Hi. I have an old Orbit XL-ii road headset. Its well used and probably 20 years old. Rather than replace the bearings I am going to get a new headset. The steering tube measures 1". But, when I bought the bike, the headset had a shim between the steering tube and headset. So, does that mean I need a 1-1/8" headset? How do I know what I need?