Question: As I understand a gravel bike, it's basically a road frame but perhaps with a slightly more upright riding position. It has wider tires with much deeper treads and a stiffer rubber than standard road bike tires. What is the theory behind these changes? I had always thought that the thicker and stiffer tires were to prevent small bits of gravel from pinching flats, but is the theory instead that the deeper treads and wider tires are supposed to increase traction? And what is the rationale for the upright riding position?

Answer: 
My theory and it is just a theory. In the U.S. at least there has been a proliferation of unpaved bike trails due to the conversion of abandoned railroad rights of way to bike paths. They are for the most part either flat or have a slight grade. Most of these trails are too uneven for a conventional road bike. At the same time they are not much of a challenge for a mountain bike and are mostly an access point to more technical trails. So now we have a reason to buy yet another type of bike. With a gravel bike the gearing allows much higher speed than on a mountain bike. You're on a route that is pretty much guaranteed to be free of motor vehicle traffic so you can basically go as fast as you're comfortable riding. The larger tires allow better traction on loose surfaces while increasing comfort. So while the riding environment is similar to cyclocross the two frame geometries are different in a sense like a Tri bike and a road bike, functionally the same but tweeked for a more specific type of riding.
**Q1: Riding position**

A1:

Do you know the riding position of a so-called gravel bike and a regular road bike could be 100% identical?

Let me show you my real case.

I just have a s-works diverge (so-called gravel bike) and a giant advanced tcr (so-called regular road bike).

I have carefully studied their differences which include geometry. Here is part of my study work.

[![enter image description here](https://i.stack.imgur.com/dNUch.png)](https://i.stack.imgur.com/dNUch.png)

And, let's put them together now and check it again.

[![enter image description here](https://i.stack.imgur.com/BpWNC.png)](https://i.stack.imgur.com/BpWNC.png)

They are almost 99% identical. Surprised? But, too see to believe, right!

The so-called gravel bike has slightly higher handlebar but it is under the range of fitting and adjustment. Actually, the riding position of my diverge (so-called gravel bike) is more aggreesive than the tcr (so-called road bike). If you like to, they can be adjusted to 100% identical easily.

**Q2: The tires which gravel bikes use.**

A2:

The key characteristics of a so-called gravel bike (here is the diverge) might include:

1. It is much more comfortable and enjoyable riding experience.
2. Slightly longer wheelbase.
3. It is also an adventure machine.
4. It is as fast as the regular bike or even faster. (I have multiple new PR with the diverge)
5. It can not replace the XC and DH MTB. For technical off-road, I will wish I ride a MTB or a specific purpose bike.

It is quite similar to the relationship of a SUV and a regular car.

Thus, the so-called gravel bike usually uses wider tires (>=38C).

But, some of your knowledge about gravel bike might be not so correct.

The thread of gravel tires is not necessarily deeper. There are gravel tires without thread (e.g. Gravelking)

Check here to find the thread of a gravelking plus tire: <https://www.panaracer.com/lineup/gravel.html>

Ok, it is my study work. It might not be your expected answer but I wish it will be helpful.

**Final words and it is an important reminder.**

The upper case is just only one of gravel bikes which are recoginized by the gravel players' community. Actually, there is not a single kind of gravel bikes but many many kinds.

That's the reason I use "so-called gravel bike" but not "gravel bike" in the article.

Cheers