Short answer: choose the rider first. Fit, intended use and riding position decide the frame geometry and material you need. The frame's standards then decide which groupset, wheel and brake options are actually compatible. Only once those are settled should you pick the finishing kit. Chasing a groupset or wheelset before the frame and fit are confirmed is the most common way a custom build ends up with expensive parts that do not work together.
Start with the rider, not the parts list
A custom bike should be built around how you actually ride, not around a spec sheet you liked online. Before any component conversation, settle three things:
- What you will use the bike for: road, gravel, commuting, mixed terrain or a mountain bike project.
- Your riding position and fit needs, including reach, saddle height and any past comfort or injury issues.
- How hard and how often you ride, since this affects gearing range and durability priorities.
These answers shape the frame geometry, sizing and material before a single component is chosen.
Then the frame, and what it locks in
The frame and fork set the boundaries for everything else. Once you have a frame in mind, or an existing one you want to build around, several standards need checking early:
Frame and fit checks
- Geometry and sizing against your riding position
- Bottom bracket shell and axle standard
- Headset type and steerer diameter
- Brake mount type, since rim and disc brake groupsets are not interchangeable
- Axle spacing front and rear
- Tyre clearance for your intended terrain
- Cable and hose routing, particularly if you want electronic or wireless shifting
Get these confirmed before spending on a groupset. Our custom bike build page sets out how a frame-first approach works in practice.
Groupset, wheels and finishing kit as one system
Once the frame constraints are known, the groupset, wheels, tyres and finishing kit should be chosen together, not in isolation. A groupset that suits your riding style still has to match your frame's brake standard and bottom bracket, and your wheel choice has to match the groupset's freehub and cassette range. Cockpit and finishing kit then follow your fit measurements rather than the other way round.
Compatibility is where most self-specified builds go wrong. Two different 11 or 12-speed groups can need different freehub bodies, and electronic groupsets add battery placement and wiring routes to the checklist. Our groupset compatibility guide walks through the checks in more detail before you order anything.
A practical order to follow
- Define riding use, terrain and how you want the bike to feel.
- Confirm fit and position, including sizing against your current bike if you have one.
- Choose or assess the frame, and record its bottom bracket, headset, brake mount, axle and routing standards.
- Check tyre clearance for your intended terrain.
- Choose a groupset that matches the frame's brake standard and shifting preference.
- Match wheels and tyres to the groupset's freehub, cassette range and the frame's axle spacing.
- Finish with cockpit, contact points and finishing kit, sized to your fit.
- Have the full parts list checked for compatibility before ordering.
What to bring to a specification conversation
A short list helps get a useful answer quickly, whether that is with us or another workshop:
- The frame, or the frame details and size if you have not bought one yet
- Any parts you already own or plan to reuse
- Your riding use, terrain and typical distance
- Fit details from a current bike, or your height and inseam if this is a first build
- A rough budget range, so the specification stays realistic
If you want a working estimate before committing to parts, the bike upgrade quote planner is a useful starting point for budgeting a groupset, wheel or full custom specification.
Frequently asked questions
Do I need to choose a frame before a groupset?
Yes. The frame sets the bottom bracket, brake mount, axle and routing standards that decide which groupsets are actually compatible, so it needs to come before a groupset decision.
Can I mix and match components from different brands?
Some mixing is possible, but brake standard, bottom bracket, freehub and cable routing all need checking first, since not every combination is compatible or safe to run.
How do I know which wheels will fit my frame and groupset?
Wheel compatibility depends on axle spacing, brake mount type, and freehub or cassette body matching your groupset, so these need checking against both the frame and the drivetrain you have chosen.
What should I decide before getting a custom build quote?
Have your intended use, fit details and any parts you already own ready, since these shape the frame and component choices a workshop will quote around.
If you are planning a custom specification and want it checked properly, get in touch and we can talk it through as one system rather than a list of separate parts.