What is a Gravel Bike Part 3. Geometry and terms.
The heart of any bike is its frame.
The geometry is the most important. Get the wrong geometry and set up for your unique size and it doesn’t matter how good the components are, what its made of or how ‘light’ the bike, it will never deliver the optimal SPH rating for you or your riding preference.
It’s even more crucial on a Gravel Bike.
Why? I’m glad you asked.
One of the single biggest fun factors of gravel is the variety and diversity of where you ride.
This means you can encounter all sorts of environmental factors, even on a local suburban ride. And so you’re seldom in one position for long. You are riding in a very dynamic manner and you’ll be moving around a lot more on a gravel ride as well as using more upper body. The funny thing is, although a lightweight bike is nice, it may not be the best for you and your riding. That’s where geometry comes into it.
Every year, new bike models are launched laden with the latest tech and adorned in splashy new colors.
While new paint jobs are the easiest to notice, more often than not, they are backed up with the promise of being faster, stiffer, lighter, usually from slight deviations in measurements, angles and dimensions. It’s these details that are far more consequential. And they might not work for you!
Even the slightest change to bike frame geometry can significantly impact how bikes feel, and ride.
Bike geometry involves a lot of measurements, math, charts, and diagrams that can look overwhelming. But geometry shouldn’t be a scary monster; you just have to know where to look.
Ready to take the plunge and dive in?
Key Bike Geometry Words
Understanding what these words mean, will make the difference between a dream ride or a recalcitrant hack. Or in GVR terms, SPH … Smiles Per Hour!
- Stack
- Reach
- Wheelbase
- Head Tube Angle
- Rake
- Trail
- Bottom Bracket Drop. Or BB Drop.
Once you understand these you can gauge a good idea of how a bike will feel and handle, and whether it will give you the SPH your seeking! And remember, there is no right or wrong with your SPH, it is as unique as your fingerprint! All of these measurements apply to every bike, from BMX to Tour de France race bikes.
Manufacturers invest significant research into geometry, so don’t worry, about making the measurements yourself, the websites will be accurate.
LETS USE WONDERCROSS BIKE CHART ALONGSIDE THE SANTA CRUZ FOR COMPARISON PURPOSES.
Stack and Reach
Stack is the term for the vertical measurement from the center of the bike’s bottom bracket to the midpoint of the top of the head tube. Reach is the horizontal measurement between the same two points.
These two measurements are the fundamentals of setting the positioning of the rider on the bike.
These two measurements will provide a clue to the bikes character. It can be aggressive, aero and racy, or more comfortable and suited for endurance.
Bikes with a long reach and short stack will put riders in a low, aerodynamic position. Exaggerated, imagine a “Superman Flying” position. This is your race bike geometry for riders who want to go fast or who race. To really get the most from this style of bike, you need to be prepared to develop flexibility and good strength conditioning.
Conversely, bikes with a shorter reach and higher stack offer riders a more upright position, taking pressure off the upper body and back. However, don’t think this means it is a slow bike. Far from it. Ultimately it is your fitness that will determine how fast you can ride. But is your SPH (Smiles Per Hour) is all about long rides, more adventure and exploring and rides to far away bakeries, this is probably the style of bike you might love. Descriptions like “endurance” are found for these bikes. Gravel bikes though are the ultimate expression of this style of bike. And the right gravel bike is far from dull!
If you don’t know where your own fitness lies, check out these other blog posts HERE that our professional physio partners have curated. If you are relatively new to cycling, no matter what form, Road, Mountain Bike, Gravel or even Hybrid, we strongly recommend a professional fitness assessment. Have a look HERE for what Barefoot Physio offers.
Wheelbase and Chainstay Length:
A bike’s wheelbase is the distance between the front and rear axles – centres of the wheels.
Bikes with a shorter wheelbase will turn a lot quicker and are sometimes described as agile or direct, while longer wheelbases tend to feel more stable but will lack some of the immediate turn. Now this is the interesting thing, on gravel you want a bit of slack in the steering because heading down hill, over a rough surface, you want the bike to be stable, you don’t want to spend your time ‘over correcting’ the bike which at best is tiresome, at worst and accident waiting to happen. The trick is to find the sweet spot.