Chicagomarkk

All

I recently purchased a GT Transeo 3.0 and still learning about parts and accessories. what I'm looking for is a mountain bike type of tire. The current tire size I have is 28x1 5/8 x 1 3/8. Do I have to stay with those exact measurements or is there a little flexibility?

JonathanGennick 

It's mainly about what will physically fit into the frame. Look at where your current tires sit between the chain stays and the seat stays, and in the fork. Look at how much room is on either side. Keep in mind that you do want some amount clearance, maybe an eighth-inch on either side just to be safe. It's the clearance that is your limiting factor.

I you are trying to push the limits, sometimes you just have to mount a tire on the bike and see whether it fits.

BTW, 700c tires will fit that bike. So it's ok to buy one that reads, for example, 700c x 40, or 700 x 40c. (In Europe it's common to refer to tires like have as 28-inchers, and your brand Schwalbe is a European brand).

You can also look at 29-inch tires, which are the same as your 28-inch. For example, here is a 2.0-inch-wide tire that would fit your rim (but maybe not the available width in your frame):

https://www.universalcycles.com/shop...5&category=196

This is an urban tire close to a half-inch wider than you currently have. You may not have that much available space on either side of your current tire in your frame.

Edit: Found some images online. The spacing looks tight in the chain stays, just behind your crankset. Hard to tell from an Internet photo, but that spacing there looks to be your limiting factor, and I'm not sure you can go much wider than your stock tires.

Wanderer

Mark, what sizes are you considering? Its easy to go more narrow, for different characteristics. You have to measure to go wider.