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Old 11-24-2012, 04:12 PM   #11 (permalink)
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I've measured it. Nothing to brag about. Actually, it was embarrassing. Need more testing . . .
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Old 11-24-2012, 07:13 PM   #12 (permalink)
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Originally Posted by bidwell View Post
A modern sport bike can easily exceed 1g cornering loads especially with a little camber thrown in. In this article a Ducati 1098 went as high as 1.56 against a Ferrari 458's 1.41: Ferrari 458 Italia vs. Ducati 1198 S - Motor Trend
I have to agree, infact, watch this youtube vid of Dave Moss with a G meter on his cycle as he tests suspension set ups.

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Old 11-24-2012, 08:33 PM   #13 (permalink)
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I just picked up a GPX Pro 4, wish I would've had it at Barber 2 weeks ago. The g forces in T12 and T14 had the skin on my face sagging. Well over 1g for sure.
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Old 11-25-2012, 01:06 PM   #14 (permalink)
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I'm no expert by lateral G's cannot be "felt" accurately since the bike and rider at at equilibrium with gravity during a turn.
Also, a lateral G measuring device will have to stay parallel to the horizon during a bike lean to measure lateral G's.

The only accurate way to measure lateral G's of your motorcycle is radius of turn and your speed around that turn.

I've been reading alot on the net about how a car can outhandle a bike around corners and most of people's reason is extra tires on the ground. 4 vs 2 on the bike. I disagree with that actually. If a bike had 4 tires inline, it would still suffer the reality that a bike must lean to turn.

Regarding sticky tires here is my question.

If I'm on a normal street tire in a constant speed constant radius 360 turn riding all the way to the edge of the tire while footpeg is 1mm above the ground and I am producing 1.1G's what would extra sticky tires give me? I cannot imagine the G's getting higher. It seems as if the bike is limited by its physical dimensions touching the road during a lean...

Thoughts?
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Old 11-25-2012, 07:15 PM   #15 (permalink)
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I'm no expert by lateral G's cannot be "felt" accurately since the bike and rider at at equilibrium with gravity during a turn.
Also, a lateral G measuring device will have to stay parallel to the horizon during a bike lean to measure lateral G's.
If you follow me through Turns 12 and 14 at Barber, trust me you WILL feel the G forces. You're right though, the best way to measure the phenomenon is with radius and speed data.
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Old 11-26-2012, 05:35 AM   #16 (permalink)
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Originally Posted by noamkrief View Post
If I'm on a normal street tire in a constant speed constant radius 360 turn riding all the way to the edge of the tire while footpeg is 1mm above the ground and I am producing 1.1G's what would extra sticky tires give me? I cannot imagine the G's getting higher. It seems as if the bike is limited by its physical dimensions touching the road during a lean...
It is, but modern sport bikes are very tucked in and have the ability to lean past 45 degrees and use most of the extra grip of racing tires if the rider is brave enough, especially if they're aggressively hanging off and/or the bike is properly setup with respect to suspension, ride height, etc. And having traction in reserve is always a good thing.

I'm not saying that street riders need race tires. As you are alluding to, a good street tire can be plenty grippy enough and street tires are designed for street inflation pressures and heat cycles. For the average rider on the street the extra grip of racing rubber may not actually be useable.

- Mark
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Old 11-26-2012, 10:23 AM   #17 (permalink)
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From the data that I have seen from telemetries yes you can have lateral G forces >1G.The same goes for braking and accelerating and I have seen those nr on my bike.All the data are from AIM telemetry (GPS+G meter from AIM EVO4).
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Old 11-28-2012, 05:47 PM   #18 (permalink)
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Default Missing perspective.

Ok, it seems some folks have not realized the whole 1G discussion usually requires some starting point. When people usually talk about pulling a G they are referring to a semi standardized test done by car magazines on a 200-300ft circle.

They can alter the circle and change the number. It could be dusty and change the number. The surface can be bad and change the number. There are a bunch of factors that can influence this loose 'baseline'.

