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To: hecticskeptic

Speaking of aerodynamics, maybe you can weigh in on this.

I ride a motorcycle. Hot & cold weather. Usually I like to stay at 45 or above in the cooler months.

No one in any of my riding groups agrees with me, but I think riding at 45 feels like the aerodynamics are minutely different than at 80. Everyone else says it’s my imagination.


112 posted on 06/23/2024 10:26:31 AM PDT by ChildOfThe60s ("If you can remember the 60s....you weren't really there")
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To: ChildOfThe60s

Everyone else says it’s my imagination.
~~~~~~~~~~~~~~~~~~~
I don’t think it’s your imagination. I’ll just comment on one aspect that at least can be easily understand... and frankly beyond this, I’m not sure what else to comment on without thinking more about this.

Let’s examine the difference between 45 and 80 degrees F. First of all, one needs to think in terms of absolute temperature values so let’s do a conversion... 0 degrees F is 460 R. You mentioned 45 degrees F and this is 460 + 45 which is 505 R. On the other side, 80 degrees F is 540 R.

Ok... Air density varies as the inverse of the absolute temperature ratio. Now there are other things besides temperature that affect density (humidity, elevation, barometric pressure etc.) but let’s assume that all those other things are equal. Bottom line is that when the temperature goes up from 45 to 80 degrees F, the air density drops by the ratio of 505/540 i.e. 0.935. Similarly when going from 80 back down to 45 degrees F, the density goes up by the ratio of 540/505 which is 1.07. Although it is a bit more complicated than this, the drag you feel as you ride your bike will vary by this amount that the air density has changed by.

Hopefully no on calls you ‘overly sensitive’.... but is what I’ve described the sort of thing that you were thinking of?


118 posted on 06/23/2024 11:43:19 AM PDT by hecticskeptic
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To: ChildOfThe60s

Here’s another thought for you on ‘feeling like the aerodynamics are minutely different’.

Much of the study of aerodynamics has to do with what are referred to as ‘boundary layers’. I won’t get into that... you can do a search to figure out what that’s all about but you probably all ready can figure out what I’m talking abot. Anyway, the difference may have less to do with the change in temperature between 45 and 80 degrees than whether the sun is shining or not. Let me explain... When the sun is shining, the black pavement absorbs more heat and a boundary layer of hot air develops close to the pavement. This essentially creates a layer of air that is more buoyant and that may relate also to what you are feeling.

Not related to the aerodynamics is the fact that at higher temperature, the rubber on your tyres is softer and that of course makes the bike feel different as far as handling.


122 posted on 06/23/2024 12:41:18 PM PDT by hecticskeptic
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