[TRZ06]

Wanted to bring up this question because of the articles I have read about the C8 so far.

The general consensus is that the C8 understeer more than the C7 & Camaro, but puts the power down better on corner exit.

Which made me think about driving dynamics. With most mid-engine cars having a rear bias weight distribution (60/40 for the C8), I wonder if a better handling car would be a front engine with a 50/50 weight distribution OR a mid-engine car with a 60/40?

It would seem to me that going from a 50/50 split to a 60/40 , even factoring in the mid-engine VS front engine would be counter productive to better handling.

So, other than being able to put the power down more in a mid-engine, is there really a benefit in the handling department?

And why, if the point of going to mid-engine is for better driving dynamics, why don't they try to achieve 50/50, instead of rear bias.

[nferr]

The C7 Corvette was at 50/50 weight distribution. The mid-engine is still considered better overall for traction.

[Scargoes]

Not exactly apple to apples, but I know many guys who build their own cars for SCCA EM and DM class. They prefer 53% rear weight bias but stick to 52% so they don't get the weight penalty. And my RC touring cars handled the best with 51-52% rear weight bias. I think the premis is that the rear weight bias works for traction during acceleration and under braking you don't have as much weight loading on the front tires so that the steering is still available.

[TRZ06]

Originally Posted by nferr

The C7 Corvette was at 50/50 weight distribution. The mid-engine is still considered better overall for traction.

The issue with the C7 was the transverse leaf rear suspension , which made it twitchy and not confident at the limits.

To me, that is the biggest upgrade from the C7 to C8, but still I would think that if you had a un-equal A-arm set-up in the C7 with a 50/50 split, that would handle better than a C8 with a 60/40 spilt.

I guess maybe they care more about traction and 0-60 numbers.

Maybe I am missing something , which is why I posed the question.

[Xaxas]

Originally Posted by TRZ06

Wanted to bring up this question because of the articles I have read about the C8 so far.

The general consensus is that the C8 understeer more than the C7 & Camaro, but puts the power down better on corner exit.

Which made me think about driving dynamics. With most mid-engine cars having a rear bias weight distribution (60/40 for the C8), I wonder if a better handling car would be a front engine with a 50/50 weight distribution OR a mid-engine car with a 60/40?

It would seem to me that going from a 50/50 split to a 60/40 , even factoring in the mid-engine VS front engine would be counter productive to better handling.

So, other than being able to put the power down more in a mid-engine, is there really a benefit in the handling department?

And why, if the point of going to mid-engine is for better driving dynamics, why don't they try to achieve 50/50, instead of rear bias.

Corvette understeers because that's generally the nature of mid engine cars, the track alignment fixes it.

If we had the option of a transaxle in the Camaro, I'd probably do it, you might get away using a Z51/Grand Sport transaxle if the eLSD works similarly to the one in the 1LE but you'd probably have to cut into the GLORIOUS Alpha Chassis to get it done

[foshjowler]

For driving dynamics, I would think 50/50 is better. It should be a fairly neutral handling car by default, and adjustments can be made if someone prefers understeer or oversteer. For speed, it seems the mid engine is the answer. It wouldn't be used by the best sports cars if it wasn't. Mid engines have a habit of biting the driver in the form of snap oversteer, and having a car that likes to spin out doesn't seem like the best for dynamics. Of course all of this can be adjusted with alignment and suspension tuning.

[Hops]

A mid engine is easier to turn because of the lower moment of inertia (more stuff closer to the axis of rotation). But, it's also easier to lose control because the forces that can get out out of shape also are amplified (compared to a front engine car) to make you spin. I learned this first hand years ago from my Fiero.... LOL

[Msquared]

There is a little bit of misinformation in this thread. In fundamental terms, the handling balance of any car in lateral acceleration (i.e. cornering) is determined by the mass at each end of the car in proportion to the width of the tire at that end. The more mass per inch of tire that has to be accelerated, the less accelerative force can be generated by the tire. The only reason this is true is that a tire's coefficient of grip actually goes down as the load on the tire goes up. Otherwise, mass and load transfer wouldn't matter. What this means is that if a car has 60% of its weight on the rear tires, then those tires should be 50% wider than the front tires. If a car's weight distribution is 50/50, then the tires should be equal width front and rear.

