Rotational Weight Question

HP HUNTER · 04-17-2015, 11:21 PM

Lets say you have C/SA 69 Camaro 375/396, If you ran a conventional 12 bolt with a steel spool non gun drilled axels and ran 10.50 with 1.36 60 foots, if you built a 12 bolt with 35 pounds less rotational weight and ceramic bearings, how much would you pick up?

GTX JOHN · 04-18-2015, 02:08 AM

I think if you picked up .01 in 60 that would be a lot.

Ed Wright · 04-18-2015, 07:10 AM

I put an aluminum spool and lightened gear set in mine, and found nothing. I don't waste my money there anymore.

Tom Meyer · 04-18-2015, 08:07 AM

My thoughts are, you could pick up more by having your rear end square in the car and all moving parts on it move smoothly with no binding. The right lube and how much is also important along with having the gears properly set up. I also don't think you could get 35# out of a 12 bolt and if you could all that it would help would be sprung unsprung weight. Tom

HP HUNTER · 04-18-2015, 09:26 AM

Quote:

Originally Posted by Tom Meyer

My thoughts are, you could pick up more by having your rear end square in the car and all moving parts on it move smoothly with no binding. The right lube and how much is also important along with having the gears properly set up. I also don't think you could get 35# out of a 12 bolt and if you could all that it would help would be sprung unsprung weight. Tom

What lube do you run?

tj310 · 04-18-2015, 09:54 AM

I remember a saying that was attributed to Colin Chapman

A gram of reciprocating weight is worth an ounce of rotating weight

an ounce of rotating weight is worth a pound of chassis weight

Take that with a grain of salt. ---Trevor

FED 387 · 04-18-2015, 02:36 PM

I was always told that rotational weight is equal to 4 times the actual weight---- that means that for every pound the effective weight that the engine is trying to overcome would be 4 pounds--- now this may depend on how great the diameter of the object is--- in other words if you have an item that is 2 inches in diameter the rotational weight difference will not be as significant as say an item that is 12 inches in diameter where it should be greater--FED 387

HP HUNTER · 04-18-2015, 09:30 AM

Quote:

Originally Posted by Ed Wright

I put an aluminum spool and lightened gear set in mine, and found nothing. I don't waste my money there anymore.

Do you think a foot brake combination might have different results? I appreciate all opinions, just trying to learn.

Andrew Hill · 04-18-2015, 07:23 PM

Quote:

Originally Posted by HP HUNTER

35 pounds less rotational weight and ceramic bearings

They may not have the same effect. Also, is the rotational weight wheels or axles? Brakes or spool? Rotational weight isn't all the same. All the weight can be quantified if you know the moment of inertia.

ron mattson · 04-18-2015, 07:28 PM

Very good replies and in my experience
there is more between the fenders than
You will ever find in the diff!! My.02$$

04-17-2015, 11:21 PM	#1
HP HUNTER Senior Member Join Date: Feb 2012 Location: Colorado Springs Colorado/Thousand Oaks Ca Posts: 656 Likes: 82 Liked 373 Times in 129 Posts	Rotational Weight Question Lets say you have C/SA 69 Camaro 375/396, If you ran a conventional 12 bolt with a steel spool non gun drilled axels and ran 10.50 with 1.36 60 foots, if you built a 12 bolt with 35 pounds less rotational weight and ceramic bearings, how much would you pick up?

04-18-2015, 02:08 AM	#2
GTX JOHN VIP Member Join Date: Jun 2009 Location: Boulder City, Nevada 89005 Posts: 2,736 Likes: 2,808 Liked 2,488 Times in 698 Posts	Re: Rotational Weight Question I think if you picked up .01 in 60 that would be a lot. __________________ John Irving 741 Stock 741 Super Stock

04-18-2015, 07:10 AM	#3
Ed Wright Veteran Member Join Date: Mar 2005 Location: Sand Springs, OK Posts: 8,132 Likes: 896 Liked 390 Times in 170 Posts	Re: Rotational Weight Question I put an aluminum spool and lightened gear set in mine, and found nothing. I don't waste my money there anymore. __________________ Ed Wright 4156 SS/JA

04-18-2015, 08:07 AM	#4
Tom Meyer Senior Member Join Date: Aug 2003 Location: Pierce NE Posts: 936 Likes: 78 Liked 354 Times in 120 Posts	Re: Rotational Weight Question My thoughts are, you could pick up more by having your rear end square in the car and all moving parts on it move smoothly with no binding. The right lube and how much is also important along with having the gears properly set up. I also don't think you could get 35# out of a 12 bolt and if you could all that it would help would be sprung unsprung weight. Tom __________________ Tom Meyer 5240 SS Stock ???

04-18-2015, 09:54 AM	#6
tj310 Member Join Date: Sep 2009 Location: Dresden On. Canada Posts: 460 Likes: 0 Liked 0 Times in 0 Posts	Re: Rotational Weight Question I remember a saying that was attributed to Colin Chapman A gram of reciprocating weight is worth an ounce of rotating weight an ounce of rotating weight is worth a pound of chassis weight Take that with a grain of salt. ---Trevor

04-18-2015, 02:36 PM	#7
FED 387 VIP Member Join Date: Jun 2006 Posts: 3,423 Likes: 538 Liked 333 Times in 180 Posts	Re: Rotational Weight Question I was always told that rotational weight is equal to 4 times the actual weight---- that means that for every pound the effective weight that the engine is trying to overcome would be 4 pounds--- now this may depend on how great the diameter of the object is--- in other words if you have an item that is 2 inches in diameter the rotational weight difference will not be as significant as say an item that is 12 inches in diameter where it should be greater--FED 387

04-18-2015, 07:28 PM	#10
ron mattson Member Join Date: Nov 2005 Location: cloquet mn Posts: 467 Likes: 17 Liked 68 Times in 31 Posts	Re: Rotational Weight Question Very good replies and in my experience there is more between the fenders than You will ever find in the diff!! My.02$$ __________________ Ron Mattson 5015 STK Last edited by ron mattson; 04-18-2015 at 07:32 PM.