# 20" vs 24" - Decisions??



## RallyPunx (May 5, 2009)

I'm in the market for a mountain bike for my 8yo son. He's been riding a 16" Mongoose BMX bike for the last year and he wants to ride with me on the trails (needs gears). I began looking at 20" mountain bikes and then realized that both 20" and 24" mountain bikes have the same 12" frame. 

I thought about buying him a 20" frame for him to feel more comfortable with mountain bikes and as he grows upgrade the wheels and tires to 24" and the cranks to a bigger size better suited for him when he needs them. If I do this, he can use this frame until he is ready to make the jump to 26". 

Am I thinking out in left field or is this doable? As he grows, is there anything else I would need to change other than the cranks, wheels and tires? I will appreciate your inputs. Thanks.


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## JonathanGennick (Sep 15, 2006)

Try him now and see whether he fits a frame with 24" wheels. My son fit a 24-inch-wheel bike far earlier than I had expected. The dealer saw it, and I didn't. 

To put 24" tires and wheels onto a frame designed for 20" wheels, I doubt that's even going to be physically possible.


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## abeckstead (Feb 29, 2012)

Got my son on a 20" hotrock and have been taking him out. He'll be 8 in June and is 51" tall. On trails I had to lower his seat so he is more comfortable. Here he is with his bike, I set him on a 24" tired bike and it was too big. Thankfully I also have a 5 yr old daughter who will get the hotrock when it's time.


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## TwoTone (Jul 5, 2011)

RallyPunx said:


> I'm in the market for a mountain bike for my 8yo son. He's been riding a 16" Mongoose BMX bike for the last year and he wants to ride with me on the trails (needs gears). I began looking at 20" mountain bikes and then realized that b*oth 20" and 24" mountain bikes have the same 12" frame.
> *
> I thought about buying him a 20" frame for him to feel more comfortable with mountain bikes and as he grows upgrade the wheels and tires to 24" and the cranks to a bigger size better suited for him when he needs them. If I do this, he can use this frame until he is ready to make the jump to 26".
> 
> Am I thinking out in left field or is this doable? As he grows, is there anything else I would need to change other than the cranks, wheels and tires? I will appreciate your inputs. Thanks.


Not sure where you got that from?

They may call them 12 inch frames, far from the same. Here a small table of the bikes I was looking at.

Look at the difference from the Marin 20 to the 24.

Then look at the difference from the Marin 24 to the Spec 24s, both the 11 and 13.

Here's the link to Specialized 20 inch: Specialized Bicycle Components : Hotrock 20 6-Speed Boys

Still believe it's the same frame?








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## hammy35 (Jan 2, 2009)

How tall is your son? 

I got my daughter a 24" Scott Scale Contessa JR for Xmas. She was 7 and measured 48" at the time. Honestly, she was about 85% of the way to fit on my wife's old small chromoly Raleigh 26". It seemed like a "lot" of bike for her at the time, but honestly she grows so fast that 4 months later it's just right with the seat slammed. It took her about 14 minutes to get used to the extra size and wheelbase. The bigger wheels roll so much better than the old 16s she was on.

I highly recommend the Scott. It has decent components and is decently light. The fork actually works under her weight... It was $400 at the LBS. I have a 2 year old who will inherit this one day so it made sense to spend a little more on a quality rig.


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## RallyPunx (May 5, 2009)

I thought they were both 12" frames, as my LBS advertise them both 20" and 24" as 12" bikes. I might have to do further research on the bikes I'm looking at for my son. 

The last time I measured him, he was 51", but that was months ago. I'll have to measure him again when I get home tonight. I think he could ride a 24" bike height wise, but he is super skinny and might have trouble with the extra weight of the 24". These kid's mountain bikes are really heavy for their size. 

Anyone had any experiences (good or bad) on having an 8yo ride a 24" mountain bike?


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## IAmHolland (Jul 8, 2010)

RallyPunx said:


> I thought they were both 12" frames, as my LBS advertise them both 20" and 24" as 12" bikes. I might have to do further research on the bikes I'm looking at for my son.


12" is in reference to the seat tube length. It doesn't mean that the frames are the same. FWIW, my son's Hotrock 20" is a 10" seat tube.



RallyPunx said:


> Anyone had any experiences (good or bad) on having an 8yo ride a 24" mountain bike?


I'm building my son a 24" now (custom build). He turned 8yo a month ago.


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## TwoTone (Jul 5, 2011)

My son is 9 but short and skinny for his age, he's only 51 high with an inseam in the 22-23 range.

I'm also building him a somewhat custom 24 inch bike. I started with the $175 Marin 24 I started a thread about. I like the Marin because it's a little smaller than the Hotrock.


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## RallyPunx (May 5, 2009)

TwoTone said:


> My son is 9 but short and skinny for his age, he's only 51 high with an inseam in the 22-23 range.
> 
> I'm also building him a somewhat custom 24 inch bike. I started with the $175 Marin 24 I started a thread about. I like the Marin because it's a little smaller than the Hotrock.


