Mountain Bike Reviews Forum banner

1 - 20 of 59 Posts

·
MTB Ninja
Joined
·
41 Posts
Discussion Starter · #1 ·
My son is 4.5 years old. He is 3' 8". I am looking at getting him a mini or micro-mini bmx bike as opposed to a 25-30 pound bike. Anyone have any experience with kids riding these things? General thoughts on going this route?

I would probably put fatter tires on the bike, the lowest gearing possible, add a front brake, and loose the bear trap pedals for something more shin-friendly. Any other tips on setting one of these things up?

Sizing?
I can't find one in a shop to try out and they are kind of expensive just to take a guess. According to the Redline sizing recommendations my son is right on the line between a micro-mini and a mini. I am leaning towards the mini because it would probably last him a couple of years, he might outgrow the micro in 6 months. The mini also has 20" wheels so it might be smoother on the trails.

Thanks
Paul
 

·
Rollin' a fatty
Joined
·
5,863 Posts
Both frames have low standover, I would go with the Mini.

My kid started on one (Haro CR Mini) and the problem that he had was crank lenght and gear ratio, the cranks were too long and the gear to low. After swapping cranks and installing a bigger cog the problem was solved.

The skinny tires are puncture prong, fatter tires are a must for sidewalk attacks, parks and trails.

Give it a try and adjust as needed.
 

·
MTB Ninja
Joined
·
41 Posts
Discussion Starter · #3 ·
Thanks for the advice DiRt DeVil.

I am looking at an Intense Mini XL. I think it brings 140mm cranks. I havent found anything smaller at QBP. Hopefully the 140s are small enough. The gearing is 36x16 in this bike. I can get it as low 34x18 or 34x20. I'll probably start with replacing the freewheel and work from there.

Not sure how i will handle the tires. They look too skinny for trail use. Not sure how big of a tire will fit but Schwalbe makes some sweet kevlar bead tires for BMX bikes that will shave a ton of weight and they are bigger to boot so hopefully more puncture resistant as well.

I think i am spending more time researching my son's new bike than i did on researching my own. :p
 

·
Registered
Joined
·
46 Posts
my daughter used a Redline Pitboss, geared down to make it more of a singlespeed trailbike, and I'd recommend that over a mini unless you're going to race bmx. the 16" wheels gave her a lower center of gravity than any mini or micro-mini (they have really high bottom brackets, proportionally, compared with adult rides). we changed the 140 cranks to 135s, ran a 34t in the front and something like a 22 in the back. she was more confident and faster off-road than she is now on a mini.
 

·
Registered
Joined
·
37 Posts
Mini

Hi. My son has just turned 6. He's riding on a redline mini. He's quite a bit shorter than all his mates at his age so this will fit him for a while. Tyres can be an issue. He started riding the bike on our local trails in summer, but as soon as it got wet we had problems, mainly with the tyres sliding out on tree roots. Mini run a 20 x1 1/8 tyre. In reality this equates to a 21" wheel. I brought 2 standard BMX wheels and they fitted good. Only issue then is the lining up of the brakes on the rim. Redline mini came with a removeable brake post system which I just reversed and swapped sides. I also had to make up a bracket for the front brakes to reach the rim. I have photo's stored on another computer which I post when I get access to it again. My son loves his bike and can ride most places with me. I put this down to the light frame. It's making him learn some great riding skills (we all learnt this way didn't we?). Shane
 

·
MTB Ninja
Joined
·
41 Posts
Discussion Starter · #7 ·
I ended up getting my son a 2008 Intense Micro Mini for XMas. I went with the micro as opposed to the mini xl because I found a good deal on the micro. It looks like it will fit him pretty well but obviously he will outgrow it sooner. I have a daughter that can inherit the bike after my son outgrows it so it wont be a loss.

The big downside I see right now is that the bike has 1" tires. According to Intense I can fit up to a 1 3/8" tire on there (same goes for the mini XL if you were wondering). So I will probably get som bigger tires for it and lower gearing and be done with it.

After XMas I will get some pics of my son on the bike.

Paul
 

·
Registered
Joined
·
16 Posts
You can fit a 20X 1" , 1 1/8 " or a 1 3/8 " tire on those rim . My kid runs Kenda Small Block eight 20 x 1 3/8 , at 75 psi.,40 x 16 gear and 160 mm crank , on her BMX race bike . Also take your kid to the local BMX track ( ABABMX.com for a location ) its a great place to learn good technique and parents could also sharpen their freeriding skills on mountain bike too .
 

