recently took off my tubed 29x2.25 riddlers but if I remember correctly I was very happy with 25psi front / 35 psi rear & I currently add a decent 240lbs w clothes, trunk & water bottles, etc to the weight of the bike. I used the bike on a mix of surfaces & love the width & speed of the riddlers. recently mounted up some 29x2.0 studded marathons which are yet to be tested. it's a lower volume tire so I may try 40 front 50 rear today