I have a custom steel bike. Given my height (5') it was impossible for me to find a gravel/CX bike for my size and, being somewhat new to the world of bike geometry, I trusted my builder's design. However, people often mention how much offset my fork has (Framebuilder said this was to avoid toe overlap in a very small frame). Will this be a problem if I want to use a different fork? (I wanted to upgrade to a carbon fork, eventually). I'm assuming there *will* be toe overlap, but how will handling be affected?

Here's the original diagram from before it was made and an actual pic of the bike.

HT Angle is 69º.

Modelo Any Road Estivalia.jpg
IMG_6325_2.jpg

Thanks in advance for any insight (:

I don't know the answer to your question, but I do know that toe overlap is not really a problem. You'd get used to it quickly.

Here are a couple of articles that talk about this issue:
https://calfeedesign.com/tech-papers/...bike-handling/
https://www.cyclingabout.com/understa...rame-geometry/

That huge amount of fork offset is there to compensate for the very slack head tube angle.

Short answer. The builder knows what he is doing. It all comes out in the wash. It may look weird but don't change forks without understanding the geometry.

I'm not expert enough to teach you either but I know enough to say that it actually looks right to my eye.

The number that is REALLY important is, "trail".

Bicycle Steering Geometry

EDIT: having read your question again. I don't recommend you change the fork. The head tube angle, NEEDS that amount of fork rake. Don't change anything without understanding it back to front.

Thanks guys. I have no immediate plans to change the fork, it was something I had in the back of my mind for the future. It's good to know that this bike is made to work with this fork only. I'll ride the heck out of it and hopefully by the time I can afford/fancy a new frame+fork there will be more options in my size.

At my height, I'm sure I've had a bike with overlap at least once, but I've never noticed. I didn't even know there was such a thing until I started getting into road bikes lol.

OK, I was reluctant to directly answer the question, "How will the handling be affected by a new fork", earlier because I had forgotten some of the details but now I've done some reading and reminded myself so here goes.

Short answer. If you fit a new fork with less Rake (Offset) to this frame you will slow down the steering and it will feel sluggish. All that Rake is there to speed up the steering by compensating for the VERY relaxed (68 degree) head tube angle.

Longer answer. The concept/measurement that is important here is, TRAIL. See the link I posted above for a diagram and it works like this. Draw a line along the axis of the head tube to the ground. Draw another line from the front axle vertically to the ground. The point where the vertical line from axle hits the ground is ALWAYS behind (trailing) the point where the line parallel with the head tube hits the ground. The less this distance, the more direct and fast the steering feels. The greater this distance the slower and more stable the steering feels.

Now, lets say you have one fork with a fixed rake already made and you fit it to bikes with different head tube angles. The bike with the steeper head tube angle (larger number, lets say 72 degrees) will have LESS trail(shorter distance between where the two lines fall on the ground), and more direct feel to the steering. The bike with a slacker head tube angle (lets say 68-69 degrees) will have more trail (greater distance between where the two lines fall on the ground) and less direct steering but feel more stable.

Now, the head tube angle is not the only factor in this equation that can be adjusted. You can change the rake of the fork. So, lets say we have a frame with a 68 degree head tube angle. To speed up the steering and make it feel more like a bike with a steeper head tube angle what you do is fit a fork with a greater Rake (offset). This pushes the axle forwards so its closer to the line from the head tube and consequently reducing the Trail.

With me?

It can get more complicated than this and wheel size is another factor in calculating Trail.

Some people panic when their foot hits the front wheel. As a result, some bike makers avoid the possibility. The collision happens only when you are going at very low speed, and there is enough time to move your foot or the wheel.