Gear ratios for kids' road bike

[[email protected]]

Hi All,

I've settled on 10 speed Campy Xenon group for my kids' road bike
project. Now I'm trying to decide on suitable gear ratios. I'm not
using the Campy crank, but a different short one with 110 spacing that
comes without chainrings. Since I have to buy chainrings and a
cassette, this gives me many choices. But which is best?!?

The bike has 24" wheels and 140mm cranks. The kids are ages 6 and 7
height 135cm (4'5") and 140cm (4'7").

I'm thinking 34-46 chainrings and 13-29 cassette. This gives a min
rollout of 210cm or a 25.8" gear, and a max of 620cm or 77.7" gear. I
don't plan on taking the kids to any hills steeper than 5-6%, and
rarely at that.

The high gears kind of make me nervous. On downhills I'd like them to
coast and concentrate on steering and braking rather than being
tempted to go even faster by pedalling like crazy. In theory they will
spin out slow enough that it won't be a problem if I disable the big
chainring until they (or I at least!) am comfortable with it.

So what do folks think? Is a 34x29 with 24" wheels a super light gear
even for kids? Would tighter ratios and a 13-26 be better? Should I go
down to a 44 instead of the 46?

Joseph

 

[Hank Wirtz]

On Aug 17, 10:49 am, "[email protected]"
<[email protected]> wrote:
> Hi All,
>
> I've settled on 10 speed Campy Xenon group for my kids' road bike
> project. Now I'm trying to decide on suitable gear ratios. I'm not
> using the Campy crank, but a different short one with 110 spacing that
> comes without chainrings. Since I have to buy chainrings and a
> cassette, this gives me many choices. But which is best?!?
>
> The bike has 24" wheels and 140mm cranks. The kids are ages 6 and 7
> height 135cm (4'5") and 140cm (4'7").
>
> I'm thinking 34-46 chainrings and 13-29 cassette. This gives a min
> rollout of 210cm or a 25.8" gear, and a max of 620cm or 77.7" gear. I
> don't plan on taking the kids to any hills steeper than 5-6%, and
> rarely at that.
>
> The high gears kind of make me nervous. On downhills I'd like them to
> coast and concentrate on steering and braking rather than being
> tempted to go even faster by pedalling like crazy. In theory they will
> spin out slow enough that it won't be a problem if I disable the big
> chainring until they (or I at least!) am comfortable with it.
>
> So what do folks think? Is a 34x29 with 24" wheels a super light gear
> even for kids? Would tighter ratios and a 13-26 be better? Should I go
> down to a 44 instead of the 46?
>
> Joseph

Seems appropriate. Specialized's Allez Junior 24 has a 46-34 and a
12-28, also with 24 inch wheels.

http://www.specialized.com/bc/SBCBkModel.jsp?spid=21903

 

[dvt]

[email protected] wrote:
> The bike has 24" wheels and 140mm cranks. The kids are ages 6 and 7
> height 135cm (4'5") and 140cm (4'7").

Tall kids!

> The high gears kind of make me nervous. On downhills I'd like them to
> coast and concentrate on steering and braking rather than being
> tempted to go even faster by pedalling like crazy. In theory they will
> spin out slow enough that it won't be a problem if I disable the big
> chainring until they (or I at least!) am comfortable with it.

I'd use the high gears. With an under-geared bike they'll attempt to
spin like crazy on a descent, and that's when things get wobbly. If
you've seen this happen (or done it yourself , you'll understand why
that makes me nervous.

My $0.02... take it for what it's worth.

--
Dave
dvt at psu dot edu

Everyone confesses that exertion which brings out all the powers of body
and mind is the best thing for us; but most people do all they can to
get rid of it, and as a general rule nobody does much more than
circumstances drive them to do. -Harriet Beecher Stowe, abolitionist and
novelist (1811-1896)

 

[[email protected]]

On Aug 17, 8:07 pm, dvt <[email protected]> wrote:
> [email protected] wrote:
> > The bike has 24" wheels and 140mm cranks. The kids are ages 6 and 7
> > height 135cm (4'5") and 140cm (4'7").
>
> Tall kids!

