Hi
My caliper ring seems out.
How can I fix this?

I'd suggest getting new seals, removing the piston, replacing the inner seal, then the outer and slowly sliding the piston back in, assuming there's no other damage.

If the piston has been out for some time, there could be corrosion and other dirt in there.

Cleanliness will be key to success.

Mike

Those rubber boots can only be fitted before the piston is inserted.
As said by mpirie, you need to remove the piston & boot first.
Ideally, remove the piston seal, clean the caliper bore, piston, seal & boot.
Then lubricate the piston seal with brake fluid & re-install.

Insert the outer diameter of the rubber boot into its retaining groove in the caliper housing.
Make sure it is pushed hard into the groove OR it will come out again !
lubricate the piston outer diameter with brake fluid & the small internal diameter of the rubber boot
The next bit is the difficult bit ! :
Insert the large diameter of the piston into the small diameter in the boot, stretching the boot lip over the piston with your fingers or eg a clean, but lubricated flat screwdriver.
At this stage the piston is NOT being inserted into the caliper bore.

It's not easy, but it is possible & may take a few attempts until you find the best method to suit you.
Once the boot is stretched over the piston, you can then line up the piston with the caliper housing bore & making sure it is "square!, slowly push the piston in until it reaches the bottom of the bore.
Job Done !

Good luck
(PS Practice makes perfect ! ) Paul,
2001 Discovery 2 TD5, 211,000 miles & climbing
2006 FFRR TDV8 Vogue 145,000 miles & climbing
Member of Midland (Land) Rover Owners Club, www.mroc.co.uk

Having done this myself numerous times, Pawl's explanation is word perfect. The only thing I would add is, if the piston has any heavy rust on it that won't clean off and leave a smooth surface, bin it and get a new one.

Thanks for responses.
Taking caliper apart is a little stressful for me.
Other issue is all pads are about same accept the one on the right outer side. That was almost on the metal.
Last week I changed the rears and the same side outer of right pad was on metal .
Is this a coincidence? 2010 3.6tdv8 180k km.
sold 06 td6 160k
Sold 03 td6 260k

I find the easiest way to get the seal over the piston is to fit the seal, offer the piston up pushing back against the seal, pull it forward a couple of mm to give clearance, use a pice of wood or one of the old pads to restrain the piston, then blow the seal over the piston with an airline...

Seal in position...

Click image to enlarge

Click image to enlarge

Great advice thanks Haylands. 2010 3.6tdv8 180k km.
sold 06 td6 160k
Sold 03 td6 260k

Can that piston cause vibration?
It happens if I brake while turning a corner mostly.
Will pad stick more if wheels are turned?
Because when cold it is all good. 2010 3.6tdv8 180k km.
sold 06 td6 160k
Sold 03 td6 260k

Yes the piston was stuck and was the cause of vibrations.
I tried to take it out myself but could not and almost dropped the car from jack while pumping the brake.
I took out the caliper and took it to a brake shop.
But while putting back caliper realized one seal was not fully in place at the rear side.
Always check job before leaving the shop  2010 3.6tdv8 180k km.
sold 06 td6 160k
Sold 03 td6 260k