# Hotrock 16 build - thank you



## griffter18 (Jul 3, 2009)

Well the build is finaly complete, although the plan is to add 3 gears in the next few months.

Can I extend a great big thanks to those on the forum who provided the ideas; inspiration & shared knowledge to make this possible.

My little 4 yr old princess is thrilled and can't wait to get out on the trails with me later on today.:thumbsup:


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## 08FXT (May 3, 2012)

Nice! I wish I had something like this for my 4 yo back then! Great work!
I am just finishing a 24 inch build with pretty much the same look...


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## griffter18 (Jul 3, 2009)

Build details for others considering the mods:

Frame - Specialized Hotrock 16 (top tube 15")
Front Fork - Suntour XCT 20" JNR (sprung) 1 1/8
Headset - FSA 1 1/8
Cranks - Sinz 115mm (110mm bcd)
Chainring - FSA 34t 110mm Bbcd
BB -TH Industries BB-7420AL 58 x 116mm
BB Adaptor - DMR Wondercup
Wheels - OSET 16" with disc mountings
Freewheel - 16t bmx
Brake Discs - OSET 160 round
Brakes - Avid Elixir R hydraulics
Rear Disc Brake Mount - 6mm Alloy cut to fit ISO spacing
Pedals - Premium Expert Magnesium (BMX)
Bars - Bikehut XC 25.4m
Stem - unknown provided by LBS FOC - 1 1/8 x 25.4mm
Paint - Sandblasted & Powder coated gloss black to match fork
Graphics - Silver vinyl self adhesive from local car graphics
Tyres & seat - from original bike

Work to be done in coming months:-
Lighter spring for fork or switch to air (Spinner / White Bros)
3 speed freewheel (21/18/16), DMR Chaintug/Mech hanger,Derailleur and shifters.
Change front Chainring to 40t when required.
Remove inner tubes and go tubeless.

Longer term look at other areas of weight saving - Stem, Bars

Majority of components (Breaks, crank etc) to be moved to 24" when required.
Planning on trying to skip the 20" if possible as I believe she will be better of riding a slightly smaller bike and having more control over it than having to overstretch.


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## NYrr496 (Sep 10, 2008)

Excellent looking bike. Looks like she likes it.


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## Roc1 (Jun 25, 2009)

I don't see how you can skip 20". I got a 6 yr old and 16" was so small her knees were cramped but a 24" is too much for her small muscles to hold up. Also it may be 7 or 8 before her inseam is long enough. I think you would be smarter to go 20" then skip to a 26" rather than 24" to 26". I am doing mods at this time to a hotrocks 20. 

Nonetheless nice bike.


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## griffter18 (Jul 3, 2009)

I accept what you're saying, and only time will tell depending how and when she grows.
As said my preference is to keep her on a bike thats slightly too small but made to fit through the use of all available adjustments; seat, seat post, stem etc
Don't forget the bike is already fitted with 20" forks.
This would only be for potentially and extra 12-18 months and then move her to a small framed 24".
BMX riders at 6' all manage to fit onto 20" after all 

The key issue with all kids bikes is weight (wheels/tyres/frame) more so than fit.
At 20" theres very few air forks other than Sinner & White Bros but at 24" the range significantly increases and id still the option to move to 26" forks on a 24" frame. 

Theres no right or wrong in this and I know 6yr olds who are still having loads of fun on 12" wheels.


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## griffter18 (Jul 3, 2009)

Quick update.
As posted above I sourced a 3 speed freewheel from Amazon.
I was hoping to put SLX shifters on as there is no point in having indicators.
Sadly Shimano have chosen to discontinue them and no one is currently stocking much except for 10speed.
I've ended up going with micro shift shifters which are 9 speed and where cheap but do what I need.
Derailleur, I have a few options but to start with I've picked up a bottom line shimano 9 speed mech. By altering the cable bolt position and limiting the high & low stops I got things to work. I've had to use a few cable ties to hold things in line but a reasonable shift up and down has been achieved.
As for I would want to add gears, well to help my little one up some of the small hills and provide a gear she has the strength to turn over. She's had no problem with the shifter dropping from the big gears to the small but needs a bit more strength to move the other way. Some of this is down to strength but I know I can do more by looking to further reduce friction in the cable and elsewhere.


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## ProjectMayhem (Aug 23, 2013)

Sounds good. Would you be able to post another photo as I can't see it.


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## ProjectMayhem (Aug 23, 2013)

Does anyone know how lightweight the oset wheels are?


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## griffter18 (Jul 3, 2009)

Photos attached.
Oset wheels arent light but are no heavier than standard ones

This is pre-gears


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## ProjectMayhem (Aug 23, 2013)

Oh wow that is nice. I'll be happy if the bike I'm building looks half as good!


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## ProjectMayhem (Aug 23, 2013)

This might be a stupid question but can you use rim brakes with the oset wheels?


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## griffter18 (Jul 3, 2009)

yes you can.


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## snowbeaverking (Nov 9, 2009)

how did you get rear disk tabs on that bike buy out kit or fab ? Will you post a close up of the rear?


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## ProjectMayhem (Aug 23, 2013)

griffter18 said:


> yes you can.


Thanks for your help


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## griffter18 (Jul 3, 2009)

If you zoom in to the photo of the left side of the bike it will explain a bit more and I'll get a close up sorted out.
It's not actually my idea I got it from someone else on the forum.
Search the web for ISO disc brake dimensions and you should find a tech drawing showing all the dimensions you need. I transferred them across to a sheet of 5mm plate.
2 holes for break mount, 1 hole for wheel, then worked out where this would match up with the bolt that held the back-pedal brake (stops the unit rotating).
Once this was done it was just a case of sawing out the best shape to fit the frame.
I then cut a smaller piece of 5mm to sit over the brake mount holes to attach to the caliper. 
In total it took about 20mins to fabricate and cost me less than £10
Downside is if you get a flat you need a spanner to remove the whole unit to repair.
I've since moved it to Ghetto tubeless to save time & trouble


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## griffter18 (Jul 3, 2009)

ISO Dims are attached showing where the relevant holes need to be to mount brake calliper and also hole for axle and hole sizes.
Hope this helps

Also attached is a close up so you can see how the lower part of the bracket fixes to where the original back-pedal brake arm used to attach.


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## ProjectMayhem (Aug 23, 2013)

Quick BB question for you. How did you decide on the spindle length of 116mm?


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## griffter18 (Jul 3, 2009)

I took the frame into LBS and explained what I wanted to do.
They then provided the adaptor to convert to a threaded BB and also figured out what else would fit vs what they had in stock and sensible prices.
They were also kind enough to put it together in the frame to save me needing any additional tools.
I could have possibly gone with 113mm but it would have needed to be ordered in.


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## ProjectMayhem (Aug 23, 2013)

Thanks for your help. I have got the adaptor and read up as much as I can about bottom brackets (head in a spin now!). I think I might wait until the cranks arrive, and have a look at everything then.

We are lucky enough to live fairly near a community bike workshop where you pay a small fee (£2 for 30 mins) to use the workshop and tools with friendly mechanics on hand. Also you can book on-to-one support with a mechanic for a fiver for 30 mins.


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