Introduction: Why Geometry Matters (Even If You’re Not a Nerd)
When most people shop for a new bike, they look at brand, groupset, colour, maybe weight… and then pick a size like it’s a T-shirt. “I’m probably a 54.” Done.
The problem? A size 54 from one brand can fit completely differently than a size 54 from another. Same goes for “Medium,” “Small,” and all the other labels brands love to throw around. It’s like guessing your shoe size based on what your mate wears.
That’s where Bike Insights comes in — a free online tool that lets you compare bike geometry across brands and models in a visual, easy-to-understand way. Whether you’re deciding between two bikes, trying to replicate a fit on a new frame, or just want to understand what “stack and reach” actually mean, it’s incredibly useful.
In this post, I’ll walk you through how to use Bike Insights step by step, explain what all those numbers mean in plain English, and show you how to make smarter, more informed decisions about your next bike
Bike Comparison Overlay
What is Bike Insights?
Bike Insights is a free online tool built specifically to help cyclists understand and compare bike geometry. Instead of relying on size labels like “54” or “Medium,” it gives you the actual geometry numbers that define how a bike fits and handles — and lets you overlay and compare different bikes side by side.
Whether you’re a casual rider, bike nerd, or somewhere in between, Bike Insights is one of the most powerful tools for:
Comparing bikes across brands and model years
Understanding how one frame differs from another in shape and fit
Visualising how changes in geometry affect your position on the bike
The platform pulls geometry data from thousands of road, gravel, mountain, and commuter bikes. You can:
Search for a specific model
Compare two or more bikes visually
Dive into the raw geometry numbers
Even upload your own geometry manually if it’s not listed
Bike Insights is especially useful if:
You’re buying a new bike and want to compare it to your current one
You’re switching brands and want to avoid size surprises
You’ve had a bike fit and want to match stack and reach numbers on a new frame
Think of it as a bike geometry comparison supertool — one that takes the guesswork out of figuring out if a new frame will actually fit you.
Why Geometry Matters (In Plain English)
Bike geometry isn’t just for engineers or people who say “compliance” too often. It has a huge impact on how your bike fits, feels, and handles — and it affects everything from comfort to performance to injury risk.
Here are some of the key geometry terms you’ll see on Bike Insights — and what they actually mean for you:
Stack
This is how tall the bike is at the front end — measured vertically from the bottom bracket to the top of the head tube.
Higher stack = more upright, comfortable riding position (common in endurance bikes)
Lower stack = racier, more aggressive position
Reach
This is how long the bike feels — measured horizontally from the bottom bracket to the top of the head tube.
Longer reach = more stretched out position
Shorter reach = more compact, upright
Stack-to-Reach Ratio
This is a quick way to get a sense of the bike’s personality.
A higher ratio (>1.5:1) usually means an upright, endurance-style fit
A lower ratio (<1.4:1) points to a race-focused, aggressive fit
Seat Tube Angle
This affects how far over the cranks you’re positioned.
A steeper angle pushes you forward — good for performance and aero
A slacker angle puts you further behind — better for comfort or climbing
Top Tube Length, Head Tube Length, Chainstay Length…
There are more — but the main point is this: small changes in geometry can lead to big changes in how the bike feels. Two bikes might have the same size label, but completely different personalities.
And that’s exactly why Bike Insights is so helpful. It takes all these abstract numbers and turns them into something you can actually understand — and use.
Road bike geometry
How to Use Bike Insights (Step-by-Step)
Using Bike Insights is refreshingly simple — no engineering degree required. Here’s how to compare two bike frames side by side:
Head to the homepage. No login required, no paywall — just straight into the good stuff.
bike insights tutorial 1
Step 2: Search for Your First Bike
Use the search bar at the top to type in the bike brand, model, and year. For example: Giant Defy Advanced Pro 1 2015
Once you find it, click on the model to open its geometry page.
bike insights tutorial 2
Step 3: Add it to the Comparison Tool
On the bike’s page, click “Add to Compare”. You’ll see a visual overlay area pop up on the right-hand side or at the top (depending on screen size).
Step 4: Search for Your Second Bike
Repeat the process to add your second bike. This could be:
The bike you’re currently riding
A model you’re thinking of buying
A newer version of the same frame
Click “Add to Compare” again — now you’ll see both frames in an overlaid diagram.
bike insights tutorial 3
Step 5: Review the Geometry Comparison
This is where the magic happens.
