Been quite a few threads on kids' geared mountain bikes lately, and ideas on how to get their weights down, so I thought I'd present my own project.
A little background: I have a 6 y/o son who started racing BMX shortly after his 5th birthday in 2008, and quickly accumulated local and state wins, eventually taking an ABA Northern California State Champion title/plate for his age class that year on an 11-lb. bike built and spec'd by myself. He used the very same bike (re-geared, and with slightly modified ergos) to earn a championship title for his age group in a local kids' triathlon series (50m swim, 4 mile bike, 1 mile run) in 2009. For these little guys (and gals!), bike setup can be every bit as important as how quickly they can spin those pedals -- especially when you have a little guy like mine, who at 46" and 45 lbs, is in the 15th percentile for his age.
So when he mentioned that he wanted to start MTB racing in 2010 (same club that runs the triathlons), I adopted the same (admittedly obsessive) approach that I had with his BMX and Tri racing. (He's grown tired of BMX, but will continue with Tri's for 2010.) After a fair amount of research, it became quickly apparent that even the respected manufacturers are not willing to put too much effort in spec'ing geared 20" mountain bikes (and perhaps, justifiably so). Some of my priorities were:
Geometry - This always comes first, whether it's my bike or my kids' bikes. If the bike doesn't feel right, they won't want to ride them. Fortunately, with experience from his BMX bikes, I had a ballpark idea of what types of numbers I was looking for -- around 17" top tube, and 12" or less of seat tube. The first MTB he tried was a Gary Fisher Precaliber, and while he was able to ride it, it was quite apparent that the top tube was too long -- his upper body was too stretched on it. (And the Fisher website confirms it -- 504mm top tube, almost 20"!) Most other bikes were in the more reasonable 16.5-18" top tube range. You also want to consider crank size -- you will see everything from 120mm to 160mm on these kids' bikes -- a 40mm range of variation! That's a huge range for an adult, let alone a young child. My son was spinning 135mm cranks for BMX and Tri's, but I wanted to focus on 140mm cranks for this project -- he's growing, and he can use the additional leverage when climbing bigger hills.
Weight - A high priority, but it seemed that everything was at least 25 lbs. Hmm, being somewhat of a weight weenie, I knew I was going to need to do some tweaking regardless of which bike I chose. Based purely on subjective feel, the Scott Scale JR 20 seemed the lightest (albeit not by much). The Kona Shred 2-0 (last year's model, with double chainring) was an absolute TANK -- in a bad way. I really wanted to like that bike, especially with its disc brakes and shorter frame, but its heft was undeniable.
Gearing - The types of riding we do locally require some climbing, so that ruled out single speed. Most of the bikes I was looking at were 2x6 or 2x7, but I was initially convinced I needed a triple up front (and for a while was looking only at the Ibex Alpine 320k, which fits that description). But for a 6 y/o with no previous multi-gear experience, I realized that managing gears front and back would be sensory overload at this age. So I was determined to come up with an optimal range of gears with a single chainring up front, even if it meant some customization.
Suspension - Unfortunately, at this price point ($300-400ish for a complete bike), they can't afford to spec a quality suspension fork for 20" wheels -- nor is there a market for one among the OEMs. In fact, you're pretty much going to find your choices limited to Spinner Grind, RST Capa, and SR Suntour -- all simple spring/elastomer designs. Make no mistake, these all pretty much work the same (which is to say, badly), and any differences you may see can be attributed to varying quality control (or lack thereof). I have seen a Spinner Grind on a one bike require my full weight to compress, but another Spinner Grind feel properly sprung on another bike. Similar results with RST Capas. So my advice is, don't let the fork model be a deciding factor in your choice of bike -- they're all crap, but it's what we are given, so once you've found the model of bike that suits your child's needs, make sure the fork can compress without Herculean effort.
With the above in mind, I was leaning toward the Ibex Alpine 320k, the Scott Scale JR 20, or the Marin Hidden Canyon. The Ibex was hands-down the best-spec'd out of the bunch -- and also unavailable, with Ibex now out of business. The Scott was nice, but nearly the same cost as the Ibex. Marin was not particularly a standout in any area, but it fit my son reasonably well, but my sister-in-law works at a local sporting goods chain that carries them, and I could get 25% off its $330 retail price. Knowing that I was probably going to spend some money customizing the bike, I decided that buying the Marin at discount was my most cost-effective choice.
