Totally confused about hydraulic disc brakes...

[roger06]

Hi

I've bought a Dawes MB with Shimano M395 hydraulic discs. I've never had hydraulics until now.

I'm in the Alps doing a bit of gentle off-roading but using the brakes a lot so I don't keep over taking my boy (and I'm a bit scared to tell the truth!). I'm assuming the pads have, quite naturally, worn down as on mechanical discs.

So, while they still work, there's now a lot of travel in the lever, having to pull it almost to the bars. I've googled it but I don't recognise any adjusters and I've no idea whether I need to bleed, find an adjust screw, or take the wheel off and pull the lever as one vid suggested.

I'd really like to get them biting a bit sooner so would be very grateful for some advice.

Thanks

 

[lpretro1]

Do not take the wheel of and then squeeze the lever - you will push the pads to far out and have beggars own job getting them separated again!
There is no 'adjustment' on a hydraulic brake - they are self adjusting as the pads wear.
It sounds a simple case of worn pads - take the olds ones out (held in by a split pin or a small screw in pin )- push the pistons back carefully with a ring spanner or similar (not anything sharp like a screwdriver) - apply even pressure in centre of piston so you don't twist them. Insert new pads, put wheel back in. Slack off the caliper mount bolts and then squeeze the lever a few times to settle the pads then holding the lever re-tighten the mount bolts. Job done. Good idea to clean the rotor before you pop the wheel back isopropyl alcohol or a proprietary disk brake cleaner. There is no need to bleed the brake unless you have opened up the system at some point and let air in.

 

[Nibor]

Methelated spirit in the absence of isopropanol

 

[Smokin Joe]

There is no 'adjustment' on a hydraulic brake - they are self adjusting as the pads wear.
It sounds a simple case of worn pads -

A bit of a contradiction in terms there, if they are self adjusting lever travel won't be effected by pad wear. Brake pedal travel on cars never alters from new to knackered pads.

It is either low fluid level (If that is the case check for leaks) or air in the system.

 

[Yellow Saddle]

Pump the brake. If the lever stiffens up, there's air in the system and it needs bleeding.

 

[roger06]

Thanks guys.

Pumping the lever makes no difference (unless you're talking hundreds of time - I pumped it 10 to 20). Pads look like they have about 1.5mm. I think I'll see if I can replace these. I can live with a bit of lever travel for now but don't want to ruin the discs.

I assume I only have to pull out the pin and lift out the pads for a proper inspection?

cheers

 

[glasgowcyclist]

I assume I only have to pull out the pin and lift out the pads for a proper inspection?

You'll need to remove the wheel first, your pads drop out from the bottom of the caliper.

 

[lpretro1]

A bit of a contradiction in terms there, if they are self adjusting lever travel won't be effected by pad wear. Brake pedal travel on cars never alters from new to knackered pads.

It is either low fluid level (If that is the case check for leaks) or air in the system.

Yes, but it gets to the point where the pads are so worn (in this case the OP says they are only 1.5mm which is very worn) the pistons have no movement left so hence the long lever travel & lack of bite

 

[Yellow Saddle]

If there is 1.5mm pad left, you still have 3/4 of the pad material left. The

Yes, but it gets to the point where the pads are so worn (in this case the OP says they are only 1.5mm which is very worn) the pistons have no movement left so hence the long lever travel & lack of bite

No. The pistons have no limiter. You can pop them right out without a pad in there. They will travel until they hit each other.

With 1.5mm of material left, you are only halfway through the pad's life. Use them until they reach about 0.8mm - even less if they wear very evenly.

 

[Pale Rider]

You'll need to remove the wheel first, your pads drop out from the bottom of the caliper.

The pads come out of the back of the calliper.

Removing the wheel is not a good idea because you will need the rotor to gently pry aganst to push the pistons back - plastic tyre levers are good for this.

As it's a Shimano brake, there will be probably be an anti-rattle shim - bendy piece of metal - wrapped around the pads.

Look carefully as you take it out so you can replace it the same way.

 

[glasgowcyclist]

The pads come out of the back of the calliper.

I have the M395 calipers (pictured) on my bike, the pads drop out the bottom. So, unless you want to make a simple job extremely difficult, you'll need to take the wheel off. It is impossible to take the pads out the back of this caliper.

 

[Pale Rider]

I have the M395 calipers (pictured) on my bike, the pads drop out the bottom. So, unless you want to make a simple job extremely difficult, you'll need to take the wheel off. It is impossible to take the pads out the back of this caliper.

View attachment 368793

Fair enough.

But I'm perplexed because I watched our cycling group leader change the pads on a budget Shimano brake for one of our members at the roadside, and I'm sure the wheel wasn't removed.

Must have been a different model of brake.

Maybe it was the other type of mount and that made the difference.

 

[Pale Rider]

Further perplexed.

This vid, albeit for Deore and XT callipers, shows the pads going in and out of the back of the calliper.


View: https://www.youtube.com/watch?v=BEJ2TBQjUW0

 

[glasgowcyclist]

Here's the video of the pad removal, although it shows the other option of taking the caliper off the frame.

Relevant part starts at 2m30s

 

[roger06]

Thanks guys, that's really helpful. I think there's a bit of life left in the pads - I hope so as they are 16€ a pair out here! But I'll change them if really worn as don't want to wreck the disc...