My new Easton EC90SL fork on Bierwagen wouldn't fit a 28mm tire either. So, I've ended up with a 25 front/ 28 rear combo. Seems to work well for me.
Which 28s wouldn't fit?
Michelin seem to run wide. My Optimum Pros, which are listed as 25mm, ran a true 28mm on 19mm rims. While Conti GP 4 Season 28s seem to run about 27.5mm on the same 19mm rim and their 25mm run 25.5mm true. I know there are some other sizing discrepencies amongst other manufacturers as well.
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Birth Certificate, Passport, Marriage License Driver's License and Residency Permit all say I'm a Fred. I guess there's no denying it.