They are 19mm internal and 25mm external.
There is only clearance for a 23mm tyre up front
Was looking for a picture to mark up, and somebody has already done it. With a relatively high pressure road tyre and no sideways landings off jumps, you're not all that likely to encounter this situation where the hoop stress in the carcase is pulling the bead with no restraint from the bead hook.
Carcase is more British and more archaic, which fits my style. Carcass wins about 10:1 in google results, reflecting its being more American and more modern.
Was looking for a picture to mark up, and somebody has already done it. With a relatively high pressure road tyre and no sideways landings off jumps, you're not all that likely to encounter this situation where the hoop stress in the carcase is pulling the bead with no restraint from the bead hook.