I'm also having trouble with climbs while on the trail. I'm set myself a goal of riding Monday, Wednesday, Friday on mix of flat and trail w/gradual inclines for at least 5-7 miles, then going to the trail that has some hard climbs on the weekend (Sunday morning). On the off days, I'll use two 20lb dumbbells and exercise the upper body while the legs take a break. Although that really doesn't constitute as "weight training for climbs", I see it has since I'm overweight (50+lbs), I will use my own body weight on the climbs as "weight training."