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What is corner balancing?

I have finally completed collecting everything I need to do some suspension work on my 68T. New struts, shocks, bushings, turbo tie rods, tie rod ends, ball joints, strut brace & everything in between. I'm new to the Porsche world, actually I've had my car for 2 years now but I've lusted after one since seeing them race in Daytona & Sebring back in my younger days. There are still some things that I'm not real familiar with like corner balancing. I know after doing all this the front will need to be aligned & I've read about you guys having your cars corner balanced but I really dont know what you are talking about. When I take the car in to have it aligned I would kinda like to know what I'm talking about when I ask for a corner balance. Also can any shop that does alignments do corner balancing?
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Old 04-07-2005, 02:31 PM
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Uh oh.

I would suggest you do a search. There's much material; some will make your head spin.

Sherwood
Old 04-07-2005, 03:21 PM
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Honestly, I think this forum needs a good FAQ.... I mean, better than the FAQ that is already on the site. I don't know what, specifically, 'corner balancing' is!?! I've seen terms and acronyms thrown around that may be common knowledge to seasoned P-car owners and Pelicanheads, but are almost foreign to us noobies. And like 911pcars mentioned, there's so much material if we were to use the search function, we'd have to wade through all of the mentions of the term until we found an actual definition of it.
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Old 04-07-2005, 03:26 PM
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Here’s a quick, short answer:

Think of a four legged table that wobbles. One leg is longer than the others, so the table wobbles. Fixing that is like corner balancing your car.

Here’s the longer version, but still pretty simple:

The difference is that cars have springs, so if one “leg” is “longer” than the others, it’s accommodated by that spring compressing. The effect is still there, but your car won’t wobble and one wheel won’t be off the ground. But that one corner will have more weight than the other corners.

Now think of a shopping cart or something with no suspension. If one wheel is longer, and the cart wobbles, what happens when you try to take a turn? The cart wobbles, and one wheel lifts off the ground and does not contribute any traction to the turn. The same thing, in essence, happens when you make a turn in a car that is not corner balanced.

Corner balancing adjusts the weight on each corner, by raising and lower the suspension on that corner, until the diagonal weights are as close to equal as possible. You want the weight on the right front plus the weight on the left rear to equal the weight on the left front plus the right rear.
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Old 04-07-2005, 03:39 PM
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Noting that you are up in Wi. If you are near madison you may want to check this place out.

http://www.kellymoss.com/
Old 04-07-2005, 04:04 PM
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A FAQ would be nice, but the trouble is, we would want one for every situation. The search function is helpful. I know what you are thinking, "oh another, 'go search' response". When I first started looking at this forum, I couldn't search well either, but keep doing it and you will see. It's all in the archives.

Also, try this. When searching for something, say turbo tie rod installation, create your search like this:

turbo AND tie AND rod AND installation (using the caps on AND), and it will help weed out the casual references. Still not perfect, but more helpful.

I hope


-Chris
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Old 04-07-2005, 04:08 PM
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For a corner balance you need a shop that has scales. These are 4 scales, each going under one wheel. Usually they are connected into a computer / cpu. A run of the mill tire shop or mechanic does generally not own such scales. You need to go to a shop that has some connection to road racing. And you should go with a shop that knows Porsches. I recommend you contact people in your local PCA or get shop recommendations here.

George
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Old 04-07-2005, 04:08 PM
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Or you can do like we do in Coupeville ,use a bunch of bathroom scales with a 2 by 6 on them to distibute the weight of the tire (4 scales under ea rear and 3 under ea front)and they are cheap from bonmarchey.
Old 04-07-2005, 04:44 PM
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Thanks for the replies, Kang that was a good explanation. The way you explaned it made sense. The suggestion for taking the car to Kelly Moss was something that I considered but Madison is about a 2 hour drive but what the heck a 2 hour drive in a Porsche is not a bad thing.
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Old 04-07-2005, 05:17 PM
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My name will likely come up in a thread search...so let me take a stab at a summarized explanation.

Noting that the car will have certain heavy masses located in various places in the car...and that they're not equally distributed ( engine in back...battery to the side)...the car will be in proper "corner balance" when each INDIVIDUAL wheel carries the load it should. Because of the the mis-match of weights...this will not be the same for the two front wheels, nor for the two rear wheels.

However, since the car's masses are where they are....you'll find that ANY TWO ADJACENT WHEELS ( the sum) will never change. If you change the weight on ONE CORNER ( say, by making it heavier as described by others)...the opposite diagonal will also get heavier. Likewise, the other diagonal gets lighter on each end. You can't change the *total* ( sum)of the front of rear TWO tires..since you didn't move the actual masses around.

There is a recent thread that says a thoughtful, purposeful, "imbalance" ( weight jacking) to get the front two wheels EQUAL...is a good thing. It makes for good braking...at the expense of non-optimized cornering. The "hit" on cornering is considered "small" ...in this compromise.

Still too long...huh ?

Wil
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Old 04-08-2005, 03:10 AM
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i have thought about this lately too and agree that a FAQ section might be useful - a glossary perhaps?
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Old 04-08-2005, 04:05 AM
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Its a controversial operation with no correct answer

* CORNER balanced - numbers from this...and the weight
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Old 04-08-2005, 08:29 AM
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Craig:

I think what I last said...

" ...There is a recent thread that says a thoughtful, purposeful, "imbalance" ( weight jacking) to get the front two wheels EQUAL...is a good thing. It makes for good braking...at the expense of non-optimized cornering. The "hit" on cornering is considered "small" ...in this compromise...."

... gets us as "close" to a correct answer as we can hope for..unless we have very specific other corner weight targets to consider. For that to be true...you'd need a ton of experience and even at that..the "other answer" would only work for a narrow, specific..application.

