuck on.  Upon closer inspection I found half of the clamshell fitting that holds the cable to the backing plate was off and wedged between the backing plate and the swing arm.  The cable was still connected to the brake, but it was wrapped half way around the wheel assembly.  After a lot of head scratching I cut the end of the cable to separate it from the backing plate (it was under considerable tension, locking the clamshell in it's wedged-in position) and was able to free the clamshell and cable.  The backing plate itself is loose.  Apparently, the backing plate rotated, breaking the clamshell fitting from the plate housing and winding the cable around the wheel assembly.  Upon inspection I found the other backing plated is also wobbly.  The wheels are solid, but the backing plate has significant play, and although it doesn't seem to want to rotate at the moment, it feels like it would with a bit of force.

Are these backing plates usually loose like this?  Any idea how they are secured to the wheel assembly?  Any thoughts on a fix?

Thanks,

Nelson

[Nelson Howe]

Additional jpeg.

[Charles Mampe]

It's been a while since I looked, but I believe it's a few bolts through the backing plate into the axle housing. No, the plates need to be solid to work properly, not wobbly.

On Monday, August 24, 2026 at 8:31:05 AM UTC-4 nbh...@gmail.com wrote:

Additional jpeg.

[Mark Mocho]

If you look closely at the last photo, you can see that the hole the Bowden Cable clamshells are normally held in is broken. The larger hole and ragged edges are a dead giveaway. You will need to replace (at least) the backing plate, the Bowden Cables, the clamshells, and possibly the brake shoe assembly. Maybe you will get lucky and not have to replace the drums, but if everything came apart, the drums may be damaged. Wings and Wheels show the parts on their website ( Brake Drum COBRA Trailer). Get someone with brake experience to disassemble your existing brake assemblies and determine what parts you will need. You may not need everything, but at least you do not have to buy the entire assembly. W&W allows you to check the parts you will need. Call them to see whether the parts are in stock. Then call your pharmacist for drugs to revive you after you see the price and tariffs. BTW, the backing plate is not held by bolts. Rather, there are holes in the plate that align with lugs on the axle swingarm.

That's the route I would take, determining only what is needed depending on condition. A more complete and secure solution is to buy the entire assembly, including new axle spindles. The whole kit is held by the large hex socket bolt shown in the last photo. Probably more expensive, but the best solution if you are unsure of the existing parts. You will also have to buy a 17 mm hex impact driver tool as the hex socket bolt is really torqued down. (For obvious reasons) It will take a pretty big torque wrench or impact driver to remove it and reinstall it to meet torque specs.

[Mark Mocho]

Correction: It appears that the entire brake drum assembly comes as a kit, with the backing plate, shoes and springs. Individual parts may not be offered. The spindle is not included on the 1600 kg 5 lug kit (according to the photo) Check with Sean at W&W for details. Unfortunately, the website shows "out of stock" on these items.

[Mark Mocho]

As a follow up, I suspect that the whole problem arose from the likelihood that the last person who repacked the bearings, or disassembled the drums, did not tighten the spindle bolt enough. As I mentioned, the backing plate is held to the swingarm by about 16 raised lugs on the swingarm that mate with 16 holes in the backing plate. These lugs only protrude about .100 inch from the surface of the swingarm. If the spindle nut has any play, the backing plate will be loose enough to wobble under load, wear out the lugs or the holes and eventually break loose, allowing the backing plate to rotate and lead to exactly the situation you are experiencing. If the lugs are worn too much, they may not hold, even with a new backing plate. You might need an entire axle. But the entire axle assembly is actually not much more than the individual brake drum kits, and everything is preassembled with the axle, spindles, backing plates, brake shoes, bearings, and brake drums. Of course, these aren't in stock either, but.... Cobra Axle

Nelly- if you have any questions, give me a call.

[Mark Mocho]

OK, I disassembled a brake drum on an AL-KO axle today and discovered that the spindle bolt on the end of the axle has no effect on whether the backing plate can become loose. The shoulder on the spindle is what holds the backing plate to the swing arm. If the hex socket bolt gets loose, the backing plate could shear the locating lugs and allow the backing plate to rotate under braking load. I suspect that Nelson's axle may have been improperly assembled, and the socket bolt was not torqued sufficiently. I've never heard of this failure happening, so maybe it is a rare anomaly.