Define big bore. I decided to use 14.5mm diameter pistons because I found that they worked the best on my car. It is very light so the bigger shocks just didn't let the suspension work, it felt like a plank. Losi is 15mm and considered bigbore, THE Shocks are 0.5mm less, that 0.25mm difference on the radius. Not a whole lot, but it makes a difference.