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Discussion Starter #1
I was kinda wondering about this one.

Which would be better, to add weight where its needed to get a perfect 50/50 front to rear weight ratio.

Or, would it be better to just live with a bad f/r ratio, like a 58/42 , and not add any weight?
 

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I asked that same question to one of the guys at MM a couple of years ago, maybe Mike K.

I was thinking of adding iron weights in rear to achieve a perfect 50/50 balance. He said no, never add weight, weight is the enemy drop as much weight as possible. Only time you need to add weight is for spec races where there is a minimum weight.
 

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Because tire traction goes up at a lower rate than weight does, and because all weight resists acceleration in any direction, it's better to leave it imbalanced than it is to add weight.
 

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Unfortunately, the formula is not so simple, especially for rwd cars. You can turn better lap times with ballast depending on how far off your weight distribution is, where your ballast is relative to your wheel base and center of gravity, and how much power you have generating forward bite.

A simplified example to demonstrate the physics, image a 1000lb rwd car with a 90/10 F/R split, a 100" wheel base, tires with friction mu of 1.0, and a very low center of gravity. No matter how much power that car has, it can only generate 100lbs of forward thrust coming off the turns (0.10 lineal g's).

Now add 50lbs of ballast 25" behind the rear axle center line. This heavier 1050lb car can now generate 163lbs of forward thrust, or more than 0.15 g's (50% greater), until it reaches it's power/traction limit speed.

Ballast decisions need to made on a case by case basis, and lap times (or lap data) will tell you the answer. Email me with your vehicle specifics if you would like to pursue further.

FYI, I run ballast on my car.

Frank
 

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Discussion Starter #7
Unfortunately, the formula is not so simple, especially for rwd cars. You can turn better lap times with ballast depending on how far off your weight distribution is, where your ballast is relative to your wheel base and center of gravity, and how much power you have generating forward bite.

A simplified example to demonstrate the physics, image a 1000lb rwd car with a 90/10 F/R split, a 100" wheel base, tires with friction mu of 1.0, and a very low center of gravity. No matter how much power that car has, it can only generate 100lbs of forward thrust coming off the turns (0.10 lineal g's).

Now add 50lbs of ballast 25" behind the rear axle center line. This heavier 1050lb car can now generate 163lbs of forward thrust, or more than 0.15 g's (50% greater), until it reaches it's power/traction limit speed.

Ballast decisions need to made on a case by case basis, and lap times (or lap data) will tell you the answer. Email me with your vehicle specifics if you would like to pursue further.

FYI, I run ballast on my car.

Frank

I'm thinking the way Frank is. If you adding only around 100lbs to the rear, and ends the gains in weight transfer, and traction should negate a mere 100lbs weight gain.

Also, think of it this way you should be able to offset the mere 100lbs with a little more hp.

Now if we're talking about something like adding 500lbs to the rear to get a perfectly neutral balanced car, then I would have to say it wouldn't be worth doing.

Does any of that make better sense, or am I way off?
 

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Moving existing weight would be a far better choice than adding weight.
100lbs of ballast, especially at either extreme end of the vehicle is a really bad idea.
As little as 25lbs can dramatically change (good or bad) the performance of a vehicle.
 

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Discussion Starter #10
Moving existing weight would be a far better choice than adding weight.
100lbs of ballast, especially at either extreme end of the vehicle is a really bad idea.
As little as 25lbs can dramatically change (good or bad) the performance of a vehicle.
Sure, that would be the absolute best IF you can get the engine back far enough, but for most here aren't going to able to do that. Not to mention that you will have to do something to clear the rack/pinion.

I moved my front suspension forward about 3.5 - 4", and in the future I might be able to get the engine back about an inch or so.

I disagree about 100lbs of ballast as that really isn't huge weight, and I don't mean to put it right on the rear bumper, but somewhere low, behind the drivers seat. Maybe a bit more on the rear passenger side to off set the weight of the driver
 

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Sure, that would be the absolute best IF you can get the engine back far enough, but for most here aren't going to able to do that. Not to mention that you will have to do something to clear the rack/pinion.

