Brake bleeding question (bit long winded sorry)

[insane1400]

I have done my fair share of bleeding brakes over the years, mainly cars and only a few bikes (but never from when the system was bone dry). I recently rebuilt both my front and my rear caliper. I bled the rear yesterday without any issue.
So today I tried to bleed the front. All the pistons were in their fully seated position to start with, the bike has braided lines which were empty as was the resovoir. After 3 hours I wasnt getting any more air bubbles, but there was no movement in the pistons. So with the calipers fitted I put compressed air into the banjo bolt hole which got the pistons moving and continued to re-bleed the system.
After another 2 hours I wasnt getting any more air bubbles but I realised the inner side of the calipers hadnt moved, my compressed air from the banjo bolt pushed the outside pistons only and was also causing the pads to bind on the disc.

To try to fix this I am thinking to push the outside pistons back, then put a 5mm thick piece of steel between the pads but pack it between the caliper body to stay central and then pump the brake to get both sides to work evenly.

Your comments on wether this may or may not work will be appreciated.

[Hooli]

You're making it over complicated.

Just get a big syringe & fill the brakes from the bleed nipples, it pushes the air out much easier that way. Then when you're not seeing air bubble at the master cylinder, rebleed them in the normal manner.

[gsxbarmy]

I've certainly done it that way before @insane1400 but more so to free the pistons off.

Given you've just rebuilt your calipers - did you use red rubber grease on the seals/dust seals? What I found in the past (more so with the dust seals) is that they can make the piston "stick" when new until they wear in a little. If you haven't used red rubber grease (or don't have any) the other way I found I could lubricate them was to let the piston come out (almost all the way) then I wiped new brake fluid around the piston and pushed it back. Did this a couple of time so the piston moved a bit easier and it all bled ok. Depending on how much fluid you may use to lubricate though you may have to wipe away the residue once bled.

So all i can recommend is lubricate the dust seals and try again

[insane1400]

@gsxbarmy  When I assembled them I used brake fluid. Reason being I had read or seen something that said never use anything other than brake fluid in the calipers.
I agree that the pistons may be a bit stuck, worse case senario I suppose I will have to split the calipers again.....

[Basil Brush]

Once fitting new lines. I couldn't get it to bleed. Must have been there about an hour. Missies saw it wasn't going well. Ordered me in for a cuppa and a bun. Came out half an hour later - it had done it itself. Air rises...I'd left cap off and nature did its best.

[insane1400]

So my plan with the bit of 5mm plate worked a treat. it got the inside pistons working quick smart. After that maybe 15 mins of bleeding and I have a decent front brake. I have left it cable-tied overnight and see how it looks tomorrow.