Building a small/kids road bike.

[Hacienda71]

My 9 year old son is starting to get keen on the idea of road cycling. He currently has a hardtail mtb which is fine for a few miles on trails but he has tried a 48cm 650c wheel Btwin in Decathlon and wants a proper road bike.
It got me thinking, I have a Sora triple 8 speed groupset in the garage. I know I can get shims for the levers to suit smaller hands or even put an inline cyclocross lever on the tops. If I can pick up a cheap extra small frame and some budget wheels, then it would seem a cheaper option than Decathlon. I am a little worried about the cranks being 175 on the groupset.
My question
Has anyone done it and were there any pitfalls?

 

[Lanzecki]

If you already have a Sora 8 Speed, use it. Maybe lockout the granny gear. That said if his mountain bike has 3 chain rings what's the problem.

My ten year old barly has the reach/strength to change up on the front derailier. That would my main concern.

 

[Globalti]

Save yourself the grief and buy him a Luath 24:

 

[Dusty Bin]

I've built several kids road bikes, including the two we currently have. Plenty of 700c frames available in 44 or 48cm dependinig on how tall he is and square taper cranks are easily available from Lasco and others in 155 & 165 sizes. Islas are good, but comparitively heavy. Ask away...

 

[Dusty Bin]

Save yourself the grief and buy him a Luath 24:

er, he's nine?

 

[Hacienda71]

Strength wise he shouldn't have any problems with changing gears. He is a pretty muscular for a nine year old, he might need to get his head around when to use them, rather than spinning like a loonie or grinding like a pro from the 60's.
I suppose my queries were is the crankset ok with175mm arms for such a small bike, or do I get a single ring crank with shorter arms for his initial road riding? It sounds like that may be the way to go. Do you use narrower bars I have some standard drop ITM bars off an old bike lying around, but suspect they would be a little deep for him. Shorter stems? I do have a 90mm stem somewhere but would this seem long on such a small frame? etc. I know that there is a huge element of it depends how big he is and I need to look at this to get the right fit but any general observations about building a bike up of this size would be good.
Also 650c versus 700c wheels, again I know it is down to the individuals size but if he can fit with 700's albeit just, given he is growing at a rapid pace is this right way to go rather than 650's with plenty of adjustment space?

My friends daughter does have an Isla dropped bar bike which he could try but with a groupset in the garage which would only go on ebay otherwise and various bits and bobs including stems bars etc in the parts bin, it seemed like a bit more fun to build a bike for/with him. I could probably even pinch a wheelset of my winter bike. It needs an upgrade.

 

[Globalti]

We bought an Islabike for our son when he was about the same age; we even went to their place near Wolverhampton and he bombed around their yard on two Bheinns, one with 24" wheels I think and one with 26" wheels. The 24" bike was the right size for him and the 26" right at its limit, with the seatpost as low as it could go. In the end we went for the bigger bike and that turned out to be the right decision because we got a good 2 or 3 years of excellent service out of it, raising the saddle every few months, before we resold it for not much less than we'd paid.

 

[Dusty Bin]

Strength wise he shouldn't have any problems with changing gears. He is a pretty muscular for a nine year old, he might need to get his head around when to use them, rather than spinning like a loonie or grinding like a pro from the 60's.
I suppose my queries were is the crankset ok with175mm arms for such a small bike, or do I get a single ring crank with shorter arms for his initial road riding? It sounds like that may be the way to go. Do you use narrower bars I have some standard drop ITM bars off an old bike lying around, but suspect they would be a little deep for him. Shorter stems? I do have a 90mm stem somewhere but would this seem long on such a small frame? etc. I know that there is a huge element of it depends how big he is and I need to look at this to get the right fit but any general observations about building a bike up of this size would be good.
Also 650c versus 700c wheels, again I know it is down to the individuals size but if he can fit with 700's albeit just, given he is growing at a rapid pace is this right way to go rather than 650's with plenty of adjustment space?

My friends daughter does have an Isla dropped bar bike which he could try but with a groupset in the garage which would only go on ebay otherwise and various bits and bobs including stems bars etc in the parts bin, it seemed like a bit more fun to build a bike for/with him. I could probably even pinch a wheelset of my winter bike. It needs an upgrade.

I would strongly suggest that a 175mm crank is way too long for a 9yo. It's too long for most adults. Like I say, Lasco and others make square taper 110mm bcd double cranks in 155 and 165 lengths which are ideal for youth riders. We use 40cm compact/short drop bars on both bikes - standard bars will be too deep. Stem length depends on frame size, but if you are using a 44/48cm frame, then 90mm will probably be too long. Our bikes use 60mm and 70mm stems. 650c is a bit of an interim size, tbh. Useful if he is small, but if he can fit on a 700c then I would go that way.

 

[veloman]

Get bikes that fit, struggling on bikes too big or small makes the whole experience at best uncomfortable and at worst dangerous if they are racing.

I started my two off on a cheap Decathalon 600c bike, son jumped directly up to a 44 700c, daughter a 650c bike. I have found that they grow far too quickly BUT by constantly checking seat post length, moving saddle backwards and forwards and changing stems, I have been able to keep up (just).

Use compact handlebars, and if possible brakes that can be adjusted, little hands really struggle with adult reach brakes. A shorter 165mm crank certainly helps to start with.

BTW, good luck, do you know you are potentially starting the long struggle of two bikes (MTB and road) for your son .. every time he grows.