Hydraulic Road Lever Bleed - London

timmyotool

Hi,
Would someone be able to recommend a bike shop/mechanic in London (preferably South) that has successfully bled a Shimano road hydraulic calliper for them.
The last bike shop I used apparently bled it 10+ times and I'm still left with a brake lever that bites just before it hits the drops, trapping my finger underneath every time which is very irritating!

I'd like to find somewhere that will be able to establish if this is an issue with the lever or the way it's been bled as it was fine when new.

fenix

Why would you have your fingers there in the first place ?

The Rookie

Because most people brake 2 fingered and with the natural hand position to do that it leaves the third finger under the lever tip.

Very easy to bleed, but maybe it doesn't need bleeding? Look at the pads, are they close on the disc or do they move an excessive amount before biting which would give you a long lever travel?

timmyotool

Well the bike was fine until a small loss of fluid (my fault, unscrewing something I shouldn't) so the solution was to refill the system.

As far as I'm aware on hydraulics the distance between the pads is basically governed by the fluid/pressure and there isn't really any customisability apart from that? (I know some levers have a free stroke screw).

The Rookie

Your awareness is wrong I'm afraid, the pads resting position is set by the square edged piston seals, sometimes when they are fresh built they are 'wetter' than normal and the pistons retract too far and it can take a while for them to settle.

To bleed the system to the right fill level the pistons are pushed back fully to ensure the system isn't overfilled, so every time they are bled the self adjusting process has to start again, this is usually quite fast on Shimano (Avid/SRAM can take a while) unless as noted above the seals are 'wetter' than normal for some reason.

There is no pressure in the system until you pull the lever, if it 'worked' off when there was no pressure they could never self adjust for wear!

So have a look at pad travel and compare the two ends of the bike.

timmyotool

Hi, thank you for the information, really helpful.

The pads are slightly further away than the other lever. And it is that distance that causes the late bite. i.e. there is no free lever movement before the pads start to move.

So in terms of a solution is this something that can be fixed or is it just a case of waiting for the pistons to settle and "un-retract" themselves?

ugo.santalucia

timmyotool wrote:

Hi, thank you for the information, really helpful.

The pads are slightly further away than the other lever. And it is that distance that causes the late bite. i.e. there is no free lever movement before the pads start to move.

So in terms of a solution is this something that can be fixed or is it just a case of waiting for the pistons to settle and "un-retract" themselves?

Normally if you squeeze the lever a hundred times, it should sort itself out

The Rookie

Or Google 'advancing the pads' basically take the wheel out and squeeze the lever so the pistons go out further than they can with the disc in the way and then when they retract they may end up closer to the disc.

Or pull and hold the lever and then lift the wheel and bang it down a few times, this can help the seal creep back a bit so you get less piston retraction.

timmyotool

Okay great, thanks for the advice, I'll give it a go.