20" kid's bike modifications - advice needed.

Bike Forum

20" kid's bike modifications - advice needed.

18 posts & 8 voices | Started 4 months ago by martinhutch | Latest reply from moniex

Tags:

No tags yet.

martinhutch - Member

I bought my two eight-year-olds 20" bikes a year or so ago. She's got a Merida Dakar and he's got an older Scott Radical.

It's the Scott I've got issues with. It weighs quite a bit, and he has quite a bit of trouble keeping it going on longer uphills - is getting quite dispirited, so I'm trying to work out the best way to tweak it.

At the moment it has a double crankset with a 32 smaller ring with a 6-speed at the back, going up to 28. The cranks are 160mm (!). He's not using the bigger ring at the front so I'm tempted to get rid and save a bit of weight. Shorter crank seems a must.

Has anyone got any views on the best configuration for a smallish 8-year-old lad?

Slightly guilt-tripped because his sis got a new bike, and his was second-hand, so want to make it up to him. Bling pedals are already on the way...

This is the beast in question:

http://www.bikepedia.com/quickbike/BikeSpecs.aspx?Year=2005&Brand=Scott&Model=Radical+MX+240&Type=bike

Posted 4 months ago #
midlifecrashes - Member

This any good?

Budget 152mm triple
Edit: my daughter has a Scott 24" wheeler (Voltage?) and it has a triple, she never gets in the big ring either

Posted 4 months ago #
martinhutch - Member

Maybe. Might have to come up with a new shifter too, though, he doesn't seem to have the wrist strength to for the big movement needed on his front mech Revoshift. Which hasn't been a problem because he's constantly on the smaller ring.

Posted 4 months ago #
igm - Member

Islabikes spec'ed 1x7 SRAM with gripshift. Seems to work OK. Losing the second ring at the front also saves on shifters and cables so it can add up.

Next up service the hubs, bottom bracket, derailier etc. Get all the friction out of the system. Then fettle the brakes and gears to make sure there's no drag. It can add up when you're small.

Consider tyre choice and rolling resistance. If they don't go out in deep mud, then get some summer slick on there. Play with tyre pressures while you're at it - low pressure for you is probably high pressure for your children. My son has 2" tyres and runs fatbike pressures.

Posted 4 months ago #
martinhutch - Member

Yep. I took the hubs to bits and greased them up last weekend, made some difference, and tweaked the brakes again today, so they are fine.

I did buy him some knobbly tyres after a couple of sideways incidents at trail centres, but the slicks may end up going back on.

Posted 4 months ago #
Crell - Member

For a kid that age I wouldn't bother with a triple. The front / rear thing means there's just too much going on. 1 x n would be the best setup IME.Ideally something like a 28 on the front, though if its just 28 at the rear I'd maybe go even lower.

There are a few cheap 150 chainsets out there, though my son struggled with the hills where we live until he got a low enough gear. He still tends to spin out in the little ring but does use the middle as well now.

Light, easy rolling tyres would be a good upgrade.

My son also gets on a lot better with trigger shifters than he did with gripshift.

Posted 4 months ago #
Matt24k - Member

If I understand your post correctly his lowest gear is 32 front 28 rear.
No wonder he is struggling up hills! I know it has small wheels but that seems like a very tall gear for climbing. In the specs on Bikepedia it originally had a triple on the front with 24/34/42 teeth. So the lowest gear would have been 24 front 28 rear, approx 20% easier to pedal.
You have 2 options as I see it:
1) Get a some smaller rings for the front.
2) Feed your kid exclusively on a special diet of Sunny Delight and Wotsits

Posted 4 months ago #
creaser - Member

I got my son a scott voltage 20" for xmas and totally stripped it, got rid of the triple chainset and put on a funn hooka single ring 34t set up with superstar chain device, continental explorer tyres, hope 50mm stem, easton carbon bars,sdg i beam post with i sky jump bike saddle, lightend it up loads, most of the parts sorted from the forums

Posted 4 months ago #
martinhutch - Member

Thanks all, some good advice here.