·
@wishEMT
Joined
·
344 Posts
i think the skinny tires will do fine as long as you keep air in them, theres kids around here riding street on minis. if you cant find an aba track around you try looking up nbl. the fact that bmx in the us has two distinctly differently sanctioning bodies competing against each other i find ridiculous, but what can you do.
 

·
MTB Ninja
Joined
·
41 Posts
Discussion Starter · #10 ·
My son JUST started riding without training wheels (like on Dec 26, 2008). I dont think he is ready for bmx racing for at least a couple of weeks yet. :) Rest assured, when he shows the slightest bit of interest in racing I will get him to the event. :cornut:

At any rate I ended up getting my son an Intense Mini. I think it sizes up more as a micro mini. It is just a tad bit too big for him which is exactly what i wanted.

I am going to replace the tires with 1 3/8" tires. I am also going to gear the bike down a bit to make it easier for him to get going and pedal uphill.

One thing I almost missed was the brake lever reach adjustment. Putting the lever closer to the bar made it much easier to grab the brake so we had no accidents. Other than that I cut the handlebars down 1" on each side. I could probably go another 1/2" or even a full inch on each side.

Here he is on his new bike, seat is lowered all the way down right now so he can touch the ground easier while learning to ride. I am going to slowly raise the seat on him maybe 1/8th inch per ride until he can pedal somewhat efficiently. Right now the seat seems kind of low for him but he needs that close to the ground feeling while learning.

Video of first day without training wheels:
https://www.youtube.com/watch?v=LFDwGJkV88c

 

·
Registered
Joined
·
2 Posts
Junior or Mini?

Hey all... such great feedback on a topic I never knew existed! I can't stand the typical bike options from the stores and having been looking to convert an old Free Agent Jr full bike for my recently just turned 4 Year Old just at about 3' 5" tall. I thought about taking the bike down to the bike shop and seeing if they can put on some 16" rims, smaller cranks, better sprocket ratio. The last thing I'm wondering is if the headset can be turned around to make the seat to handlebar distance shorter until he grows into the jr frame... or is the deal breaker making me have to buy a mini frame?

Thoughts?

Thanks!
 

·
Registered
Joined
·
1,958 Posts
I think the critical dimensions will be the top tube and crank length.

My 6y/o at 3'-8" is at the beginning part of the "mini" frame fitment. I've had to make all the adjustments to make things compact and it fits him well.
 

·
I live to bike
Joined
·
2,397 Posts
vigitalmoe said:
Hey all... such great feedback on a topic I never knew existed! I can't stand the typical bike options from the stores and having been looking to convert an old Free Agent Jr full bike for my recently just turned 4 Year Old just at about 3' 5" tall. I thought about taking the bike down to the bike shop and seeing if they can put on some 16" rims, smaller cranks, better sprocket ratio. The last thing I'm wondering is if the headset can be turned around to make the seat to handlebar distance shorter until he grows into the jr frame... or is the deal breaker making me have to buy a mini frame?

Thoughts?

Thanks!
vigitalmoe - go with a mini or, better at his height, a micro mini. You'll run into some issues trying the conversion you describe on the Free Agent. One, brakes won't line up to the rims if you put 16" wheels on a frame made for 20" wheels, so he'll have no brakes (unless you put a rear coaster brake wheel in, I guess). Second, turning the stem around will work, but will make for odd steering. And by the time you buy all of those parts and swap it all around, you'll probably be near to the cost of just buying a bike that already fits him. Save the bigger bike as for when he'll fit it in a few years.

OP: your son looks very happy on his bike. Now it's a few months later, hope his smile is still just as big!
 

·
Registered
Joined
·
264 Posts
Mini Single Speed all the way!!

Both my boys started riding at 3yo. Both went from 16" RedLine PitBoss to 20" Minis (FreeAgent & Intense) at 4yo. I like the Intense better because it had 125mm cranks, as opposed to 140mm on FreeAgent. Both boys road/raced BMX, but I under-geared both bikes and let them race XC with them as well. SingleSpeed all the way. Keep it simple and let them learn how to ride the bike.

We have the advantage of having a 800m MTB trail around the house, as well as a small BMX/Pump track. My oldest at 7yo has graduated to a Spec 24" Hardtail w/ some crank/gear mods, but my 4.75yo still is best suited with the simplicity of the Intense Mini.

