Playbook, bike shop
Size charts, geometry and the gap a bike fit closes
Frame size is not one number that follows a rider around. Geometry differs enough between models that the same person takes a medium in one and a large in another from the same brand, and the figures that actually separate two frames are ones most riders have never been shown. Getting it wrong does not produce a return, it produces a bike somebody rides uncomfortably for a year.
Why this is not the general answer
The handling pattern for sizing and fit holds across every trade. What follows is the part that does not.
- Frame size is not consistent across a range, because geometry differs enough between models that the same rider takes different sizes from the same brand.
- Height alone places a rider in a band, and inside leg, reach, flexibility and riding position decide which end of it, none of which arrive in a chat message.
- Reach and stack are the numbers that genuinely compare two frames, and most riders have never had them explained.
- The consequence of a wrong answer is not a return, it is a bike ridden uncomfortably for a season and then blamed, which makes the offer of a fit a real service rather than an upsell.
How it arrives
- what size frame do i need
- i am 5 foot 9 what size should i get
- am i between a medium and a large
- what is reach and stack
- can i size down for a shorter reach
- do you do bike fits
What has to be indexed for this to work
| Geometry tables per model, with reach and stack | The full table rather than the height band, because reach and stack are what separate two sizes and what let a rider compare a new frame to the one they already ride. |
|---|---|
| Height bands, labelled as bands | The manufacturer's recommended heights per size, indexed with a note saying they are starting points with overlaps rather than answers. The note is what stops the number being read as a verdict. |
| Your bike fit service | What it covers, how long it takes, what it costs, whether it is credited against a purchase and what the rider leaves with. Somebody deciding whether to book wants to know if it is a measurement or a sales appointment. |
| What can be adjusted afterwards and what cannot | Stem length, bar width, saddle position and seatpost setback against frame reach and stack, which are fixed. Riders think a frame can be tuned to fit and mostly it can be nudged. |
The reply
On this model your height falls across the top of the medium and the bottom of the large, which is a genuine overlap rather than a rounding problem. The figures that separate them are reach and stack in the geometry table: the large is longer and taller at the front, which suits a stretched position, and the medium is the one to start from if you are coming off something more upright. A stem change moves reach a little afterwards and the frame length itself cannot be changed, which is why we would rather measure you than guess. Book a fit and you will leave knowing which.
It treats the overlap as real information rather than as an inconvenience, which is what a rider caught between sizes needs to hear. Explaining reach and stack teaches something usable on every future bike they look at. Being clear about what a stem can and cannot rescue is what stops somebody buying the wrong frame in the belief it can be adjusted later.
Where it stops
The trigger. The visitor asks the assistant to choose a size, or describes their body, flexibility or riding style so that one can be chosen.
I can give you the geometry and the band you fall into, but not a size, because the things that decide it are things we would measure. Leave your name, email and your height and we will book you a fit.
It stops answering before it guesses, says who will pick it up, and asks for the one thing that makes a reply possible. Nothing about it reads as a dead end.
Never say this here
Out of bounds
- Never name a frame size for a rider from their height alone.
- Never carry a size across from another model or another brand.
- Never say a frame that is too long can be fixed with a shorter stem.
- Never advise sizing down because the right size is unavailable.
Questions
- Riders just want a size. Does explaining geometry help?
- It helps the ones who are between sizes, which is most of the people who ask. Reach and stack give them a way to compare a new frame against the bike they already ride, which is the comparison they were trying to make with height because nobody had offered them a better one.
- Is pushing the bike fit not just selling?
- Not when the alternative is a guess in a chat window. A fit is the shop doing the thing that actually answers the question, and a rider who gets a comfortable bike keeps riding it. The wrong frame comes back as a resale and a bad year, not as a return.
- What if we do not offer fits?
- Then the handover is to whoever does the sizing conversation in your shop, and the material should say so. The point is not the service, it is that the last step happens with the rider and the bike in the same room.
Keep reading
- Everything for a bike shopFrame sizing, service turnaround and whether a part fits are the daily questions. Safety critical repair advice is an escalation.
- Handling sizing and fit in generalThe highest volume pre-purchase question in clothing and the biggest driver of returns. Quote the chart, never guess a size for a person.
- Stop riding it: the handover that begins with an instructionThe first line of the reply is an instruction to stop riding. The handover comes second, because a soft brake will not wait for email.
- Stock in a bike shop is a grid, and size is the axis that mattersHaving the bike is not having it in the size that fits. Floor stock, allocation from the brand, and why a restock is a season not a date.
- The shop can quote a named job and not the repair it turns intoBike tickets and a workshop labour menu are both quotable exactly. A repair is not, until the bike is on a stand and stripped.
Try it on your own material
Upload a document or point it at your site, paste one line of HTML, then ask it something only your business could answer.