# Help me lighten this Scott Scale RC Jr



## joeadnan (Oct 21, 2003)

Last week, I bought the Scott Scale RC Jr for my 9 year old daughter. This is the second Scott in the family -- my 12 year old is using her elder sister's 2006 JR 24.









We are both pleased with the bike, though I was a little disappointed with the weight: 11.71kg (25.76lbs), with bottle cage and pedals, which is half a kilogram heavier than advertised. Nonetheless, I think it's good platform to start with, with a 9 speed freehub and light wheels (or at least I am assuming they are light!).

I'd like to lighten the bike, hopefully make it sub-23lbs. I've lost touch slightly with the state of weight-weenie technology today, and would like some advice and suggestions on weight savings.

I'll document the weights of the various parts as I go along.


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## joeadnan (Oct 21, 2003)

Not the best picture, but this is the 2006 Racing JR 24, which I built up using mostly spare parts from the parts bin. I did however buy a pair of 165mm RS7 Middleburn cranks. Total weight is sub-22lbs.









The fork is a vintage titanium IRD expedition fork, with the crown lowered to fit 24" wheels.


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## joeadnan (Oct 21, 2003)

For the cranks, I think I will go with 160mm RS-7s. Toying with the idea of a 1 x 10 drivetrain, and using a Wolf Tooth Components 30T direct mount chainring. Their website says that the ring is designed for the RS-8 cranks, and hence the chainline will be wrong if used on the RS-7.

I'm assuming the difference will be 2mm. Will it still work though? I have a spare Ti Phil Wood BB that will allow me to adjust the chainline a little.

The alternative is get a 4 arm spider and just go with the 30T 104mm BCD ring.


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## joeadnan (Oct 21, 2003)

Some of the weights of the stock parts are as below.

Syncros 620mm Handlebar: 247g
Syncros Grips: 84g
Syncros 6 degree 90mm stem: 142g
Syncros seatpost (26.8/350mm): 282g
Seatpost clamp: 38g
Syncros Jr RC saddle: 269g

The good news is that the parts are actually quite decent, in particular the stem, which is reasonably light. The bad news is that it'll be harder to save weight.

The handlebars are too wide at 620mm. I have a Titec Ti bar that I might use, which is about 150g. I will have to shim it to 31.8mm though. The alternative is a lightweight carbon bar. Any recommendations?

The seatpost is a bit of a conundrum. The only decent post I know that comes in 26.8mm is the Thomson Elite. I worry though that my daughter might soon outgrow its 330mm length. Are there any light posts in 26.8/400mm?

The alternative is to ream the seattube, which I know Nino did (twice) to his son's bike. Anybody think this is a bad idea? It seems like the seattube is thick enough, although it would be wise to seek counsel from the experienced.


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## xc71 (Dec 24, 2008)

A few idea's here.
http://forums.mtbr.com/families-riding-kids/scott-spark-rc-24-mods-697418.html


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## kabayan (Oct 25, 2004)

joeadnan said:


> Are there any light posts in 26.8/400mm?


eBay has a couple of RF Deus 26.8 x 400 posts for ~$40.


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## joeadnan (Oct 21, 2003)

Thanks Kabayan. I also see that Tune has 26.8 posts in 420mm lengths. I don't have to make that particular decision yet; my local bike shop has located its seat tube reamer, so I might have a go with that first.


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## SoFlo2008 (Jul 31, 2011)

May I ask where you bought the bike? I'm looking for one for my son and the local Scott dealers don't have stock and they tell me no stock at the factory either.


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## joeadnan (Oct 21, 2003)

SoFlo2008 said:


> May I ask where you bought the bike? I'm looking for one for my son and the local Scott dealers don't have stock and they tell me no stock at the factory either.


I live in Malaysia, and bought it from the local dealer here in Kuala Lumpur. It took a bit of time though.


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## joeadnan (Oct 21, 2003)

*Tyres... 626g!*

The stock tyres are wire bead Schwalbe Smart Sams. Decent tyres, but not Kevlar bead as advertised! I am sure there are some consumer laws that have been breached here...









Somewhat fittingly, the heavy tyres are already halfway into the wastebin.

















The two Rocket Rons came in slightly above the claimed weight. Still, approximately 350g saved here, or more than 3/4 of a pound in old money.


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## joeadnan (Oct 21, 2003)

*Ashima discs*









I went with 160mm Ashima Airotor discs. Cheap, and free delivery from Taiwan. I've used them on my wife's Maverick for 5+ years, with no problems. 66g savings over the stock Tektro rotors.


