Hi,

Now I actually don't have a fat tire bike. It's the one bike I have never had ... yet. So I asked around and did a little research. Tire pressure seems to vary depending on the surface you ride; the soggier the surface the lower the tire pressure. So if you're on packed gravel or road/paved path your pressure could be low. But I suppose you already know that. Depends on your tire width and the surface.

A friend who rides a fat tire bike said they run as low as 5.5psi on muddy trails and more like 4.5 on sand and slightly higher than both on paved. They told me if you go too soft you'll actually feel the rims contact the surface rather than the tires absorbing a lot of the shock. I've managed to pinch flat many a road tire because it was too low so I suppose that could be an issue.

Try a tiny bit more pressure would be my guess.