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Weight balance and scaling set up

Hello, this is my first post in the forums and I was wondering if you guys have scaled your race cars and what kind of weight balance you've found to work best.
I have been fighting understeer all year and getting ready to put the car on scales to get the front to rear weight balance a lot better. I think I just have too much weight to the front right now.
 

ArizonaBOSS

Because racecar.
Moderator
8,545
2,376
Arizona, USA
Tell us more about your car. I'm assuming you are tire size limited in AI. Are you running a square tire setup Front/Rear?

Do you have adjustable swaybars on the car already? What suspension do you have?
 
ArizonaGT said:
Tell us more about your car.

No need.

165424_652381944777441_1242279957_n.jpg


Answer: Skyfall

Question: What would happen if you put a Mustang in orbit?

He has a Mustang. Yes, there is too much weight and too much of it sits on the front end. ;D

Sorry for this not useful post, but welcome to BMO. When we stop clowning around, we usually get to the answers we are looking for.
 
I have access to scales anytime at various friends' race shops. Just trying to get a starting % point to shoot for.
The wheels are 18x9.5 all around per AI spec.
Every suspension component is adjustable. Not much is left stock, and what is won't be for long.
I have been searching for a neutral balance on the track and have it the best it's been but the nose weight is killing me now. Once I get the weight balance correct, I am sure I will have to start all over with the sway bars, shocks, etc etc to regain a neutral balance.
 
jay45dee said:
I have access to scales anytime at various friends' race shops. Just trying to get a starting % point to shoot for.
The wheels are 18x9.5 all around per AI spec.
Every suspension component is adjustable. Not much is left stock, and what is won't be for long.
I have been searching for a neutral balance on the track and have it the best it's been but the nose weight is killing me now. Once I get the weight balance correct, I am sure I will have to start all over with the sway bars, shocks, etc etc to regain a neutral balance.
Welcome to BMO and please tell us more about your car. I'm of no help with the balance but good luck with this.
 
NFSBOSS said:
Welcome to BMO and please tell us more about your car. I'm of no help with the balance but good luck with this.

A lot more, please...

Not going to be easy troubleshooting this without some significant data..

Nevertheless, how about some easy stuff, for starters:

What sway/anti-roll bars and what settings?

What have you done to remove weight from the front end??
 
I have been building this car into a full race car over the past year with help from RSR Racing from the American Le Mans Series.
I've been replacing each suspension component one at a time to learn how to keep the car balanced along the way.
Weight reduction is the next step. Will be switching to Kenny Brown stuff to get the nose lighter. K-Member, radiator support, A-Arms and the Boss 302s bumper beam for starters. I know I won't be able to get the weight right until all that is done because the front end is so heavy now but I still wanted to get a weight balance set up researched for when I get it on the scales to have a goal to get to.

The suspension has been a work in progress and we are still trying different things.
Right now the sway bars are Whiteline Performance solid bars with 4 mounting points. We started with the front on mount 2 (4 being stiffest) and rear on mount 4. The car had some understeer still so we went to the 4th hole on the front as well and it helped. (this was at Waterford Hills raceway in Clarkston, MI)

The front camber is at negative 2 degrees.

Currently I have Koni yellow shocks/struts with Ford Racing springs (M-5300-K) on the car.
I am working on a sponsorship deal through AirLift Performance and they claim their air shocks are running quicker lap times then the top coil over setups so that will be the next shock setup I am going to try.

The rear has adjustable panhard bar and control arms with control arm location brackets which are mounted in the center holes. A Whiteline Watts link is going in soon as well.
 
How much track time do you have in the car?

Have you tried softening the front or adding a little rebound in the rear?

I was looking at changing my K member, but I don't think it's worth the time and money. I don't know how quickly you are making all of these changes, but if you aren't already, go to the track and play with different settings one at a time.
 
We've been out 5 times with it. The last time to Waterford was with the new sway bars. We stiffened the front bar, which helped in the lower speed corners. Now it's just a matter of getting the corner speed up over all. We haven't tried putting any preload on the sway bar end links yet either which could help it out as well, but I'm still not sure which way to go with that.

I would love to know what the ideal rear weight percentage is for these cars so that I can get the weight distribution set before going any further, If the weight is way off and I set up the chassis to counter act for that, the thing will need a ton of work to get back to neutral after we get the rear weight percentage correct. I'm afraid to spend any more time with the chassis setup until I know how far off the weight balance is. Then of course I will know for sure if I need to replace all the front end braces with lighter stuff.
 

JScheier

Too Hot for the Boss!
jay45dee said:
I would love to know what the ideal rear weight percentage is for these cars so that I can get the weight distribution set before going any further, If the weight is way off and I set up the chassis to counter act for that, the thing will need a ton of work to get back to neutral after we get the rear weight percentage correct. I'm afraid to spend any more time with the chassis setup until I know how far off the weight balance is. Then of course I will know for sure if I need to replace all the front end braces with lighter stuff.

