Shimano hydraulic brake (rear) not working

[mattc_uk]

Hi

Im relatively new to cycling, I bought myself a Carerra Vengence Race 3 months ago (used it only 4 times due to the winter weather). Suddenly my rear brake handle is flexing right up to the handle bars and not engaging the brake at all !

My bike has Shimano hydraulic disk brakes (BR-M445?). Im new to hydraulics and couldn't find the reach adjust for the brake handle anywhere. I need some advice as to where to start with resolving it. Any advice greatfully received

Cheers

Matt

 

[Moodyman]

Sounds like the brakes need bleeding, though they shouldn't need it after 3 months and 4 rides.

Try cleaning your rotor (disc) first - could be dirty or worse, you might have got some grease on it when lubing your chain, etc

 

[Howard]

There's usually a small grub screw behind the lever that gives you some control over the reach. But it sounds like there's something gone wrong in your brake system though.

Possible causes:

a) Brake line is punctured. Is there fluid leaking out? It should be pretty obvious if this is the case. Look for gunk.

b) More likely - there's air in the brake line. Does it make a quiet squeaking noise when you press the lever, and does the leaver have a kind of light but lumpy feel through it as you depress it? If you've had the bike upside down or crashed it air can get into the hoses, and as air compresses, your brakes get disabled. If this is the case a trip to the LBS is required to either fix the brakes for you or for you to pick up a bleed kit. You'll then need to bleed the brakes and then top them up with oil. Tutorials Online.

c) Caliper problem - do the calipers (the bits that actually grab the discs when you brake) look OK? Do they look the same as the ones on the front?

Hope that helps.

 

[mattc_uk]

There's usually a small grub screw behind the lever that gives you some control over the reach. But it sounds like there's something gone wrong in your brake system though.

Possible causes:

a) Brake line is punctured. Is there fluid leaking out? It should be pretty obvious if this is the case. Look for gunk.

b) More likely - there's air in the brake line. Does it make a quiet squeaking noise when you press the lever, and does the leaver have a kind of light but lumpy feel through it as you depress it? If you've had the bike upside down or crashed it air can get into the hoses, and as air compresses, your brakes get disabled. If this is the case a trip to the LBS is required to either fix the brakes for you or for you to pick up a bleed kit. You'll then need to bleed the brakes and then top them up with oil. Tutorials Online.

c) Caliper problem - do the calipers (the bits that actually grab the discs when you brake) look OK? Do they look the same as the ones on the front?

Hope that helps.

Hi

Yes that helps thanks, Im suspecting its problem b) reason being, I remember tilting the bike right up on its back wheel, to get past our wheelibin on the side of the house lol. Could this have got air in the fluid?

Im guessing this kind of manauvre with a hydraulic brake bike is a no no ?

There's no way of fixing this without the need to bleed the whole lot out?

Cheers
Matt

 

[Bman]

Ideally, there shouldnt be any air in the brake line. So normally, standing the bike up on end should be no problem. I regularly do this getting it in and out of the house.

If there is enough air in the lines to prevent braking, the only fix is bleeding the system.

 

[Howard]

Yes that helps thanks, Im suspecting its problem b) reason being, I remember tilting the bike right up on its back wheel, to get past our wheelibin on the side of the house lol. Could this have got air in the fluid?

Possibly, if you squeezed the leaver at the time, too.

And yes, as above, you do have to bleed out the whole brake. It's not much fun but it teaches you a few things about hydros.

 

[mattc_uk]

Ideally, there shouldnt be any air in the brake line. So normally, standing the bike up on end should be no problem. I regularly do this getting it in and out of the house.

If there is enough air in the lines to prevent braking, the only fix is bleeding the system.

Im not confident with this malarky, looks like a visit to Halfords! :-S

 

[TheDoctor]

No, don't go to Halfords!! Go to a decent bike shop.

 

[mattc_uk]

No, don't go to Halfords!! Go to a decent bike shop.

Well, its where I bought it from 4 months ago and probs still under warranty... so its my preferred option for a bleeding service. They seemed to know their stuff in there (Halfords vary from store to store)

 

[Howard]

Well, its where I bought it from 4 months ago and probs still under warranty... so its my preferred option for a bleeding service. They seemed to know their stuff in there (Halfords vary from store to store)

Just check the brake works when you pick it up again after the repair. Hope it goes well.

 

[mattc_uk]

Just check the brake works when you pick it up again after the repair. Hope it goes well.

Yeh good call :-)

Thanks all