My theories on force-feeding have proved correct! Just kidding. But
from the very start we have tried to encourage our kids to eat semi-
high protein diets with a wide variety of differnt things. They eat
Indian, Sushi, salads, plain yogurt, feta-cheese and all manner of
other things that often kids don't like probably because they have
never tried them and always have the same boring low nutrition food.
When we have friends of the kids over for dinner, when I see how the
other kids eat it is no surprise to me that mine are as big as they
are.

> > The high gears kind of make me nervous. On downhills I'd like them to
> > coast and concentrate on steering and braking rather than being
> > tempted to go even faster by pedalling like crazy. In theory they will
> > spin out slow enough that it won't be a problem if I disable the big
> > chainring until they (or I at least!) am comfortable with it.
>
> I'd use the high gears. With an under-geared bike they'll attempt to
> spin like crazy on a descent, and that's when things get wobbly. If
> you've seen this happen (or done it yourself , you'll understand why
> that makes me nervous.
>
> My $0.02... take it for what it's worth.
>

I'm worried about at what speed the crazy spinning wobble happens.

I was figuring that with low enough gears they would spin out way
before they even got close to going fast and would give up and coast.
I guess I'll probably just have to play it by ear and see. The last
thing I want to happen is for them to have a high speed crash and get
hurt and/or get turned off the whole idea as a result. The speeds they
are able to attain on their heavy 20" wheel MTB type bikes have been
modest in comparison making potential crashes less worrisome. The
current bikes have max gear rollouts of 430cm, and they can get going
plenty fast on those. If I disable the big ring so 34x13 is the max
gear that has a rollout of 460cm.

Joseph

 

[Paul Myron Hobson]

> [email protected] wrote:
>> The bike has 24" wheels and 140mm cranks. The kids are ages 6 and 7
>> height 135cm (4'5") and 140cm (4'7").

dvt wrote:
> Tall kids!

Well, he is a Viking

\\paul, hoping to not be pillage by a vengeful Joe.

 

[Paul Myron Hobson]

> [email protected] wrote:
>> The bike has 24" wheels and 140mm cranks. The kids are ages 6 and 7
>> height 135cm (4'5") and 140cm (4'7").

dvt wrote:
> Tall kids!

Well, he is a Viking

\\paul, hoping to not be pillaged by a vengeful Joe.

 

[[email protected]]

On Aug 17, 9:21 pm, Paul Myron Hobson <[email protected]> wrote:
> > [email protected] wrote:
> >> The bike has 24" wheels and 140mm cranks. The kids are ages 6 and 7
> >> height 135cm (4'5") and 140cm (4'7").
> dvt wrote:
> > Tall kids!
>
> Well, he is a Viking
>
> \\paul, hoping to not be pillage by a vengeful Joe.

The kids are at least part Viking, but I'm not! I'm an Italian guy
from Brooklyn. I explain the dark hair on my back to them by claiming
I am only HALF monkey.

Joseph

 

[M-gineering]

[email protected] wrote:
> Hi All,
>
> I've settled on 10 speed Campy Xenon group for my kids' road bike
> project. Now I'm trying to decide on suitable gear ratios. I'm not
> using the Campy crank, but a different short one with 110 spacing that
> comes without chainrings. Since I have to buy chainrings and a
> cassette, this gives me many choices. But which is best?!?
>
> The bike has 24" wheels and 140mm cranks. The kids are ages 6 and 7
> height 135cm (4'5") and 140cm (4'7").
>
> I'm thinking 34-46 chainrings and 13-29 cassette. This gives a min
> rollout of 210cm or a 25.8" gear, and a max of 620cm or 77.7" gear. I
> don't plan on taking the kids to any hills steeper than 5-6%, and
> rarely at that.
>
> The high gears kind of make me nervous. On downhills I'd like them to
> coast and concentrate on steering and braking rather than being
> tempted to go even faster by pedalling like crazy. In theory they will
> spin out slow enough that it won't be a problem if I disable the big
> chainring until they (or I at least!) am comfortable with it.
>
> So what do folks think? Is a 34x29 with 24" wheels a super light gear
> even for kids? Would tighter ratios and a 13-26 be better? Should I go
> down to a 44 instead of the 46?
>
> Joseph
>
tallest gear a 8 year old boy is allowed to race on over here is 5.46m.
Now I'm the first to admit that cyling regulations are usually **** but
this seems to work

