Funky idea.
 

While in the shed I got a funky idea in my head. Hear me out.

I currently use 140mm short cranks @75cm inseam, being a follower of Mike Burrows' line of thought. Now such short cranks are already very controversial thought to many,
but I have no plans to ever go back higher. I tried many lengths and incremental size differences and 140 feels perfect. It just fits me and my style of riding, which is down and low. No more knee issues or hip angle issues.

However, using these short cranks on my roadbike, means that compared to the 175s that were originally on it, I have to raise my saddle 3.5 centimers, the bars 3.5 centimeters, basically the whole setup, and I can no longer effectively reach
the ground with my shoes while on the seat. I don't like this side effect of shorter cranks -- sitting up higher on my bike.

The best solution to this problem would be to have a frame with a lower BB. My BB height could drop by 3.5 centimers without increasing the risk of pedal strike compared to what there was. This would solve my problems.
However as far as I know there are no frames with such low bottom brackets to accomodate a standard 140mm crank length. Smaller wheeled bikes instead use horizontal chainstays to keep the BB height the same height as larger bikes...I would need
a special frame built, which I cannot afford.

So now I got this idea in my head. Considering I already ride in somewhat of a TT position. Why not swap my front wheel and fork for a 24 inch wheel and fork. This would
effectively turn the geometry into a TT bike, making the seattube more vertical instead, and making the compact sloped top tube almost level with the ground, while dropping the BB height.
It would lower my overall height on the bike again, giving me an aerodynamic advantage and slightly increasing safety in case of a crash.

What do you think of this idea? Is it doable? Would it mess too much with the handling of the bike?

Why not...

https://i.stack.imgur.com/6YQ7P.jpg

You are aware that on the typical road bike setup that your feet shouldn't reach the ground while on saddle? This is one of the reasons that top bar height is important, such that you CAN "step out" of the saddle over the top bar without risking damage to the package of eggs...

You sure did. Now go back to the shed.

Not sure you'll get much help with touching the ground with your feet from the saddle with that smaller front wheel. And if you want your saddle further forward to be more like a TT bike's saddle to BB relationship, then turn your seat post 180°. Remount the saddle so it points the proper direction. Still might have to use a seat post with more setback to give you enough setforward in this instance to get your butt where it would be in relation to the bb on a TT bike.

At least then we won't readily perceive you as strange when we pass by. With that smaller front wheel, I might chuckle so hard I'll fall off and wreck. Please don't cause me to wreck! <grin>

This would significantly change just about everything to do with the front end and handling of the bike - HT angle, trail - I'll leave others to weigh in on the math. It might improve things, but I doubt it. As long as you can put your feet on the ground while stationary without crunching your nuts on the top tube, that's as good as you can get with your current setup.

I went even funkier and tried it with a spare 20 inch front wheel and fork I had laying around. They don't fit but it gave me a rough idea of how it looks and what the angles are like.
Even with the 20'' I still have decent ground clearance even with my short cranks although 24'' would prevent any pedal strike issues.
With the 20'' fork and wheel seated, the --previously-- sloping toptube is now completely level. The angle of seat tube is not completely vertical but definitely a lot straighter.
The whole bike is significantly lowered and so is the BB height. The chain angling downwards. The position feels awesome, I feel much closer to the ground, I can basically look recumbent bicycle guys in the eyes! I think it would be hella fast , with much less draft for guys behind.

It might look dorky to boring people who don't dare to challenge conventional standards, but once you understand my reasoning it actually starts making some sense.

Of course a frame with a lower BB built in would simply give me what I look for as well, but these frames would have to be custom.

Going to two 650B wheel would also lower the bike a bit, although not that much, and require vastly more expenses and investment.

Of course two 24'' wheels or smaller would significantly alter the whole gearing and introduce more expenses, including requiring disc brakes.
So only swapping out the front wheel and fork makes sense, and possibly a longer stem -- for what I am trying to achieve !

The simple fact is that once 140 mm cranks become your '' standard '' , the whole frame in essence has to be redesigned, or you have to deal with a significantly higher saddle height and thus center of gravity and catching more wind.
The bottom bracket with 140mm cranks can simply be a lot lower. Low is aero and safe.

I am definitely going to do backyard experimentation with this as time goes along but I am not gonna throw a lot of money at it.

Congratulations, you've created a Funny Bike! Well done, Columbus; Welcome to 1987!

https://cimg9.ibsrv.net/gimg/bikefor...ed2fada95b.jpg

Rider positioning is ultimately more important than the size of the front wheel. Go back to the shed and scrap this silliness.

Thats normal. You shouldnt be able to reach the ground with your shoes while you are on the saddle. If you are able to do that, your road bike is not properly set up.