Hello, I have a tire size question. I have a Specialized Hybrid with 700 38C tires. I would like to upgrade these tires to something a little wider with a more aggressive tread for some mild trail riding. Does anyone have any recommendations on size and type? I would prefer not to have to replace tubes if I don't have to, they're relatively new. Many thanks in advance.

Randy

700C 40s are made and should still fit the frame. Bigger 700s are made but they may hit your frame. Roger

There is a limit both in what will clear your frame and in what will be stable on your rim. https://www.sheldonbrown.com/tire-sizing.html (Width Considerations). The tube is a non-issue, will just be very marinally thinner with a slightly larger tire.

More agressive tires may have clearance problems even in the size you currently have so be sure anything you choose will clear your fork and stays. Consider cyclocross tires as they are intended for off-road conditions and are made in sizes from 700x30 on up.

+1 on the advice above on frame clearance/mudroom.

In addition, while shopping for tires, note that the ISO rim diameter for 700c is the same as 29 inch. So you can look for not only for 700c but 29'er tires with ISO 622 diameter which should fit your hybrid rims. This can offer more choices than only what's under the 700c category of tires.

As for inner tubes, they usually just work with wider tires and go on easier in fact. However, if you have a smaller tube inside a significantly larger tire (e.g. two sizes up or more), and then you get a flat, unless you carry older style vulcanizing cement and semi-cured rubber patches, the newer patches won't likely stretch as much as the older patch, which means, any patches while the tube is deflated, will likely not hold if the tube stretches substantially to fit the larger cavity. I carry a spare tube for these purposes and save the punctured tube for home where I use traditional thin, soft rubber patches with vulcanizing fluid.