Helderberg

These are the wheels on my 7, Cannondale C4, double wall, 32-hole, and they came with Kenda K192, 35c 700 tires. I would like to go with a larger tire for gravel and light trail riding but am not sure how large a tire I can go. Unfortunately this is all of the information I have. Any help would be greatly appreciated and I will look for any additional information to add to this post.
Frank.

FiftySix

That bike has V-brakes? If so, the brakes shouldn't limit you.

What's the inside width of your fork, seat stays, and chain stays where the tires pass through?

hokiefyd 

You can measure to be sure. I assume no fenders, right?

Your fork should be no problem. Most are plenty large. You'll be tightest at either the seat stays or the chain stays. Typically, clearance is tightest at the chain stays, where they taper in to meet the bottom bracket shell. I'd imagine you could fit 38mm or possibly 40mm tires. But a quick measurement should tell you for sure.

Helderberg

The area at the base of the seatpost between the chainstays is 47mm. I am guessing a tire width at the sidewall of no more than 44mm?
Frank.

xroadcharlie

I've had a sort of obsession with fat tires (up to 2" / 50 mm) myself as of late as the best all purpose tire, But I see Giant has some expensive gravel bikes with 30 - 40 mm tires. Also many hybrid bikes, Which work well in gravel and on many trails have 32 - 35 mm tires. The stock 35mm might be fine, I'd probably go no larger than 38mm with some, but not too much tread, Especially on the front.

The roads and trails, Sometimes sidewalks I ride on are often rough and are shared with pedestrains, So the 1.95" tires on my bike are less of an impediment to my progress than then my riding conditions. Still I will probably go with a narrower tire next time. If I where commuting on good gravel roads any distance I could get up speed I think I would be inclined to go with the 38mm tire.

Weight might also play a role. I'm 160 lbs, So I might be better off with a 35mm tire. For heavy people, say 220 lbs, a 40 - 42mm tire might be best.

Helderberg

Thank you for this. What pressure do you run? I have been running 70-73 as close as I can tell with my gauge. I weigh 185-7 and would ride on mostly rough paved and small gravel.
Frank.

xroadcharlie

Your Welcome.

The pressure you are running seems reasonable. It will likely prevent pinch flats and provide low rolling resistance. I estimated 75 psi - rear / 65 psi front since it likely takes 45% of the total weight and will improve ride slightly. You could probably get away with 70 rear / 60 front. My 180 lb friend came over on his 35mm tires with under 30 psi. I was surprised he made it here without a pinch flat.

I think the main advantage of a wider tire, To 38 - 45mm is it would provide a better ride on less pressure. 35 - 38 might not even be worth the effort unless you need new tires.

FiftySix

That only leaves 1.5mm per side. Not enough room left over to get home if your tire or rim gets a good whack on a ride. Also prone to get sticks or rocks jammed between the tire and frame.

I'd guess 40mm would be the widest I'd go on the back tire. That'd leave 3.5mm per side.

Plus, tires don't always measure to their factory specs. Some are skinnier, some are fatter. The way the tire mounts to the rim has something to do with that, too.

hokiefyd 

You could run a 40-42mm tire with that clearance. At about 185 pounds, I'd probably try lower pressures. I'm 240 pounds and I used to run about 40 psi in the front and 50-60 psi in the rear on my 700x42 tires. With 650 wheels now, with about 50mm tires, I'm running 30 psi in the front and 45 psi in the rear. Larger tires are wonderful for this. The ride is so much more comfortable (especially on gravel) and the rolling resistance is on par with narrower tires with higher pressures.