Weak Rear Brake

kesher

My rear brake (cable operated Tektro Novelo) is weak. Just using it alone it only gently slows my bike (a Carrera Centos) no matter how much pressure I apply. The front brake works fine and the rear is correctly adjusted.

I have tried swapping the rear brake pads to the front and the front pads to the rear; but the result is the same so it can't be the pads. Do you think I need to replace the brake cable, although it does not seem to be sticking and neither is the brake itself? In April the bike will be 2 years old.

THANKS

Antm81

Being cable operated, have you advanced the Pistons to compensate for pad wear?

kesher

Yes

The Rookie

Not sure you advance the pistons on a cable brake!

Sounds like you've contaminated the pads (had any WD40 near the rear of the bike?), new pads and fit only after cleaning the rear disc with alcohol.

kesher

I understood advance the pistons as adjusting the moving arm and tightening the cable anchor bolt to compensate for any pad wear (left side) and then fine tuning, if necessary, via the cable barrel adjuster. This is followed by adjusting pad wear (right side) via the allen bolt on the opposite side of the brake.

I have occasionally used GT 85 on the chain; but I did immerse the rear pads in brake cleaning fluid for at least 24 hours and gave the rotors a wipe with the fluid and still rear braking is poor. Surely if the rear pads are contaminated then when I swapped them to the front they would have braked poorly; but they didn't. Just as the when the front brake pads, which are not contaminated, when switched to the rear failed to improve things.

Chunkers1980

There's your problem. Don't spray lubes near them and don't soak them in 'cleaning' fluid. Also don't use brake cleaner - only IPA, water or nothing. New pads and clean rotors with IPA.

The Rookie

^^^^ This, a tiny amount of GT85 on the disc (and the stuff mists everywhere) and the pads are contaminated, not to mention that it performs no useful function on a chain other than water dispersal if they are actually wet.

I have had some success in getting pads back to vaguely usable by soaking in petrol for 24 hours and then baking in the oven on max for 30 minutes, I doubt the solvent in brake cleaner is aggressive enough.

FishFish

As you've swapped the pads then it is not to do with them. It may be that the rear cable is elastic - try changing it for a beter quality one or artificially stretch it- put it in a vice and apply loads of tension and then refit.

The Rookie

Except the rear disc may have contaminated the new pads, happens often enough, you must clean the disc with the right stuff WHEN you change.

kesher

I've switched the pads back round and things are as before: no cross contamination, OK front brake; poor rear. I think I will try a new brake cable first before I do anything else, although not sure whether to replace the outer cable as well. I will use IPA in future as the brake cleaner I used was just something I picked up in Poundland (made by 151). I contacted 151 and they told me it does not contain IPA.

Chunkers1980

Poundland brake cleaner. :shock:

It won't contain IPA, as it needs to be IPA - it's the purity of that that makes it.

If the lever doesn't come right back to the bar then it can't be the cable.

kesher

It doesn't come right back: not even close.

kesher

Fitted new inner brake cable: problem fixed.