Best way to mount the new treads

Q: I am installing oak treads on my stairs. I will be putting these over the ping treads already in place, that were under the carpet. I have cut the lip off the old tread. I would like to know the best way to mount the new treads.

I would prefer not to have to face nail. Can I use a good adhesive? I do not have access to the under side of the stairs.

A: I would use a polyurethane adhesive; but without a couple of nails to hold it in place, I think you risk the tread shifting out of its spot.