Thanks for the info. I went ahead and pulled the trigger on the Marin from your other thread. It was too good of a deal to pass up. My son is 52" tall with a 23" inseam. He should be able to ride it with the seat all the way down and he will grow into it nicely. Since you have the Marin already, any components you would recommend be changed? The specs look nice in comparison with other 24" bikes.

Thanks everybody for all the feedback.


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## abeckstead (Feb 29, 2012)

Can some of you with a 7-8yr old post a pic with them next to or on their bike? The pic of my son... his seat is way low, but it's where it must be so he can touch the ground in tech terrain. I dunno... I thought a 24" tired bike was too big for him. Here's a better angle on flat ground. Please Excuse the Sasquatch next to him ;p


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## griff71 (Feb 21, 2012)

I just moved my 48" 8yr old onto a 24" bike. It's a bit of a stretch for him, but the 20" he got for Christmas was a little small. 

The Trek MT220 has 2 pedal positions on the crank to help with sizing. The Marin Bayview mentioned in this thread had one of the tallest stand-over heights that we tried. The Specialized HotRock 24 and Kona Hula had the lowest.


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## NYrr496 (Sep 10, 2008)

My son is 7 1/2 and 53". He's starting to look funny on his 20" GF Precaliber, so I picked up a 24" GF from Craigslist. I'm building some light wheels and getting some Mow Joes for it and he'll be on it soon.


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## IAmHolland (Jul 8, 2010)

My son just turned 8yo last month. About 54". He's on a 20 inch still, but it looks small on him. His seatpost is maxed out.

I'd keep your son on the 20 until he feels comfortable with "tech" terrain and can raise the seat. "tech" in quotes because there's not much they can ride with 20" unless they can huck the bike and manhandle it. That's doubtful, lack of upper body strength. My son rides his over rocks and roots, no problems at XC height other than at a much slower speed. I might drop it a bit for steep descents, but nothing more than an inch or so. I haven't taken my son over really rocky terrain, the bike does not have enough clearance to avoid bashing the rings and pedal strikes would be insane as I strike my pedals on those trails.

When he gets his 24", he will ride it. It's in process of being built right now. I'm just waiting for the Rocket Ron tires and a spare tube to arrive, so I can set it up tubeless.


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## abeckstead (Feb 29, 2012)

My son has also been riding dirt bikes since 3.5yrs old. Upper body strength isn't an issue, he can definitely huck his hotrock around. After following him on real single track trails that I ride... I just can't see him on a bigger frame yet. Oh well... Got upgrades planned for his bike. Just gonna stick to what I think is best for now.


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## IAmHolland (Jul 8, 2010)

abeckstead said:


> My son has also been riding dirt bikes since 3.5yrs old. Upper body strength isn't an issue, he can definitely huck his hotrock around. After following him on real single track trails that I ride... I just can't see him on a bigger frame yet. Oh well... Got upgrades planned for his bike. Just gonna stick to what I think is best for now.


Why worry? I'm not sure I understand your concern. When he gets more proficient and bigger, he'll move up. Or you can keep it BMX style and have him ride that till he's 10. :thumbsup:


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## Brett Nichols (Sep 9, 2016)

Is it too late to bring this 2012 thread back to life? My son will be 8 in a week, and is 3' 11 1/2."

He's been growing a 1/4 inch a month now for many years. His Hotrock 20" seems about right, but the lack of back suspension is terrifying to watch, and we get a pinch flat about every other ride. I could put 50psi in the back tire but that would exacerbate his back end bouncing side to side 18 inches. At $1,000 used, the Commencal Supreme 20" full squish seems like a dumb use of our expendable income. Used Ripcord, Gromhit, and Commencal Supreme 24s are readily available in Seattle and Vancouver, for around $1,000. The Norco Fluid 4.2 is a contender too. I don't like the 68-degree head-tube angle, but he threw a leg over one at our LBS and it seemed much smaller than the Kona Stinky 24". I'm concerned about the long wheel base, but he was able to muscle the front end up enough off of curbs to land both wheels at the same time. He'd get one year out of the 20" Commencal, but maybe 3 out of a smallish 24". There's a little brother, 2 years younger, so stuff gets a second wind as that kid comes along. Does anyone have 2 cents they wanna lob my way?


