hydraulic disc brakes - should the wheels lock?
Discussion
Have a Specialized rockhopper pro disc with shimano hydraulic disc brakes, so quick simple question. If I squeeze either front or rear brake as hard as I can should I be able to lock the brakes ? Currently it slows down ok but with a big squeak as it slows to a stop. All this from say 20mph->0mph.
I'm thinking they need adjusting/bleeding.
Its done naff all miles so they can't be worn out.
Cheers
Dave
I'm thinking they need adjusting/bleeding.
Its done naff all miles so they can't be worn out.
Cheers
Dave
David A said:
I'm thinking they need adjusting/bleeding.
Its done naff all miles so they can't be worn out.
If the lever fells spongy, then they need bled - you should fell the pad bite and the lever stop moving - air is compressible, oil isnt.Its done naff all miles so they can't be worn out.
Doing no miles maybe indicates that they need bedded in - go up a long hill, come down it dragging the brakes, do it a few times and the braking performance should improve a fair bit - dont do what i did with my first set of disc brakes and touch the rotor to see how hot it gets under braking, the answer is fairly obvious.
Parsnip said:
David A said:
I'm thinking they need adjusting/bleeding.
Its done naff all miles so they can't be worn out.
If the lever fells spongy, then they need bled - you should fell the pad bite and the lever stop moving - air is compressible, oil isnt.Its done naff all miles so they can't be worn out.
Doing no miles maybe indicates that they need bedded in - go up a long hill, come down it dragging the brakes, do it a few times and the braking performance should improve a fair bit - dont do what i did with my first set of disc brakes and touch the rotor to see how hot it gets under braking, the answer is fairly obvious.
Ta
Sure the pads aren't contaminated? I'd pop them out (easy job on disc brakes) and check for any glazing. My front HFX9 was doing this a few weeks ago, turns out the pads were glazed to hell. Quick rub down and squirt of brake cleaner before torching with a blowtorch and they're gripping better than ever now.
I touched my brakes the other day having come down a hill with the brakes on. Don't ask why, I knew damn well they would be hot 
It's either;
Brakes need bleeding.
Contaminated pads.
Pads need bedding in.
Bedding in has been covered. FYI you need to bed in all pads.
To bleed them you'll need the bleed kit, instructions and some mineral oil.
Contaminated pads. The easiest option is to replace with new. Depending on the type of contamination you may be able to clean them up by soaking them in brake cleaner - don't forget to clean the rotors too.
Brakes need bleeding.
Contaminated pads.
Pads need bedding in.
Bedding in has been covered. FYI you need to bed in all pads.
To bleed them you'll need the bleed kit, instructions and some mineral oil.
Contaminated pads. The easiest option is to replace with new. Depending on the type of contamination you may be able to clean them up by soaking them in brake cleaner - don't forget to clean the rotors too.
How old is your bike? I believe that Shimano recalled some of their hydraulic disc brakes last year because of a fault which gave the same symtoms as you describe.
Otherwise people above have given you the possible causes of this. But yes, any hydraulic disc brakes should be able to lock the wheels good and proper!
Otherwise people above have given you the possible causes of this. But yes, any hydraulic disc brakes should be able to lock the wheels good and proper!
fadeaway said:
How old is your bike? I believe that Shimano recalled some of their hydraulic disc brakes last year because of a fault which gave the same symtoms as you describe.
Otherwise people above have given you the possible causes of this. But yes, any hydraulic disc brakes should be able to lock the wheels good and proper!
Looks exactly like this one so this must be it http://www.specialized.com/gb/en/bc/SBCBkModel.jsp...Otherwise people above have given you the possible causes of this. But yes, any hydraulic disc brakes should be able to lock the wheels good and proper!
Have now cleaned the pads but its still the same. How much would a shop charge for changing the oil and bleeding (as I can't be bothered to do it my self!)
Cheers
Edited by David A on Thursday 25th June 20:03
How much would a shop charge for changing the oil and bleeding (as I can't be bothered to do it my self!)
Its an easy job in reality
You just need a bleed kit or be friendly with a nurse who can blag you a syringe and drip tubing
I do my own maintenance exactly because I am lazy
My local bike shop would almost certainly quote me a 4 week wait for this
And the time it takes to drive there and back twice is more than enough to do the job
David A said:
fadeaway said:
How old is your bike? I believe that Shimano recalled some of their hydraulic disc brakes last year because of a fault which gave the same symtoms as you describe.