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## joeadnan (Oct 21, 2003)

Other changes for which there are no pictures:

Loaded X-Lite Ti 5°/90mm: 100g (42g savings)
Race Face Next carbon bar at a more reasonable 530mm width: 132g (115g savings)

Total weight reduction thus far: 571g, bringing the total bike weight to 11.14kg, or 24.5lbs.


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## joeadnan (Oct 21, 2003)

Here is an interesting photo. The front wheel is a porky 834g! Not what I was expecting for a 24 spoke wheel. I might ditch the hub and rebuild the rim with a lighter hub.


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## stom_m3 (Jun 28, 2011)

Here's what I did. Though doesn't look as extreme as you may want to go, it could give you some ideas.

http://forums.mtbr.com/families-riding-kids/scott-scale-rc-jr-w-mods-weights-883229.html


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## joeadnan (Oct 21, 2003)

joeadnan said:


> ...The front wheel is a porky 834g! Not what I was expecting for a 24 spoke wheel...


Correction. It's a 20 spoke wheel! Which makes it porkier.


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## joeadnan (Oct 21, 2003)

stom_m3 said:


> Here's what I did. Though doesn't look as extreme as you may want to go, it could give you some ideas.
> 
> http://forums.mtbr.com/families-riding-kids/scott-scale-rc-jr-w-mods-weights-883229.html


Thanks very much, Stom. Your thread, xc71's thread and Nino's thread on the weight weenie board are very much the inspiration for this little project of mine, which I will admit is as much for my own personal amusement as well as for the benefit of Daughter No. 3!

Edit: these are nino's threads, for future reference.

http://forums.mtbr.com/weight-weenies/24-kids-bike-8-4-kilos-18-5-lbs-526024.html

http://forums.mtbr.com/weight-weenies/lightweight-150-155mm-cranks-kids-509499.html


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## stom_m3 (Jun 28, 2011)

joeadnan said:


> Some of the weights of the stock parts are as below.
> 
> Syncros 620mm Handlebar: 247g
> Syncros Grips: 84g
> ...


Just a heads up Price Point has the Truvative World Cup 145g handlebars for $19.98. A good buy for the weight.

Truvativ Stylo World Cup Flat Bar | TruVativ


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## joeadnan (Oct 21, 2003)

*Drivetrain Upgrades*

I had some time over the weekend to make some changes to the drivetrain, which further reduced the weight by another 1.5lbs or so.

The aim is a 1 x 10 drivetrain, but I am still waiting for the 10 speed shifter and Dyna-sys derailleur. In the meantime, I've set up the bike as a 1 x 9, using one unit from my hoard of CS-M770 11-34T cassettes.

First are the original parts:









FSA Alpha 165mm 44/32/22T cranks.









The FSA splined BB.









Stock crank bolts









CS-HG400-9 11-32T steel cassette. The largest cogs are pinned together, but there is no separate aluminium cog-spider.









Deore front derailleur (FD-M590). This was removed.









Also removed was the Alivio front shifter. Weight included cable and housing.









Ditched the spoke protector. A free 21 grams here.


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## joeadnan (Oct 21, 2003)

*New (and not so new) drivetrain parts...*









There is nothing quite so nice, in my opinion, as polished cranks. 160mm Middleburn RS-7 square taper cranks, purchased from mtbtandems.com.









Used some NOS M900 Ti crank bolts. I could have probably flogged this off at the VRC board for a pretty penny. I'll get more satisfaction putting it on my daughter's bike though. The aluminium dust caps wouldn't fit on the cranks.









Wolf Tooth 30T direct drive chainring. This chainring is offset and in fact designed for use with the RS-8 x-drive cranks. Using it with the RS-7 crankset will place the chainring close to the granny position. I took a gamble here because I thought that this might be a good solution to the problem of the chain dropping off the 42T when backpedalling, as the chainline would be optimised for the big cog.

I haven't installed the 42T GC yet, but the alignment looks good, and there are no problems with the 11-34T 9 speed cassette. I didn't even have to touch the RD adjustment.









108mm Phil Wood Ti bottom bracket. I pulled this off one of my Ti bikes some years ago. There was what I think is galvanic corrosion on the aluminium shell of the BB, probably due to the aluminium cups reacting with the Ti frame in the high humidity conditions. Still works fine though, and I installed it without the threadlock this time, but with generous amounts of copper anti-seize grease. Steel cups this time.

The BB has adjustable cups on both sides, allowing me to adjust the chainline. In the end, I offset the axle to the drive side by about 3-5mm.


