Stability and Wheel Diameter?

[newbert]

Generally speaking, and assuming all else is equal - is turning a bike with a smaller wheel diameter (say 20") inherently more difficult/less stable to make tight turns than a bike with, say 26" diameter wheels?

The reason I ask is that I'm having a tougher time than I should making U-turns on my Rad Mini ST2 (20" diameter wheels). This is the my first bike with 20" wheels. So is this due to physics somehow, or just my old age (67 yrs old)?

Thanks!

 

[phoenixtoohot]

I've had a Dahon folding bike with Schwalbe Big Apple tires (20x2.0)for 10 years. Yes, it's definitely "twitchy" (aka more agile) compared to my 700 bikes, but I still love it for it's purpose. If I was looking for a city bike, I would definitely consider a 20 inch e-bike, but for commuting, I prefer the 700 wheels, electric or not.

 

[harryS]

The 20" fat tire is actually more like a 24" wheel, and it's a relatively long wheelbase. The rake/trail of the fork, plus angle and height of the handlebars has some major effect on turning too. My fat tire 20" also turns like a big boat.

My true folder with 20x1.25" tires turns quite well.

 

[newbert]

Thanks guys! Glad to hear that it's not (totally) me!

 

[steve marino]

The larger the outside tire diameter, the more stable the bike.

 

[rich c]

The larger the outside tire diameter, the more stable the bike.

Could you define stable? Your center of gravity would be higher with larger tires. I thought large diameter tires were chosen for mtb because they could handle rocks and roots better. Not sure how diameter changes stability unless I'm not understanding the stability term.

 

[phoenixtoohot]

This is as good as any:

: the property of a body that causes it when disturbed from a condition of equilibrium or steady motion to develop forces or moments that restore the original condition

My 29er mountain bikes feel stable to me, my 20in folding bike, with 2-inch diameter tires, feels Twitchy. Of course as someone has already said a 20in Fat Tire Bike could feel like a boat.

The real answer to this question in my mind, is to really try out the various bikes you're interested in, because look and feel is so subjective. I like my 20in Twitchy folding bike 4 running around the neighborhood but I prefer my 29er for longer rides and commuting.