Can give you 3 reasons: 1. It's a shit grind 2. You put tar on a shit grind 3. Your frame is stiff as it is, the booster is making it worse. I promise you! Had the same exact problem with my 06 zoo.
Every time I watch that vid I die a little inside. Sidewop at the end is just massive. And dude who's looking for an Adamant, a friend of mine is selling one, he's called Shaun H on here!
Halfords 2.1-2.5 tube. I've been running them since I can remember and hardly EVER pinch. What tyre you got at the moment? If it's a single walled one, that's why!