I’m a new rider (since February, age 49), and I’m currently riding a Nimbus II that has been moderately “Muni-ized” with 145mm Qu-ax cranks, K-rad 24 x 2.3 tire, and metal Odyssey pedals with the little spikes. I just purchased a new Nimbus 24 Muni for my 13 year-old, who has been riding a 20" that he got for Christmas.
Anyway, it is quite shocking how much heavier the Muni feels compared to the Nimbus II when you grab one in each hand. I rode them back-to-back tonight, and I definitely expended a lot more effort on one of the usual loops I do when riding the Muni. Part of this was probably due to the greater rolling resistance of the larger tire, but the weight difference seemed to play the major role. My Nimbus II felt like a sports car after hopping off the Muni! On the plus side for the Muni, the increased mass seemed to cut down on a lot of the “jerking” that I do when riding across rough ground–it was easier for me to be “smooth” (relatively speaking:)).
My son is having a rough time with his new Muni. Even though his skills far exceed mine, he only weighs about 85 lbs, and he gets tired on the new Muni very quickly when we ride any distance. He is growing fast however, and I’m sure he will be doing fine in no time.