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Old 07-13-2009, 06:18 PM   #1
cdill35
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Question I must be a glutton for punishment...

asking another serious question on MH.

Hypothetically speaking...

Let's say 2 bikes are set up identically. Same suspension, tires, etc. Tuned for each riders weight and riding style, exactly.

Can a taller heavier guy carry the same lean angle and corner speed as a smaller light guy? Or would a heavier guy hanging off require more of a contact patch before the tire gave?
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Old 07-13-2009, 06:21 PM   #2
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Old 07-13-2009, 06:37 PM   #3
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actually, yeah, good questions,,,
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Old 07-13-2009, 06:39 PM   #4
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Anybody? I was always wondering how those little bitty racers could make the bikes lean at crazy speeds being so freakin' small.
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Old 07-13-2009, 06:54 PM   #5
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More mass requires more grip/traction I would think.
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Old 07-13-2009, 06:54 PM   #6
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I would think at some point, weight will be a concern.

Think about the adhesion factor of the tires. The more mass zooming around a curve, the harder the tires are working to grip.

My hypothesis: no.

Good question, CD.
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Old 07-13-2009, 06:58 PM   #7
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Excellent question. I'm looking forward to the responses.
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Old 07-13-2009, 07:05 PM   #8
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Given a contact patch at a certain sustained speed and lean angle, lets have one rider say 20 lbs heavier then another.

Now that 20 lbs is forced in the adhesion angle of the tires, and significantly on the rear also through sprung weight of the suspension.

So, a tire loses traction at 38 deg w a 180lb rider, 180 degree radius w sustained 140mph speed.

If that rider weighed 20lbs more, the angle would be greater to sustain the speed or the rider would have to ride slower.

Remember the tires are rolling, not constant, so as you come into a curve the are rolling forward and being forced into the corner... the wear on the tires isn't a straight line on the tire, it angles into the corner slightly.

Just my theory as of now... we'll see how it alters.

(sidenote: Cdill always has the best posts to make us think and really analyse riding... Countless threads that have made me think about things I wasn't curious about before but became instantly addicted to the advice of professional and seasoned riders. Thank you!)
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Old 07-13-2009, 07:10 PM   #9
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Quote:
Can a taller heavier guy carry the same lean angle and corner speed as a smaller light guy? Or would a heavier guy hanging off require more of a contact patch before the tire gave?
Logic would imply some impact/effect. Consider horse racing, jockeys tend to be fairly small..., don't see some 300lb giant racing with em all. Taller & more weight would result in a higher center of gravity.

Consider the guys on the 250's outriding the bigger bikes though. :-)
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Old 07-13-2009, 08:25 PM   #10
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Shouldn't this be in general moto discussion?

I think Brandt would probably get more "useful" answers that way.
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Old 07-13-2009, 08:36 PM   #11
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If both guys are cornering at the same speed and both guys are hanging off equally, then the heavier guy's bike will have less lean angle/more contact patch since he is able to move more weight towards the center of the turn's arc.
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Old 07-13-2009, 08:59 PM   #12
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In Larry's race school, he made me work on body position all day, practically. He advised that bigger guys do not need to hang off as much. I didn't feel like I was hanging off, but he said that only 1/4 of my should be off the seat. One part of me wants to think that the traction would be better with more weight on the tires, and at the same time, I am led to believe that the additional weight may overload the level of available traction. On my little R6, I can barely hang off before my knee is touching. The bike isn't even leaned over, so I think the bike does have quite a bit to do with it.

I am looking forward to hearing some of the knowledgeable rider's advice, too.
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Old 07-13-2009, 09:24 PM   #13
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Quote:
Originally Posted by cdill35 View Post
Can a taller heavier guy carry the same lean angle and corner speed as a smaller light guy? Or would a heavier guy hanging off require more of a contact patch before the tire gave?
In my opinion, the taller heavier guy can carry the same lean angle and corner speed as a smaller light guy. The heavier guy doesn't need to hang off as much as the light guy due to the effect of gyroscopic force (?)(I don't know if this (gyroscopic) is a correct term for this but it's about the faster you go the bike will just want to stand up straight, therefor the getting off will help the turn and weighting it down)
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Old 07-13-2009, 09:33 PM   #14
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The basic equation for cornering force is

Force = (mass * velocity^2) / radius of curvature

So, all things being equal, a lighter bike & rider will go around a corner at great speed than a heavier counterpart.
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Old 07-13-2009, 09:34 PM   #15
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Equally important, the lighter rider will be able to use softer springs resulting in a more responsive, easier to ride motorcycle.
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Old 07-13-2009, 09:45 PM   #16
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Putting some numbers to this, let's assume a fully geared rider is 160 lbs and he's riding a bike that is 400 lbs wet, so total mass is 560 lbs. Compare that to a rider that's 260 lbs fully geared (like Brandt) riding the same 400 lb bike giving us a total mass of 660 lbs.

Recalling the equation: Force = (mass * velocity^2) / radius of curvature

The lighter rider will generate (660-560)/660 * 100 = 15.2 % less cornering force which is to say he will have 15.2% more traction available. All things being equal, he should be able to go through the corner 3.9% (square root of 15.2) faster than the larger rider.
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Old 07-13-2009, 10:19 PM   #17
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I have a screw up in my math.... it's not 3.9% faster.

mass vel rad Force
660 100 50 132000
560 100 50 112000 (the lighter rider generates 15.15% less force)

560 108.5 50 132000 ***

Holding mass, radius constant and keeping the force at 132000, we see the lighter rider can go through the turn 7.9% faster.
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Old 07-13-2009, 10:23 PM   #18
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Curt pretty much summed it all up.
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Old 07-13-2009, 10:35 PM   #19
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Looking at the pics from the race, you have noticeably less lean angle than quite a few of the other guys. Good reason to lose some of that belly Brandt! I'm gettin on a workout, better quality eating program my self. Gained some LBs since getting married. No better time than now!
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Old 07-13-2009, 10:43 PM   #20
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Quote:
Originally Posted by Patrick View Post
Curt pretty much summed it all up.
Except for the small detail that 108.5 is 8.5 percent more (faster) than 100.

100 is 7.9% slower than 108.5.

Jeesh.
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