I still don't understand the effects of crosswinds on a bike

[Stig / Major Tom]

This morning I rode through the strongest crosswinds I've experienced since riding across Oklahoma as a kid in the 60's after I rec'd my orders for Vietnam. I was taking my Honda CB350 to my parent's house in Topeka Kansas before flying out.
 
The same thing happened to me as it did 50 yrs ago!

The wind blew hard from my left.....and my scoot moved right! and tilted left - into the wind!
Pretty alarming the first time this happened!
Honestly - this morning's wind took me right back there to that N/S highway in Oklahoma!
I didn't understand the dynamics of this phenomena, then - and I still don't...just hang on and ride it out, hour after hour there in Oklahoma.
Seconds after these photos the rain blew in again....and by gosh the Rain-X For Plastic seemed to work this time! In that wind the droplets stood no chance on my face shield!





Stig

A pleasant PS....while I was goofing along this stretch of road, putting on my less expensive gloves as the rain started, taking snaps, etc. - two P-Ups stopped to check on me...."You good?"....
"Yes, thank you for asking!"

[rjs987]

First time I REALLY paid much attention to that is when I took my wife riding with me on my Gold Wing GL1500. We started out going west, then south, then turned west again. Several miles alone that road we saw a wall cloud coming really fast... like that scene in Independence Day when the alien ship first burst through the dark cloud. Then a 50 mph (minimum) wind hit us directly out of the west. Talk about a head wind. It hit fast and was gone. The bike lurched back violently but since I was headed due west and the wind was coming directly from that direction no issues with stability. I could see heavy storms were following that wall cloud so turned around and sped back the way we came. I actually caught up to that blast of wind and the bike lurched forward from what was now that massive tail wind. We turned back north (only way home) and here's where it got real interesting. On a country 2 lane road riding gentle curves on top of a ridge that 50 mph wind, still coming from the west, caught up to us again. This time it was a direct side wind. That monster GW was pushed toward the outside of the lane about half the lane across (I had a habit of riding close to the center line when no traffic) and the big bike leaned WAY over. I thought I could reach out to the left and touch the road, or so it seemed. I know I wasn't leaning that much but it was more than I have ever leaned over in a curve in a long time. All this happened automatically, the lean that is. I figured out later that I think it has to do with how being pushed sideways effects the steering causing the same effect as when you counter steer right to go into a left turn. For a turn it's a subconscious action (for experienced riders). For the wind push it's how the directly sideways travel of the bike acts on the steering geometry to do the same thing. I'm sure some of it, maybe a lot of it, was also subconscious as well. I was essentially going into a "turn" from the perspective of the strong motion of the air mass resulting in continuing in a straight line with respect to the road surface. Oh, we did make it back to the house dry, but as soon as I pulled into the garage (I had a garage door opener button on the bike so I could ride right in without stopping) the rain came down... hard.

My wife only went on another dozen rides with me and shortly after another few very windy rides decided she preferred to stick to riding her Metropolitan around town and not ride pillion any more with me. Been riding solo ever since.

[Neil955i]

Yes, I've noticed that too.  I'm no physicist Stig, but I'm betting it's force (wind blast) and gyroscopic effects (steering) coming into play here?  Like counter steering when you push you left handlebar to turn left.  Counter-intuitive, but it works!

[klaviator]

It makes perfect sense to me.  If the wind blows from the left and you don't lean left you would fall over.  You are doing it subconsciously to stay upright. 

[CROSSBOLT]

It makes perfect sense to me.  If the wind blows from the left and you don't lean left you would fall over.  You are doing it subconsciously to stay upright.

Yes, but the trailing front wheel contact puts the aero center forward of the pivot axis pushing the front wheel in a counter-steering action, leaning the bike upwind.

[Stig / Major Tom]

The best part about riding in strong side-winds for me is that I do not need to think about anything.
The stuff I learned at age 7 takes over.

Stig

[Neil955i]

The best part about riding in strong side-winds for me is that I do not need to think about anything.
The stuff I learned at age 7 takes over.

Stig

Exactly.  You don't need to understand the physics to cope with side winds!