front wheel cross-ventilation on a motorcycle

[Koncretekid]

Before I have to ask the technical committee (kinda afraid to ask), does anybody know how the 25% open area is calculated for the front wheel on a motorcycle?  The rule reads as follows: "the front wheel must have cross-ventilation at a minimum of 25% of total wheel surface."  If the "wheel surface" includes the tire, then nearly all disc brake wheels with the disc on would not pass by my calculations.  If the "wheel surface" pertains only to the wheel not including the tire, then the disc can stay if it is small enough.
Tom

[donpearsall]

Hey Tom,
I am not an inspector, but here is how I interpret the rule.
1. The "WHEEL" cannot include the tire because the rule says wheel, not wheel and tire.
2. The disc brake can't count for blockage, because it too is not part of the wheel. Additionally it does not close off wheel ventilation.
3. The wheel area includes the entire wheel, including the rim and spokes. So take your wheel radius and use the area of a circle formula to get the area. For instance if you have a 17" diameter front wheel, 8.5^2 * 3.14 = 227 square inches.

4. Then calculate the area your spokes and hub take up and if that figure is 75% or less of the total wheel area (170 sq inches in the above case) then you are OK.

Don

[Stainless1]

Tom, try to not over-think the rules.... you can't have a solid front wheel, that is where it starts, they want it ventilated so it is not a sail.  I don't think there are many wheels that are not solid, not 25% ventilated. 
As Don said, the brake does not count... the rule is the wheel.

This is why we always say read the rules multiple times but try not to read anything into the rules

[AHG]

"Before I have to ask the technical committee (kinda afraid to ask)"  
It would benefit you and your racing efforts greatly to overcome that fear.

BTW-Stainless basically summed things up correctly.
 

[Koncretekid]

Thanks for the opinions.  "The front wheel must have cross-ventilation of  a minimum of 25% of the total rim area" would be easier to interpret, in that case.  On my new wheel I have made a disc that is 9" in diameter to replicate the old 9" drums, and the math didn't work out unless it is calculated as Don has outlined. It is the only way it really makes sense.
Tom

[Stainless1]

Tom, while I'm not sure why you want to replicate the old drum on the wheel, that wheel looks to easily meet the 25% rule.
And you might also like to know... 

"Before I have to ask the technical committee (kinda afraid to ask)"  
It would benefit you and your racing efforts greatly to overcome that fear.
 

AHG is the Chief Inspector for the Bub events... 

[Koncretekid]

Stainless,
I think Tom Mellor still uses an old 9" drum on the front of his 192 mph Triumph, so it must not be too bad.   My comment about not asking is that sometimes you might get one interpretation that you don't like, that might not be the consensus.   I assume some of the inspectors keep an eye on the forum.
Tom

[Uncle Jimbo]

Do you really need the front brake ?  Except for a Production Class -  What would the purpose be, even slowing from triple digits there is plenty of room to slow down with just a rear brake.
At 170 rear brake only no problem slowing in a shy mile shut down and get off da course.  What class are you running ?   
Just a conversation piece.   

Have fun !   

[salt27]

I do not know the AMA or FIM rules, only SCTA and that's debatable.

My question, would this (the hub cover) be legal in open class (naked) or only partial streamlined?

The concern being, would it be considered streamlining in front of the rider.

  Don

[55chevr]

I don't run front brake at Bonneville.   

[Seldom Seen Slim]

At Bville I don't use the brakes at all - other than MAYBE loading/unloading from the trailer.  And that's with my going 200+ on the production ZX14.  We need to have the brakes be there, but nothing says we can't spread the brake pucks from the rotors - and we do.  Cross the 5 and lift, then maybe 160-170 start to sit up, then start downshifting -- and I still usually make a turnoff BEFORE the 6.  Even when coming to a half on the return road I don't use the brakes, but rather drag my feet a la Fred Flintstone.

[Koncretekid]

No, I don't  need a front brake (500 APS-PG, 137mph), even at Loring.    In fact, I like to get off at the 5 mile because the turn off at 4 can be a little rough.  I have to keep the power on just to get to the 5. The disc that I made is just to cover up the disc mounting lugs and cover 6 large holes that look like they would suck up salt.  The reference I made to Tom Mellor's 9" drum is just to justify being allowed to add that disc I made - - keeping within the 25% open rule, and because I'm in APS, it should be allowed.  I don't know about the open class, but if you have a bike with a big disc as stock, I don't see how they could not let you leave it on.

While we're on the subject, the hollow spoke wheels are nice, but has anyone had any problem with them sucking up salt into the several holes around the hub?

Tom

[fredvance]

Tom, The busa's have big holes in the wheels. Do they "suck up" salt?? Beats me I have never looked in there.

[AHG]

Thought: Since your bike is in an "A" class, and not "Production" perhaps consider doing a bit of research (ebay?)
and finding another front wheel that would be compatible, and does not have that big 6 lug casting in the center.
Thus, removing the want for a nonfunctional disc to improve its look.

p.s.
"My comment about not asking is that sometimes you might get one interpretation that you don't like , that might not be the consensus."
Can't help with that. However, with absolutely NO disrespect to anybody on this forum; I still believe that when possible,
going to those who are directly involved with the AMA and or F.I.M. rules should prove quite beneficial.

[Koncretekid]

I hope I didn't ruffle any feathers with my comment.  I think what I really should have said was that perhaps posting the question on the forum first might get answered by someone who has already asked or in this case, knew how the formula was being calculated.  And that that information would be useful to others besides me.

As for wheel research, I did.  I couldn't find a website with wheel dimensions so I used ebay.  But I wanted a wheel 2-1/2" or less, which is a little harder to find in the 17" diameter.