You’ll now see:
A visual overlay showing how the two bikes differ in shape
A geometry table listing measurements side by side
A stack/reach comparison with clear percentage differences
Indicators showing if the difference is small, moderate, or significant
Screenshot
Optional: Explore Further
Use the interactive slider to flip between bikes
Click on geometry terms to learn what they mean
Filter by category (e.g. road, gravel, MTB) if you want to explore similar bikes
Bike Insights turns what used to be a guessing game into a clear, data-driven decision. Once you’ve compared two bikes, it’s much easier to see if the new one fits similarly — or if you’re accidentally buying a completely different ride.
Understanding the Comparison: What to Look For
Once you’ve got two bikes side by side in Bike Insights, you’ll see a detailed geometry chart and a visual overlay of their frames. It’s a lot of data — but here’s how to make sense of it.
1. Look at Stack and Reach First
These are the most important numbers when it comes to how a bike fits you.
Stack tells you how upright or low the front end will feel. A bigger difference here can affect comfort and posture significantly.
Reach affects how far you’re stretched out. Even 10–15mm can make the difference between a relaxed ride and neck pain halfway through.
💡Tip: If you’ve had a bike fit, match stack and reach numbers to your fit report. That gives you a great baseline for new bike options.
Screenshot
2. Check Saddle Position (Seat Tube Angle & Top Tube)
The seat tube angle affects where your saddle ends up over the bottom bracket. A steeper angle moves you forward; a slacker one pushes you back. This changes hip angle, pedalling efficiency, and even how easy it is to get into an aero position.
Top tube length and seat tube height are also worth noting, but remember — bar and saddle position can be tweaked with components (like stems and seatposts).
3. Consider Handling Differences
Head tube angle affects steering. A steeper angle is more responsive, while a slacker one is more stable.
Chainstay length and wheelbase impact how nimble or stable the bike feels at speed.
Comparing an endurance bike with a race bike? Expect shorter wheelbases and lower stacks on the racier models — and a very different feel on the road.
4. Use the Visual Overlay
The frame outlines are colour-coded and let you see, at a glance, where the shapes differ — top tube slope, head tube height, bottom bracket drop, and more.
If one bike’s front end sits 40mm lower in the overlay, that’s not just a subtle change — it could put you in a completely different riding position.
5. Pay Attention to Small Numbers
Don’t dismiss 5–10mm differences. It might not sound like much, but it can totally change how the bike fits. Think of it like shoe sizing — you wouldn’t casually jump from a size 43 to 45 and expect no issues.
Limitations & Things to Keep in Mind
While Bike Insights is an incredibly useful tool, it’s not a crystal ball. Like any good tool, it works best when you understand its strengths and its limits.
Here are a few important things to keep in mind:
1. Geometry ≠ Fit (Not Entirely)
Geometry gives you a solid starting point, but fit is also personal. Two riders with the same height and inseam might need completely different setups based on flexibility, core strength, and injury history.
So while matching stack and reach is helpful, it’s not the full picture. A proper bike fit will still go deeper into cleat position, saddle tilt, and riding goals.
2. Components Can Change Fit Too
Stem length, headset spacers, saddle fore/aft, bar reach — these all tweak your position significantly. A bike might look aggressive in the geometry table, but with a few changes, it can be made much more comfortable.
That’s why you’ll often see the same frame ridden in different ways by different riders. Geometry is just the foundation — the final fit comes from building on it properly.
3. Not Every Bike Is Listed
Bike Insights has thousands of models, but it’s not every bike ever made. Some older or niche bikes might not be in the system, and newer models might take time to appear.
The good news? You can manually add geometry data if you have it from the manufacturer’s website. It takes a few minutes and gives you the same comparison tools as any other model.
4. Don’t Obsess Over Tiny Differences
Yes, small numbers matter — but don’t let a 3mm difference in reach stop you from buying a bike you love. Geometry is a guide, not gospel. Combine it with personal feel, your fitter’s advice, and real-world testing wherever possible.
Bike Insights gives you a smart, visual way to make sense of sizing and geometry, but it’s one part of a larger picture. Use it as a tool to narrow your options, spot red flags, and make smarter decisions — not as a rigid checklist.