--
/Marten

info(apestaartje)m-gineering(punt)nl

 

[Hank Wirtz]

On Aug 17, 12:53 pm, M-gineering <[email protected]> wrote:
> [email protected] wrote:
> > Hi All,
>
> > I've settled on 10 speed Campy Xenon group for my kids' road bike
> > project. Now I'm trying to decide on suitable gear ratios. I'm not
> > using the Campy crank, but a different short one with 110 spacing that
> > comes without chainrings. Since I have to buy chainrings and a
> > cassette, this gives me many choices. But which is best?!?
>
> > The bike has 24" wheels and 140mm cranks. The kids are ages 6 and 7
> > height 135cm (4'5") and 140cm (4'7").
>
> > I'm thinking 34-46 chainrings and 13-29 cassette. This gives a min
> > rollout of 210cm or a 25.8" gear, and a max of 620cm or 77.7" gear. I
> > don't plan on taking the kids to any hills steeper than 5-6%, and
> > rarely at that.
>
> > The high gears kind of make me nervous. On downhills I'd like them to
> > coast and concentrate on steering and braking rather than being
> > tempted to go even faster by pedalling like crazy. In theory they will
> > spin out slow enough that it won't be a problem if I disable the big
> > chainring until they (or I at least!) am comfortable with it.
>
> > So what do folks think? Is a 34x29 with 24" wheels a super light gear
> > even for kids? Would tighter ratios and a 13-26 be better? Should I go
> > down to a 44 instead of the 46?
>
> > Joseph
>
> tallest gear a 8 year old boy is allowed to race on over here is 5.46m.
> Now I'm the first to admit that cyling regulations are usually **** but
> this seems to work
>
> --
> /Marten
>
> info(apestaartje)m-gineering(punt)nl- Hide quoted text -
>
> - Show quoted text -

But that's more to prevent knee injury than to constrain speed, no?

 

[Tom \Johnny Sunset\ Sherman]

Paul Myron Hobson wrote:
>> [email protected] wrote:
>>> The bike has 24" wheels and 140mm cranks. The kids are ages 6 and 7
>>> height 135cm (4'5") and 140cm (4'7").
>
> dvt wrote:
>> Tall kids!
>
> Well, he is a Viking

Lots of Scandinavians are named Santaniello.

--
Tom Sherman - Holstein-Friesland Bovinia
BEER IS FOOD

--
Posted via a free Usenet account from http://www.teranews.com

 

[A Muzi]

>>> [email protected] wrote:
>>>> The bike has 24" wheels and 140mm cranks. The kids are ages 6 and 7
>>>> height 135cm (4'5") and 140cm (4'7").

>> dvt wrote:
>>> Tall kids!

> Paul Myron Hobson wrote:
>> Well, he is a Viking

Tom "Johnny Sunset" Sherman wrote:
> Lots of Scandinavians are named Santaniello.

Or Santaniellossen maybe.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

 

[Paul Myron Hobson]

Tom "Johnny Sunset" Sherman wrote:
> Paul Myron Hobson wrote:
>>> [email protected] wrote:
>>>> The bike has 24" wheels and 140mm cranks. The kids are ages 6 and 7
>>>> height 135cm (4'5") and 140cm (4'7").
>>
>> dvt wrote:
>>> Tall kids!
>>
>> Well, he is a Viking
>
> Lots of Scandinavians are named Santaniello.

A lot of French folks I met during my stay in Paris had Italian names.
His (great)(grand)father could easily had been Italian...

Plus his English is so good, I figured there was no way he was from the
US.