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Front to rear weight bias T/S and PM builds
#2509310
06/16/18 12:58 PM
06/16/18 12:58 PM
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Joined: Feb 2006
Posts: 698 Alberta Canada
Edge
OP
mopar
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OP
mopar
Joined: Feb 2006
Posts: 698
Alberta Canada
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Anyone know what the trend is for front to rear weight bias on newer t/s and pro mod builds ? A friends former RJ car was 53% on the nose however I have heard of cars being built even heavier on the front as well. I am going to have to add some weight to bring my car to min weight and need to determine how much and where to put it.
76 Duster
work in progress
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Re: Front to rear weight bias T/S and PM builds
[Re: Edge]
#2509322
06/16/18 01:28 PM
06/16/18 01:28 PM
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Joined: Oct 2007
Posts: 4,205 New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,205
New York
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Excellent question: too many variables in how the weight transfers on launch to predict, unless you just duplicate what already works.
Boffin Emeritus
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Re: Front to rear weight bias T/S and PM builds
[Re: Edge]
#2509332
06/16/18 01:55 PM
06/16/18 01:55 PM
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Joined: Dec 2005
Posts: 11,408 Fulton County, PA
CMcAllister
Mr. Helpful
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Mr. Helpful
Joined: Dec 2005
Posts: 11,408
Fulton County, PA
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I would add tabs and mounts for ballast in different locations in the car. Both ends and in the center. Use lead filled bars or pucks to get the weight where you want and need it. Moving 10 pounds can make a big difference as to whether it's dragging the bumper or blowing the tires off, especially with radials. Make the car light, use the ballast to get the extra weight where it's most helpful.
Last edited by CMcAllister; 06/16/18 01:56 PM.
If the results don't match the theory, change the theory.
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Re: Front to rear weight bias T/S and PM builds
[Re: Edge]
#2509384
06/16/18 05:14 PM
06/16/18 05:14 PM
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Joined: Oct 2007
Posts: 4,205 New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,205
New York
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Good idea - build in some adjustment. Remember that height has a great effect on transfer without changing the F/R proportion.
Boffin Emeritus
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Re: Front to rear weight bias T/S and PM builds
[Re: CMcAllister]
#2509419
06/16/18 07:29 PM
06/16/18 07:29 PM
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Joined: Oct 2004
Posts: 8,165 Left Coast
BobR
master
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master
Joined: Oct 2004
Posts: 8,165
Left Coast
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I would add tabs and mounts for ballast in different locations in the car. Both ends and in the center. Use lead filled bars or pucks to get the weight where you want and need it. Moving 10 pounds can make a big difference as to whether it's dragging the bumper or blowing the tires off, especially with radials. Make the car light, use the ballast to get the extra weight where it's most helpful. I agree...sort of. Weight in the middle is seldom of any practical use. The ends of the car is quite another story.
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Re: Front to rear weight bias T/S and PM builds
[Re: Edge]
#2509448
06/16/18 10:17 PM
06/16/18 10:17 PM
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Joined: Oct 2007
Posts: 4,205 New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,205
New York
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Weight in the form of a solid bar across your halo behaves very differently than weight under the floor. Weight behind the axle center is cantilevered: it adds weight to the whole chassis, but subtracts weight from the front wheels. Weight directly above the axle center becomes cantilever when the front end rises; the higher it is the faster is affects distribution.
Boffin Emeritus
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Re: Front to rear weight bias T/S and PM builds
[Re: Edge]
#2509505
06/17/18 02:09 AM
06/17/18 02:09 AM
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Joined: Dec 2005
Posts: 11,408 Fulton County, PA
CMcAllister
Mr. Helpful
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Mr. Helpful
Joined: Dec 2005
Posts: 11,408
Fulton County, PA
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With substantial power, 53-54% on the front should be close. Weight on the nose will help keep the front end down, weight on the rear will help it pitch rotate (pick the nose up), weight in the center is more neutral and just makes the car heavier. Weight up high raises the CG, usually not desirable in a fast car. Suspension and every other detail about the car also matter, but moving weight is a quick way to change how the car is behaving. Video is your friend.
If the results don't match the theory, change the theory.
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Re: Front to rear weight bias T/S and PM builds
[Re: CMcAllister]
#2509577
06/17/18 12:38 PM
06/17/18 12:38 PM
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Joined: Feb 2006
Posts: 698 Alberta Canada
Edge
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mopar
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OP
mopar
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Alberta Canada
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Thanks for the information, we are at 56 and a bit on the nose right now and will plan to add some more tabs rear of the axle as suggested to moving some lead around.
76 Duster
work in progress
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Re: Front to rear weight bias T/S and PM builds
[Re: Edge]
#2509989
06/18/18 02:03 PM
06/18/18 02:03 PM
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Joined: Jan 2003
Posts: 19,304 Las Vegas
Al_Alguire
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 19,304
Las Vegas
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More power more weight up front in general. My car is at 53% now but it moderately powered TS car. New heads and intake should be back soon and we will see what improvements have been made. I would also add, moving the weight as far forward or rearward is also a good idea to change the bias around. For instance my weight is mostly on the fuel cell mount in the very front of the car. Not all of it but a fair amount. My car is fairly light and needed quite a bit to make the TS minimum.
"I am not ashamed to confess I am ignorant of what I do not know."
"It's never wrong to do the right thing"
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