legacycentral bbs

My friend let me borrow his rims and the only problem i have is that center part of the wheel is not wide enough to seat flat against the rotor. Could a hubcentric ring possibly fix this problem?

It may.....but I don't know I'd recommend that due to the offset issues caused by the spacer. The wheel most likely wouldn't clear the fender since it's moved out further.

I think the rim would have to be too big for it to work,not too small.

^correct.
A hubcentric ring centers a wheel on the hub for use w/ flanged lugnuts. If the center hole of the wheel does not fit over the hub, a hubcentric ring won't help.
What I'd like to know is whether a hubcentric wheel can be used w/ conical-seat lugnuts.

with tapered lugs you don't really need it to be hubcentric or have a ring. The lugs are going to keep it centered regardless.