Brake bleeding - didn't push pistons back... does it matter?

mcj78

Hi all,

As it says - bled my '07 Hope Mono Minis few days ago & just realised I didn't remove the pads & wedge the pistons back when I did so - they feel fine power-wise & modulation is good, however the lever seems to travel a bit before I can feel any resistance. Have I introduced the extra lever travel by not fully retracting the pistons? I bled them with everything in-situ, or has my bleeding maybe happened at a time when the pads need changed too & maybe this is causing it? Or is the main reason for removing the pads for avoiding contaminating them with brake fluid? Confussed.com

Cheers,
John

supersonic

You may have overfilled the system, so could get probs if they over heat.

I would remove the reservoir cap or lever bleed nipple, and push back home, catching excess fluid. Then replace the necessary bits carefully to stop air getting in. The bleed should still be good.

mcj78

Cool, sounds good - i've been going over it in my head & trying to work out the possible machinations of what's going on... i'll try that later if I ever get out of work... is it lunchtime yet btw?

Cheers,
john

TheEnglishman

The only reason to push the pads back is when changing fluid you make sure you change as much fluid as possible - old contaminated fluid is to be avoided at all costs.

When bleeding it doesn't matter as all you're trying to do is get all the air out.

Do cycle fluid brake systems not have a resevoir? I can't see them not but I've only ever done car and motorbike brakes. If they've got a resevoir then you can't over fill, unless you go over the guide 'max' line on the resevoir bottle. If you've got spongy brakes then you've either not got enough fluid in the system or you've(more likely) got an airlock.

mcj78

TheEnglishman wrote:

The only reason to push the pads back is when changing fluid you make sure you change as much fluid as possible - old contaminated fluid is to be avoided at all costs.

When bleeding it doesn't matter as all you're trying to do is get all the air out.

Do cycle fluid brake systems not have a resevoir? I can't see them not but I've only ever done car and motorbike brakes. If they've got a resevoir then you can't over fill, unless you go over the guide 'max' line on the resevoir bottle. If you've got spongy brakes then you've either not got enough fluid in the system or you've(more likely) got an airlock.

Hey, not sure if car & bike systems are different re. the workings of the reservoir - there is a reservoir of sorts, but it's not very big. On my Hope's at least I thought the order of the day was to have as much fluid in the reservoir as possible to combat the possibility of trapped air being compressed instead of the fluid being pushed along the lines & moving the pistons - I get you re. the air in the lines though, i'll re-bleed when I try re-setting the pistons back as far as they'll go, I used a fairly long hose to bleed them & made sure to keep drawing fluid through after bubbles stopped appearing, i'll maybe reverse the bleeding this time & use a syringe to pump fluid up from the bleed nipple end just in case that helps dislodge any air that might still be there.

Cheers guys
john

supersonic

They have a very small reservoir: but if you overfill the system (which can be done!) then when the system heats up it is too much for the reservoir as it expands (with some brakes).

The Rookie

bikes run a sealed system, cars and MBs open, so if you overfilled you can get issues as SS said, also you won't be able to fit new pads without letting the excess out!

supersonic

Sealed, but still an 'open' system, ie an expandable bladder to cope with heat, and to self adjust pads. Problem is it can be overwhelmed.

Closed systems have no bladder and use an adjustable screw.