The New Specialized Riprock bikes are innovative bikes for kids with 20x2.8 tires, low stand over height and a decent parts spec. There is just one problem though, they are heavy. The fork alone weights in at 5 pounds and doesn't work all that well anyways. The goal with this bike was to lighten it as much as possible and as affordable as possible. Well, since I build wheels, and wheels are the best upgrade you can make on a bike, i will start with that. The Rear hub spacing is 135mm QR and the front fork is a specialized 110mm qr design. You wont find any aftermarket Boost QR hub, so i will be using a Bitex 100mm QR standard hub and will be swapping forks too. The stock rims have about the same profile as a Velocity Blunt 35, 35mm external width and 30mm internal width, 28 holes drilling. The Rims are non tubeless and are said to be made by Alex rims. I will be reusing the stock rims because it is hard to find a lightweight wide 406mm 20 inch rim, so here we have one at 342 grams. Sapim Race spokes and polyax nipples are my go to and are much higher quality than stock, and they are also lighter so less rotating weight.
Drinking Cappuccino and building wheels mixes well.
Stock front wheel weight- 1012 Grams
Stock rear wheel weight- 1510 Grams with Cassette @300 Grams
Custom front wheel weight- 790 Grams
Custom rear wheel weight- 1208 Grams with Cassette @300 Grams
So the total weight saving of the wheelset comes in at 524 Grams, which is 1.15 pounds of rolling weight, this has to make a huge difference for a 45 pound kid!!! I haven't played with going tubeless, but would assume you could save some weight there too. Each tube weighs a little over 200 grams.
-I measured the rim ERD at 392.5, just for reference.
So, what about the whole bike you ask? while I didn't weight the stock bike, it is said to weigh in at 27 pounds, the weight after wheels, a new fork and a few parts is 21 pounds.