How to Use Bike Insights to Compare Bike Geometry
Introduction: Why Geometry Matters (Even If You’re Not a Nerd)
When most people shop for a new bike, they look at brand, groupset, colour, maybe weight… and then pick a size like it’s a T-shirt. “I’m probably a 54.” Done.
The problem? A size 54 from one brand can fit completely differently than a size 54 from another. Same goes for “Medium,” “Small,” and all the other labels brands love to throw around. It’s like guessing your shoe size based on what your mate wears.
That’s where Bike Insights comes in — a free online tool that lets you compare bike geometry across brands and models in a visual, easy-to-understand way. Whether you’re deciding between two bikes, trying to replicate a fit on a new frame, or just want to understand what “stack and reach” actually mean, it’s incredibly useful.
In this post, I’ll walk you through how to use Bike Insights step by step, explain what all those numbers mean in plain English, and show you how to make smarter, more informed decisions about your next bike
Bike Comparison Overlay
What is Bike Insights?
Bike Insights is a free online tool built specifically to help cyclists understand and compare bike geometry. Instead of relying on size labels like “54” or “Medium,” it gives you the actual geometry numbers that define how a bike fits and handles — and lets you overlay and compare different bikes side by side.
Whether you’re a casual rider, bike nerd, or somewhere in between, Bike Insights is one of the most powerful tools for:
Comparing bikes across brands and model years
Understanding how one frame differs from another in shape and fit
Visualising how changes in geometry affect your position on the bike
The platform pulls geometry data from thousands of road, gravel, mountain, and commuter bikes. You can:
Search for a specific model
Compare two or more bikes visually
Dive into the raw geometry numbers
Even upload your own geometry manually if it’s not listed
Bike Insights is especially useful if:
You’re buying a new bike and want to compare it to your current one
You’re switching brands and want to avoid size surprises
You’ve had a bike fit and want to match stack and reach numbers on a new frame
Think of it as a bike geometry comparison supertool — one that takes the guesswork out of figuring out if a new frame will actually fit you.
Why Geometry Matters (In Plain English)
Bike geometry isn’t just for engineers or people who say “compliance” too often. It has a huge impact on how your bike fits, feels, and handles — and it affects everything from comfort to performance to injury risk.
Here are some of the key geometry terms you’ll see on Bike Insights — and what they actually mean for you:
Stack
This is how tall the bike is at the front end — measured vertically from the bottom bracket to the top of the head tube.
Higher stack = more upright, comfortable riding position (common in endurance bikes)
Lower stack = racier, more aggressive position
Reach
This is how long the bike feels — measured horizontally from the bottom bracket to the top of the head tube.
Longer reach = more stretched out position
Shorter reach = more compact, upright
Stack-to-Reach Ratio
This is a quick way to get a sense of the bike’s personality.
A higher ratio (>1.5:1) usually means an upright, endurance-style fit
A lower ratio (<1.4:1) points to a race-focused, aggressive fit
Seat Tube Angle
This affects how far over the cranks you’re positioned.
A steeper angle pushes you forward — good for performance and aero
A slacker angle puts you further behind — better for comfort or climbing
Top Tube Length, Head Tube Length, Chainstay Length…
There are more — but the main point is this: small changes in geometry can lead to big changes in how the bike feels. Two bikes might have the same size label, but completely different personalities.
And that’s exactly why Bike Insights is so helpful. It takes all these abstract numbers and turns them into something you can actually understand — and use.
Road bike geometry
How to Use Bike Insights (Step-by-Step)
Using Bike Insights is refreshingly simple — no engineering degree required. Here’s how to compare two bike frames side by side:
Step 1: Visit bikeinsights.com
Head to the homepage. No login required, no paywall — just straight into the good stuff.
bike insights tutorial 1
Step 2: Search for Your First Bike
Use the search bar at the top to type in the bike brand, model, and year. For example:
Giant Defy Advanced Pro 1 2015Once you find it, click on the model to open its geometry page.
bike insights tutorial 2
Step 3: Add it to the Comparison Tool
On the bike’s page, click “Add to Compare”. You’ll see a visual overlay area pop up on the right-hand side or at the top (depending on screen size).
Step 4: Search for Your Second Bike
Repeat the process to add your second bike. This could be:
The bike you’re currently riding
A model you’re thinking of buying
A newer version of the same frame
Click “Add to Compare” again — now you’ll see both frames in an overlaid diagram.
bike insights tutorial 3
Step 5: Review the Geometry Comparison
This is where the magic happens.
