No spreading of frame necessary. I upgraded old bianchi 126mm rear spacing with 6600 group 2x10. Kept the old wheels with 7 speed cassette/hub. I took old cassette off. Modified the 10 speed cassette minus one cog. put the extra spacer at the very back near wheel, then place "9" speed cassette then lock ring. I used 10 spd chain and tuned the shifters & derailleurs. Smooth shifting, no skipping or delays.