What is the widest tire that can fit on a trailblazer short swingarm? I just bought the suggested 4.00 dunlop, but it looks too small with the big valanced fenders. I have a 120 shinko on the rear, but it fouls the chainguard!!! Any suggestions??? thanks BRian
Risking telling you something you know already, the "4.00" and "120" are 'section widths', not overall widths. And, perhaps curiously,the same 'section width' from a different tyre maker can be wider or narrower overall (but not by much).
The 4.00x18 K70 is 4.17" wide overall. Otoh, 4.00x18 tyres in modern designs like the Avon Roadrider, Bridgestone Battleax, etc. are around 1/2" wider (e.g. the Roadrider is 4.6" wide overall). However assuming the Shinko 120/90x18 is the 230 Tourmaster(?), Shinko reckons that's 4.8" wide overall, so not a lot of difference.
Btw, one thing to bear in mind with 120-width tyres is makers don't usually recommend 'em on the old British rim widths. Trailblazer's rear rim is WM3? If so, that's equivalent to modern "2.15"; 120's are normally recommended on a 2.75-width (WM4.5 equivalent) rim and not narrower than 2.50 (WM4 equivalent).
Obviously, a 120-width tyre can be fitted physically on a WM3/2.15 rim but how the carcase bends varies between tyres from different makers - e.g. I know a 120/90x18 Roadrider enlarges the overall diameter!
Otoh, while a 2.50-width (WM4 equivalent) rim is normally recommended for a 4.00x18 tyre, minimum is 2.15 (WM3 equivalent).