Looking for a 29x2.25 tire for my first sprint tri-athlon I have entered a sprint triathlon on a whim and have a 29er mountain bike. Is there a road suitable tire for a 29x2.25 wheel out there? Looking for something that will give me good roll and as little resistance for my 110kg as possible.
Yes, there are tires out there that are smooth and will fit that rim.


Your rim diameter is 622mm. Same as most road bikes, most cyclocross bikes, many touring bikes, many hybrids, and some cruisers.
Figure out your rim width in millimeters. It might be printed on the wheel somewhere, it might be in the specs for your bike, and you might have to borrow some calipers to figure it out. You're looking for the inner rim width that fits outside the beads.
You should now have figured out the ISO size of your rims.
Work out what the acceptable tire widths. Something like Sheldon Brown's tire width to rim width chart should help.
Look for tires within the range you've worked out. I suspect 45-622 will be your smallest acceptable size and 60-622 is probably a tiny bit bigger than your current tire. If you go a bit smaller (35-38mm), you'll be risking pinch flats and rim damage, but there's a lot more tires available.


You'll probably find that tires marketed for comfort hybrids, cruisers, touring  or "urban/trail" bikes are were you'll find a big enough smooth tire.

Schwalbe makes the Super Moto in 60-622, which is specifically marketed as a competition-appropriate smooth tire for a 29er.

If you're willing to spend a lot more, consider replacing the wheels with Cyclocross wheels, some other 622mm wheel with a slightly narrower rim than a 29er usually comes with. That would allow you to get into the wide end of regular road tires where there's a ton more choices made for competition on paved surfaces.

Note: smaller tires will change the handling and lower the bottom bracket closer to the ground, so don't get too crazy.