I moved my front suspension forward about 3.5 - 4", and in the future I might be able to get the engine back about an inch or so.

I disagree about 100lbs of ballast as that really isn't huge weight, and I don't mean to put it right on the rear bumper, but somewhere low, behind the drivers seat. Maybe a bit more on the rear passenger side to off set the weight of the driver
I was thinking in slightly smaller terms...but yes, moving the engine back would be an amazing improvement.

You have definitely made some huge gains if you've already moved the front axle center line 3.5" - 4" forward!

As for the weight...I was just going off of personal experience...&, you must have a lot more H.P. than me. :D My suggestion would be to start with 25lbs & move up in 25b increments...if you can, on the scales first, then out on track.

I must have misunderstood you as to where you intended to place the weight.

On three of my track cars we played with moving the battery (approx 48lbs) around that approximate location, while the cars were on the scales...all the cars had factory front axle C.L. locations.
In the first car, the best result on the scales (with driver in the car & 1/2 tank of fuel), came from placing the battery in the front passenger side seat location, towards the rear mounting holes of the seat.
On that car we left it in that location until we finished testing & decided to install a passenger seat. We moved the battery to the rear passenger side seat location because of clearance issues. There was a felt difference in sharp left transitions when we moved the battery (probably due to the weight being moved up as well as being moved rearward). That difference was muted a bit when we had a passenger in the car, but the passenger also changed all the handling, acceleration & braking dynamics.

With your modified front axle C.L. location, the front passenger side seat location might work even better for you! Only the scales & testing will tell.

All the other cars were mostly street driven & had passenger seats...so the rear passenger side seat has become my default battery mount location.
In your case, placing your ballast around these areas might help.
 

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Discussion Starter #13
I can imagine seeing the wife's face as I return home one day with 24 bathroom scales......................lol.
 

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I can imagine seeing the wife's face as I return home one day with 24 bathroom scales......................lol.
LMAO!!!:rofl:

Yeah no kidding...

How does that guy have a Porsche, an in-ground lift, etc...why the heck does he not have a real set of scales. LOL!!!

The Mathis book has a design for a 4:1 ratio lever type scale set up so that you can use (4) regular bathroom scales. The wife shouldn't be to hard on you for that...as long as they stay in the garage.
 

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LMAO!!!:rofl:

Yeah no kidding...

How does that guy have a Porsche, an in-ground lift, etc...why the heck does he not have a real set of scales. LOL!!!

The Mathis book has a design for a 4:1 ratio lever type scale set up so that you can use (4) regular bathroom scales. The wife shouldn't be to hard on you for that...as long as they stay in the garage.
Maybe he's using the money to pay for his Porsche, and lift?

Anyways, it still a pretty good way for the guy on a budget to check the weight of his vehicles.

Now of course if your wife is a bit, well, "big bone'd", you might have some splan-in to do dragging home that many scales.
 

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Because he lives in SoCal with barely any space and he's very much a DIY experimenter.
LMAO!!!:rofl:

Yeah no kidding...

How does that guy have a Porsche, an in-ground lift, etc...why the heck does he not have a real set of scales. LOL!!!

The Mathis book has a design for a 4:1 ratio lever type scale set up so that you can use (4) regular bathroom scales. The wife shouldn't be to hard on you for that...as long as they stay in the garage.
 

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Because he lives in SoCal with barely any space and he's very much a DIY experimenter.
So do I...I can sympathize.

I am very much a DIY'er as well...My first set of "scales" was a very basic version of the 4:1 lever system as found in the Mathis book. They worked pretty well.
I think we spent about $120-$150 total.

Then, as I got older & had a little more money, I had Dick Guldstrand corner weight & set up my cars. (Money very well spent!!!)

Now I'm back to the DIY approach with a $1000 set of longacre scales & some hand fabbed ramps.

I must say that his approach was creative!
 

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Discussion Starter #18
Actually I will most likely try the bathroom scales approach one day is its, simple, and affordable.
 
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