Trek 820 MB (adult) vs. Trek Superfly 24 MB (kids) for 10 year old 4'9"?
 

It was time to get new bikes for my kids and I'm a bit torn on what to do for my son after visiting my local Trek dealer where I have been a happy customer for 13+ years for our family bike needs. My son just turned 10 years old and is 4'9". It's predicted he will have an adult height of around 5'7". He was on an unusably small Trek Superfly 20 (that's a 20 inch wheel MB) and I assumed when we went to the shop I would get him a Trek Superfly 24 (24 inch wheel MB) to replace it. The Superfly 24 is aluminum framed and the website shows it is for 8-12 year olds who are 4'4"-4'11" in height. That was the same progression his older sister had in the girls version of these exact bikes. The dealer salesperson (who I felt was trying to push his 2018 in-stock models over 2019 models they could order for near immediate delivery) tried him on a adult XS 13 inch frame Trek 820 MB, their steel framed entry level MB. This is a 26 inch wheel real deal MB, and heavy, because it is the cheapest Trek adult MB. The 13 inch frame is what Trek considers an "XS" for adults and suggests heights 4'10'5" - 5'1.5" so about an inch more than my son is. The bike of course has a sweet matte black finish my boy loved and you could certainly adjust the height of the seat so he can ride comfortably but he does look pretty small on the bike but that maybe because I'm used to him being so large on his 20" wheel bike that it looks like a BMX! He rode it around in the parking lot and LOVES it and badly wants it over the Superfly 24. The salesperson seems to think the 820 is the way to go as he is just on the bottom edge (actually just below it) of the suggested height for the 820 and therefore it would last us longer by nearly 2.5" of height so at least an extra year or two before he would outgrow it vs. the Superfly 24 where he would already be smack dab in the middle of the size range.

I'm concerned I'm about to buy him a heavy steel framed adult man's bike for a skinny 10 year old soccer kid vs. a lighter aluminum "kids" bike that would fit him better with smaller, thinner tires that wouldn't tire him out as quickly. What would you all do, the "kids" bike is actually $70 more I assume because its aluminum vs. steel since both bikes have similar grade components. Money isn't an object but I'd rather not get the bike he doesn't want as much and see it only last a year or two vs. get a bike he thinks is awesome and would last him 3-4 years and even costs less. My real concern is that it is a bit too big right now and I bet with the bigger tires and steel frame it will tire my 10 year old skinny soccer kid out way faster than the other bike that he is already right-sized for. Our riding is all flat-land suburbia with at worst gravel trails and the most gentle of hills.

Thoughts? Thanks!

Is your boy going to be riding this bike on real mountain bike terrain or will it be mainly on paved roads and similar surfaces? When our daughter was 10 I bought her a 26" wheel Trek mountain bike under the assumption that she would be riding it almost entirely on paved surfaces where having a frame slightly on the large side wouldn't be a problem - and it came in a color she loved. I did have the bike shop take off the standard knobby tires intended for trail riding and substitute lighter and easier rolling street tires. It worked out fine as a bike for her to ride to/from school and around the neighborhood and it was the bike she took with her to college where it was her main transportation.

For sure mostly paved flat surfaces, suburban streets and bike paths. Occasionally small gravel bike paths. What tire would you recommend for a 26 inch MB tire for smoother rolling while still at least being able to handle prepared gravel trails? Could I use the same rims etc.? Thanks!

Lots of choices, and yes, you can use the same rims. Tires that are the 26" MTB diameter (559mm bead seat) are very common and will fit the 820 rims. Examples of good tires that are more street oriented would be the Continental Town & Country (26" x 1.9"), Serfas Drifter (26" x 2.0"), and many others - your LBS probably has some suitable ones in stock.

Is Trek not making the 26" Dual Sport Kids model anymore? That seems like it would be perfect for your needs -- a kid's sized 26" wheel bike with an aluminum frame: https://www.trekbikes.com/us/en_US/b...colorCode=grey

My 9-year old is 4'9" and on a 24" and I don't think she has much more growing room, so I think a small 26" could work.

Another good options would be the Woom 6. 26", extremely lightweight, lots of growing room. Not as cool looking as the Trek though. https://us.woombikes.com/products/6 We've got the Woom 5 and really like it.

I'd take a higher end lighter kids bike over an entry-level heavy adult bike. Or, based on what you've described as your intended uses, I'd go with something like a Trek FX hybrid instead of a mountain bike.

For what it's worth, I'd go for the 24" on the grounds that the lighter a bike is the more kids enjoy riding them. There's also the fact that a heavy adult entry level steel mtb may not fetch that much when the time comes to sell, whereas parents looking for a lighter bike that will fit their kid are usually prepared to spend a bit more.