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## joeadnan (Oct 21, 2003)

*So far: 22.7lbs, 3lbs lost*

Weight saved from the drivetrain alone was 906g, although I will add a bit more back once I install the 42T GC.

A further 79g saved by switching to Loaded Ti QRs and a Tune seatpost QR. Weight now is 22.7lbs or 10.30kg. It's not looking likely that I will be able to dip below 20lbs.


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## joeadnan (Oct 21, 2003)

Installed 10sp shifter, 42T cog, 11-36T 10sp cassette with 16T Wolf Tooth cog replacing the stock 15T and 17 cogs. Also installed XTR trail levers (and learnt how to bleed hydraulics in the process). Trimmed and re-routed the housings to cater for the right/front brake arrangement. Shifter cable goes into the cable stop on the left side of the head tube, and crosses under the down tube to the right side of the bike, so that the housing doesn't rub against the head tube.









Weight now is 9.97kg, or a smidge under 22lbs.









This is the stuff I used to install the ESI grips. Not only does it come in a convenient spray applicator, but also leaves the bike minty fresh.


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## stom_m3 (Jun 28, 2011)

A couple of other things you could try;
- Swap out the Suntour Air for the RST F1rst fork will save you 180g.
- Replace the Syncros seat post @ 279g w/ a Chinese (i.e. FLYXII, Dengfu, Dashine) carbon fiber one @ 170g.

I'm surprised the front wheel was so heavy at 834g. Last year they were 692g sans disc brakes. I guess they went cheap on other components to add the more expensive disc brakes. It also shows on the rear cassette too. Last years came with an XT cassette vs. the stock HG400 boat anchor. You may want to see if Trailcraft sells the Stans NoTubes 24" wheels which come on their current bike. I've yet to see another manufacture use them. The Stans No Tubes setup runs 1290g.

With all these changes, you may be below 20lbs.


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## stom_m3 (Jun 28, 2011)

Also, forgot to ask. How is the 42T rear cog working out? Cool mod. I may have to do that to.


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## joeadnan (Oct 21, 2003)

*Gear ratios*

I wasn't quite sure what gear ratios would be suitable, so I used as a benchmark the gear ratios on my own bikes, which had low gears of either 22 x 32T or 22 x 34T. My second daughter was running 42/32/22 chainrings and a 8-speed 12-32 cassette with the smallest cog removed, with the stock 7-speed shifter.

The 30T chainring and 42T cog would yield a gear ratio of 71.4%, or just slightly higher than the 68.8% with the 22/32 combination.

If I take into account the smaller wheels, the gear inches would be in between a 22/32T and 22/34T set up for 26" wheels. The 30/42T combination on 24" wheels will give 53.9 gear inches vs 52.9 inches for 22/34T on 26", and 56.2 inches for 22/32T on 26".

Of course, these calculations ignore the differences in the crank arm lengths.

Can't wait for some field-testing this coming weekend!


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## joeadnan (Oct 21, 2003)

stom_m3 said:


> Also, forgot to ask. How is the 42T rear cog working out? Cool mod. I may have to do that to.


http://forums.mtbr.com/drivetrain-s...eup-vs-wolf-tooth-897313-76.html#post11825628

I took a bit of a gamble using the offset chainring, but it turns out that my reckoning was correct. I have near perfect shifts on the bike stand, and practically flawless shifting on the road. The proof of the pudding will be this weekend, when we hit the trails!

I was lucky in that I had a spare BB with fully adjustable cups. Not sure if there are other fully adjustable BBs out there still, apart from the Phil Wood.


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## joeadnan (Oct 21, 2003)

stom_m3 said:


> A couple of other things you could try;
> - Swap out the Suntour Air for the RST F1rst fork will save you 180g.
> - Replace the Syncros seat post @ 279g w/ a Chinese (i.e. FLYXII, Dengfu, Dashine) carbon fiber one @ 170g.


Thanks again for the suggestions. I've contacted RST Taiwan, and they say they will sell a fork to me directly. I've made payment, and am waiting for acknowledgment of receipt.

For the seat, I've ordered a small Ergon SME3 Pro Carbon (185g). It's a bit of a gamble to buy a saddle sight unseen, but I figure I can always use it to replace one of my own ratty saddles if my daughter finds it disagreeable.