Then fortune struck. The local sporting goods store had an unridden 2008 model onhand that they could not sell at retail because it had unusable cranks (long story). They were willing to sell me the bike for $100 (while signing disclaimers acknowledging it was not warranteed or returnable). I jumped at the opportunity to take the bike down to bare frame and fork, and start from scratch on a custom build.
Within hours of taking the bike home I was removing old parts, placing orders for new parts, and scrounging around for other parts from around the garage. Here are some of the key components that were replaced:
End result: a sweet 1x9 setup that weighs 20.2 lbs. sans pedals (20.8 lbs with), compared to its stock weight of 25 lbs., and has already provided the little guy with tons of grins on his first trail ride during winter vacation. Only changes I plan on making are going with a 34t chainring to give him some extra advantage for climbing, and a chain guide like the one from Paul Components.
I could have easily saved a bit more weight by going with SUN CR-18 rims (350g each, vs. my 410g Crupi/Rhythms) but I'm a sucker for blingin' white rims. Other areas for weight savings would come at significantly higher cost: SRAM X-0 short cage rear derailleur (100 grams ligher, $160); KCNC Scandium seatpost (40 grams lighter uncut,$90); Xpedo flat pedals (60 grams lighter, $80). But a combination of these could easily take the bike weight below the magic 20-lb. mark.
A few pictures below.
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A little background: I have a 6 y/o son who started racing BMX shortly after his 5th birthday in 2008, and quickly accumulated local and state wins, eventually taking an ABA Northern California State Champion title/plate for his age class that year on an 11-lb. bike built and spec'd by myself. He used the very same bike (re-geared, and with slightly modified ergos) to earn a championship title for his age group in a local kids' triathlon series (50m swim, 4 mile bike, 1 mile run) in 2009. For these little guys (and gals!), bike setup can be every bit as important as how quickly they can spin those pedals -- especially when you have a little guy like mine, who at 46" and 45 lbs, is in the 15th percentile for his age.
So when he mentioned that he wanted to start MTB racing in 2010 (same club that runs the triathlons), I adopted the same (admittedly obsessive) approach that I had with his BMX and Tri racing. (He's grown tired of BMX, but will continue with Tri's for 2010.) After a fair amount of research, it became quickly apparent that even the respected manufacturers are not willing to put too much effort in spec'ing geared 20" mountain bikes (and perhaps, justifiably so). Some of my priorities were:
Geometry - This always comes first, whether it's my bike or my kids' bikes. If the bike doesn't feel right, they won't want to ride them. Fortunately, with experience from his BMX bikes, I had a ballpark idea of what types of numbers I was looking for -- around 17" top tube, and 12" or less of seat tube. The first MTB he tried was a Gary Fisher Precaliber, and while he was able to ride it, it was quite apparent that the top tube was too long -- his upper body was too stretched on it. (And the Fisher website confirms it -- 504mm top tube, almost 20"!) Most other bikes were in the more reasonable 16.5-18" top tube range. You also want to consider crank size -- you will see everything from 120mm to 160mm on these kids' bikes -- a 40mm range of variation! That's a huge range for an adult, let alone a young child. My son was spinning 135mm cranks for BMX and Tri's, but I wanted to focus on 140mm cranks for this project -- he's growing, and he can use the additional leverage when climbing bigger hills.
Weight - A high priority, but it seemed that everything was at least 25 lbs. Hmm, being somewhat of a weight weenie, I knew I was going to need to do some tweaking regardless of which bike I chose. Based purely on subjective feel, the Scott Scale JR 20 seemed the lightest (albeit not by much). The Kona Shred 2-0 (last year's model, with double chainring) was an absolute TANK -- in a bad way. I really wanted to like that bike, especially with its disc brakes and shorter frame, but its heft was undeniable.
Gearing - The types of riding we do locally require some climbing, so that ruled out single speed. Most of the bikes I was looking at were 2x6 or 2x7, but I was initially convinced I needed a triple up front (and for a while was looking only at the Ibex Alpine 320k, which fits that description). But for a 6 y/o with no previous multi-gear experience, I realized that managing gears front and back would be sensory overload at this age. So I was determined to come up with an optimal range of gears with a single chainring up front, even if it meant some customization.
