# Diamondback Octane 20 build



## CaseyS (May 8, 2008)

Just thought I'd share a few pics of my son's Diamondback Octane 20 I am having fun modifying. Bought the bike back last xmas and caught the UGI bug.

List of mods in the approximate order that they were done

36 tooth OPC front sprocket (40t stock). Much needed for any type of climbing
13-34 megarange freewheel (6 to 7 speed conversion)
Old sram 7 speed shifter from my old trek
Serfas grips
Ghetto tubeless setup
Nashbar 2014 seatpost
Nashbar 6061 40mm rise bar
Front fork conversion :
RST Capa 20 fork (1650 g)
Al steerer
Cane creek S3 headset
Kalloy 100 mm stem
Acera rear derailluer (stock tourney is garbage)

Bike is 25.0 lbs with pedals now. There is an easy lb. by getting rid of the OPC steel crank which is the next mod. Overall, not the highest end mods but all significant improvements to stock. And yes, I do realize I could have spent a bit more money on a higher spec bike to begin with (see: ibex 320) but it seems all of the offerings in 20" mtb are all basically 1x6 and similarly spec'ed.


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## CaseyS (May 8, 2008)

oops, no pics :madman:


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## Bikemonkeys (Dec 3, 2005)

Does that fork really work or is it more for show? I just got my daughter a Trek 20inch mountain bike, the fork is junk. Her Redline BMX bike makes the Trek look like garbage. It was cheaper, but a little more money and some better parts would have gone a long way.

She loves it (it's her first girly bike) and she loved being able to go mountain bike riding, so I guess that makes the money well spent.


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## CaseyS (May 8, 2008)

Absolutely not for show.

I replaced the stock suntour s2000 fork with this one, according to my son, his favorite mod. The suntour was only 30mm travel and was very stiff.

My son weighs 45 lbs and the fork is plush enough at the lowest preload adjustment. There is actually a bit of sag with just him on the bike and can compress the fork at least 25mm just with him weighting the handlebars while riding. I would say the fork would be good enough up to a 100 lb rider before bottom out would be a issue at the highest preload adjustment. The fork comes in at 1650 grams as advertised (w/o steerer). You can get either an aluminum or steel steerer (available separately) and the whole package for less than $100.

Money well spent in my opinion.


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## [email protected] (Jul 21, 2010)

*Diamond Back Mods*

I was just sitting here trying to do the same thing to my little guy's DiamondBack , turns out he cant climb the hills, not for lack of ability, but due to limits of his bike. I wanted to find a 3 sprocket crankset and derailer to turn his bike into an 18 speed , any suggestions?


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## TigWorld (Feb 8, 2010)

You can sometimes get Suntour triple's in 152mm crank arms on fleabay. I have never seen any shorter triple cranks. You could also use some BMX sqaure taper crank arms which go down to less than 140mm long for little legs and are 110mm BCD. They are only single speed but can work with a double converter chain ring like the IRD triplelizer .


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## NYrr496 (Sep 10, 2008)

I put that exact same fork on my son's Gary Fisher Precaliber. It's leaps and bounds above the Suntour fork that came on his bike. I just wish it was lighter.


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## nbwallace (Oct 8, 2007)

*How did the tubeless conversion go?*

I was thinking of trying to convert my son's 24" to tubeless. Did you use gorilla tape or split tube?


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## EBasil (Jan 30, 2004)

That's a very cool 20! Nice work!


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## CaseyS (May 8, 2008)

Cool to see some interest on this.

In my opinion, it would not be worth the trouble on a double or triple up front. I have several new mods that aren't documented here yet. It has since been converted to 1x8 with an x.5 derailleur and trigger shifters. This is leaps and bounds above the stock setup. I had to build a new wheelset to put a standard cassette (not freehub) on it to get the 8 speed.

