Ykick said:
CST Ciudad makes a nice 700c “city” tire. Supposedly kevlar and my coworker reports holding up great on his 45lb eBike.
All this Kevlar business, I dunno? Seems like an awful lot of “sales engineering”. I’ve had dozens of flats on motos & bicycles. Yep, I’ve used Marathons and Big Apples and no measurable improvement.
It seems that given the right angle, a somewhat sharp solid object will always find a way to puncture/damage a tire. Kevlar be damned.
The CST Ciudad is a good example of a moderately armored tire using multiple prevention measures. It has an aramid (Kevlar) textile belt, plus an elastomer breaker belt probably made of urethane rubber. I have used this model in both 32mm and 42mm sizes, and it's a good utility tire. I expected it to be a faster tire based on its tread pattern, but its generous puncture protection makes it a relatively slow tire. Its modest drag should not prove to be a problem for any e-bike, though.
A Kevlar or other textile belt offers good protection against tearing of the casing, but it's a woven material. Its usefulness is limited against finely pointed objects like wires, thorns, and glass slivers, which can simply pass through gaps in the weave. I have observed damage to my Big Apples from objects that sliced away a flap of rubber all the way down to the casing, but failed to breach the Kevlar belt.
A rubber breaker belt uses a different approach that offers protection against small sharp objects that might be able to pass through a textile belt. First, it simply thickens the tire's wall, so a foreign object must be longer to reach the tube. Second, it's not made to provide grip like tread rubber, so it tends to eject penetrating objects rather than holding onto them like tread rubber does.
Some breaker belts, like those in the Ciudad, are relatively thin and hard, like Mr Tuffys. Others, like those in the CST Salvo or Schwalbe Marathon Plus, are composed of thicker, softer rubber for increased protection. They all add weight and harm ride quality to some degree, but they're much more effective and convenient than similar belts applied inside the tire as an add-on.
Tires like the Maxxis Hookworm and CST Cyclops resist punctures by virtue of their thick and robust construction. They have no additional puncture-specific protective measures built in.