What do people reckon about crank length? - he's about 1m28cm tall.

Should I be thinking 140 or 150?

Posted 4 months ago #
creaser - Member

i put 145mm ones on £29 from crc

Posted 4 months ago #
martinhutch - Member

Cheers - do you have a link to those? I can't find them on CRC.

Posted 4 months ago #
Speshpaul - Member

Lots of good advice, also look at the cassette you can get some screw ons with a 36t bail out gear.
Bars and stems and seat posts are worth looking at, they are often steel or lumpy alloy. I've fitted used flat bars in the past. You can pick very light stuff keep. But even new lower gear is a lot lighter than whats fitted.

Posted 4 months ago #
martinhutch - Member

OK. In terms of simplicity, would it be easier (and cheaper) to pick up a double chainring with a smaller cog (28 or 30t), on the basis that he will default to that, and add shorter cranks?

Certainly a heavier option, but how difficult/more expensive is it to find cheap 28t/30t singlespeed chainrings which can take shorter cranks, and which presumably would need bashring/spacers anyhow?

Posted 4 months ago #
martinhutch - Member

I've found the search for 140mm cranks tough going. Any reason I can't use these on a kid's mtb? They seem similar to the ones coming off, and are a darn sight cheaper than most of the dedicated 140mm cranks out there.

http://www.firetoys.co.uk/juggling/cotterless-cranks.html?utm_source=googleshopping

Posted 4 months ago #
martinhutch - Member

Thanks again to everyone for their help.

He's now got a new triple crankset, BB, 7-speed freewheel (with a nice big 34t big ring), and inherited my 7-speed shifters and rear mech.

He was amazed at the difference when riding uphill.

Now I just need to find a way to make front shifting a bit easier - even I have to work hard to move his revoshift, so he's got no chance.

Posted 3 months ago #
moniex - Member

Not sure if I am really wrong here, but at 8 maybe just move him up a wheel size? Really helped my kids, especially on climbs. Rolls better, much more confidence. Unless your 8 year old is reall short, I should easily fit. Most 24" wheeled bikes have very small frames.

My own 8 year old is the size of his 11 year old brother and has outgrown his 24" bike and now has a 26" bike with tiny frame. Old rockhopper frame built with light parts of the forum, he loves it and has really improved. He also stopped complaining his back hurts since moving up ( must be a size thing as he went from a spesh full suss to a hardtail ).

I'd say consider moving up instead of spending money on the 20" bike. Just a thought....

Posted 3 months ago #
martinhutch - Member

Unfortunately he's quite small for his age, and a 24 would be too big a step for him for at least a year or so. Haven't spent a huge amount on him, certainly a lot less than I'll be spending on his next bike.

Posted 3 months ago #
moniex - Member

Maybe it's just my youngest that grows like a weed! He is 4"7 ish now, or was that yesterday...

Still his 24" spesh frs was getting too small in summer when we sold it. They do only have 12" frames mind you, the 13.5" spesh hardtail would have still fitted him. It seems to be all about the frame and standover height. My kids ( oldest is 11 ) also have a norco b line 24" bike, wich still fits them easily as the frame comes up really big.

They seem to be most comfy on bigger wheels, small frame, short stem and cranks. This also gives them growing room. Small light frames with short reach are hard to come by though in 26".

Still, i did not consider my kids big enough for 26" wheels till they tried them in tiny frames, they loved them. My friend got them to give it a go. When we owned a 26" for my oldest and a 24" for my youngest, my little one prefered the 26" and would always choose that when asked.

We ended up hardly using the 24" bikes as we kept them on the 20" hotrock for as long as poss. They really shoot up at this age! I sometimes teach 10 or 11 year olds that are my height at 5"4.

Good luck!

Posted 3 months ago #

RSS feed for this topic

Reply

You must log in to post.

Singletrack Mountain Bike Magazine

Bike Forum

20" kid's bike modifications - advice needed.

Reply

Don't miss…

Singletrack

Website & Forums

Exits