Trying to fit the bb7 on my chineses road frame and the front wheel wont go in , the disc hits the caliper .

Disc is 160 , forks are post mount .

i have the correct spacers .

Any ideas ?

in what way does the disc hit the caliper – does it go into the slot but catch at the top, or what ?

Yes, catches at the back. Wheel won’t go .
Measure the post mount and it is 74mm which I think is correct.

Have you tried more spacers?

Are you using the avid tri-align washers? If not, then I think you may need to in order to get the spacing right.

Using the spacers which came with the brakes.

Is it possible that the fork has been designed around a 140mm rotor?

But it is same at the rear , so I think you could be right .

Looking at the Sram website, I have ordered some long bolts and spacers.
Hopefully it will do the trick.

I found that initially the BB7 would foul / with the rotor, but when came to align it all up, it sorted itself out. I think it fouled particularly when I used normal bolts and skipped the Avid bolt/washer combo.