Originally Posted by
fietsbob
Open end headset wrenches are 1/8" thick, and can be purchased thru many sources.
I have a pair of 40/36mm wrenches for a 9/8" headset.
from Park, a bike tool company.
(and some 32mm ones for 1" headsets.)
the half MM is odd, .. Maybe a pair of 36 will do,
36 is also used on the threaded headsets on my Brompton,
another 1.125" threaded type.
Just to disambiguate, 9/8", 1.125" and 1 1/8" are all the same size. I know I've fallen for it before. 36mm certainly points towards a 1 1/8" headset.
If you're only picking up one headset wrench and plan to use an adjustable for the locknut, you'll need at least a 12" adjustable. A large adjustable will solve the .5mm (500 micrometer?) discrepancy as well.