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How to reduce rotating mass
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#47 GODSPEED BAMBAM
 
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How to reduce rotating mass - March 12, 2008, 12:07 PM

Drill that rotor out!!!!! Took out 1/2 lb of weight!!!



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Typical Stripper
 
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March 12, 2008, 12:10 PM

Do you think there will be any adverse braking effects with the lower surface area? Higher pad wear?


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#47 GODSPEED BAMBAM
 
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March 12, 2008, 12:14 PM

Quote:
Originally Posted by Nudist
Do you think there will be any adverse braking effects with the lower surface area? Higher pad wear?
Well this is the rear brake and pad wear should go down a bit. It will be harder to slow the bike down with the rear only but it is for a race bike. I want to dyno the change also to see if it picks up some HP.


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March 12, 2008, 12:16 PM

There was plenty rear brake before, a little less friction area can't hurt, we modify rear pads on the Kawasaki to limit the friction area, this is a little more permanent and less rotating mass. This is actually a Buell rotor, it needs all the dieting it can get.
thanks Mike


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Typical Stripper
 
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March 12, 2008, 12:18 PM

Quote:
Originally Posted by dodge131
Well this is the rear brake and pad wear should go down a bit. It will be harder to slow the bike down with the rear only but it is for a race bike. I want to dyno the change also to see if it picks up some HP.
Gotcha - for some reason I thought it was an SRAD front rotor...


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March 12, 2008, 01:58 PM

Why not ride w/o any rotors?

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March 12, 2008, 02:00 PM

Me likey.
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March 12, 2008, 02:12 PM

Dodge and Rick speak the truth.
You don't want to do this to a front rotor...


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March 12, 2008, 02:15 PM

What about balance? Or are you offsetting any adverse issues from the rotor with weights on the rim?

Interesting concept.


Edit: nevermind, missed the fact that it was a rear rotor. 8 hours of sleep divided over 2 days doesn't do good things to me.


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  (#10)
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March 12, 2008, 02:36 PM

Mike was cool enough to have 1 of my fronts and the rear drilled out too! Shaved some weight off of each! You know I'm a lightweight junkie...er....that didn't sound right.

Front comparision:



Rear comparision:



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A.


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Last edited by shiphteey; March 12, 2008 at 03:11 PM..
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March 12, 2008, 05:39 PM

Quote:
Originally Posted by SteveZX9
Dodge and Rick speak the truth.
You don't want to do this to a front rotor...
Good point! The one Mike did for me will only be used for strip purposes. Hence why I have one remaining stock.

A.


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March 12, 2008, 06:39 PM

Quote:
Originally Posted by dodge131
Well this is the rear brake and pad wear should go down a bit. It will be harder to slow the bike down with the rear only but it is for a race bike. I want to dyno the change also to see if it picks up some HP.
Well, if its a proper dyno, you shouldn't gain any hp. However, the numeric gain you will see on an inertia dyno is indicative of the decrease in rotational inertia.

Given the diameter of the rotor the effective weight loss is ~1.2 times the amount of actual weight reduced.

Also, you probably also reduced the resistance to turning by about 1-2%, which you might be able to feel


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March 13, 2008, 03:07 PM

yeah what the nerd said!


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  (#14)
B
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March 13, 2008, 03:20 PM

Quote:
Originally Posted by birdman
Given the diameter of the rotor the effective weight loss is ~1.2 times the amount of actual weight reduced.
Out of curiosity what kind of effective weight loss would you see on a regular front rotor? Isn't this the general concept of wave rotors, rotating weight reduction by removing mass, and if so why is it a bad idea to drill fronts?

Looks freakin hot dodge, can you do mine?


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  (#15)
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March 13, 2008, 03:56 PM

drilling the fronts is bad because you create stress concentrations for cracking. When they drill them at the factory, they are heat treated afterwards, and the holes are chamfered.

the weight loss equivalence for a front rotor is going to be 1.4-1.6 I would guess (without going into the math), for wheels its about 2, for flywheel/crank/clutch parts its gear dependent, but goes from a little more than 1 in like 6th gear to 2-4 in lower gears (or more)

hmm...maybe I should just find the spreadsheet I made a while back and post it up


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