ERGON BIKE ERGONOMICS



stom_m3 said:


> I'm surprised the front wheel was so heavy at 834g. Last year they were 692g sans disc brakes. I guess they went cheap on other components to add the more expensive disc brakes. It also shows on the rear cassette too. Last years came with an XT cassette vs. the stock HG400 boat anchor. You may want to see if Trailcraft sells the Stans NoTubes 24" wheels which come on their current bike. I've yet to see another manufacture use them. The Stans No Tubes setup runs 1290g.


Tell me about it! The wheels are the single most disappointing aspect of the stock bike. If the rims are 400g, rim tape 20g, twenty 15G spokes 110g, that will put the front hub at over 300g! Which leads me to believe that they used depleted uranium.

I was able to order ZTR Crest 24" rims directly from Stans. I'm waiting for the hubs and spokes to arrive.


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## joeadnan (Oct 21, 2003)

The Ergon SME3 Pro Carbon saddle arrived on Friday.









It's a nice, reasonably light saddle with decent padding. It's a whopping 82g lighter than the stock saddle, although my daughter still seems to prefer the stock Syncros saddle. I've told her to give it a try for a few rides to see how it feels.

The saddle comes with two widths, which is great. This is the small saddle, which is just 2g heavier than advertised.

It's slightly longer than the stock saddle, so I initially adjusted it slightly more forward, to aid in behind-the-saddle descents, but that made it caused by daughter to struggle when she was standing across the bike, as the saddle would poke the small of the back. I moved it about 1cm back, which was better but meant that it would be more difficult for her to get behind the saddle.

Perhaps a shorter stem might be in order.

Unfortunately we weren't able to get to the trails to fully test the saddle, due to an accident involving a large tub of coffee, my car, and its electronics (long story), so we cycled to the park instead.









Minoura cage and steel bolts supplied by the LBS.









King Ti cage with Ti bolts. I also changed out the mounting bolts for the brake levers and shifter to Ti.









Weight now about 21.7lbs, or about 4 pounds lighter than stock.


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## GSJ1973 (May 8, 2011)

joeadnan said:


> The Ergon SME3 Pro Carbon saddle arrived on Friday.
> 
> View attachment 973306
> 
> ...


Wow, XTR brakes = lucky kid!!!

What hubs are you using on your wheel build?


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## joeadnan (Oct 21, 2003)

I've just received the Tune King and Kong hubs ordered from Starbike. The front hub is slightly heavier than claimed



















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## joeadnan (Oct 21, 2003)

The Tune Starkes Stück seatpost turned out to be 20g lighter than claimed. It looks like a new design, with machined "talons" (rather than extruded), and a carbon fibre cradle. There is no longer a hole in the cradle, so no worries about crud getting into the frame.

The design is not optimal for carbon fibre railed saddles. I torqued the bolts carefully, by feel.










The AEST pedals also arrived yesterday. These are the ones with the Ti spindles.

I'd consider both these parts weight limited, in that I wouldn't use them for an adult, go-anywhere jungle bike. I'm a little more sanguine about their use on a kid's bike.










Total weight now approximately 21.2lbs. Next job will be to build up the wheels, which will probably take a couple of weeks, unless I can steal some time from somewhere.

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## joeadnan (Oct 21, 2003)

*Rear Wheel*

I managed to find some time to build up the rear wheel over the weekend.

To start with: the stock parts.









The rear wheel was just over a kilogram!









As suspected, the culprit was the hub and its depleted uranium axle.









Which, by a strange coincidence, weighed exactly the same as the Syncros-branded Alex ACE20 24 hole rim. Considering that this is a rim designed for rim brakes, the weight is not too bad. I will reuse this rim on my other daughter's bike, to be used with v-brakes.









I re-used this rim strip. I am sure I can save 10g per wheel with lighter ones.


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## joeadnan (Oct 21, 2003)

*Rear Wheel*

The Stans ZTR Crest 24" weighed 10g more than the claimed weight.









Total weight of the rear wheel. ZTR Crest 24" (320g), DT Competition 14/15/14G spokes (152g, plus 28g for brass nipples) and Tune Kong hub, built cross 3. This is a 28 spoke wheel.









Stock Maxxis tubes were actually pretty decent. Possibly another 40g per wheel once I get a hold of some 20" tubes.









Total weight is now 20.5lbs, with the just the front wheel and fork to go.


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## stom_m3 (Jun 28, 2011)

Thanks for the update. I see sub 20 once you get the front wheel completed.


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## joeadnan (Oct 21, 2003)

Got the front wheel built over the weekend. Approx 200g lighter than stock



















Tune King 28h hubs, ZTR Crest 24" rims and DT Competition 14/15/14G spokes, brass nipples, built cross two. (Ever wondered what the weight difference between cross two and cross three spokes? 4g, for 28 spokes. Whoopee.)

