Landracing Forum
Bonneville Salt Flats Discussion => SCTA Rule Questions => Topic started by: stay`tee on February 16, 2008, 07:38:08 PM
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is there a minimum ground clerance (bodywork to ground) ruleing for motorcycles competing at bonneville?, if so what is the distance required?...
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im sure someone will argue with me on this but there is no mininum ground clearance just remember that you have to turn off the track though what kind of bike you got -------there is a rule though 7.B14 if a technical inspector or chief starter judges a motorcycle unsafe it will not be allowed to compete willie buchta
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And Production class must meet the manufacturer's document stated minimum.
The wording would make some presume that it can be neither higher or lower, but uncommon sense insinuates the intent is to use the oem's stated clearance as a minimum.
Todd
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BTW, welcome Stay'tee and nice signature :roll:
Todd
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Todd......you are spending too much time on the computer.
Get Deb's bike done so you can do some work for yourself.
FREUD
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thankyou for the welcome, although i have frequented this site before under a different user name,
willie, i ride a 02 kawasaki zx12,(tried posting a avatar with a photo of it, dont know why it didnt work) running a best of 208 at our last speedweek meeting in 2006 at lake gairdner,, at present it has approx 2" ground clerance. there are a contingent of aussie bikes planing on coming over too run at bonneville (mecca) in 2009, i am planning on bringing my "aussie blu" over, hence the question, no doubt there will be more questions, as i want to have a bike that is legal, yes i do have a 07 scta and ama rule book :-)
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sorry, correction to the above post, 204mph, not 208 (i wish) :oops:
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welcome hope you all can make it in 09 this is a good place to ask questions if you have a 07 rule book there are a few changes that you can find at this site to upgrade your book you should be good to go willie buchta
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Todd......you are spending too much time on the computer.
Get Deb's bike done so you can do some work for yourself.
FREUD
Ohh how true Freud... but she doesn't let me near it unless it's to help her working on it.
For one of my bike's just to have access to that corner of the shop again, mmmm :-P :cry:.
BTW, if she'd let me put the "It will be waiting for you" picture that you sent us in front of the lift, I think progress would increase significantly. :wink:
Todd
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How low can you go and why do you want to, or not.
The rules for a production bike , with few exceptions, require the bike be "OEM picture perfect" when presented to run.
Your objective to lower the bike is limited, but still possible within the rules.
You can actually cause the bike to settle down to the end of the suspension travel and do it within the visual rules you are held to.
Do you really want that ?
I think not.
You will do better with a little bit of suspension compliance until the perfectly flat earth is completely smooth, and still with good grip.
Lets just say for discussion purposes you have 4 inches of travel now and want to drop it to a minimum , but avoid the hammer you get when the travel bottoms out with a bump.
Stock shocks are really pretty good and well matched to the characteristics of the bike with some adjustment to suit the rider.
If the rear spring is exposed to scrutiny, you can collapse the end coils with a torch and that will cause the bike to sit lower if that is the objective.
You didn't remove any thing so it will pass the visual.
The added benefit is the remaining coils will be effectively stiffer, because the travel that remains is working on fewer coils over the same distance.
You can do the same with the front coils inside the forks.
Remember, you don't want to slam it to the bottom of the travel because it will slam your traction when you need it the most.
You can get away with a lotta stuff if conditions are perfect or you don't make enough power to get into the trouble you can easily fall off or into. :wink:
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Has anyone experimented with not seeing how low they can go, but to keep ground clearance under the bike for better aero?? In THE LEADING EDGE Aerodynamic Design of Ultra-streamline Land Vehicles by Goro Tamai for a rounded bottom they suggest about 6 inches of ground clearance if I remember right to avoid compressing the air under the vehicle and for better Cd. Maybe Rex can elaborate on this more. This is the reason I'm keeping the rounded bottom of my lakester a minimum of 6 inches from the ground. Seems to me that a partial or streamline bike might fall also into this category if it had a rounded shape on the bottom.
If it is flat bottomed like Costella's cars/bikes you want them on the ground and don't want air under there.
Even with a bottom higher you would still want the distance from that point to the top most point, probably the rider, as short as possible to minimize frontal area.
c ya,
Sum
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Start with a lower rider and finish higher in the standings. :wink:
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Our problem is that Nancy's legs don't reach quite as far as necessary to control the bike at zero speed. The bike's specs include a "ground clearance" number -- but nothing else that might give us a hint on how much, if any, we can lower it to better fit her. Aero be damned -- she's gotta be able to touch the ground. Sure, we can help her keep the bike upright at the start -- but at the other end of the course she's on her own.
Don't laugh when you see her wearing stacked sole and heel on her boots.
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Be sure to take out the coldfish first. :wink:
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Production bikes cannot legally be lowered by sliding the fork tubes up or using different rear shock links. The factory ground clearance spec. must be maintained. Modified & Altered bikes benefit from lowering ( less frontal area). 1 1/2" to 2" travel has always worked for me. The Guppy ran a strut at 229 and Mark said it was the smoothest ride ever. Long WB and weight help. Since the other bike hasn't worked in 5 years, I will stop now. :roll:
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thanks for the imput, i recon i will leave it at 2" as it handles as if on rails at that clerance, also have a set off 7" over swingarm extenshions, strut and some ballast in the package :-)
sumner, you raise the ole flat verses round debate, this is a subject that has teased me for a long time,,, i feel 4 wheel aero (below wheel axel line) cannot be compared against 2, reason being with a motorcycle you have the rudder out frount,, :|