We've had, over the last 20 years our Saturday club has been running, any number of parents who've gone the lighter route after they've tried the "grow into it over longer" strategy.. There's also the factor of component size. While a lot of kids bikes are appalling in that respect, decent brands usually put some thought into it, so he'll find it easier, and therefore safer to use, especially the braking side of it, assuming that the adult bike has longer reach levers, of course.

Anyway, good luck - I hope he enjoys it whatever decision you make.

Well I've had a variety of opinions here but I pulled the trigger... I ended up getting my son the Trek 820 (26 wheels) in a 13 inch frame but I did replace the tires with smoother running Serfas Drifter City tires. My son is 4'9" and a pretty strong soccer kid and although the frame to his body looks a bit big his leg extension with the seat set properly is great and he has no problem controlling it at a stop. Bottom line is he *loves* it and wanted it strongly over the 24 inch kids Trek Superfly. He will grow even better into it soon and if I'm being honest we aren't a high mileage family so the whole "he will get tired on a long ride" doesn't apply so much, plus he had better cardio than his parents LOL. I didn't honestly think too much about a youth version of the Trek DS (26 inch wheels) which perhaps I should have since it seems like it would be perfect, but my son also likes that he is the only one in the family with a "mountain bike".

My 13 year daughter who is barely under 5'1" got a new 2019 Trek DS2 Women's (what used to be called the Neko) out of the deal too and she also loves her bike. It fits her very well and may well end up being the right size for her even as an adult.

My real problem? My low mileage 2012 Trek 8.4 DS (in white) looks lame compared to the new neon yellow/green 2019 Trek DS3 with its new frame design (new for 2019, much cleaner and modern looking) and integrated cable paths etc. I have absolutely no reason to get it AT ALL but damn I want it!

When my son was younger, we went directly from a 20" to a 26" bike. I wound up buying an used Trek 800 with GEAX street runner tires. I just had a feeling that given how fast he was growing, he wouldn't get much use out of the 24" wheel bike. He got about 3 seasons out of it before he outgrew it. I don't recall exactly how tall he was, but he was under 5' when he got it, and was about 5'6" when he finally had to get into something bigger. The Trek 800 was a fantastic bike for him, and it came in a nice silver and black color scheme. He rode it on rides of up to 35 or 40 miles. Apparently nobody told him you aren;t supposed to ride long distances on a converted mountain bike. If there were someone in our household short enough to still ride, it, I probably would have kept it as a beater.

Good call on the tires! That was a thoughtful move, swapping in something more pavement-friendly.

I realize I'm a bit late to this thread, but I was in a similar predicament. My son was turning 10 and wanted a new bike. While he was a bit small for the Trek 820, there was no doubt that he would quickly outgrow a 24 inch bike. In addition to that, he insisted that his new bike cannot have grip shifters - due to a bad experience with a Walmart bike. After some long research & discussion with my LBS owner, we decided to go with the 820 in the 13 inch frame. He loves it. I have taken him out on some easier trails and he really enjoys the bike. He does occasionally have to get off and push it up some rocky hills. There is no doubt that he will be able to overcome this once he grows a bit and gets a bit stronger. In addition to that, this bike has become his primary transportation. He is on this bike from dawn to dusk. I believe the stock tires on his 820 are a good mix of trail & pavement. Overall, it was a very worthy investment and I am thinking I probably should have stepped up to the Marlin 4.

https://cimg6.ibsrv.net/gimg/bikefor...7a94e5e0a2.jpg
Typically, his saddle is lower than this. In this photo, he was getting tired so we left the single track & hit the paved road to get back to the trailhead. I raised the seat for him because there was a 1/3 mile section of a 4-5 degree climb on this section of road. This was our break when we were almost at the top.

I'm enjoying this thread. My 10 year old has outgrown his 24 inch wheels bike. We inherited an old 26 inch Diamondback (size S?) which is just a little too big and the cranks are too long, but it has big knobby tires and front shocks so he loves that it's a real off road machine (monster truck). We mostly ride pavement, but he likes jumping curbs etc. The Diamondback is a tank, which is good so he hasn't killed it, but it's also heavy like a tank! (33? 34? lbs) I do not like loading it on the rack on the back of the car.
I'm an "avid" cyclist (+/- 1,500 miles a year) and I'm trying to encourage him to enjoy riding. I'm also trying to get him to enjoy 'reality' fun more often than 'virtual reality' fun (online). Also he is very mechanical inclined - very interested in hands on, making stuff, seeing how things work.
So we carefully researched and ordered parts on ebay and we're almost done building his next new bike. Carbon fiber "kid size" (14") MTB frame (direct from China), carbon fork (rigid), hydraulic brakes, 26" wheels, several other carbon bits (stem, bars). It will cost less than a new one at the store, but the real value has been that he's engaged in building it. I'm hoping it will be about 20 lbs when finished. We had a couple of mis-cues in ordering, but were able to return or re-sell the parts. The delays were frustrating, but have built the anticipation. I know this path isn't for everyone, but we're enjoying the ride. YMMV.