Changing the Emira's Weight Distribution

[sbproducer]

Preface:

The V6 stock weight distribution is 39 Front and 61 Rear (this doesn't include the fat ass driver). If a car is super front or rear heavy, you can imagine this can present a challenge with handling characteristics. Theoretically, a 50/50 weight distribution is sought after for better handling dynamics so the fatter you are the better in terms of cornering in an Emira, but not acceleration. Basically, if you are fat, the Emira handles better, if you are skinny, the Emira accelerates better. But, there is another dynamic that plays a role. In a rear-wheel vehicle, the more weight you have over the rear wheels, the better the traction and acceleration, since there is more force pushing the rear wheels down. So, there is a case for arguing that you want a little rear bias when it comes to weight distribution. It's not just a simple go for 50/50.

Google AI Summary:

Corvette weight distribution varies by generation, but a 40/60 rear-biased split is characteristic of the mid-engine C8, while earlier generations like the C7 (front-engine) had a near 50/50 split (often measured at 49.4% front, 50.6% rear), and the C6 aimed for a perfect 50/50 balance. The C8's mid-engine design allows for superior traction and acceleration by placing more weight over the rear wheels.

Thoughts:

Is there a good target weight distribution for the Emira? Should we even be trying to move the needle towards 50/50?

After I finally get a chance to install some of the parts I have, I'll be losing close to 100 lbs. rear. Couple that with my fat ass getting in the car... and the needles moving left for sure. I always thought this was a good thing because the Emira is definitely back-heavy.. I can feel it.. but maybe the 39/61 isn't as bad as we think.

 

[jp129]

Static weight distribution is only one factor. While it does contribute to chassis handling and balance it does not dictate it. My suggestion is drive the car at pace and assess what it is about the chassis handling or balance you don't like.

Does it understeer or oversteer? At what phase of the corner is it exhibiting this? What are your inputs when this is happening? Slow or fast corners or all the same? Etc etc

From there you can address elements like spring rates, damping, sway bars, geometry, track width/tires, and aero to tune the balance to your preference.

I believe those tools are easier to tune and adjust then changing static weight balance, especially as a street car. Race cars have more flexibility in what you can move around to achieve a weight balance.

In the end, it's all a compromise. You just tune the setup to be good at certain things/preferences and less sucky for the rest.

 

[CarGuy11]

This helps reduce rear bias.

 

[MiamiBlue]

I don't like how the car pushes wide when accelerating through a corner. I don't think it's actual understeer (I'm not aware of any tyre grip lost, and you have the effect at lower speeds), but you can feel the turning circle get bigger. If you then come off the power the nose comes back in and tightens the turn.

Is this a result of the weight distribution or something else?

 

[jp129]

That's weight transfer, normal vehicle dynamics - physics.

Overimplication - as you accelerate, you transfer the weight/load to the rear. As you lift, you transfer weight/load to the front. Static weight distribution influences the magnitude of change, but does not dictate the effect.

 

[Ft.S]

Preface:

Theoretically, a 50/50 weight distribution is sought after for better handling dynamics so the fatter you are the better in terms of cornering in an Emira, but not acceleration. ... It's not just a simple go for 50/50.

Thoughts:

Is there a good target weight distribution for the Emira? Should we even be trying to move the needle towards 50/50?

In my opinion and experience, 50/50 distribution represents the best all around compromise for static weight. This is to mean that no matter what you do, how you drive or where you drive, the chassis does not favor one situation over the other.

Weight bias towards the front or rear moves that compromise in a way that the driver can exploit in some situations. Front-bias is very difficult to drive, especially if it is a front-wheel driven vehicle. Mid- or rear-bias is far more easier to drive and exploit.

Generally, mid-engine cars have a weight distribution of ~45F/55R. This gives the driver the advantage shifting weight on the front axle under braking without overloading the tires, while doing the opposite during acceleration to the rear axle. In each case shifting the weight where it is needed when it is needed. Of course, the same is valid in a 50/50 vehicle, but the disadvantage is that too much weight would shift towards the front axle during braking, and corner entry, while not enough weight would shift to the rear axle during accelerations.

Keep in mind that we can generate more than 3 times the negative Gs under braking than positive Gs under accelerations. This means more weight can be shifted on to the front axle under braking that onto the rear axle under acceleration. Consequently, a rear weight biased vehicle should have an advantage just standing still.

The weight distribution of Emira is perfect in my opinion. Under maximum braking the car's weight distribution might be 55 or 60% on the front axle, while still keeping 45-40% weight on the rear axle, hence near optimum dynamic weight distribution. Moreover, the driver can manage that distribution solely based on the brake pressure with a pedal.

If you look at a BMW M3, for example, its static weight distribution is 52f/48r. You might think that is near ideal. The G8x series M cars are amazing under braking, in spite of their total weight. However, they not only rely nearly on just front axle for braking, but also significantly lack traction under acceleration and have difficulty putting all the power their engine produces, particularly during corner exits and even with their tricked-out 4WD and eDiff.

I collected expanded amount of data from the vehicles I drove for over 15 years on track, including BMWs, mid-engine and rear-engine cars. I kept analyzing and analyzing so many things to improve my driving; I am just over-analytical. At the end, I came to three conclusions: (1) Rear weight bias is good, mid-engine bias is best for great drivers, (2) every driver has their preferences and beliefs about weight distribution on what is best for them (rear-bias suits me the best), and (3) I will never be a great driver.

So, I would suggest instead of trying to change the weight distribution of the Emira, see if you can unlock some of its hidden gems as a driver. I am personally looking forward to doing so once I finish the break-in and get on a track.

Respectfully,
Ft.S