Hello, just bought a bike off eBay. It arrived with the front brake unmounted. I’ve mounted it but whatever I do, the brake pads rub on the rotor thing.

Also, the rear brake is really lacking stopping power. You need to pull the lever right to the bars to get it to bite at all.

I have no experience with disc brakes (I’m old and a roadie). How do I adjust them?

Depends on what brakes they are

Can you provide more details front or rear, make and model

Depends on the brakes, what are they? Some have more adjustment than others.

Front pads may be too far in. Take the wheel of and separate the pads with a tyre lever or screwdriver. Then put the wheel back on and try a few squeezes of the lever. Once the gap is right then centre it.

For the back it might need a bleed. First I’d give several squeezes in quick succession and see if that makes a difference. You can also give it a few squeezes with the wheel out which may move the pads in a bit.

Rear brake: either needs a bleed or take wheel out, pump pistons out, reinsert wheel. If still spongy, bleed.

Front brake: Put wheel in, loosen caliper bolts (or attach them so they just have a tiny bit of movement with your fingers). Spin wheel, gently stop wheel with front brake. Once stopped, lock front brake firmly, then half a turn at a time, tighten each bolt.

Usually works, if not the rotor is a bit warped usually and it will take some more fettling or doing by eye.

Can also buy a caliper alinmnet tool (or you used to be able to) which was pretty damned useful.

Are they cable disks or hydraulic?