* CORNER balanced - numbers from this...and the weight

[911pcars]

This is an interesting discussion, and I appreciate the qualified opinions from those who contribute. However, from my POV, let me try to summarize the prevailing thought of this thread (at this point):

- Attempt to balance the front end as close to 50-50 (L to R) as possible.

- LR and RR balance is not as important during braking as long as the LF and RF are the same (or close to it).

- Braking should take precedence over the L and R side weight proportions, thus equalizing the side-to-side, front to rear proportions shouldn't be a high priority.

- The torsional strength of a street car is suspect, thus chassis balance attempts "in the ballpark" should be good enough.

- Equal or approximate diagonal weight totals (LF+RR = RF+LR) are no longer an indication of chassis balance.

....... unless you're referring to serious track cars and equally serious drivers.

For the typical pcar owner then, perhaps "chassis balancing" isn't as important as front end balance. Have I summarized that correctly? I'm seriously biting my tongue on this guys, but I may need to adjust my belief system.

Sherwood

[Wil Ferch]

From my view, Sherwood, I would say this is a very fair summary of what emerged on this thread. Maybe only some small caveats....

- the desirability of equal front weights is undeniable from the standpoint of high-G braking...for all types of cars. Randy seems to indicate that the imbalance this causes for the rear pair...may be of less consequence for our 911, rear weight biased cars ( rears won't lock)...so this ends up being a very handy compromise to shoot for. Meaning? Still valid for other layouts...but maybe not as "strongly" as for our 911's.

- the diagonal-pairing within 2-5% error-band... may still be important to target, since it "regains" some of the lost optimization that "my" earlier method ( "apportioned weight") gave in creating equal steering for left-right scenarios. In other words, if left-right turning was all that mattered ( not braking)...then my method would optimize the cross balance better. Since braking is (correctly)given a higher importance factor... if we find ourselves within this 2-5% bias error, we regain a good portion of this goodness.

- Wil

[patkeefe]

Gentlemen:
I try to learn something new every day, so I've just had about five days worth of learning.
I feel like I've been the batboy on the '27 Yankees.
Sincerely,
Pat

[ttweed]

Originally posted by Wil Ferch
For you to say ( "just get it into the ballpark").....is exactly the point of this whole discussion! Just what * IS * ballpark???

The Porsche factory spec for street cars is 20 kilograms on the diagonals. That's around 44 pounds. Fred Puhn says if any corner is off its ideal weight by 10 lbs., you may want to adjust it, and if it is off by more than 50 lbs., you certainly want to adjust the weight distribution. For me, that's the "ballpark."

I guess I would turn the tables on you Tom and ask, why is trying to (at least) *understand* an issue "bad"...even if the dicussion takes a turn toward a fine-cut on the numbers ???

Nothing at all wrong with understanding an issue. Never said that was "bad". I was just trying to point out the myriad variables in suspension setups, of which corner weight distribution is only one, and the compromises involved, and compare them to something that may be even more important: driving skills. Let's talk about camber curves now, shall we? I think it is even more important than corner weights.

My only objection is to becoming too focused on perfection of a single issue and losing track of the rest of the "system" goals, which may contain even more important issues waiting to be addressed. In this case, the goal is lower laps times, no? My father spent his life managing engineers in highly technical projects, and he always told me that the most difficult task for him was to keep them focused on the overall goal, and actually achieving an end product. It is very easy to get caught up in perfecting intriguing details using the latest technology, beyond what is useful or practical, in a "real world" sense.

No real argument, Tom, but I'm surprised at the aggressive tone of your letter.

Sorry about that, Wil, I'll blame it on the ASCII. No offense intended- I respect your thirst for knowledge and your contributions in this forum and on the Rennlist. I even agree with your original position regarding weight distribution and have set up all my non-centerseat cars to equalize left/right cornering balance at the expense of equal front weights, according to what Puhn says in his book, i.e., that weight jacking is for oval racing. I guess I'm sacrificing braking ability, but I've never noticed it. Of course, you could put Cort Wagner in the most evil handling POS car in the world and he would be lapping me in the first 10 minutes of a session at most tracks.

TT

[911pcars]

This edition is 1976, but I think the principles still apply.



While suspension dynamics is a complicated science, this thread started by "merely" focusing on adjusting the static corner weights of a 911. And look what a fine mess we've gotten ourselves into, Ollie.

Sherwood

[KobaltBlau]

Well said, Tom

[Wil Ferch]

Tom:

No issues....I do ( at times) become overly focused on "drilling-down" on issues.... sometimes to the point of diminishing returns.

Mostly...this is fine, and the indivudual can then "stop along the way" at whatever level of detail suits him....

Camber curves....hooboy!, ....let's start a new thread !!!!....

- Wil

[ttweed]

Originally posted by Wil Ferch
I do ( at times) become overly focused on "drilling-down" on issues.... sometimes to the point of diminishing returns.

That's the engineer in you coming out, Wil.

This reminds me of a saying that has stuck with me since college. I don't even remember who said it, and I may be paraphrasing a bit, but here it is:

"A generalist learns less and less about more and more until eventually he knows nothing about everything. A specialist learns more and more about less and less until eventually he knows everything about nothing."

