# Micro BMX wheel size 18 or 20



## terrasmak (Jun 14, 2011)

Looking to get my soon to be 3 year old a new bike for his birthday. I want to get my kids into BMX soon, well I'm looking at 2 micro bikes. The Redline proline that comes with 18's and the DK Swift that comes on 20's. 

The big hang up is wheel sizes, well color play a part too. Green is the favorite color and The DK wins hands down there.

Who has micro racers , and what advice on wheel size can I get ?


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## Delgado (Sep 9, 2016)

My 6yr-old is just about to outgrow his 20" Mini and move on to Junior next season. I'd say the biggest things to look for are:
1) Standover height on the frame
2) Gear ratio (rollout) based on wheel diameter, cog, sprocket
3) Crank length

If your 3yr-old's hips move back and forth when he/she pedals the cranks may be too long. A lighter gear ratio will make it easier getting up those hills when they don't carry enough speed around the corners. A 20" wheel with the same gear ratio will be noticeably harder to pedal than an 18" wheel. BMX frames are pretty small, but so are the kids; make sure your kids can mount/dismount comfortably, even on a hill, because there aren't many nice flat bits on a track!

This may help figuring out the right gear ratio: Gear Calculator | bmxultra.com


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## Delgado (Sep 9, 2016)

That said, it's pretty easy to swap out cranks and gearing if it's too hard at first... The DK might have more room to grow.


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## terrasmak (Jun 14, 2011)

I just checked, the 18 inch wheel bikes has full sealed bearings and 130mm cranks. The 20 has open bearings with 140mm cranks


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## Delgado (Sep 9, 2016)

The shorter cranks will give you a better circle for shorter legs, but they also give you slightly less leverage. Have your kid take it around the block?

The Redline Proline Micro has 38/14 gears on an 18" wheel = 42.75 gear inches
The DK Swift Micro has 36/16 gears on a 20" wheel = 45 gear inches

The Redline should be a little easier to pedal despite the shorter cranks. Both bikes are geared for light/small riders so you should be fine with either one I think.


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## terrasmak (Jun 14, 2011)

Sucks that the two local shops I deal with do not have one in stock. So no test rides, doubt I could get much feedback from a crazy 3 year old 

I can always swap to bigger cranks and different gears later. I think easier to pedal will be better for starting. 

He does pretty good on his 12 inch wheel bike, but there is no leverage with those tiny cranks


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## silvascape (Sep 11, 2014)

Hi
The issue with going straight to a 20" micro is standover height - they really need to be able to put their feet down comfortably to feel secure. 
In my experience most 3 year olds need a 18" micro with 115mm cranks. 4-5 year olds 20"micro with 130 cranks they 6-7 year olds - mini with 130 to 140 cranks. 
Dont discount the benefit of sealed bearings unless you want to be rebuilding bearings every month or so. 
The downside on going 18" is that tyres are hard to get and expensive. The benefit is that the bike with fit him well and resale is excellent. Benefit of the DK is that the bike will fit him for 3 years or so even though its a bit big to start with. Downside is that the unsealed bearings will need a lot of maintenance. (I am assuming you are buying it for his 3rd birthday - if buying it for his 4th birthday the 20" wheels would not be a deal breaker for me)


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## silvascape (Sep 11, 2014)

Oh and for the record as a 3 year old me son rode a Redline Proline 18" micro. At 41/2 he moved to a Crupi micro which has 20" wheels and at almost 6 he moved to a Crupi mini.


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## terrasmak (Jun 14, 2011)

Called up the shop and ordered the Redline, he turns 3 next weekend and will get it on his birthday.


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## silvascape (Sep 11, 2014)

Sounds good.
Here is my son at 3 on his redline micro (which we put 115mm cranks on):
With his first trophy 







Racing 








Here he is just before turning 5 - learning to manual on his Crupi Micro (with 120mm cranks)







And here is one of him at 5 racing on his 20" Crupi Micro


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## Delgado (Sep 9, 2016)

We started with a used 20" Redline Proline Mini at age 4-1/2.
The cranks were a bit long and it was geared quite heavy, so we swapped to 135mm cranks and a 34t cog. Now that he's six we're running 37t in the front and it seems just about right.

Here's one when he was still 4 Novice right beside a younger 4 Novice on a Redline Proline Micro:








Here he is racing in 6 Novice on the same bike








It doesn't really matter too much what they're riding, as long as they're having fun - and they all walk away with some bling on trophy night


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## Delgado (Sep 9, 2016)

@terrasmak I'm sure he'll love it - can't wait to see pics 

@silvascape Nice manual!


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## silvascape (Sep 11, 2014)

Delgado - looks like you will get at least another year out of the mini. My son has just turned 7 and still has a fair bit of growing room on his Mini - has just moved up to 135mm cranks. Those manuals are now pretty automatic which is awesome to watch and the jumps are just getting bigger and longer which is just plain scary for Mum.


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## terrasmak (Jun 14, 2011)

I'm actually getting a Mini pretty soon too. My daughter is almost 5, going to make BMX a family thing. I figure bikes are going to get passed around between the kids over the year. 


Going to need a S+1 for myself before long. Just don't know XXL pro 20 inch wheel bike or 24 inch cruiser.


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## Delgado (Sep 9, 2016)

@Silvascape, just waiting to see how much he grows over the winter - our season ends in October and starts again in May. If he grows as much as last year I'm sure we'll be shopping for a new bike. Luckily the resale value on these things is quite high - there's always another kid looking for a bike 

@terrasmak, that's great! We've got a pretty big mom & dad rider community here at our track. I haven't worked up the courage yet but I do see that the really fast kids have parents who ride around the track with them at gate practices. I'm tempted to pick up a used cruiser to share with the wife!

We do a quite a bit of mountain biking together, I know the BMX racing has helped his trail riding immensely. I'm hoping some of the MTB skills we're developing are helping his BMX riding as well.


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## silvascape (Sep 11, 2014)

@Delgado - Its a big jump from Mini to Junior in a lot of brands. Try putting Junior bars and a 45mm stem on his mini to make the transition smoother.

I am a 40+ Mum who now races BMX. If you had asked me 5 years ago to jump on a BMX bike I would have laughed. Its great fun and a really good family sport. 

@terrasmak - Cruisers are a bit more stable and most adults seem to find them easier to keep rubber side down.


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## terrasmak (Jun 14, 2011)

silvascape said:


> @Delgado - Its a big jump from Mini to Junior in a lot of brands. Try putting Junior bars and a 45mm stem on his mini to make the transition smoother.
> 
> I am a 40+ Mum who now races BMX. If you had asked me 5 years ago to jump on a BMX bike I would have laughed. Its great fun and a really good family sport.
> 
> @terrasmak - Cruisers are a bit more stable and most adults seem to find them easier to keep rubber side down.


I haven't ridden a 20 inch in 13 years, I tried my friends a year ago and just felt so off on it. That's why I was leaning more on a cruiser. I cruiser may be an easier swap between my mountain bikes and BMX


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## terrasmak (Jun 14, 2011)

Turns 3 tomorrow, but his party was today.


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## Delgado (Sep 9, 2016)

Is there anything more fun than a kid with a new bike?


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## terrasmak (Jun 14, 2011)

Absolutely crazy how far this has evolved. I went from knowing just a hair over nothing to dam near factory mechanic. It’s been a venture and both kids are still riding. Son and I race both class and cruiser , my daughter just races class


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