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Kids DH bike

kickstand

Turbo Monkey
Sep 18, 2009
3,441
393
Fenton, MI
I don't recall exactly, but a 113 is too narrow. I honestly don't have a proper way to measure it (no calipers). The stock bb was 130-135 (can't remember what the bike shop told me). A 118 mm may work.

The bb I pulled out of his bmx is tight but cleared the rear suspension.

We rode yesterday at Boyne Highlands bike park yesterday. Even with the 140 cranks he still actually had some pedal strikes but that was more a result of pedaling at the wrong time. He still swims on the bike but the cranks made it a lot better to pedal and he handled the bike pretty well.
Im posting from my phone, when I purchase a working computer I'll get some gopro up
 

Jim Mac

MAKE ENDURO GREAT AGAIN
May 21, 2004
6,352
282
the middle east of NY
OK, this isn't quite DH, but my 4 year old hit his first DS race yesterday at Whiteface. Thanks to the crew there for doing some events to get kids into gravity racing!

Riders Ready:


Dad's chasing:


Medals handed out by the current national DH champ:
 

weedkilla

Monkey
Jul 6, 2008
362
10
I love those vids! Save it and do the run again in a couple of years. Seems to take a long time for them to hold speed on the little uphills, but once they start to jump and rail corners its awesome.
 

bizutch

Delicate CUSTOM flower
Dec 11, 2001
15,929
24
Over your shoulder whispering
Just snagged this today after selling some bike parts. 20" Hot Rock 6 speed for my youngest.

http://boone.craigslist.org/bik/3507407387.html

The fork needs some love. Any reccomendations on what's inside and how to clean/lube/soften it up? Also, tips for making the Tektro's a little easier to squeeze would be appreciated.

Oh, and last...36/28 is the easiest gear they give little kids for mountain biking? What the heck? Did they know I bought it so she could ride UP a hill??? It's got DH race bike gearing....
 
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student

Chimp
May 28, 2012
30
0
I have build my son Hotrock 20, I have stripped it down to frame. Changed spring, and cut down the elastometer bottom and top out stops in the fork.
Got new hubs to get 9sp gearing, changed stem, bars, saddle, V-brakes, cassette, shifter, mech, and chain. About half of the parts were used in my or my friends garage not being used. He loves his bike!
The original bars and stem weight in at 755 grams, the old DH bars I had and a new stem weight 451grams!!!
In summer he rode 2 weeks in the French Alps, often riding past kids more then twice his age (and some adults)! :D

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As far as the fork, its extremly simple inside. Get softer spring from Rock Shox Judy, cut down the elastometers, lube it and re-assemble.
http://forums.mtbr.com/families-riding-kids/increasing-sr-suntour-40mm-travel-fork-60mm-729468.html Here is a thread about the fork.

Hope it helps, riding with kids is so much fun, enjoy!
 

student

Chimp
May 28, 2012
30
0
RE gearing, to get good range of gears, you will have to change the rear hub, so you can get 9 or 10 speed cassette on. My son has 9sp 11-32 and can ride up most hills. If you live somewhere really hilly, you may want to get 10sp 11-36 cassette. Once they have 36-36, they can ride up almost anything.

If you really want 2x transmission, you can get some cranks shortned by bike smith, and run 2 rings and bash. But the kids may have problem pulling (or twisting) the front mech shiftter...
 

bizutch

Delicate CUSTOM flower
Dec 11, 2001
15,929
24
Over your shoulder whispering
Would a modern 32 tooth front mount to those cranks? Also, a guy who just bought a 2013 top of the line hotrock 24 offered me.the fork.off it for my oldest for $50. is that a good deal?
 

student

Chimp
May 28, 2012
30
0
I dont think you can change the chain ring on the cranks, I'll double check when bike comes back from school :)

Personally, I think the biggest advantage of 24 inch bikes is that you can run real 26 inch forks.
You can get any 80-100mm used fork and it will be more adjustable then any stock fork on kids bike.
But that may be just my opinion, as I am fussy what my boy rides.
 

student

Chimp
May 28, 2012
30
0
Well that's up to you, I didnt want to spend too much money, as I knew my son would be riding it only for one season. So I had the original rims, spokes and nipples laced to Shimano Deore hubs.
If you can change the whole wheels, you could really lighten up the wheels, go with less spokes etc...

But to go 9 or 10 speed, you need at least new rear casstte hub, as the one on the bike is freewheel hub, which only accept 6/7 speed and are super heavy.
 

sbabuser

Turbo Monkey
Dec 22, 2004
1,119
57
Golden, CO
For the v-brakes, the way to make them easier for little hands is to first back off the caliper tension screws as far as possible. If that's not enough, you can lighten the spring return on the calipers by bending them toward the rim gently by hand.