I guess somewhere in the middle is the place to be, or "moderation in all things" are words to live by?

Who knows?
TT -- still wondering how I'm going to put my B.A. in Philosophy to use after 35 years...

[larry47us]

Originally posted by ttweed
TT -- still wondering how I'm going to put my B.A. in Philosophy to use after 35 years...

Tom:

Looks like you just did. Was that worth a college education?



BTW, I am going back to Souk's Garage this weekend, and we will do an alignment and corner balance. I hopefully will have shots of the display before and after, showing the individual wheel weights.

larry

[lateapex911]

Originally posted by ttweed

TT -- still wondering how I'm going to put my B.A. in Philosophy to use after 35 years...

Well you live in La Jolla, and you drive P cars on those roads...I have done same, and whatever you're doing, keep it up!

[smurfbus]

Bump for a good thread! I just got my numbers and I was curious about the formula (or example) you gave earlier that did not get discussed at all:

Originally Posted by Wil Ferch

Anyway....if you do this...the effect of a 150 lb weight ( in the driver's seat) of a 911 results in THIS effect on the original corner weights:
LF= Adds 61 lbs
RF= Ads 11 lbs
LR= Adds 50 lbs
RR= adds 28 lbs

Different weights ( other than 150) can be scaled up or down accordingly.

Wil

So my numbers fullish tank 75kg are below and should rise with 150lb (me, Ok I was 156lbs with clothes but I used those 150lb numbers that were available) driver as follows :
FL= 199.5kg (+61lb =+28.6kg) =228.1kg measured= 225.5kg = +2.6kg delta
FR= 219kg (+11lb =+5kg) =224kg measured= 227kg = +3kg delta
RL= 357.5kg (+50lb =+22.7kg) =380.2kg measured= 380.5kg = -0.3kg delta
RR= 340.5kg (+28lb =+12.7) =353.2kg measured= 354.5kg = -1.3kg delta

So with the driver the weight affected much more in the front compared to your example and my question is why?
Do I sit more front than the formula assumes


From reading this thread again the car seems to
be in a pretty good spot regarding front bias and diagonals. I have CF front lid and sun roof to install which are equal weight side to side but lid negative for front/rear. A small help will come from DP rear tail light buckets and high torque starter. Not much can be done with the rear left heavyness. Maybe changing the heavy Holset to some lighter/smaller Garret but thats too much $ for the gains.

[GaryR]

I had my car aligned/corner balanced with 1/2 tank, my weight in the drivers seat, and my 12qt coolsuit cooler full of water. I also use Mobil1 20W-50 and Castrol SRF..

[911pcars]

Originally Posted by smurfbus

Bump for a good thread! I just got my numbers and I was curious about the formula (or example) you gave earlier that did not get discussed at all:

So my numbers fullish tank 75kg are below and should rise with 150lb (me, Ok I was 156lbs with clothes but I used those 150lb numbers that were available) driver as follows :
FL= 199.5kg (+61lb =+28.6kg) =228.1kg measured= 225.5kg = +2.6kg delta
FR= 219kg (+11lb =+5kg) =224kg measured= 227kg = +3kg delta
RL= 357.5kg (+50lb =+22.7kg) =380.2kg measured= 380.5kg = -0.3kg delta
RR= 340.5kg (+28lb =+12.7) =353.2kg measured= 354.5kg = -1.3kg delta

So with the driver the weight affected much more in the front compared to your example and my question is why?
Do I sit more front than the formula assumes


From reading this thread again the car seems to
be in a pretty good spot regarding front bias and diagonals. I have CF front lid and sun roof to install which are equal weight side to side but lid negative for front/rear. A small help will come from DP rear tail light buckets and high torque starter. Not much can be done with the rear left heavyness. Maybe changing the heavy Holset to some lighter/smaller Garret but thats too much $ for the gains.

As opposed to purpose-built race vehicles, passenger cars seldom have equally proportional weight at each corner. To achieve that, you must add/delete and/or move existing weight; e.g. a passenger (or equiv.) and other significant components (e.g. battery, oil tank, ballest, etc.) or other components or lighter component materials strategically added or deleted to help offset any differences.

Realizing that goal is usually not achievable in a passenger car, attempt to balance the chassis by having equal proportional side-to-side weights with attention paid to the preferred ride height at each corner. Again, your efforts will most likely be a compromise.

Using your weight data, your L vs R side proportional weights are 59% (L side) and 64% (R side). If my calcs are correct and if ride heights allow, slightly raise the left side ride heights and/or lower the right side ride heights to bring that L-R percentage closer. There's close/achievable perfection (Mercedes-AMG F1 W11) and there's best-effort compromise (the rest of us).

Sherwood

[smurfbus]

Thanks, I need to read about that L vs R side proportional weight. I could move my WMI tank 5kg from right side frunk to left fender. My 1.6 kg battery is at the smuglers box so I think it would not make much sense to move it to the original battery location. Also I rarely go to tracks anymore so this is just for spare time fun.