Corner balance after weight reduction

[drl911]

What is the theory regarding corner balancing target numbers after a car has under gone a weight reduction program?

If the standard target is a 60:40 weigth distribution of rear to front on a stock 911, does your target corner balancing values change if, for example, you exclusively removed significant weight from only the rear of the car? Or would you still take the total new weight of the car and "put" 60% on the rear and 40% on the front?

Thanks,
Dan

[jpnovak]

Ideally you would want 50/50 F/R balance. This will not happen on a 911. The target of corner balancing is not to adjust the f/R weight bias. It is to equally distribute the weight to each front and each rear tire so the car will handle the same in left and right hand conering.

that said it is beneficial to remove weight from the rear of the car first. This is not always easy to do but will depend on the car.

[daleflesburg]

You cannot effect front to rear ratio much....but balance is something that will improve the way the car handles..

Once left front = right front, and left rear equals right rear with the weight of the driver in the drivers seat, ( it will be impossible to get it perfect, but the object is to get them close ), then:

You should check diagonal weight. Left Front + Right rear should equal Right front + left rear. This diagonal should be done with the weight of the driver in the drivers seat, and the diagonal weight should be as close as possible to equal. (Again, perfection is impossible, but you want it to be as close an you can get it.

I am under the impression that the diagonal balance is the most important.

[drl911]

Jamie,
I understand your response, but I want to know how would you determine the exact target values after removing for example 200lbs from the car?

Let's say a stock Carrera weighs 2800lbs. 60% in the rear means 840lbs at each rear tire and 40% in the front means 560lbs at each front tire. Now if one were to remove 200lbs exactly at the rear axle centerline would the new rear tire target corner weight be 740lbs (100lbs at each rear tire = 200lbs total)? If so, your car would become 57:43 (I agree that is better).

My real question is how do people know how to set-up their cars after removing lots of weight from all over the car?

[Wil Ferch]

None of the posters ( here) understand the core issue ....

When you remove weight off of a car that ( for example) originally started out at 40 fr / 60 rr...and if you remove the weight in the back so that it now has 43/57 weight distribution....the car will only have "what it has".... in this case, a 57% rear weight bias. That will never change after you removed the weight this way.

Period.

In corner balance...you don't change the weight of *any two adjacent wheels*..... they will remain *constant*. Once you removed weight from the rear such that it only carries 57% of the total weight... you won't change that.

This is the biggest single hurdle most people have to overcome in understanding "corner balance". Any *one* wheel may change....but any Two Adjacent wheels will ALWAYS be the same.....

Plus..if you change "one" wheel ( say... making the LF heavier)...the diagonal opposite ( RR, in this case) will go heavier by the *same* amount.

A lot of text floated between me, Chuck Moreland...and also with Randy Blaylock and Craig911 on this topic. Related topic of "weight jacking" is also discussed. Do a search.

- Wil

[Craig 930 RS]

That was a great discussion - I recall that post.
Wil, do you have a link to it - I can't find.......

[Wil Ferch]

Oh...BTW... Cliffs Note Version of the original question.

If you indeed took a lot of weight off the rear of a 911...and the car ( actually) ends up being 43/57.... you find this out by either placing the car on corner scales...or AT LEAST put the front of the car on a commercial scale ( both front wheels)...and then turn it around to put the back-two wheels on the scale. Record the numbers. If it's 43/57...it'll then always be 43/57 no matter what you do to the *corner* balance. Meaning?...the back two wheels will always show the same (total) weight.....the front two wheels will always show the same total weight....the RF + RR ( total ) will ALWAYS be the same....and the LF+ LR (total) will ALWAYS be the same...no matter what you do in corner balance activities. Any two adjacent wheels will always show the same total value.

The ONLY way to change this rule...is if you ( then) actually move things around in your car...like moving the battery location.....

- Wil

[Wil Ferch]

Craig...yeah, I found it ---> * CORNER balanced - numbers from this...and the weight

..but this is like "post graduate" corner balance stuff.... we need to cover the basics ( Corner balance 101 ! ... ) first by getting some misconceptions staightened out....

- Wil

[drl911]

Thanks Wil!

I guess that's why it's called "corner balancing" after all. The name and process actually answers my question in hindsight.

I just remember doing it after I first got the car and have since removed close to 200lbs. in total from several different areas. Maybe worth checking it again.

Dan

[hobieboy]

Originally posted by drl911
I just remember doing it after I first got the car and have since removed close to 200lbs. in total from several different areas. Maybe worth checking it again.

Dan

Yes, if you have removed 200lb all from, say, right side of the car, I'm sure you'll want to do another corner balance.

