24" wheels on a 26" frame

My youngest has put on a growth spurt that has meant she has outgrown her 24" FS frame. It's been great but its now a bit short in the top tube. Now that my eldest has moved up to a medium Anthem X, I had her old frame - an Xtension XS frame. I feel a bit bad for the youngest having to cop all of the hand-me-downs so I asked her what sort of colour scheme she wanted and she replied with a unambiguous "I want it blue". I had some leftover automotive paint in sky blue, so I did a bit of masking off and made some key bits blue. I didn't want to paint any of the wear areas as the brushed alu finish on this frame is really hard wearing and can take a truckload of abuse without looking crap (unlike anything painted). I needed a place to put some decals so an overcoat of some white and then a final coat of black finished the paint job. Linkages, derailleur hanger and seatpost clamp were all sand-blasted, primed and finished in the same blue.


Xtension frame repainted with blue highlights

Transferring all the parts took about an hour. Only two parts didn't make it across:

  • the seat post as this frame takes a 31.6mm post and the 24" frame uses a 27.2mm post; and
  • the carbon fibre chain guide because of the different seat tube diameters

Completed bike

I'm really pleased with how it turned out and my daughter loves it.


Rear view

Build list

It's a fairly lightweight build with components selected for a 30kg girl.

ComponentDescriptionWeight (g)
FrameXxtension, 4" horst link frame2688
ForkRockshox SID Race 20071290
WheelsCircus Monkey HDW2 front/HDW3 rear hubs, 16 x Ti spokes, 16 x straight gauge stainless, Velocity Aeroheat rims1343
SkewersCircus Monkey47
HeadsetToken105
SeatpostCustom carbon, carbon cradle, Ti bolts142
Seatpost clampCustom, Ti bolt18
SaddleSDG Allure266
CranksTruvative FiveD (shortened - 150mm)505
ChainringBlackspire Mono Veloce NW 30t40
Bottom bracketToken Carbon218
ShifterXT 9 Speed135
Rear derailleurXTR short cage189
ClusterXTR 11-34 9 speed244
ChainKMC x10SL212
BrakesAEST435
Brake boltsTi74
Brake adapters24
Front rotorAries 160mm79
Rear rotorKCNC Razor 140mm61
BarsProX120
StemExotic 60mm108
GripsFoam18
PedalsAEST platform with Ti spindles284
Front tyreRocket Ron445
Rear tyreRocket Ron446
TubesSchwalbe 20"170
C-Guide18
Bottle cagecarbon28
Cables68
=======
Total weight9820

Concerns

With the 24" wheels the bottom bracket height is at 28cm. I'm not sure yet whether this will be a problem with rock strikes and pedal clearance which pedalling and cornering. The cranks are short at 150mm, so it should be no worse than a 30.5cm BB height with 175mm cranks.

To do list

Shock

The frame has a Manitou Radium QRL shock. It worked fairly well for my elder daughter, but she was bigger and heavier than my youngest is now. I'm at full negative on the rebound at the moment and it is still a bit on the slow side, so the rear packs down over repeated closely spaced bumps.

As a result, I have revalved a 2011 Monarch R to go on this bike, but I need to make some new bushings for it to fit. I had a choice between a Float R, Float RP2 or the Monarch R and decided to go with the Monarch R primarily because of the ease with which you can DIY revalve it. The Fox Float series are painful because of the need to use a fill needle for the IFP. When you are disassembling the shock frequently to test different settings, it is a real PITA to get the IFP charge right. The Monarch R uses a fill adapter for a standard shock pump.

Finally outgrown - April 2018

The day has finally arrived that my youngest has outgrown this bike and I've moved her on to a medium Giant Anthem X.  A few things have changed over the years:

Related articles:

Modifying 26" fork for 24" wheels

My daugther's 24" FS bike came with a Suntour SR coil spring fork. The spring rate was quite good for my daughter's weight but the fork had no noticeable damping and was almost 2.1kg....

Roval Traverse 26" wheelset

Quick facts

Velocity 24" rear wheel

This sweet little 24" wheel was built by Velocity using their Aeroheat 24" rim which is a twin wall rim with shallow V profile and a Velocity sealed bearing disc hub. The spokes are straight guage with brass nipples.

Trance X 29er frame

I bought this frame new from a Giant dealer with warranty.

AEST jockey wheels

about 9g each;

A2Z Disc Front Hubs

Over the years there have been a number of versions of A2Z disc front hubs: