I am a fan of big tires especially on bikes that go fast. I found this Kenda 3.5″ wide tire on ebay for cheap and had to try it out. I believe the stock Urban front tire is 16 x 2.25″ so we added 1.25″ of girth to the original. The 3.5″ tire is also much taller despite still being a 16″ tire. I had to raise the front fender to keep it from rubbing. I’ve also put on a 3.55″ (90mm) rear tire on my current Urban Express. Wider tires are also taller tires. If you can spin them at the same rate, you’ll go faster.