I doubt you will get an answer to this question as each and every car is going to be different it what it can and cannot achieve in weight distribution and balance. Simple things such as cage design and the materials used can have large effects on distribution and bias. 50/50 is usually the ideal number that people shoot for. With an aftermarket K-member and engine setback, you might get close. Usually 52-55% of the weight up front is S197 territory... use that as you will.

If it were me (and it isn't, so take this as more useless internet blather)... assuming I'm not getting free air-ride suspension (how much does that weigh?)... I'd move to a coil-over setup and start working with spring rates. 425 front / 175-200 rear is a good place to start with a square setup S197 chassis (you can definitely go higher with smoother tracks, but the F/R ratio seems to be pretty common). Start with the bars in the middle setting, with zero pre-load, and work with spring rates to bring the handling in-line with what you are expecting. Then, using the adjustments on the sways, dial-in that last bit of handling you desire. Fine tune with damper settings.

Things to account for:
1. alignment settings
2. tires (how many cycles? Useless tuning a chassis on crap tires)
3. spring rates front / rear
4. sway settings front / rear
5. damper settings front / rear
6. tire pressures front / rear

Good place to start. As Mark notes, seat-time, seat-time, seat-time with lots of notes will make this all easier and repeatable.
 

Grant 302

basic and well known psychic
Before you get into the fine tuning of corner balance, you need to look at improving your front grip first.

How does your front tire wear look? What pressures? Have you tried more negative camber? Positive caster? Tall ball joints? Bumpsteer kit?
 
Thank you for all the info guys! I will definitely focus more on the front end geometry before working with the weight balance. We don't have the cage in yet so that will definitely make a difference. So can probably wait to start moving weight around until after that is in. Thats the winter project to prepare for next season to run in the American Iron Series.

I will try more negative camber and more caster along with the taller ball joints next time out.
Hopefully we can get where we want with the airlif setup, if not I will definitely take the spring rate advice and give that a try.
 
I'm guessing that from the op comments he may mistakenly think front/rear distribution can be adjusted with threaded spring perch / coilovers...
 
u00mem9 said:
I'm guessing that from the op comments he may mistakenly think front/rear distribution can be adjusted with threaded spring perch / coilovers...

not a chance. Only by physically taking weight off the nose or adding ballast to the rear.
Unless is it has stock car style weight jackers and of course it does not.
 
JScheier said:
I doubt you will get an answer to this question as each and every car is going to be different it what it can and cannot achieve in weight distribution and balance. Simple things such as cage design and the materials used can have large effects on distribution and bias. 50/50 is usually the ideal number that people shoot for. With an aftermarket K-member and engine setback, you might get close. Usually 52-55% of the weight up front is S197 territory... use that as you will.

If it were me (and it isn't, so take this as more useless internet blather)... assuming I'm not getting free air-ride suspension (how much does that weigh?)... I'd move to a coil-over setup and start working with spring rates. 425 front / 175-200 rear is a good place to start with a square setup S197 chassis (you can definitely go higher with smoother tracks, but the F/R ratio seems to be pretty common). Start with the bars in the middle setting, with zero pre-load, and work with spring rates to bring the handling in-line with what you are expecting. Then, using the adjustments on the sways, dial-in that last bit of handling you desire. Fine tune with damper settings.

Things to account for:
1. alignment settings
2. tires (how many cycles? Useless tuning a chassis on crap tires)
3. spring rates front / rear
4. sway settings front / rear
5. damper settings front / rear
6. tire pressures front / rear

Good place to start. As Mark notes, seat-time, seat-time, seat-time with lots of notes will make this all easier and repeatable.

Some sound advice...

My 2 SAE HP..

Jettison the air bladder idea.

Ask any classic Range Rover owner who actually wheels their ride, or any high KM BMW HP2 or Audi Allroad owner, or not

Your move,

VTBoss302

"I'm Uncle Sam, that's who I am..." ::)
 
yeah I'm not completely sold on AirLifts product. They have a 2007 GT that they want me to test drive on the track to get me convinced but I haven't done it yet.
If they're willing to put a set on the car I will give it a shot. Doesn't necessarily mean that's what will be on the car by the start of race season lol
 
jay45dee said:
yeah I'm not completely sold on AirLifts product. They have a 2007 GT that they want me to test drive on the track to get me convinced but I haven't done it yet.
If they're willing to put a set on the car I will give it a shot. Doesn't necessarily mean that's what will be on the car by the start of race season lol

Must be nice getting free stuff...

Ah, to be rich enough that people actually give you s**t..

Sew on and sew forth,

VTBoss302
8) 8) 8) 8)
 

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