From the original bike pictured here, the front sprocket is 36 and the large cog in the rear is 34, plenty of gearing with that bike to climb just about anything. The 13 in the rear will get you to 18-20 mph on the downhills. Plenty of speed for kids. Not to say that kids wont learn how to manage front and rear shifters, but the range you would gain over a single ring in the front would rarely be used.

@tscann. PM me i can probably send you that whole drivetrain setup for a cheap price. It has since all been upgraded.

New upgrades to the bike include:

FMF 110 bcd 145mm crank with 36t aluminum sprocket
N-gear jump stop
BBG ultralight bash guard
sram x.5 rear deraillleur
sram x5 trigger
wheelset : velocity aeroheat 28h, front hub: shimano xt 28h, rear hub: shimano deore:28h

Cranks
Ring

I'll post some new pics when I get a chance

Edit: the tubeless conversion is ghetto tubeless


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## CaseyS (May 8, 2008)

Some updated drivetrain pics (crappy cell phone cam, sorry)


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## TigWorld (Feb 8, 2010)

Nice work. Love the new wheels.


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## IAmHolland (Jul 8, 2010)

CaseyS said:


> FMF 110 bcd 145mm crank with 36t aluminum sprocket


What size bottom bracket does FMF use and what chainline does it put it at? Or better yet, what size did you use, and what chainline is it? I assume the chainring is on the inside of the crank and the bash guard is on the outside.

Thanks!


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## CaseyS (May 8, 2008)

I used a 113mm ISIS bottom bracket. That crank is setup for a single chainring on the inside, but does not have provision for a ring in the normal outside position. I used a file to create a flat on the arms where the bash guard now resides. You may be able to get by without the bashguard, but it really helps as an outer chain guide. I remember the chainline at 48mm but I can double check it for you this evening.

Edit: 48mm chainline is correct


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## IAmHolland (Jul 8, 2010)

CaseyS said:


> Edit: 48mm chainline is correct


Thanks a bunch, CaseyS. If I'm measuring my son's hotrock 20 correctly it's close to 48mm as well.


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## BikingCivic (Aug 19, 2011)

I KNOW THIS IS OLD...i got the same bike for my daughter...any updates?


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## Rondo (Oct 14, 2011)

Very cool thread! 

Picking up an Octane for my daughter tonight.

CaseyS, is your son ready to sell his yet? I need one for my son.

:thumbsup:


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## Rondo (Oct 14, 2011)

Girls Octane is in hand. Let the mods begin LOL!

My 7yr old's first geared mountain bike coming off a 16" Trek single speed! Who-hoo!!! I couldn't be more excited!

Daughter took it for a test spin and agrees the gearing is not the best. But she's totally diggin it!

Sooooooo, guess I need to go with the BB~Crank~Chainring~Bashguard mod.

I notice there is a 68 or 73 x 113 BB. Does the Octane take the 68? And does anyone know if there are any brands to stay away from? I've read up a little on ISIS BB's an see their bearing design wasn't the best....


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## BikingCivic (Aug 19, 2011)

dont you guys hate the w ater bottle placement? lol the grip shifter sucks too


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## Rondo (Oct 14, 2011)

Yeah the H2O bottle is not the best. Well, she will need to stop and take a break everytime she wants a drink. She already does that anyway, You know how everything is an adventure with kids and they've got at least 50 questions between gulps. LOL! 

The shifter is a bit hard to shift. Have already bought a replacement for that. (X5 Trigger) She says the brakes were hard to pull so I adjusted the little set screw on the levers below the cable stops to bring the laver a little closer to the grips for her little hands. She says they're still hard to pull. :-( So I think I'm going to go over the cable housing and replace with something really nice, smooth and resistance free. Maybe some Jagwire.

Still wondering about the bottom bracket if it's a 68 or 73? How do you tell? They are so close... Wife thinks I should ditch the pink H2O bottle cage and go with silver. What do ya'll think?

Some of my mods so far....

