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The Reason That Race Bikes Have Higher Seats.


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Kind of carrying on from the Contact patch Vs grip thread, I was doing some further reading on Steve's website and out of the blue came across an answer to a question I had long wondered about.

 

If you look at race bikes, whether it's at a local or national race, World Superbike or MotoGP, it has always stood out to me that the seat height is noticeably higher than on production street bikes. I thought this was just to do with body position. I never thought it could have been because a higher centre of gravity is more desirable for cornering, because whenever I had been riding my BMX around MTB and fire trails etc. I always got around corners faster than guys riding MTBs. I figured it was because of the lower centre of gravity, so I always thought that lower CoG = better.

 

Not so!

 

From: http://www.stevemund.../leanangle.html

 

What's the real lean angle?

 

The concept of the lean angle is not as trivial as one would imagine. If we had infinitely thin tires then it'd be obvious: Just draw a line from the center of mass to the contact point and measure the angle between that line and the horizontal or vertical. But we have fat tires. The actual lean angle must be measured from the center of mass to the center of the contact area, which will be to the inside of the tire. So the apparent lean angle — using a line parallel to the forks, say — will be greater than the actual lean angle, using the center of the contact area of the tire. Note that this means that a motorcycle with a lower center of mass will lean more than a motorcycle with a higher center of mass, for a given corner radius and speed.

 

 

Well, hot damn! Mystery solved! (For me at least.) biggrin.gif

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Narrower tyres needs less lean. Taller wheels need less lean. Taller bikes (CoG) needs less lean. Shorter bikes need less lean. For any given speed, all else being equal.

 

There is more to it as well; taller CoG (at least to a point) gives more stability as well as easier/quicker steering.

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Narrower tyres needs less lean. Taller wheels need less lean. Taller bikes (CoG) needs less lean. Shorter bikes need less lean. For any given speed, all else being equal.

 

There is more to it as well; taller CoG (at least to a point) gives more stability as well as easier/quicker steering.

learned something today, thanks!!

 

 

 

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