However, the above is subject to a lot of other variables, such as relative front and rear wheel rates (springs and sway bars in steady-state, damper rates in transition), alignment, anti-geometry forces (e.g. anti-squat and "roll centers"), and whether the car is also accelerating forward or backward (i.e. accelerating or braking). This is where handling starts to get "complicated".

Also, another concern is polar moment of inertia. Simply put, the more centralized the car's mass is, the faster it can yaw (change lateral heading) and the easier it is to catch a slide in yaw. Most front-engine cars aren't great in this aspect, but the C4-C7 Corvettes were true front-mid-engine cars. Their engines were fully behind the front axle line, and so they generally have fairly low PMOI. A Camaro is not so lucky in that regard, but neither is a Porsche 911. In general, mid-engine cars make it easier to get a low PMOI.

I haven't done the math on the C8's weight distribution or tire widths, so I don't know what it's fundamental skidpad balance would be. But it does have the typical wider-rear-tire setup. If tires were all the same width, then a rear-biased car like the C8 would fundamentally tend to oversteer. This is not a good thing, generally. Of course any manufacturer in modern times would take steps to reduce that, because understeer is typically thought of as easier to recover from and therefore safer. The C8 is no exception, so it has wider rear tires and suspension tuning to minimize oversteer. This last weekend I got to watch a good driver in a C8 nearly win Super Street at the Peru Champ Tour over a couple smaller/lighter/awesome Porsche Cayman GT4s. It was clear that even with an aggressive alignment, the C8 tends to understeer heavily. The driver was able to adapt and get ahead of the front end, so to speak, and go quite fast. But it's also clear that for the class, upping the rear sway bar rate (you can replace one bar in Street classes) on a C8 will be an important strategy to make it more neutral and get the most from the car.

While a 50/50 weight distribution with a square tire setup is theoretically "perfect" for pure lateral acceleration (cornering with no brakes or acceleration), in the real word any autocross or road course entails a lot of acceleration and braking. Therefore, the "perfect" 50/50 distributions that so many magazines and ad copy talk about is pure crap. In general, pure RWD race cars are designed with a distribution of around 42/58 in mind, as that seems to work best as a compromise for cornering, accelerating, and braking. And again, they will be equipped with wider rear tires to make that work well. Even more rearward bias would be great for acceleration and braking, but it tends to come with penalties such as higher PMOI. It also makes it harder to tune the handling balance because it as you stiffen the front roll rate you start to pick up the inside front wheel, meaning you've reached 100% front lateral weight transfer and you can't tune any further (the same thing happens to the rear of many FWD cars that are very front-heavy).

So in short, the reason the C8's rear-mid-engine setup is better is because it improves PMOI and it improves acceleration and braking traction quite a bit. I would bet that it also gives some advantages to aero tuning for the GTLM program, by allowing a better front splitter/floor setup as well.

Originally Posted by TRZ06

The issue with the C7 was the transverse leaf rear suspension , which made it twitchy and not confident at the limits.

That's not true at all. It's a common misperception that somehow coil springs have magic properties that make them better than a monoleaf system like the C4-7 used. That misperception has been heavily reinforced by a lot of aftermarket vendors trying to sell coilover sets to Corvette owners. A mechanical spring does one thing: it stores energy and releases it back. That's all it does, and a C4-7 monoleaf does it just as well as a coil spring. I wrote an article for my local NCCC about this topic that goes into a lot more detail. I would tell you that most credentialed drivers don't think the C7 is inherently twitchy or unconfident at the limits. They are blazingly fast on a road course or autocross - faster than the C6 despite being heavier. The one handling quirk many of them have is that they tend to oversteer on acceleration out of corners. AFAICT, that's related to the active differential's calibrations. A C7 without the eLSD doesn't exhibit this trait. But a Camaro with the eLSD does the same thing, and it doesn't have leaf springs.

[BMR Sales]

Originally Posted by Hops

But, it's also easier to lose control because the forces that can get out out of shape also are amplified (compared to a front engine car) to make you spin. I learned this first hand years ago from my Fiero.... LOL

I disagree. I raced and A/X'd a Mid-Engine Porsche for about 20 years. The easiest controlled car I have ever driven.

I think you didn't have enough power or good suspension in your Fiero!