FMF140mm Aluminum Cranks
34T Aluminum Chainring
Sram X5 Trigger Shfter
BBG Aluminum Lightweight Bash Guard
N-Gear Jump Stop
Pink Ultralight Chainring Crankset Bolts


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## BikingCivic (Aug 19, 2011)

keep the pink...i was prolly gonna do the sram upgrade too....what do you think the best mods are for the bike?


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## Rondo (Oct 14, 2011)

Hi BikingCivic.

I take a two step approach to my mods. 

1.Make the bike effective meaning work or feel better.
2.Make it lighter. Less weight = More fun.

First things first, the brake levers are pretty ineffective because they are too far from the handlebar for little hands to pull. (Had to linearally adjust them all the way in.) Even those ergo levers that are molded to sweep in then back out a little would have been better. 

The cables do not move freely and probably need to be replaced. (This is amazing because they are hard to operate and are three times shorter than the ones on my bike! (Me thinks $30 worth of all new cabling is going to make this a completely new ride btw...)

The jury is still out on the derailleur. It’s a little stiff to shift up ie., 2nd to 1st but I’m going to work with it a little bit to see if it is just the shifter or cable. I’ll install the trigger shifter and new cables to see if that solves it. My daughter has little hands and not a lot of strength in her forearms so grabbing the grip shifter to turn it is a little difficult. We’ll experiment a bit & see what works.

The other problem we’re dealing with is the gearing. It is good, just not good enough. She felt a HUGE difference coming off the single speed bike but if we hit something with any type of grade it’s all over. I’m going to take a simpler and less expensive approach than CaseyS and just do the crank & chainring mod instead of rebuilding the rear cluster, and see if that will suffice. On ebay I found a singe 34T 110 for $10 so will see if this is good enough. (that's 6 teeth less than stock!)

The seatpost and handlebars are both steel on this bike so going aluminum or carbon is an easy no brainer that will shed a lot of weight.

Oh btw, I forgot to mention, when deciding on the ISIS BB I found one at 290 g. and another at 190 g. I believe that’s 3.5 oz’s lighter. The Extralight Bottom Bracket has a hollow axle and is a VP model# MB-602. About $20 They aren’t the strongest BB in the world and are not highly recommended for adults but for my 7 yr. old daughter who weighs a whopping 40 lbs. this will work just fine.

I’ll have her ride for a while with this setup then see where her next analysis comes. 

Here’s a pic of her practicing her transitions and rocking a little night ride last night in front of the house to check the bike for adjustments.


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## BikingCivic (Aug 19, 2011)

what age and how tall is your daughter? mines a shorty she turned 7 in august....she cant even sit on the seat and put her feet down she stradels the top frame....my other daughter is 5 and is about the same height lol


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## Rondo (Oct 14, 2011)

7 yrs. old right now. She's 50" tall and weighs 47lbs. Prolly going to take after her 6'1 daddy. ;-)


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## BikingCivic (Aug 19, 2011)

ha ya she looks really tall...ill have to measure mine and see how tall she is


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## texacajun (Jan 20, 2004)

Those Tourney rear der's are kinda junky but I did get the brakes & der operating much more efficiently once I put some higher quality cables & housing on the Hotrock. Every one I've ever tried in a shop has a ton of drag...low quality garbage for cables on kid's bikes. :nono:

Cage location on the Octane doesn't look perfect but I don't think the one on the top side of the down tube on my daughter's Hot Rock is any better. With the step down top tube there's not much room inside the triangle. Even with a side entry/exit cage I can only find one very small bottle of mine that will fit and the cap rubs. It's a bit of a struggle for her to get a full bottle in there since it sort of wedges in there. :nonod: We only use it for short rides since she has a camelbak. Still it's frustrating for her when we do use it.


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## Rondo (Oct 14, 2011)

Hey CaseyS,

Has your son grown out of his Octane yet so you can sell it to me?


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