I ride a Giant XTC on Kenda SB8. I keep them heavily inflated (pretty hard, my pressure gauge came up missing so I'm not sure on the exacts) but it seems after just riding to work and back I end up with tires deflated to the point i ride them for the trails and not the road. I'm a big guy (210lbs) but is it normal to need to keep repumping the tire EVERY time i hop on and ride the 1km to work? It seems like this problem is much more prevalent in the rear where i got a pinch flat a few weeks ago and replaced the tube. Thanks for any advice.