I removed the Stans stickers on the rims, not to lose weight but because they were annoying me when I was truing the wheel. Since I had them off, I just had to weigh them, didn't I?


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## joeadnan (Oct 21, 2003)

The RST F1RST 24 fork arrived from Taiwan. RST were able to sell the forks directly to me (USD248, shipped) because there is no distributor here.










Uncut steerer. Just under 200g savings from the fork.










Stock fork has a steerer cut to 184mm, and a star fangle nut installed.

I didn't have a new fangle nut in hand, so wasn't able to finish assembling the bike to check its final weight.


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## joeadnan (Oct 21, 2003)

Final weight is 8.88kg, or about 19.5lbs. I probably ended up with weight weenie fever, as my original aim was to knock off 2-3 lbs...


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## stom_m3 (Jun 28, 2011)

Thanks for the update!

What's your review of the 42T rear cog? Are there any issues with the derailleur handling it?


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## GSJ1973 (May 8, 2011)

What was the cassette weight with big cog? 

Curious why you use brass nipple?


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## joeadnan (Oct 21, 2003)

stom_m3 said:


> Thanks for the update!
> 
> What's your review of the 42T rear cog? Are there any issues with the derailleur handling it?


42T works like a dream. Absolutely no issues with the dérailleur. The chainline with the offset chainring also works very well. The chainline is optimised for the big cog, such that the chain doesn't fall off when back-pedalling. At the same time, there is sufficient clearance when the chain is on the smallest cog. The inside of the chain comes very close to rubbing on the second cog, but clears it.

The XTR M9000 dérailleur is rated to 40T, versus 37T for the earlier models and the XT, which was why I forked out for the XTR. I didn't have to use a longer B-tension screw, nor is the B-tension screwed in all the way.

The gearing yields gear-inches that are equivalent on 22x32T low gear on a 26" bike, which is the gear I need to clean some of the steepest technical ascents that I ride. So I'm hoping that this will be adequate.


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## joeadnan (Oct 21, 2003)

GSJ1973 said:


> What was the cassette weight with big cog?


Stock CS-M980 11-36T cassette










The 15T and 17T cogs were removed










And replaced with the Wolf Tooth 16T










And this is the WT 42T GC










Final weight is 344g, which is in fact HEAVIER than the stock CS-400 (319g), but allows the removal of the FD, front shifter and two chainrings.


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## joeadnan (Oct 21, 2003)

GSJ1973 said:


> Curious why you use brass nipple?


Selecting the parts is an exercise in the art of compromise. There is no right or wrong solution, just preferences shaped by experience.

I build most of the wheels for the 6 bikes in the family, and my experience with aluminium nipples were not great. I have a pair of 1996? Mavic Crossmax, the very first system wheelset, which used alumunium nipples. The downsides of aluminium nipples, as perceived by me are:

- I have to use much more care not to round them out when building a wheel

- I can't attain the desired tension on the drive side rear wheel with aluminium nipples

- long term durability is poor. When I rebuilt the Crossmax, some of the spokes could not be removed because the nipples had seized. I am not sure whether this is because of the peculiar to the conditions in the tropics or to our corrosive soils, but it is fact that none of the brass nipples on my other wheelsets had a similar problem. The point may however be made that the spokes and nipples shouldn't be reused anyway, which I accept.

On balance, based on the factors above, I prefer brass nipples.

When I ordered the parts for this wheelset, I saw that DT Revolution spokes were not available in the desired lengths, which is why I went for DT Competition. I was not aware at that time that Sapim Laser spokes are made in shorter lengths. If I had to do this over, I would have gone with Sapim Laser or perhaps CX-Ray (which helps monitor spoke wind-up better, but costs a lot more).


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## joeadnan (Oct 21, 2003)

Here is the list of parts used


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## wellcraft (Feb 7, 2009)

Whats are the specs for the stock bottom bracket? I need to replace mine and I dont know which one we need. Is a spark but I would assume is the same as the scale.


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## joeadnan (Oct 21, 2003)

I have no idea, beyond the fact that it has a splined interface, like an ISIS or Octalink BB


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## joeadnan (Oct 21, 2003)

An update on this bike.

I have finally gotten around to running tubeless. I bought a new bike for myself that has a tubeless system, and am now convinced of its advantages. So I've converted both my younger daughters' bikes to tubeless as well.

Weight now is 8.69kg, or 19.12lbs.



















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