Coasters Running slow In the Cold

Well everyone pretty much knows that coasters run slower in the cold.

But does anyone have any idea why, or a detailed explanation to the reason why?

Sorry if this has been brought up before but I tries the search feature and nothing came up.

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http://coasterplace.web1000.com

It mostly has to do with the viscosity of the grease used to lubricate the wheel bearings. Grease is nothing more than oil held in suspension in a base material, such as clay. Modern greases have more sophisticated synthetic bases. It is formulated to give it's maximum performence with in a specific tempeture range. Low viscosity greases are for low temp, high for warmer temp. Since the coaster train will be operating for the most part in warmer to hot conditions the higher viscosity greases are used. At the lower temp range the grease thickens increasing drag, or friction in the bearings.Thus a slower ride.

Denser air has some effect, but grease viscosity is the major factor.

So why does it feel like they're so much faster? Cold air harder to breathe or what? Cause until I read these boards, I was always under the impression that colder coasters went faster because that was always what I felt ...

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"You know we got a good thing goin and I don't wanna see it end" --Reel Big Fish
-- Brett

Maybe you are effected by the cold more than some of us. The lower speed in most obvious in the reduced air time. It's not just a perception. On a cold morning, Nitro's speed sensors clearly show that it is moving slow. As the day goes on it moves faster until the automated trims start cutting in to limit its speed.