You seem to understand how this stuff works, please explain what unit to use when quantifying rotating mass then tell us how to use it, so we can get past the definition stage, on to the understanding stage and to the application stage.

Ron

 

Conversation is a rotating mess, you boys need to get outta the books and go ride. Apply Trottle buddy and rotate da mass LOL[img]i/expressions/face-icon-small-wink.gif[/img]

 

What about tire weight and diameter? (rotational inertia) This would have a much greater bearing on performance than the weight of an aluminum sprocket.

 

competition buffed tires shaved paper thin on the lightest rims equals a big gain, this is the weight that is farthest from the center that dsengineer talks about, and is also a significant amount of weight no matter how you look at it.

when it comes to the lightest rims - the smallest dia. rim for the DS is a 9", but hpr and others offer lightened wheel hubs that can be bought with honda bolt patterns to run 8", taking it even further. but if your running heavy rubber the smaller rim can be counterproductive in terms of weight.

no single thing done amounts to a whole lot, but do it all and its seriously noticable. but like any and all mods that equal gains - it aint cheap.

 

Amen!!

 

For about 25 years now, we've either ran or helped to run the local 300ft dirt drags. They have always been stuck on the spotting system allowing handicap starts for extra weight of the machine or rider and allowing for certain mods to be made within a class, but getting penalized for them on the starting line.
So, it has been important for us to be fairly accurate in the rules to account for this spotting mehtod.
Here are the numbers I've found in 300 ft on a dirt track, racing many equivalent machines over the years with only the weight or the horsepower changed to get comparisons

35-50 lb dead weight = 5 ft = 2-3.5hp
the horspower has a range because some mods add 2 hp everywhere, while others add 3.5 hp over a narrower range. The 2hp everywhere probably wins.

So, a 35-50 lb lighter rider will cross the finish line 5ft ahead of you in a 300ft race. You will need to bolt on 2-3.5hp to catch back up.

Hope this helps, it's worked for us pretty good for years.
222

 

200lb rider vs me in 300ft. I would need a 15ft head start or 10.5hp more than him to run equal[img]i/expressions/face-icon-small-confused.gif[/img]

Its all good!!

 

im right there with you !!!

 

so, if you pull up to a 200lb "jock", just remember that if you get within 10 bikes in a 300ft dirt drag, you really won!

Now put that weight up a 600ft hill, and it all gets even worse!


222

 

Dont even want to think about that yet!! Give me the Hp first and then will see how everything falls.