hi. im sure this is a dimwit question for all of you tech experts, but ive got no experience with hydraulic discs. when i got my bike (2nd hand but well serviced) my shimano deore m525s worked great, but over the past couple of months the performance has become very poor, to the point where i cant even do a stoppie! so i bought some new pads for the front, cleaned the disc with some soapy water to make sure there was no oil on it, and tried to bleed the brakes (i had to release the nipple to get the piston back enough to fit the new pads). i used a syringe and pipe on the nipple to bleed the air up to the reservoir at the top as shown on internet how-tos, and made sure both the nipple bolt and master cylinder bolts were tightened before i released the pressure on my syringe to ensure no air got back in. my brakes feel exactly the same now as they did when i started- they are not worse, theres plenty lever pressure so im assuming i have bled them correctly, but i still cant get enough braking grip to do a stoppie :(. what am i doing wrong? anybody have any ideas why my brakes are just very poor. and before anybody says the obvious thing and suggests i go see an expert and pay him to do it, i cant, because i live on an island! im always struggling with tech issues like this, im the same with my rs125! any help with this would be much appreciated, and might save me from dying!!

I thought this post was just going to say 'aaaarrrrghhhh…. crash'

ha ha, in other words you only came in to see what id written out of a sense of morbid curiosity- thats not very nice lol!!

Well, you lost me about 'hydraulic discs'. Don't do tech stuff, but always interested in a good crash! Hope someone can help.

have you tried cleaning the rotors with isopropyl alcohol or whatever it is? rather than soapy water? cant imagine soapy waters done them any good. but there again, if there were traces of soap on them already, that could have transferred over to the pads. cant imagine soaps good for rotors or pads.

You tried squirting some lube on the pistons? Might be a bit sticky?

Can't help you with bleeding (others will I'm sure). But a common problem is contamination of pads and discs with minute amounts of oil and soap. You could try this: get some very clean emery paper and sand away at the pads. Clean disc and pads with alcohol ideally 100%; I use some horrid schnapps I got from Austria but you could use cask strength malt as I expect your island is swimming in the stuff, though it seems a terrible waste to me! Keep you grubby fingers away from all braking surfaces.

Before you return the pads to the callipers, do gently pull levers and watch the pistons move – sticky piston is another cause of issues.

If any of this works, send me a bottle malt! Best of luck.

isopropol alcohol 😐 ❓ never heard of that, but i like your thinking, so im away to do some research. my guess is that my problem is due to filthy discs and pads rather than it being a bleeding issue. im guessing your isopropol cuts through the grime and gives me back 2 surfaces that can actually bind together. thanks mate, i`ll try it! anyone else got any thoughts??

You tried squirting some lube on the pistons? Might be a bit sticky?

Eh? Sticky pistons wouldn't cause poor braking performance, they would result in rubbing brakes, or the pistons wouldn't pump out properly, meaning the levers would hit the bars before the brakes are fully applied.

If you think your pistons are sticky, you should remove the pads, pump the pistons out as much as you dare (about 6mm?) and apply a drop or two of brake fluid to the piston sides, then push the pistons back in, and repeat until smooth. If the pistons are so sticky they won't pump out and just retract when you release the lever, hold one piston in whilst pumping the lever to extend the other.

Don't use normal lube, and definitely don't squirt it 🙂

Isopropanol can be got from Maplins or chemists, though you may have to convince the chemist that you have a legit use for it. I have also used automotive clutch/brake cleaner from halfords.

wors- thanks, but my pistons are definitely ok, i inspected them closely earlier as i did suspect foul play from them.

buzz- i tried sanding the pads already, but it made no difference. as i said to sadexpunk tho, i think the 2 of you may be on the right track with the dirty disc theory, thats why i tried cleaning them with fairy liquid and water. ive got an open bottle of laphroiag downstairs, but im scared to use it bcoz its the quarter cask one and itll probably burn right through the disc lol! seriously, i`ll get onto it with the alcohol tomorrow.

this is great folks, thanks very much for helping!!

I recently had problems with my hope brakes. I solved it by replacing the seals in the lever they only cost about a tenner (dont know about shimano spares). If the seals are worn they will struggle to hold pressure.

Before trying this try tieing the levers back with a cable tie or shoelace for a day or two. i was told to do this with my hopes and sure enough they are noticibly sharper. This is probably why i had to change the seals in the lever so dont do it too often.

I'm going to ditto seany_e_boy – tied back my hope levers and the feel came back

Have you tried dribbling sandy water over the discs – if you can endo with gritty discs – its a pad/disc problem.

Else there's a leak – you can even get fluid getting trough the hose inner – but no the outer – any bulges or blisters in the hose?

im pretty sure the hoses are ok, i had a good look at the front one when i was bleeding it today. I`ll try the alcohol tip first (my wife has just informed me she has alcoholic wipes that are soaked in isopropyl-good girl!), and if not the levers will get tied back- i can see how that would work, but i can also see how it would destroy the seals too :wink:.

if the pads are contaminated you could always try baking them in the oven for a while. thats one little trick. or if you got some spare pads try them first once youve cleaned the rotors. if theyre ok with new pads then you know you need to sort the old ones. so try the oven maybe, or ive rubbed em up brickwork before to scuff em up a bit.

<cough>
sandy water
</cough>

ok, stuey, i

ll tell you tomorrow if i can endo again 😉

Thank you 😆