[Thrasher]

Originally posted by drl911
I just remember doing it after I first got the car and have since removed close to 200lbs. in total from several different areas. Maybe worth checking it again.

Dan, just curious where you unloaded the 200 lbs?

[Wil Ferch]

You need to ask..."Where was the original 200 lbs that is now gone"?

.....if it's fairly well distributed....( meaning, if it's all in the back...evenly spread left-to-right)...then the "corner balance" may still be OK.

If, however, all the weight ( or most of it) came off the right-rear ( for example)....then the RR is now disproportionately light, as will the LF.
To compensate, the opposite diagonal pairing will get heavier. The amount of "load" each corner changes... will have to take into account that ANY TWO adjacent wheels will still be the same, in the final configuration...because after the car was lightened, you're not "moving" actual mass around, like relocating a battery.

We can look at two example ways you lost 200 lbs

Original corner weights
560 560
840 840..... total is 2800 lbs....fr/rr = 40/60....l/r= 50/50


If you lost all the weight in the back...evenly left-to-right....

Case 1, lost evenly left-to-right:
560 560
740 740...total is now 2600.... fr/rr = 43/57....l/r= 50/50

At this new weight of 2600 lbs...no matter how you re-distribute the corner-weight from this point-on, any two adjacent wheels will still end up with the same TOTAL. Front total is 1120. Back total is 1480. Right ( or left) total is 1300.

Now, if you instead lost 200 lbs ( from the 2800 l original car) on the right-rear...making it 640, and knowing that the resulting car has to weigh 2600 lbs, the RF then has to be 660 ( Why?...so that the right side stays at 1300). If RF is 660, the LF has to be 460 ( for the front total to remain 1120). OK, so now we have 640+660+ 460 + (?) = 2600. That means that the LR has to be 840.

You end up like this, when all the actual weight was removed from the RR:

Case II, lost all the weight on the RR:

460 660
840 640

total is 2600..right (or left ) total =1300, - checks
front total = 1120, - checks
back total = 1480, - checks
f/ r = 43/47, ..........- checks.....

So..in both cases, the car will show 43/57 front to rear, will show the same total overall weight, and will show the same individual right or left side weights...but have completely different "ideal" corner weights, compared to taking all the weight out evenly in the rear.

Simple, eh ?? ....

Wil

[Thrasher]

Wil, I'm with you... I was sort of asking which pieces/parts he had removed/replaced to get a sense of which corners/diagonals were missing the original weight.

I recall this article being a big help in "getting it" when I corner balanced at home.

It's probably also worthy to note that something like the A/C compressor which is more "outboard" on the extent of corner will have a greater impact than something more centrally located, e.g. the center console. Is that logic sound?

Dan, can you list the items you removed or replaced with lighter versions?

[drl911]

Removed or changed so far:

Complete AC system removed, everything!
Complete heating system removed, everything!
Headers and megaphones only.
No Spare tire.
Fiberglass rear bumper.
All sound deadening removed.
No center console. Shift tower only!
Electric flag mirrors changed to manual aero mirrors.
Whale tail changed to fiberglass ducktail without lift supports.
Windshield washer system removed (at least 16lbs of H2O).
Single windshield wiper arm system, removed unnecessary linkages under the cowl.
Removed airbox, changed to cone filter.
Removed plastic/rubber door sills.
Fresh air blower for windshield only, everything else removed!
Removed fiber board in front trunk area.
Rear aluminum solid motor mounts.
Single horn.

Next project - Carbon Fiber rear deck shelf!

My name is Dan and I have a weight reduction "problem"

[Wil Ferch]

Ok... now I get it....you're taking stuff off all over the car.

The best thing to do ( in sequence)...
1.) Take all the stuff off you want to remove.
2.) Find out new total weight and new fr/rr distr. Minimum....front total weight and rear total weight. Better...get on 4 corner weight scales. Report back on findings. We'll go from there.

The epiphany I got was that you may want to target equal LF=RF weights, even if the corner balance "formula" tells you not to. Why? This will promote superior threshold braking, at the small expense of not having the "correct" corner balance numbers for best cornering in both directions. The trade-off is "overall" better....that is what I learned after my long-ish thread with Craig / Blaylock / Moreland, etc.....

- Wil

[Thrasher]

so 2 of the heavier items, the AC Compressor and windshield tank, are offset (RR and LF), but come off the same "diagonal" when corner balancing, which would seem to really affect your CB numbers.

Did you by any chance weigh the above items to see how much each took off?

[Wil Ferch]

These are really fine-cuts... I would recommend getting the car ( with all the stuff removed) back on scales to determine the new baseline.

- Wil