I am hope to change my calipers tomorrow from 2 pot to 4 pot.Any tips would be helpful.
When bleeding them after fitting do i need to bleed the whole system or can i just do the fronts(i am not realy touching the rears at the moment).
Also should i top the brake fluid up with 4 dot or 5.1 dot (i did read somewhere that 4 dot was better for more everyday use)

 

You will just need to bleed, well fill and bleed the new calipers. But depending on when the fluid was last changed it will do no harm to bleed all the calipers and put in new fluid.

Dot 4 is what comes as standard.

To bleed the calipers you need either an assistant or a bleeding 'tool'.
I recently got a 'Vizibleed' one-man brake and clutch bleeding tool. It's basically a piece of clear hose with a one-way valve at one end. Cheap and easy to use.

 

i use singal person type blead kits.

but find it still better having a second person at hand.
while one pumps the brake pedal, the other releases the presure at the caliper niple
as an old rule, i was alwat tort to start from the furthest away to the nearest. from the cylinder.
but find it not much difference in practice