Suspension - Unfortunately, at this price point ($300-400ish for a complete bike), they can't afford to spec a quality suspension fork for 20" wheels -- nor is there a market for one among the OEMs. In fact, you're pretty much going to find your choices limited to Spinner Grind, RST Capa, and SR Suntour -- all simple spring/elastomer designs. Make no mistake, these all pretty much work the same (which is to say, badly), and any differences you may see can be attributed to varying quality control (or lack thereof). I have seen a Spinner Grind on a one bike require my full weight to compress, but another Spinner Grind feel properly sprung on another bike. Similar results with RST Capas. So my advice is, don't let the fork model be a deciding factor in your choice of bike -- they're all crap, but it's what we are given, so once you've found the model of bike that suits your child's needs, make sure the fork can compress without Herculean effort.
With the above in mind, I was leaning toward the Ibex Alpine 320k, the Scott Scale JR 20, or the Marin Hidden Canyon. The Ibex was hands-down the best-spec'd out of the bunch -- and also unavailable, with Ibex now out of business. The Scott was nice, but nearly the same cost as the Ibex. Marin was not particularly a standout in any area, but it fit my son reasonably well, but my sister-in-law works at a local sporting goods chain that carries them, and I could get 25% off its $330 retail price. Knowing that I was probably going to spend some money customizing the bike, I decided that buying the Marin at discount was my most cost-effective choice.
Then fortune struck. The local sporting goods store had an unridden 2008 model onhand that they could not sell at retail because it had unusable cranks (long story). They were willing to sell me the bike for $100 (while signing disclaimers acknowledging it was not warranteed or returnable). I jumped at the opportunity to take the bike down to bare frame and fork, and start from scratch on a custom build.
Within hours of taking the bike home I was removing old parts, placing orders for new parts, and scrounging around for other parts from around the garage. Here are some of the key components that were replaced:
- Cranks - Stock: with 42/32 chainrings, 773 grams. Replacement: Crupi BMX race cranks, 140mm arms, and a FORM BMX 36t chainring, 455 grams.
- Seat - Stock: 297g (and way to big for a little kid's butt). Replacement: Odyssey Junior BMX seat, 186 grams.
- Seatpost - Stock: 290 grams. Replacement: spare Ritchey Comp I had lying around, cut down to minimum, 180 grams.
- Stem - Stock: 240 grams. Replacement: Race Face Evolve XC 70mm, 130 grams.
- Brakeset - No real weight savings here, but the stock set was pretty bad -- almost "Walmart bike" bad. I replaced them with some Avid FR5 equivalents that my LBS had lying around.
- Bottom Bracket - Stock: 311 grams. Replacement: Sinz Titanium Euro Square Taper, 166 grams. I was REALLY surprised here. The replacement came off his BMX race bike, and I was surprised by not only how much lighter they were, but much more easily the cranks spun compared to the stock BB.
- Wheelset/Tires - Stock: front and rear, including hubs and 7-speed 13-28t freewheel, Kenda 20x2.1" tires, 3676 grams. Replacement: Custom build with Crupi/Rhythm BMX rims, IRC Siren 20x1.5" tires, SRAM PG-970 11-32t cassette, Shimano Tiagra hubs, 2911 grams. About a 1.7 lb. reduction in rotational mass, not the monumental reduction I was hoping for, but still quite significant, and with more oprtions for gearing than the stock drivetrain.
- Rear Derailleur/Shifters - Stock: Shimano Tourney RD, SRAM MRX twist shifters. Replacement: SRAM X5 medium-cage RD, SRAM X7 twist shifters. No huge weight savings, but higher quality and more options for gearing / components.
- Front Derailleru/Shifters - Stock: Shimano Tourney TY-22, SRAM MRX twist shifters, est. 250 grams w/ cables. Replacement: Completely removed.
- Fork - Stock, but about 2" of unused steel cut from the steer tube.
- Handlebars - Stock (and surprisingly light), but about 1.5" cut from each end for better ergos.
End result: a sweet 1x9 setup that weighs 20.2 lbs. sans pedals (20.8 lbs with), compared to its stock weight of 25 lbs., and has already provided the little guy with tons of grins on his first trail ride during winter vacation. Only changes I plan on making are going with a 34t chainring to give him some extra advantage for climbing, and a chain guide like the one from Paul Components.
I could have easily saved a bit more weight by going with SUN CR-18 rims (350g each, vs. my 410g Crupi/Rhythms) but I'm a sucker for blingin' white rims. Other areas for weight savings would come at significantly higher cost: SRAM X-0 short cage rear derailleur (100 grams ligher, $160); KCNC Scandium seatpost (40 grams lighter uncut,$90); Xpedo flat pedals (60 grams lighter, $80). But a combination of these could easily take the bike weight below the magic 20-lb. mark.
A few pictures below.