You’ll now see:
A visual overlay showing how the two bikes differ in shape
A geometry table listing measurements side by side
A stack/reach comparison with clear percentage differences
Indicators showing if the difference is small, moderate, or significant
Screenshot
Optional: Explore Further
Use the interactive slider to flip between bikes
Click on geometry terms to learn what they mean
Filter by category (e.g. road, gravel, MTB) if you want to explore similar bikes
Bike Insights turns what used to be a guessing game into a clear, data-driven decision. Once you’ve compared two bikes, it’s much easier to see if the new one fits similarly — or if you’re accidentally buying a completely different ride.
Understanding the Comparison: What to Look For
Once you’ve got two bikes side by side in Bike Insights, you’ll see a detailed geometry chart and a visual overlay of their frames. It’s a lot of data — but here’s how to make sense of it.
1. Look at Stack and Reach First
These are the most important numbers when it comes to how a bike fits you.
Stack tells you how upright or low the front end will feel. A bigger difference here can affect comfort and posture significantly.
Reach affects how far you’re stretched out. Even 10–15mm can make the difference between a relaxed ride and neck pain halfway through.
💡Tip: If you’ve had a bike fit, match stack and reach numbers to your fit report. That gives you a great baseline for new bike options.
Screenshot
2. Check Saddle Position (Seat Tube Angle & Top Tube)
The seat tube angle affects where your saddle ends up over the bottom bracket. A steeper angle moves you forward; a slacker one pushes you back. This changes hip angle, pedalling efficiency, and even how easy it is to get into an aero position.
Top tube length and seat tube height are also worth noting, but remember — bar and saddle position can be tweaked with components (like stems and seatposts).
3. Consider Handling Differences
Head tube angle affects steering. A steeper angle is more responsive, while a slacker one is more stable.
Chainstay length and wheelbase impact how nimble or stable the bike feels at speed.
Comparing an endurance bike with a race bike? Expect shorter wheelbases and lower stacks on the racier models — and a very different feel on the road.
4. Use the Visual Overlay
The frame outlines are colour-coded and let you see, at a glance, where the shapes differ — top tube slope, head tube height, bottom bracket drop, and more.
If one bike’s front end sits 40mm lower in the overlay, that’s not just a subtle change — it could put you in a completely different riding position.
5. Pay Attention to Small Numbers
Don’t dismiss 5–10mm differences.
It might not sound like much, but it can totally change how the bike fits. Think of it like shoe sizing — you wouldn’t casually jump from a size 43 to 45 and expect no issues.
Limitations & Things to Keep in Mind
While Bike Insights is an incredibly useful tool, it’s not a crystal ball. Like any good tool, it works best when you understand its strengths and its limits.
Here are a few important things to keep in mind:
1. Geometry ≠ Fit (Not Entirely)
Geometry gives you a solid starting point, but fit is also personal. Two riders with the same height and inseam might need completely different setups based on flexibility, core strength, and injury history.
So while matching stack and reach is helpful, it’s not the full picture. A proper bike fit will still go deeper into cleat position, saddle tilt, and riding goals.
2. Components Can Change Fit Too
Stem length, headset spacers, saddle fore/aft, bar reach — these all tweak your position significantly. A bike might look aggressive in the geometry table, but with a few changes, it can be made much more comfortable.
That’s why you’ll often see the same frame ridden in different ways by different riders. Geometry is just the foundation — the final fit comes from building on it properly.
3. Not Every Bike Is Listed
Bike Insights has thousands of models, but it’s not every bike ever made. Some older or niche bikes might not be in the system, and newer models might take time to appear.
The good news? You can manually add geometry data if you have it from the manufacturer’s website. It takes a few minutes and gives you the same comparison tools as any other model.
4. Don’t Obsess Over Tiny Differences
Yes, small numbers matter — but don’t let a 3mm difference in reach stop you from buying a bike you love. Geometry is a guide, not gospel. Combine it with personal feel, your fitter’s advice, and real-world testing wherever possible.
Bike Insights gives you a smart, visual way to make sense of sizing and geometry, but it’s one part of a larger picture. Use it as a tool to narrow your options, spot red flags, and make smarter decisions — not as a rigid checklist.