The best way to size your rider’s new bike is by Inside Leg measurement.
By all means supplement with height and age as a guide, but Inside Leg is more accurate as there is a large spread of leg lengths/heights for each age. This is easy and only takes a few seconds;
- Stand your rider in socks against a wall
- Put a small book between their legs (like a saddle, high as comfortable) and against the wall
- Ask your rider to move away, measure from the top of the book to the floor, using cm or inches.
We list a Minimum Inside Leg dimension for all our kids race bikes, on each product page. We measure our bikes from the floor up to the top-tube, in-front of the saddle, then minus 2cm for shoes...
Bike Buying Guide
As we custom-build all our bikes, you have a chance to create any specification you require, to fit your rider. Here are a few tips, but if in doubt, refer to our Standard Build bike products or drop us an email...
1. Which Model?
HUP evo: this frameset can build a variety of bikes in either Drop bar or Flat bar, including: Cyclocross, Gravel Adventure, Road, Triathlon or MTB XC - as the frame can run narrow road tyres or wider off-road tyres, on Disc brakes.
HUP straatrace: this frameset can build bikes for: Road racing, leisure Road cycling or tarmac Triathlon - as the frame is limited to narrow Road tyres using it's Caliper brakes.
HUP azure: this frameset can build bikes for Velodrome track cycling only - as the frame is limited to narrow Road tyres and cannot accept a rear mech or brakes.
2. Which Groupset/Gearing?
This choice will depend on what you intend to use the bike for, alongside the relevant strength of your rider (for chainring selection). Obviously your budget, compatibility with other bikes in your household and secondary uses will also have a bearing! Our recommendations...
Cyclocross: 11-speed Microshift XCD or 11-speed SRAM Rival
Gravel Adventure: 9 or 10-speed Micrsoshift Advent or 11-speed Microshift XCD
Road Racing: 10-speed Microshift R10 or 11-speed SRAM Rival (gearing governed by BC regs)
Road Leisure: 8 or 9-speed Microshift R8 or R9
Triathlon: 10-speed Microshift R10 or 11-speed SRAM Rival (gearing governed by BT regs)
MTB XC: 9-speed or 10-speed Micrsoshift Advent or 11-speed Microshift XCD
For chainring selection (BC/BT racing regs) see guidance HERE. For other uses refer to our Standard Build bike products for a starting point. Parents often over-estimate the most suitable chainring size, for example, U10 cyclocross is best on a 30T chainring - but often a 34T is ordered!
3. Which Components?
The size of your rider dictates the best components. Here are a few tips on selection...
Drop Handlebars: match the approx shoulder width for Road, or shoulder width +1 size up for Cyclocross
Flat Handlebars: match the approx width of their press-up position
Cranks: take 10% of their height +5mm for crank length (Road & Triathlon cycling) or 10% of their height +10mm for crank length (Off-Road cycling). Example: 1350mm tall rider would choose 140mm for Road bike or 145mm for CX/MTB.
Stems: This isn't an exact science, but generally if the rider is at the lower end of the frameset's growth range, a shorter stem will be correct and vice-versa.
Saddle/Post: Our kids saddle is suited to younger riders and the Youth saddle for older riders (or younger riders Off-Road). But saddles are a personal thing. We have 2 choices of seat post, inline or rotary, the later is very useful for smaller riders at the lower end of the frameset's growth range being reversible to reduce the bikes effective length.
4. Which Wheels/Tyres/Brakes?
Your choice of wheels/tyres will be based on budget and use. The more you spend, the lighter they are, which is the single biggest improvement to any bike, but especially true for children. Tyres will be use specific: smooth/narrow for Road, knobbly/wide for Cyclocross or knobbly/very wide for MTB.
The HUP evo takes either 700c or 650b. For Road, Cyclocross, Triathlon and Road leisure, we recommend 700c for both practicality and racing regulations. For Gravel Adventure, MTB or general off-road riding, 650b wheels & tyres offer larger sizes for increased comfort, grip and off-road relaiability. The HUP straatrace & azure work with 700c only.
Brakes are often over-specified for kids, but usually 140mm front & rear for CX/Road/Triathlon, moving to 160mm front & 140mm rear from approx 11yrs+ and for Gravel adventure 160mm front & rear is plenty. On dedicated MTB bikes 180mm front & 160mm rear from approx 11yrs+ is typical. Hydraulics give more power (at a price) however that's not always a benefit to a 30kg rider in the wet, generating very little weight on their wider tyres, especially in cyclocross.
5. Which Product?
You can choose from a fully built bike, a self-build bundle or a frameset. Here are a few tips on choosing...
Fully Built Bike: you can order a Standard Build or a Custom Build bike, which is delivered in a large box, requiring just the handlebars to be turned/fitted and the front wheel to be refitted. Shipping is more expensive (only available within Europe) and the current build queue times are HERE.
Self-Build Bundle: you can order a kit containing all parts to build the bike yourself, or by your local bike shop. This is our most popular method, with shipping is more cost effective (great for overseas customers) and you can save money. You can also order without a wheelset if you already have one, saving more money. Build queue times are HERE.
Frameset: order a frameset to build using your existing components or our child-specific parts that you may require.
6. Which Size?
Refer to the size chart above, referencing their Inside Leg and Height. This is the most effective method of sizing. If you know how to interpret it, our geometry chart is below...
HUP evo:37cm: Seat Tube 37cm | VTT 49.5cm | Reach 35.3cm | Stack 50.5cm | HT 90mm | HT Angle 69 degrees
44cm: Seat Tube 44cm | VTT 50.5cm | Reach 36cm | Stack 51.6cm | HT 100mm | HT Angle 70 degrees
48cm: Seat Tube 48cm | VTT 51.8cm | Reach 37.2cm | Stack 51.7cm | HT 105mm | HT Angle 70.5 degrees
37cm: Seat Tube 37cm | VTT 49.5cm | Reach 35.3cm | Stack 48.5cm | HT 90mm | HT Angle 70 degrees
44cm: Seat Tube 44cm | VTT 50.5cm | Reach 36.3cm | Stack 49.5cm | HT 100mm | HT Angle 70 degrees
48cm: Seat Tube 48cm | VTT 51.8cm | Reach 38cm | Stack 50.6cm | HT 105mm | HT Angle 72 degrees
37cm: Seat Tube 37cm | VTT 49.5cm | Reach 37.7cm | Stack 47.2cm | HT 90mm | HT Angle 71 degrees
44cm: Seat Tube 44cm | VTT 50.5cm | Reach 38.5cm | Stack 48cm | HT 100mm | HT Angle 71 degrees
48cm: Seat Tube 48cm | VTT 51.8cm | Reach 39.6cm | Stack 49cm | HT 105mm | HT Angle 72 degrees
Take a look at our unique range of bikes here...