Wil
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Old 04-08-2005, 08:49 AM
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Now this thread started out pretty simple,as usual it gets muddy in a hurry.
So to help, would this be correct in all the xperts eys not counting therum or speculation.
It would seem to simply corner wt to some one, is the wheel has to carry the actual wt. of that cars corner w.o. any sprung into (extra preload) or less for that matter.
It would seem that ea corner would have to be weighed w.o. the suspension so the truth would show up then match that or go onto some predetermined track ra
Old 04-08-2005, 05:24 PM
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afterburn:
Yes that is correct... to be "corner weighted" is for each corner to carry its "assigned" or proportional load...without introducing a preload ( or "underload").

What you..and others...aren't grasping, is that to understand what this is...you don't need to discount the suspension. You just need to understand that ANY TWO WHEELS ALONGSIDE ONE ANOTHER will weigh the same...no matter if you are properly corner balanced or not.

Critical...any TWO adjacent wheels have the same SUM WEIGHT. ( why?....because you didn't MOVE weight around in the car..it's where it always was and you CAN'T change weight distribution unless you move the actual weight around !....quite simple).

So yes...when you adjust to get proper corner weight..if (say) the LF gets lighter...the oposite diagnal HAS to get lighter...and the two corners of the other diagonal HAVE TO get heavier. This keeps the critical point correct that any two adjacent wheels stay the same.

This is the most difficult concept to get through...and 99% of the time is because people want shortcuts toward understanding. If you noodle with the numbers long enough...this fact will become readily apparent.

Now having said this...the other thread on this topic showed that a GOOD COMPROMISE would be to get the front two wheels equal...even though this is not true corner balance...you've "weight jacked" the car. The cornering that is compromised is less effected than the "goodness" gained by better braking...when set up this way.

Not really muddy at all.....

Wil
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Old 04-09-2005, 09:55 AM
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Will and others, excellent answers to a question I was too afraid to ask and too lazy to search.

I'm all for an expanded FAQ!

Steve
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Old 04-09-2005, 10:24 AM
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So far so good,thanks!Will, could I bore you into a paragraph or two more??walk us thrue this please and I will forever shut up, say some one drives up on the scales, (start from there take a couple of short cuts as I do not want to take up your whole life) you get 800 or so on ea rear and 450 or so on ea front....these wts. have to be discounted right? beacuse one dose not know what is jacked where. So from this pt. whats next? Thankyou very much in advance and we all will get our brain around this
Old 04-09-2005, 04:35 PM
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Corner balance.....when a 914 kicks yer butt in a corner....he was corner balanced....%^B
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Old 04-09-2005, 05:16 PM
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Old 04-09-2005, 09:02 PM
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Afterburn and others...

No problem....this is something that took me a long time to figure out...you just have to work the numbers. Instead of your suggested 450 and 800 lb fr/rr weights, let me re-post an example of how the car might be to begin with..and what we do to end up "corner - balanced"...

My example uses a 1000 lb car so the math is more quickly "grasped", without having to use calculators. Hint...you have to go through ONE example for all this to make sense..and I think this one will do it...

In the formula used...recognize that 0.6 represents 60% rear weight bias...0.51 might represent left weight bias...and so forth.

=============================================

Since you'd like to see a "derivation" of how this came about...let's start with the two facts that you say we're in agreement with:
1.) Total front ( or left side..or right side..or total rear) weight stays the same regardless of the corner balance achieved. Doesn't change for any TWO ADJACENT wheels.
2.) a heavy LF will result in an equally heavy RR (etc)

So....For a 1000 lb car with a 40/60 front/rear weight distribution.....and a 51% left/49% right weight distribution....the "ideal" weights would then be this:

LF = 0.4 x 0.51 x 1000 = 204 lbs
RF = 0.4 x 0.49 x 1000 = 196 lbs
LR = 0.6 x 0.51 x 1000 = 306 lbs
RR = 0.6 x 0.49 x 1000 = 294 lbs
_________
Total weight = 1000 lbs

This should be ( IMHO)..the "target" weights for a properly corner-weighted car.

If, for example....you put individual scales under each wheel and find a different number.....you may find ( for instance) that the LF is 25 lbs "heavy". If so....the diagonal opposite to LF will also be 25 lbs heavy...the RR will be heavy. Because any two adjacent wheels stay the same..the other diagonal will be 25 lbs "light" ( from ideal) at each corner. Let's see if this is true:

Lets say Actual LF is 25 lbs "heavy" vs ideal, or = 204+25= 229
Since "total" front weight remains at 400 lbs...the RF has to be 400-229= 171

Since Total left side is .51 x 1000 = 510...then LR has to be 510-229=281

Since total right side stays the same at 0.49 x1000= 490...then RR is 490-171 = 319

So our "actual" numbers might be these:
LF= 229
RF= 171
LR= 281
RR= 319
__________
Total = 1000 lbs - checks
Total left weight is 229+ 281 = 510 lbs = 51% - checks
Total front weight is 229+171= 400 lbs = 40% -checks
Total rear weight is 281 +319= 600 lbs = 60%-checks
Total right wieght is 171 +319 = 490 lbs= 49%- checks

So...we can see that the "Actual" weights still show a 40/60 front /rear balance..and a 51/49 left-to-right balance, just as the first case....but the LF and RR are each 25 lbs heavy...and the RF and LR are each 25 lbs light. Each "corner" is not carrying the weight it "should"...it's not "corner" balanced.

The first set of numbers are the "target"..and the second set of numbers are what you might find going "in" for a corner balance...

ALL THIS ..... is identical to Chuck Mooreland's elegantly simple use of the short form... ( LF/LR should= RF/RR )


- - Wil
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Old 04-10-2005, 01:10 PM
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