You can get alot of use out of a good mini. A little bigger freewheel, a smaller chainring, and you can get the perfect gearing for your little guy, and he won't have to push the big wheels around. I additionally went to 1.375" Intense MicroKnobbies as they are the biggest tire you can get on the 20" mini rim. I run my 40lb. 4.75yo at 32f/35r and he can handle the rooty trail stuff easier than higher pressures. Just enough not to pinch flat when he's sloppy. You can size up for a while with Stem and Riser Bars. Don't cut the seat tube, you'll need it later!

Check out JRBicycles dot com for some good deals on PitBoss and Intense Minis. The have the single speed parts as well.

My oldest with his FL XC State Champ Jacket of the FreeAgent from 2 years ago when he was five.

1
 

·
Registered
Joined
·
1 Posts
@rideToLive

Nice! What sprockets/cog combo worked well for trail riding on the bmx mini? My boy is about to turn 4 and has been riding well on a 12in wheel bike for over a year, but that coaster brake don't work so good on the trails.
 

·
MTB Ninja
Joined
·
41 Posts
Discussion Starter · #17 ·
Getting a new freewheel for my son's mini in the next week or so. I think it is a 16t out of the box. Probably going to get an 18t or 20t.

I just ordered some Kenda Krankit 20 x 1 3/8 tires on special for $4.00 each directly from the Kenda. Hopefully that will prevent some of the pinch flats as he is running the 20 x 1" now and flats every ride. The 1" was fine until he figured out how to go off curbs.
 

·
Registered
Joined
·
264 Posts
37/19 at the moment

On my 4.8yo's Intense Mini, we're running a 37/19 at the moment. He can ride up steep stuff out of the saddle, but he's just about spun out on the flats chasing his big brother.

Our plan is to go to 39/19. I have 19t, 18t, 17t and 16T available with 35-40T chain rings. Remember, every tooth in the back is almost worth 3 teeth in the front. 16t to 18t is a big jump on a 20".

Here's a gear calculator you can mess around with:
https://www.jrbicycles.com/sizingcharts/jrgearcalc.html

I like the MCS Alloy Rings. Cheap, and work for the little guys:
https://www.jrbicycles.com/storefront/index.php?act=viewProd&productId=960
 

·
Registered
Joined
·
1,958 Posts
My 6y/o runs 37/16 w/145mm cranks. Bike came with a 14t stock. I just geared it down a touch to help him with the hills.

He's plenty fast on the flats.

In fact, I think he's so fast, he's parked his bmx bike in favor of a Razor scooter lately. Likes just buzzing around.
 

·
MTB Ninja
Joined
·
41 Posts
Discussion Starter · #20 ·
Just got the Kenda Krankit 20 x 1 3/8 tires a few days ago. My son now does not whince when hitting small bumps. :) No more changing tubes every time he rides the bike either. The knobies are much beefier than the Intense Micro Knobbies but really it just serves to make the bike look tougher. I now ride with my kid at least once per day. He is totally loving the new tires!

If you choose to get your kid a bmx mini that doesn't come with 20 x 1 3/8 tires then just go ahead and order the bigger tires and tubes when you order the bike. There isnt much reason to run smaller tires unless your kid is actually racing BMX and those 1 inch tires are just useless for anything else.

For reference, you cannot use any tire marked with decimals (i.e. 20 x 1.5 will not fit a typical mini), they are a different diameter. So for example, a 20 x 1.5 will not fit on a wheel designed to run 20 x 1 3/8. You need to stick with the tires that post measurements in fractions. Seems incredibly silly and i am sure that the underlying reason makes sense but it is still silly.

Oh, and one more thing, switch to presta valve tubes. The mini rims are really too narrow for schrader valves. With schraders it is very easy to pinch the tube when mounting the tire because the valve pushes the rubber underneath the bead. So what will happen is you might have rubber under there with no pinch flat at first. You have no idea that there is a problem. Kid rides bike for 5 minutes then has a flat.

I just ordered a 34T chainring from the link mentioned above. My son currently has a 36x16 setup. He can get the bike going but he is clearly overgeared (he is now 5 yrs and 1 month, maybe 1" taller). However, the real problem is that once he gets on top of the gear he just starts gunning it and while it is great to see your kid hauling ass and loving it, it is not so great thinking about how bad he is going to hurt when he clips a tree at that speed. He also has problems on even moderate inclines with the current gearing so hopefully this will help with that somewhat.
 
1 - 20 of 59 Posts
Top