Maniac Merv Posted October 9, 2015 Posted October 9, 2015 So I’ve done a couple of enduro's where I’m hard on the brakes ect ect and never had a problem what so ever , but last weekend on Day 3 of Mankele 3 towers when it was F*$% hot , my front and rear brakes seized up so bad that you could not even spin the wheel for the last 5 km. Got home and washed the bike next day and took out pads and brakes to check out whats going on and they were loose , then when transporting my bike to the shop for a check up, they seized up again while on the back of the bike rack Is this a shimano fault or a heat problem or fluid expanding or pistons ?XT with ICE rotors
clement Posted October 9, 2015 Posted October 9, 2015 It could be an air bubble in the line close to the calliper. When the air gets hot it expands and pressurises the system pushing out the brake pads and seizing up. A bleed should solve it.
Baracuda Posted October 9, 2015 Posted October 9, 2015 Mine were great at first as well. Now they make the dreaded throttled turkey noise with reduced breaking umphh
TNOSE_E Posted October 9, 2015 Posted October 9, 2015 How old are your XT brakes. The pistons get worn and don't slide as smoothly anymore and eventually seize in the levers... I would imagine the things heating up might compound this seizing. I had the same happen during Trans Baviaans to my front brake after extreme braking. The piston in the lever seized and would not release the pads. The brakes are about 4 years old with heavy use. This years 3 Towers also had some hard braking sections.
TNOSE_E Posted October 9, 2015 Posted October 9, 2015 Ohh... so my money is on the piston seizing in the lever....
fanievb Posted October 9, 2015 Posted October 9, 2015 Bleed them So I’ve done a couple of enduro's where I’m hard on the brakes ect ect and never had a problem what so ever , but last weekend on Day 3 of Mankele 3 towers when it was F*$% hot , my front and rear brakes seized up so bad that you could not even spin the wheel for the last 5 km. Got home and washed the bike next day and took out pads and brakes to check out whats going on and they were loose , then when transporting my bike to the shop for a check up, they seized up again while on the back of the bike rack Is this a shimano fault or a heat problem or fluid expanding or pistons ? XT with ICE rotors bleed is needed Mine were great at first as well. Now they make the dreaded throttled turkey noise with reduced breaking umphh 1. check for contamination and replace pads where necessary2. skim rotors3. follow correct "burning in" procedure4. bleed5. check caliper alignment
madmarc Posted October 9, 2015 Posted October 9, 2015 Replace with SRAM XO Tail brakes - Problem sorted
akneethling Posted October 9, 2015 Posted October 9, 2015 Bleed them bleed is needed 1. check for contamination and replace pads where necessary2. skim rotors3. follow correct "burning in" procedure4. bleed5. check caliper alignmentThis............. Best answer to date. I had similar issues and a clean and bleed sorted it out.
ChUkKy Posted October 9, 2015 Posted October 9, 2015 Replace with SRAM XO Tail brakes - Problem sorted And this is where the fight starts.....
worriesnot Posted October 9, 2015 Posted October 9, 2015 And this is where the fight starts..... beat me to it..."ding ding ding!!"
Bobbo_SA Posted October 9, 2015 Posted October 9, 2015 Just been through the exact same issue with some 785's, last night I started off washing them in a bucket with warm water and a brush to get them spotless, then did the "off bike" bleed, flushed out the system bottom up completely, lubed the outer part of the pistons with some excess oil, going to refit them and leave them the bike in the sun today and see if it worked. Next step will be to flush them out with IsoP and refill with oil, failing that they are off to the agents for warranty. Edit: Spelling
fanievb Posted October 9, 2015 Posted October 9, 2015 Replace with SRAM XO Tail brakes - Problem sorted http://cdn.24.co.za/files/Cms/General/d/2304/4aad279b1b63409bbc16b0723756abcc.jpg
Super_mil Posted October 9, 2015 Posted October 9, 2015 Shimano brakes are infallible. The problem must be with you.
V12man Posted October 9, 2015 Posted October 9, 2015 And this is where the fight starts.....It's not a fight - he is correct....
Bobbo_SA Posted October 10, 2015 Posted October 10, 2015 So, after doing a full bleed bottom up with the brake off the bike and using the "funnel" method (and bleed block etc), I left my bike in the sun for 5-10 mins today as a test and the rear still does the same. Is it advisable to to rinse / flush them out with Isopropyl, let them dry out and then refill with oil?
JXV Posted October 11, 2015 Posted October 11, 2015 By 'seizing' I presume you mean pads gripping the disc when there is no pressure on the lever. A better term for this is 'pumping up'. 'Seizing' is when one or more pistons gets stuck in its caliper bore. Routing to rear often has a high point in the brake line where air can collect..if this air gets warm it expands and pads may push out to the discs. Overfilling with oil can also cause this. All your issues seem to be when the brakes get warm from sun or actual braking. So I think you might still have air. Take caliper off the bike and hang it vertically down while bleeding. Good as they are, XT brakes can't be rebuilt so if they are old or abused, might be a faulty lever needing replacement. When you bleed, do it properly with the bleed blocks in place to prevent over or underfilling and follow the Shimano service instruction exactly - not some diy home video off the web with steps missed out. I've had several sets of XT brakes and used them hard - never had this problem. Hope you get it sorted....no pun intended.
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