Otherwise people above have given you the possible causes of this. But yes, any hydraulic disc brakes should be able to lock the wheels good and proper!
Looks exactly like this one so this must be it http://www.specialized.com/gb/en/bc/SBCBkModel.jsp...Otherwise people above have given you the possible causes of this. But yes, any hydraulic disc brakes should be able to lock the wheels good and proper!
Have now cleaned the pads but its still the same. How much would a shop charge for changing the oil and bleeding (as I can't be bothered to do it my self!)
Cheers
Edited by David A on Thursday 25th June 20:03
If anyone does have M485 brakes, then there's a copy of the recall notice here -> http://bike-rack.com/page.cfm?pageID=394
(posted because this is the first time I've managed to find it, so thought others might find it useful)
Only Avid and Formula use syringes for bleeding. Shimano's kit is more like you'd use for a car but smaller.
As for a price for bleeding. Well that depends on the LBS and your relationship with them. It's most likely an hours job so price could fall between £15 to £35.
If you've got a 2005 bike that you haven't used then it's most likely that the brakes just need a bleed and the rotors a good clean.
Contaminated pads will still have a good lever feel they'll just not bite. Brakes that need a bleed have a spongey lever with an extended throw.
As for a price for bleeding. Well that depends on the LBS and your relationship with them. It's most likely an hours job so price could fall between £15 to £35.
If you've got a 2005 bike that you haven't used then it's most likely that the brakes just need a bleed and the rotors a good clean.
Contaminated pads will still have a good lever feel they'll just not bite. Brakes that need a bleed have a spongey lever with an extended throw.
Edited by mk1fan on Friday 26th June 13:12
mk1fan said:
Only Avid and Formula use syringes for bleeding. Shimano's kit is more like you'd use for a car but smaller.
As for a price for bleeding. Well that depends on the LBS and your relationship with them. It's most likely an hours job so price could fall between £15 to £35.
If you've got a 2005 bike that you haven't used then it's most likely that the brakes just need a bleed and the rotors a good clean.
Contaminated pads will still have a good lever feel they'll just not bit. Brakes that need a bleed have a spongey lever with an extended throw.
Yup, gonna try and bleed them myself tonight. If i can do a cars brakes I can do a bikes theory As for a price for bleeding. Well that depends on the LBS and your relationship with them. It's most likely an hours job so price could fall between £15 to £35.
If you've got a 2005 bike that you haven't used then it's most likely that the brakes just need a bleed and the rotors a good clean.
Contaminated pads will still have a good lever feel they'll just not bit. Brakes that need a bleed have a spongey lever with an extended throw.
Seems fairly simple so fingers crossed.David A said:
fadeaway said:
How old is your bike? I believe that Shimano recalled some of their hydraulic disc brakes last year because of a fault which gave the same symtoms as you describe.
Otherwise people above have given you the possible causes of this. But yes, any hydraulic disc brakes should be able to lock the wheels good and proper!
Looks exactly like this one so this must be it http://www.specialized.com/gb/en/bc/SBCBkModel.jsp...Otherwise people above have given you the possible causes of this. But yes, any hydraulic disc brakes should be able to lock the wheels good and proper!
Have now cleaned the pads but its still the same. How much would a shop charge for changing the oil and bleeding (as I can't be bothered to do it my self!)
Cheers
Edited by David A on Thursday 25th June 20:03
Any way I tried getting a bleed kit from several LBS at the weekend but none had an avid one in stock (£35-40). So left it with the final one I tried and they quoted me £10 to bleed the rear brake - pick it up in the morning with hopefully a working rear brake. thought it saved the hassle of me doing it wrong and then having to pay them to put it right!
Right so started bleeding them, first up the reservoir was empty so they defo needed doing !!!
However, put the tube on opened the bleed valve (caliper) and some brake fluid came out. I now reckon I've got an airlock or something as I can't get the ruddy oil to flow through from the reservoir to the caliper.
Any ideas?
Dave
However, put the tube on opened the bleed valve (caliper) and some brake fluid came out. I now reckon I've got an airlock or something as I can't get the ruddy oil to flow through from the reservoir to the caliper.
Any ideas?
Dave
When I did mine a couple of weeks ago, I reverse bled them. I got a 50ml syringe and some washer jet tubing from Halfords. You put some brake fluid in the syringe, attach the syringe to the bleed nipple using a short bit of tube, open the reservoir cap and bleed nipple, and then just squeeze the fluid through until all the air stops bubbling out of the reservoir at the lever, then just tighten up the bleed nipple. Worked fine for me!
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