Ask Mountain Bike Action: Tire Questions

What’s the shelf life of a spare tube? How long is too long to have a tube rubber-banded and shoved into your backpack? Would you replace them annually?
-Steve, who avoids thorns
Mountain Bike Action: We wish we went a year without a flat tire. Tubes will last surprisingly long if they are packed properly and kept out of direct sunlight. The biggest enemy of spare tubes stashed in your hydration pack or seat pack is other stuff, like a multi-tool, pump or tire levers. These items may be rubbing against your tube, and that will make it useless when you need it. So, pack it carefully and rotate it out of the pack once a year, even if you are just swapping it with one of the tubes already in your tire. One other tip, put your spare tube in a resealable plastic baggy and mix some baby powder in there.

Does a tire have to be UST certified if I convert my wheels to tubeless? And if they have to be UST tires, do I need to use a sealant or can I just use the tape and valve?
–Catalino, ready to float on air

Mountain Bike Action: UST stands for Universal System Tubeless, which means that the tire is certified to be run on a tubeless-tire rim without added sealant. These tires are heavier and harder to mount than a traditional clincher tire made to be used with a tube. The beauty of a tubeless conversion kit is that it allows you to use a standard clincher tire with sealant on any style rim (tubeless or conventional). A rider will get the most benefit (weight savings) by not using a UST tire for his conversion. So, no, you don’t need to run UST tires for your tubeless conversion project. And no, you shouldn’t have to use sealant in a UST tire. But we would. The sealant will seal small punctures, and the tire is less likely to loose air pressure over a time.

Have a Specialized Rockhopper 29er with 2.0 tires. What is the widest tire I can mount to my wheels?
 –Heath, looking for more beef

Mountain Bike Action: It all depends on how much clearance you have between your chainstays, seatstays, seat tube and any braces that may be included in the rear triangle to add stiffness. Specialized gives the Rockhopper rider a lot of room to work with. The real catch is that tire companies measure their tires differently. Not all 2.3-inch tires are the same. The tire’s volume and sidewall construction can make one company’s 2.1 another’s 2.3. You need to visit your friendly local bike shop and eyeball the tires. (They should let you mount a tire to your rear wheel.) Put the wheel in your frame and see how close the tire knobs come to any part of the frame. There is always some amount of wheel or frame flex (especially with a 29er). Our rule is there should be at least a nickel’s worth of clearance (the thickness of a nickel, not the width) between the tire and the frame. Up front, you have a lot more room to play. Still, check the clearance between the fork sliders and the tires’ knobs. Again, less than a nickel and you will make contact while riding.

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