This :
quote author=RickS link=topic=961.msg8222#msg8222 date=1394461877]
Tires for these bikes are not the same as a standard simplex 2.50 x 26. They used a 3.00 x 27, which used a different diameter rim. Being as Coker doesn't make this size, I choose to go with a 3.00 x 21 motorcycle tire. These are close to the correct rim size, and I have seen an article where these were used with success. Being that the only tread pattern I could get for these was for a trials bike, they are very aggressive. If I was going to order another pair, I would choose to get 2.75 x 21, as the slightly smaller size would leave a little more frame clearance.
/quote
From :
http://www.simplexservi-cycle.com/index.php?topic=961.0#quickreplyPete .