i recently got my car corner balanced(997.2 gt3).left hand drive with 80kg driver and half tank.

FL 323 FR271
RL 482 RR435

Reading the figures im confused the diagonal difference is very little but left side(FL+RL) is 100kg more than the sum of the right side(FR+RR).
should i get the balancing done again?


I also had some aligment changes:

front camber (before -1.4)now -2.0
rear camber -1.4
front toe (before 0.08,0.01)now 0.03
rear toe (before 0.17,0.20)now 0.12
front stablilizer (before one from soft) now soft
rear stabilizer medium

The car feels very alive alive now,changes direction very quickly to steering input,massive understeer from before is now gone.infact i do not feel any understeer now unless its on a very dusty road.

im very happy with the car now but just want to know if i should get the corner balance done again

 

Rule One, if you are happy with the car, do nothing. The cross-weighting is your goal, not left and right.

 

If your cross is close to equal, then your car is corner balanced. The discrepancy left to right is simply due to the position of mass within the vehicle. If you change the spring preload to even out the corner weights left to right, you will preload the car to turn one way more easily than the other.

Professional race teams sometimes do this to bias a car to a particular track (or corner on a track). Amateurs should not do this.

 

thanks i guess you are right but since i payed big money for just for corner balance alone i was a little confused looking at the figures.

Thats a lot of info thanks m8.i guess without the drivers weight which is 80kg there is only 20kg difference from side to side due to maybe position of the fuel tank or engine.

 

From what I've read you want the front/rear weight distribution on the left side to equal the front/rear weight distribution on the right side.

I think the 911's have a 60%-40% balance due to the rear engine.

I calculated the weights you have listed and it comes out to:
Front: 39%
Rear: 61%
Left: 53%
Right: 47%
Total weight 3300lbs (1496kg)

There's about a 14-15lbs (6-7kg) difference for optimal corner weight balance according to the calculations in the spreadsheet I have. When I input your current weight the "optimal" weights would be:
LF: 316kg (697lbs)
RF: 277kg (611lbs)
LR: 488kg (1076lbs)
RR: 428kg (944lbs)


Looks like your tuner got them pretty close. Will you notice if you changed them to the "optimal" balance? Racing maybe..

 

Those will both be centrally located and will not affect the cross. The discrepancy normally comes from the steering system, engine accessories, and fluid reservoirs.

 

Good info there,thanks really appreciate you took the time to calculate the weights for me.Actually my current total weight comes to 1511kg.btw where did you get your %figures from,is it official sheet from porsche or from a tuner?

Now all i have to do is change the Left headlight to non xenons for perfect weight distribution

ic thanks for clarifying that.

 

Funk2k,

Yeah, 1511kg is correct. A few kgs got lost when I did the imperial conversion. Wish we were all on the metric system! haha
At first I converted kg-lbs, but I guess you can just enter the weight data in kg and come out with the same result.

Here is the corner balance spreadsheet I found online. Seems like a pretty good reference tool.
cornerbalance.xls

 

Good stuff here. Thanks guys.

 

thanks again m8 thats great help.

 

fun2k,
I have an observation regarding your corner balance job. The numbers your tuner used were apparently based on giving you a 50% "wedge". You will note that the sum of your RF + LR is equal to LF + RR. This is what a circle track driver might want. Page has given you the correct numbers to achieve equal front to back ratios. Thus you will see that those numbers yield the fact that RF/RR = LF/LR. This is what an autocrosser might desire. An excellent reference calculator will show you this at a glance at:
http://farnorthracing.com/autocross_secrets11.html
Hope this explains things to the others who replied as well. As it turns out it didn't make much of a difference in your case, but it's nice to know why it came out like it did.
Good luck.

 

ill ask my shop about this i was also curious why they only took the cross balance because it dosent actuacly give a good reference for left side vs right side.according to this calc my figures are slightly off but i dont think it would make a big difference if i did cb again for a car of this weight.

Thanks for the effort m8 gives me some more understanding of cb,i was confused at first because when i seached on google there is no definitive answer how to do cb,everyone has a differemt aproach.

 

No. You want even wedge. I am a professional race engineer. I corner balance million dollar cars. Trust me.

If you set up a car in the manner described above, you will preload one side of the car. This will affect the left vs. right performance on the car, especially at low speeds.

 

flavorPacket,
Did you realize that if the car is balanced left to right and only out of balance in the front and rear direction, that the two methods yield identical results? Say LF=600, LR=400, RF=550, RR=450. Both methods tell you to jack 25 pounds to yield LF=575, LR=425, RF=575, RR=425. It's only when the car is grossly out of balance left to right that the methods are much different in their results. I doubt that you have encountered too much of that on million dollar race cars.

 

When they are set up to only turn left, yes I have.