RSWB

[Vargas]

Is there any limit on the wheelbase smallest size? I mean, is there any geometry restriction to create a RSWB (Really Short Wheel Based) bike?
To me the driving limit for upright bikes is the distance from the bottom bracket to the front wheel, since there has to be enough free room to turn the front wheel and not hit one's toes while pedaling.
With a FWD MBB this restriction doesn't exist. The shortest possible wheelbase is one wheel diameter.
Thus, how big, or small, could a RSWB bike be? In theory, how much could the Sofrider wheelbase be reduced - the rear wheel is quite far from the front wheel?
Does the SR picture below make any sense from wheelbase perspective?

 

[MrSteve]

It would be ridable. I

It would be ridable. I think.

I know that the bike you propose would suffer from front-wheel spin
or traction issues up hills.

 

[Traqr]

From an experimental perspective, there's no real limit on wheelbase either way - consider those folding aluminum scooters with polyurethane wheels, or even a unicycle as the ultimate SWB. Skate bikes are another attempt at really-short-wheelbase vehicles, for example. On the long end, the Xtra-Cruz would be the standard-bearer, unless someone's tried a Tandem that I haven't heard about.

There will be a point where the stability triangle is too short for real-world use - that is, the triangle formed by your centre of gravity and the front & rear contact patches. You can't accelerate because you unload the front wheel too much, and can't brake because you'll tip forwards. Steering sensitivity also increases as wheelbase decreases. Then there's the packaging issue - in your photo, the seatback and rear tiralngle are flying, so at some point you'd have to figure out where to add structure in order to make those parts strong enough to hold weight.

So is there a "restriction" that says you can't shorten the wheelbase? No, that's the point of experimenting, and it's just one more consideration in addition to seat height, angle, and position, steering rake & trail, suspension settings, wheels, tires, gearing, handlebars...

Happy Cruzing!

 

[randyspann]

- I have always understood that the closer your head is to the rear axle, the harder it is to have a 'good' handling bike. I have seen some super lightweight homebuilts that violated this rule (head at or behind rear axle) and the handling was terrible.

 

[mikethebike]

Short enough?

Without comment

 

[John Tolhurst]

"I have always understood

"I have always understood that the closer your head is to the rear axle, the harder it is to have a 'good' handling bike."

I have not figured out what that might be the case. The more your head is tilted back, the more difficult it is to sense balance and line through corners. If there is sideways flex of the seat to the bike frame, that is disconcerting.

 

[Charles.Plager]

Game, set, and match.

This has got to be the shortest wheelbase recumbent ever.

 

[Jerrye]

Uh, Charles, just a minute...

Is that really a recumbent, or is it a crank forward? Just sayin.... /..\
0