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## ReXTless (Feb 23, 2007)

Brett Nichols said:


> Is it too late to bring this 2012 thread back to life? My son will be 8 in a week, and is 3' 11 1/2."
> 
> He's been growing a 1/4 inch a month now for many years. His Hotrock 20" seems about right, but the lack of back suspension is terrifying to watch, and we get a pinch flat about every other ride. I could put 50psi in the back tire but that would exacerbate his back end bouncing side to side 18 inches. At $1,000 used, the Commencal Supreme 20" full squish seems like a dumb use of our expendable income. Used Ripcord, Gromhit, and Commencal Supreme 24s are readily available in Seattle and Vancouver, for around $1,000. The Norco Fluid 4.2 is a contender too. I don't like the 68-degree head-tube angle, but he threw a leg over one at our LBS and it seemed much smaller than the Kona Stinky 24". I'm concerned about the long wheel base, but he was able to muscle the front end up enough off of curbs to land both wheels at the same time. He'd get one year out of the 20" Commencal, but maybe 3 out of a smallish 24". There's a little brother, 2 years younger, so stuff gets a second wind as that kid comes along. Does anyone have 2 cents they wanna lob my way?


Buy a hardtail and wait until he's older for the full sus.

If he's constantly getting flats on his current bike, there is a problem with either the pressure you are running or the rim tape. It's not the lack of rear suspension.

Sent from my iPhone using Tapatalk


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## Crashtestdummee (Sep 14, 2015)

Agreed, change the rim tape on the rear.


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## TwoTone (Jul 5, 2011)

ReXTless said:


> Buy a hardtail and wait until he's older for the full sus.
> 
> If he's constantly getting flats on his current bike, there is a problem with either the pressure you are running or the rim tape. It's not the lack of rear suspension.
> 
> Sent from my iPhone using Tapatalk


Agreed, unless you're riding big stuff. My son didn't get FS until he was tall enough to ride a small 29er. Always good deals on XS, S XL bikes at the end of the year.


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## NYrr496 (Sep 10, 2008)

My son is 13 now and on a Large fat bike. It kills me that NOW all the bike companies are making 20 and 24" plus bikes. These things are sheer genius. I wish they had em when my son was small. 
I've been turning people on to these for about two years now. Every single person who's bought one for their kids says it was the best bike that could have bought. 
I know Scott, Cannondale and Specialized make em. I'm sure there are more. 
We all know 99% of the suspension forks they make for kid's bikes suck. I'd much rather have them on a 3" wide tire, tubeless with the pressure dialed in.

Here's one:
https://www.scott-sports.com/us/en/product/scott-scale-jr-24-plus-bike?article=265483043


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## Brett Nichols (Sep 9, 2016)

I'm still feeling the need to explore full squish for my 8 year old. Perhaps maybe I'm rationalizing the purchase since I absolutely love buying bikes I can't afford. I mean I can afford them to some degree, but it's not called a vice for nothing. 

Curious, what's your guy's rationale for when to switch your kid to full suspension? At the rate he's growing, seems like my kid will be on a 24 til he's 14 years old. If we're riding pretty hefty freeridey stuff around town, and doing 10 one-day trips a year to Whistler, is he doing to be happy til 14 on a hard tail? Since I like nice bikes, a good hard tail is going to cost me 500. In Seattle and Vancouver there used Ripcords and Commencal Supreme 24s for down around 1000. 

Investigating my rim tape sounds like good advice. Thanks. I'm on that. I'm probably running too little pressure in his back tire too. 20 PSI seems to make his ride smoother, but 35 solves the pinch-flat problem. It makes his bike even bouncier, however.


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## RMCDan (Feb 28, 2008)

Brett Nichols said:


> If we're riding pretty hefty freeridey stuff around town, and doing 10 one-day trips a year to Whistler, is he doing to be happy til 14 on a hard tail?


That totally justifies FS, IMO. My son went from a Flow HT to a Rokkusuta 20 last summer and the improvement in his riding was significant and immediate. I'd do it again in a heartbeat.


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## Brett Nichols (Sep 9, 2016)

Oh yeah, I like the looks of that Rokkusuta a lot. I think I'd do a 24", to future proof my wallet a bit. Getting tired of needing a new bike every May. Biking should be more like baseball. I got him a really good mitt for 40 bucks. 

How tall was your son when you bought him the 20", and how tall do you think he can get before you'll have to get him a 24"? My grom is about 47.5 inches tall. I think that makes him perfect on a 20", but I'm trying to weasel my way out of dropping 1-2k on a 20" now, only to have to spend 1-2k again this time next year.


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## RMCDan (Feb 28, 2008)

Honestly, I'm not sure. I'm not even really sure how tall he is now, ha! Looking back through some info I sent to Flow in Aug. 2016 he was 43.5" then with a 18" inseam. So, he's probably 48-49" now. Spawn lists minimum heights for the Rokkusutas as 46" and 52" (https://spawncycles.com/sizing). My boy is starting to look a tad big on his 20" already, but a friend of his has the 24" and he's not quite ready to move up either.

Tough call for sure, I can certainly understand not wanting to buy the 20 at this point. You could probably make the 24 work for him with some 140 cranks, super short stem and flat bars, but that'll cost you a decent amount. Whereas, if you buy the 20 now and sell it in 3-6 months you'll probably get 60-75% back on the resale. Though I don't how the used market is in your area.


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