Corner weight distribution question.

[K4fxd]

I had a chance to do some closed track driving. I felt the car pivoting around the outside rear wheel. Confirmed in the pit by tire temps. Would the Steeda rear spring spacers help move the CG to the front?

If not what can I do short of coil overs.

Thanks

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[Norm Peterson]

Guessing this was rather brief and during corner entry. What were you doing with the throttle and/or the brakes?

So were the tire temperatures indicating that the rear tires were being worked harder or less so?


Nothing you do with rear ride height is going to throw much additional weight up front, though changing the relation between front roll center height and rear roll center height will affect transient handling as well as the car's midcorner understeer-oversteer balance.


Norm

 

[TeeLew]

"Car pivoting around the outside rear" is an unusual read. Could you describe this in a different way? It's hard to know whether you're talking about understeer or oversteer with that description. Give some context in terms of type of corner, at what part of the corner where it occurs and your inputs at the time which directly precede this behavior. Paint the picture a little.

Keep in mind, it takes physically moving bits on the car to change front weight (or left side weight if you're on an oval) distribution. All you can do it adjust the weight on individual corners, which affects the crossweight ( LF+RR or RF+LR). This allows you to either set front weights equal or set crossweight to 50%. For a car which has a conventional brake system, I err to the side of equal front corner weights, which makes the car more stable while braking. If it's an antilock car, I'll cheat it toward 50% crossweight. The difference is because antilock cars are much more forgiving on the brakes (no inside front locking at turn-in), so you can work to make the car more equal in terms of left turn to right turn balance.

 

[NightmareMoon]

Yeah, raising the rear suspension only shifts marginal mass forward. You need to physically move or remove heavy things to adjust the front/rear balance by much.

You can crossweight a car with spacers (PITA) or coilovers (better), but that's a different kind of thing.

Probably if you only have had one on-track experience, you should keep at that and target on changes you can make to the driver. The car is (more than likely) happy to do what you tell it to do.

 

[K4fxd]

It is putting more weight on the outside rear tire.

Yes it is over heating the rear tires. Netural throttle. Enough to be fast but not enough to induce wheel spin.

On a left hand 100 mph curve it feels like all the cars weight is on the right rear tire.
On a quick 90 degree right hand turn it feels like all the tires are off the ground except for the left rear tire.

Best way I can explaine it.

I was given a 20 charger as a rental when my mustang was in the body shop and it felt like the chargers weight went to the outside front tire

 

[K4fxd]

I've driven race cars before and they all felt like the weight was even between the outside front and rear tires in a curve.

 

[Brian@BMVK]

I've driven race cars before and they all felt like the weight was even between the outside front and rear tires in a curve.

Seems like you're looking for spring rate changes not corner balancing.

 

[K4fxd]

Yea, I'm not a suspension guy, I just drive em.

200 front 800 rear, what do I need to add or change. Still stock front and rear bars

 

[Brian@BMVK]

Based on your description, you may want to consider an adjustable front bar.

 

[TeeLew]

It is putting more weight on the outside rear tire.

Yes it is over heating the rear tires. Netural throttle. Enough to be fast but not enough to induce wheel spin.

On a left hand 100 mph curve it feels like all the cars weight is on the right rear tire.
On a quick 90 degree right hand turn it feels like all the tires are off the ground except for the left rear tire.

Best way I can explaine it.

I was given a 20 charger as a rental when my mustang was in the body shop and it felt like the chargers weight went to the outside front tire

If I were your race engineer and you were my driver I would change exactly nothing on the car and have you drive it until you can can actually explain it, because otherwise we're making tuning changes based on gibberish, which seldom leads to good things.

 

[Dana Pants]

So in general changing the tire pressure and sway bar on one axle can tune a car between understeer and oversteer.

an in car video would be useful.

front bar gives more understeer and rear bar gives more oversteer.

with every bar change tire pressures have to be re-determined in my experience.

 

[K4fxd]

Definitely oversteer, the outside rear tire is overheating. The jibberish is what I feel in the car. All the forces are going to the rear corner. It does not feel balanced.

 

[Dana Pants]

What is your alignment and tire pressure? Wheels and tires? Your experience doesn’t match my expectations.

 

[Norm Peterson]

Definitely oversteer, the outside rear tire is overheating. The jibberish is what I feel in the car. All the forces are going to the rear corner. It does not feel balanced.

Any chance that what you're feeling isn't starting with the nose 'tucking in' on dropped throttle at turn-in, and staying there when you return to 'maintenance throttle'?


Norm

 

[K4fxd]

It feels like the car is a sail and the outside rear tire is the shortest rope.

Could my factory splitter be angled up enough to cause this?

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