Don't forget the good cables with some silicone spray lube, and you can also disable/ remove the spring return on the levers if they are still too hard to pull. My daughter is 6 and has no trouble w/ the tektro v-brakes on her micro mini, but I try to be proactive w/ maintenance so they don't give her problems.
 
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ekruegerv

Chimp
Jan 15, 2013
2
0
Aliso Viejo

Kona Stinky 2-4

I've been browsing this thread for a while and just finished up my daughters new rig. Started at 36lbs and now pared down to 31lbs. With a new wheelset and a new fork, it will easily go sub 30lb. I switched out the stock seatpost/saddle with a tiny bmx pivotal post and plastic saddle. Saved a ton of weight and let me get the saddle lower. Newer stinky 24's (2011+) don't come with a double front setup like they used to, so I got some take off SRAM GXP cranks. I cut them down and drilled them to 150mm. I also added a X-9 front derailleur that was sitting around. Even though the bike doesn't come stock with the FD, the frame still retains the cable guides and stop necessary for proper mounting. Next up, ditched the insanely heavy Maxxis High Rollers and went with Intense BMX kevlar bead tires (1.75rear/1.85front). Lastly, I cut down an old Easton Monkey Bar from 685 to 620mm, the stock bar is heavy and has a lot of rise to it. I've also bought an old fox float 6.5 x 1.5 shock for 30 bucks that will go on and hopefully save some more weight. The rear is a little stiff for really small kids. The front is "OK" in terms of spring rate. Unfortunately, there is no adjustability besides spring preload on this fork.

The bike is still a little big for my 6.75 yr old daughter, she's on her tippy toes when standing. Riding, especially down hill is no problem. She's 51" tall right now.

Thanks to everyone who put up info in this thread, I can't tell you how many times I've read through it.
 
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bizutch

Delicate CUSTOM flower
Dec 11, 2001
15,929
24
Over your shoulder whispering
Anybody know how much it would cost to have a Gromhit shipped from Whistler to NC or a cheap way to do it? I have an acquantance who lives at the mountain part time who had offered to let them ship or drop it at his place. Thought I could have it shipped from his place.

The sellers up there are not willing to ship to the US and the one I talked to recently won't even take PayPal. :rolleyes: Yes, I know you can get them in the US from time to time, but Canadee uh has so many so often.
 

ekruegerv

Chimp
Jan 15, 2013
2
0
Aliso Viejo
Just an update on how the bike sits, overall weight, etc. Since the previous pic, I've added an x-fusion velour air fork. Saved a ton of weight and was pretty cheap. Got it on ebay for $128 (sold the stock coil DJ3 for $125). Also, I added an old fox float shock for $30. The bike with pedals is 28.4lbs, way way lighter than the 37lbs that it started with. My daughter is 50" and it fits perfect with the seat all the way down. I couldn't be happier as it'll be a bike that she can grow with for sure.

Oh yeah, built up and laced my first wheel ever. Since the fork is a 9mm QR, the stock QR20 had to go. I went with an Alienation Deviant rim. At "only" 415g its one of the lightest I could find and cheap too.

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kickstand

Turbo Monkey
Sep 18, 2009
3,441
393
Fenton, MI
Anybody know how much it would cost to have a Gromhit shipped from Whistler to NC or a cheap way to do it? I have an acquantance who lives at the mountain part time who had offered to let them ship or drop it at his place. Thought I could have it shipped from his place.

The sellers up there are not willing to ship to the US and the one I talked to recently won't even take PayPal. :rolleyes: Yes, I know you can get them in the US from time to time, but Canadee uh has so many so often.
I have had a few bikes shipped over the last couple years. I just bought a small tr450 last month and the shop charged $100 for shipping.

I just sold a specialized bighit FSR and it cost me $78 to ship usps with insurance. Total package weight was around 55 lbs.

I don't know what shipping was on my son's gromhit, the guy i purchased it from was gracious enough to cover shipping. It came from Idaho and was in a significantly smaller box than any fullsize bike has ever came in.
 

kickstand

Turbo Monkey
Sep 18, 2009
3,441
393
Fenton, MI
*edit* just realized you are talking about international shipping, that may be a fair bit different then US shipping costs. Not sure to be honest.
 

kickstand

Turbo Monkey
Sep 18, 2009
3,441
393
Fenton, MI
I need to start looking for a second gromhit.....my fiance's daughter who happens to also be 7 and only a few days older than my son is starting to get the itch that she also wants to ride DH with us.

I was hoping, and I am still hoping to hold off one more year
 

student

Chimp
May 28, 2012
30
0
So I feel I need to share my son’s new bike build as this thread has been quite an inspiration and source of information in making the build happen.

My son is 6, and most of the time he rides/races BMX. This bike is his holiday/Alps bike. He has ridden in French Alps since he was 4. Last year he has done pretty good job on modified Hotrock 20.

Due to the cost of his racing and travelling we had to build the DH bike on relatively small budget, so its bit heavier then I would like, but that’s life… It’s more important he picks up the skills from BMXing then chase few grams on his bike.

