27" x 1" says the tag on the rim. Checking out Niagra online and I run across 27"x1-1/4" or 1-1/8"...will these fit? Just how big can I go on these rims?

Also, what does anyone know about Cheng Shin tires...they are going for $7- $10 but the average seems to be around the $18 range for others....are these really that inexpensive or are they good for 20 miles only?

Last question....what's "gum" wall?

Thanks in advance.