When talking comparison to cars and that nebulous number you use that baseline. Anyone who has ever taken a car with a G meter in it, or a bike and gone out in the real world found out you can get much higher numbers depending on the road. Theoretically you can get your bike to pull as many G's as the tires can stand from compression. Say if you had a place like this:



I bet they can pull way over 1G. But for the off the cuff comparison we are talking about here with cars and different types of bikes we are assuming you are going to use that magazine 200-300ft flat circle baseline.

Watch the MotorTrend video referenced above. Notice it has N/A for a G number in testing for the 1198. They give G numbers from on the track which are NOT using that semi standard baseline. So of course they are higher. As are the ones you guys are getting at the track.

The reason of course is no one wants to go and low/high side their bike for a test. It's just not safe. Maybe Keith Code could loan you his outrigger setup but even that would skew the results.

So please try to remember the baseline people use when saying "It pulled 1G". It's arbitrary but hey, this is the magazine business and the internets.
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Old 11-30-2012, 12:43 AM   #19 (permalink)
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They can alter the circle and change the number.
Well, no. If they enlarge the circle, they enlarge the top speed to stay within it, and the max G of the car should be exactly the same. It is a pretty simple physics problem, which means you remove as many nuisance variables as possible. Get a clean, flat, smooth surface, and you can do the test. You want the circle to be large enough that you can make corrections without hitting the limits of steering, and small enough to limit your max speed. That's about it.

For a bike, you would just need a G meter. The complication comes from the bike leaning over, but with the knowledge that in a straight line, you have 1 G straight down, you can find the lateral G of the bike very easily. You take the squared sum of up and down forces of the G meter (which are really diagonal forces since the bike is leaning over), and subtract 1.0 and take the square root. Pretty sure you can do it with your iphone.

- John

Last edited by Technomancer; 11-30-2012 at 12:49 AM. Reason: removed typo
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Old 11-30-2012, 04:08 PM   #20 (permalink)
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Originally Posted by Technomancer View Post
For a bike, you would just need a G meter. The complication comes from the bike leaning over, but with the knowledge that in a straight line, you have 1 G straight down, you can find the lateral G of the bike very easily. You take the squared sum of up and down forces of the G meter (which are really diagonal forces since the bike is leaning over), and subtract 1.0 and take the square root. Pretty sure you can do it with your iphone.
Nice analysis.

Yes, this sounds correct. From the bike's perspective, all G loads are always directly down through the centerline of the bike. This is the reason we, as riders, feel no side-to-side lateral G's at all as we corner - just down. So a G-meter mounted on the bike will feel nothing but G load straight down. (As an aside, I find this the main reason I prefer to sport ride a bike vs. a car - not being throw from side-to-side and having to brace myself against the car structure.)

I think this explains some reports of G meters on bikes reporting G loads of 1.4-1.7 G's. As said above, you can compete the lateral G by the equation:

Lateral G = Sqrt (Total G^2 -1)

Plug a total G of 1.5 into such an equation and you get exactly the upper limit for lateral G I mentioned earlier - about 1.1G. (Also note that if you plug a total G of 1.0 into this equation, you get a lateral G of 0 - exactly as you'd expect for a bike traveling in a straight line.)

There have been numerous car vs. bike articles articles published over the years and while there are a lot of variables, the car typically wins. If the track is tight enough, a bike may be able to pull the advantage because of its super power-to-weight down straights and out of corners, but in the corners, a car will usually has a significant cornering advantage due to having four contact patches and more mechanical grip. And because you can put a car very near its limits of adhesion a lot more safely. Also, most cars have some aero advantages and racing cars with wings have a huge advantage. With most tracks, corner speed trumps acceleration and the car is quite a bit faster.

This is reflected in, for example, Nurburgring lap times where cars are typically faster.

The last few years, I've taken a few trips where we have mixed groups of cars/bikes. I can say from personal experience that keeping with a well-driven sports car on anything but the tightest roads is very difficult if not impossible.

- Mark

Last edited by markjenn; 11-30-2012 at 04:10 PM.
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