Technical Forum > Mechanical

Rear brake pressurising

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lockey1000:
  Hi Tony here I own a 03 Varadero  linked brakes , the front brake is working properly operating both brakes and releasing , but if I use the back brake it just goes solid and locks on , any ideas greatly appreciated .
 Cheers tony

Saxal:
Hi Tony,
having trouble myself with these pesky rear brakes. Sounds to me like it may be the caliper sticking on. Don't know if you know but there are 3 pistons in the rear caliper, 2 small, operated by the rear brake pedal, and a larger central one operated by the front brake. It could be that the smaller outer 2 are sticking on. You could try cleaning the pistons and caliper, this involves taking off the back wheel, remove the caliper bracket and pads, not as hard as it sounds, then get a bucket of hot soapy water and a toothbrush and start scrubbing the caliper and pistons. Press the rear pedal a little to bring out the pistons but not too much. When its cleaned up put it back together and try it. No gaurantee but its worth a try. Hope this helps. :) 

lockey1000:
Hi Saxal, fronts working ok removed rear calliper and worked the front  calliper on the fork leg the middle piston came out and released pressure like it should , but when I used the back brake the middle piston still came out and was solid ( wouldn't release ) I rode 80 miles incident free only using front brake used the back brake once calliper stuck on ( baffled ) hope this makes sense
Cheers Tony

Saxal:
Hi Tony,
are you saying that if you pull the front brake lever, the centre piston comes out on the rear caliper, because mine didn't when I tried that, but my front brake is fine also. Mine failed its MOT on friday due to a poor rear brake, going to bleed mine tonight to see if this helps, I've already cleaned the caliper but the centre piston didn't move when I pulled the front lever  ???. I can't see why your rear brake is activating the centre rear piston. It may be worth a call to a Honda dealer or perhaps someone here can shed a bit more light. Sorry I can't be more help.

The Prodded Dog:
Long time since I had a Vara but remember well the linked brakes.
The front brake will only activate the rear caliper when the wheel is rotating. Braking force makes the left hand caliper follow the disc activating a secondary brake cylinder that pumps fluid to the rear brake pad. These sometimes bind on the pivot and reduce/negate the linked brake effect.
I think the rear brake pumps fluid through a splitter that transfers 3/4 force to rear outer pads and 1/4 to both front calipers. Can't remember which pistons.
To check front brake is linking with the rear, roll to a stop on the rear then press hard. The front should dip just like when you use the front brake. To check the reverse use only the front from a hard stop and the rear disc should have some heat in it.
Bleeding the brakes is a dark art. Best to have a mechanic change all the brake fluid and pump new brake fluid in from the rear.
Makes an amazing difference to the feel especially if the fluid has been in there for two years or more.
Good luck with it.
The Prodded Dog

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