We have used single pivot Grom opposed to FSR one as it has 2 inches shorter seat tube and it allows him to get on and off the bike better. I have also cut 1cm (1/2)inch from the seat tube to make the bike “smaller”. After the pictures have been taken, I have also installed off-set bushes that dropped the bike further 8mm down. We have end up with 64* head angle.

When he does grow up bit more we will switch most of the parts to FSR Gromhit frame.

We used mix of old parts we had laying in the garage, some donated from friends, some from his 20” bike, fork from eBay and few we bought new. We tried to make sure the bike fits him well, and functions like mini DH bike.

We could have gone with lower profile tires to make the bike even smaller, but the large volume of the tires will protect him more from braking bumps of Portes du Soleil area (where he will be riding for 4 weeks this summer) and the triple compound will give him more grip in corners.

We have used 140mm BMX cranks to fit him better on the bike. Most other parts are visible from pictures, if anyone wants more info on the set up feel free to ask.

We both have really enjoyed the built, and can’t wait to ride together.

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kickstand

Turbo Monkey
Sep 18, 2009
3,441
393
Fenton, MI
what fork are you running?

That single Pivot grom hit really looks a lot smaller than the fsr version I have. It's kind of a wash now, but my son would have been better off on the single pivot initially.
 

student

Chimp
May 28, 2012
30
0
I have managed to find almost unused 2010 Fox 32 Van R with 15mm axle and 1 1/8 steer tube. I have bought black spring (lightest one they sell) for it. And I will service it before we go for our trip.

Yes single pivot one is good for size, for a small kid.

Its 5cm smaller then FSR one. I have cut 1cm off the seat tube. Installed off set bushes, 8mm. And BMX mini seat/seatube combo is about 1cm lower then Thomson seatpost with Odyssey Junior BMX seat, I have checked. So it all adds up! 5+1+0.8+1=7.8cm over 3inches of difference. That allows him to move around the bike quite comfortably.

If its any help he is 125cm (49 1/4inch) tall.
 
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Oldranger

Chimp
Jan 20, 2013
22
1
USA
I have a 9 year old son that has been riding DH for a couple years now. He currently weighs in at about 83 pounds and is 57 inches tall. He has experience riding on DH race courses at Beech Mountain, Snowshoe and Plattekill, and has also ridden at Whistler and a few runs on a muddy day at Windrock, TN. He has grown and progressed quickly - an expensive proposition but still cheaper than most golfing habits a lot of folks here in SC seem to have.

At the beginning he rode a Kona Stinky (didn't know much about these bikes), then we built up an SX Trail for 'year 2' of his DH riding. Now going in to 'year 3' for him we built up an XS Demo. This kind of investment is not trivial - but based on what I've seen with my son and an 11-year old he likes to chase down Snowshoe...a small person at least 80 lbs and at least 4.5 feet tall can leverage the advantages of a well spec'd DH rig. We've done our homework on this one. From the flat bars and negative rise stem, to custom IsoTuned Boxxer WC forks running at 20-22 psi, to some painstaking searches to find 32h 24" wheels and tire options...this bike is really working for him. I'm pulling off the CCDB and putting on a tuned VanRC for him for an upcoming race (btw this is a less expensive option). Sometime soon he will ask for 26" wheels...that will be the last I see of him on the trails...it is already hard enough to keep up on some sections.

In hindsight - I would skip the 24" Small SX Trail Build. The only advantage of that build over the 24" XS Demo is that it is lower cost.
 

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kickstand

Turbo Monkey
Sep 18, 2009
3,441
393
Fenton, MI
Oldranger, I spoke to you breifly at Snowshoe race #1 I believe. I should have my 7 year old with me for race #2, not sure if he will be ready to try and keep up and race with your boy or if he'll just be riding around for fun.
 

Oldranger

Chimp
Jan 20, 2013
22
1
USA
BTW: I'm highly confident that a DH headtube design (like the Demo) and Boxxer WC double crown forks are a huge factor in his riding progressing so fast on it. It allows for a few things:
1) Slacker Heat Tube Angle - better in steep stuff, rough stuff, and higher speeds. Obvious, I know, but two years ago I didn't know what HTA did...all I was thinking about was standover at that point.
2) Lower Handlebars. Yep - even with 8" of travel. The combination of a negative rise stem, flat bars, and an internal headset has his handle bars about 2" lower than what I had on his SX Trail with a 180mm travel single crown Fox Van 36. Some of that was that I missed the mark on that bike not understanding handlebars and stem choices well enough. The other limiting factor is the external cups on the SX Trail increase stack height, raising bars. The other fact is that the axle to crown on 7" single crown forks is not much less than axle-to-lower crown on a dual crown 8" fork.
3) No weight increase. Boxxer WC = 2689g. Fox Van RC = 2700g