35-54-37.5/35-54-39 bb axle?

[craigh]

If I replace the 128mm ('5T') bb axle on a cheap old hybrid with a 126.5mm ('5S') axle, will I notice any difference? Should I put a 1.5mm spacer between the r/h bearing cup flange and the frame, which would transfer the 1.5mm reduction in length to the l/h side?

[LWaB]

If you don't have >3mm of clearance at the chainrings/ RH crank to the frame, then use a spacer. Otherwise run it as it is and readjust the front mech.

[craigh]

Thanks!