thanks for the input.
215-60-15 is really close to the height (- 0,16%) of the original 185-70-15.
I think 215 is right with on an 7 inch. 185 is to small.
245-60-15 also close to the height (-1,03%) of the original 215-70-15.
I think 245 is the right with on an 8 inch. 215 is to small.
The only problem is that the only match tires i can find in this dimention is AVON and they are so expensive.