Issue with Shimano cantilever rear brakes, spring issue?

[London1986]

Hi all, I have inherited an old hand-me-down bike which I planned to temporarily use to see if I want to get into cycling more regularly.

I have attached images below.

The front brakes work fine however the rear brakes not so much. They seem to have a tension issue. I've watched countless Youtube vids and adjusted the brakes however there still seems to be issues with the tension. When I pull the brake lever, they don't seem to be as springy as the front brakes, I have to pull them quite hard and even then the brakes don't stop the rear wheel. I have tried adjusting the tension in the brake cable but to no effect.

Also when I do pull the rear brake lever, it doesn't return to its original position once released. Wondering if this is part of the issue?

I am new to bikes so please excuse my lack of terminology.

Any ideas or pointers that can put me in the right direction of what the issue is?

[Super Sonic]

Friction in the cable. It's probably rusty and needs replacing.

[London1986]

Super Sonic said:

Friction in the cable. It's probably rusty and needs replacing.

Thank you, I've googled that and it does seem like that could be the cause. I will try and replace that and see if that fixes the issue

[Salsa]

Greasing the cable for the release may help.

With regard to weak power slacken both brake cable and straddle wire, this will allow the canti arms to go wider, undo the brake pad arms and adjust them accordingly by moving them inwards, this should give you greater leverage for more stopping power, check for maximum limits on the brake pad rods as to how far they can be adjusted.

You can adjust to springs behind the canti’s as well to get them to return, there are usually 3 small holes on the brake boss these allow you to strengthen and weaken the return pull

Hope that makes sense

[OutInTheShed]

Super Sonic said:

Friction in the cable. It's probably rusty and needs replacing.

Also possibly corrosion in the alloy arm where it mounts on the steel pivot. There may be a plastic bush in between, but corrosion can still cause binding.
Strip, clean, tiny smear of grease on the metal pivot surfaces, reassemble.

Also, some new brake blocks which haven't gone hard made a difference for me.

[London1986]

Ok so an update. You were all pretty much spot on.

@Super sonic I replaced the cable and instant improvement. The old cable was knackered, very worn. This improved the issue but wasn't completely fixed.

@Salsa the issue was one of the springs on the rear brake shoe, it wasn't returning to the original position. So changing it to one of the other holes did the trick.

The brakes are now fully functioning, brakes stop instantly and the lever returns as it should. Thanks a lot for your help!