RWD vs FWD: Part 3 – Center of Gravity

Sorry, I got distracted by OkStupid for a couple days. Let’s get back to our previously scheduled content, which was RWD vs. FWD. Today, I did an experiment on Center of Gravity, which I modified from the original RWD 51.5 to FWD at 65, 60, and 55.

I’m doing all of my game launches from Content Manager, so the testing situation has changed a tiny bit. Here are the details.

Simulator Setup

• Assists, nannies, whatever: everything off
• Time 09:00
• Weather: Clear
• Track: Optimum
• Temperature: 20.0 C
• Wind: 0 km/h
• Ballast: 0 kg
• Restrictor: 0%
• Setup: base with Street 90s (SV) tires

Vehicle Setup

The vehicles are all created by modifying the NA Miata with a build script, which is located at https://github.com/iankorf/acexperiments. The only changes made from RWD to FWD are the following:

• ARBs are swapped front and rear
• Track width is swapped front and rear
• Center of gravity is changed: 55, 60, 65
• Brake bias is changed with CoG: 70, 74, 78

Nothing else is changed. There are several things I could have changed, and you could argue I should have changed.

• Weight was kept the same despite FWD vehicles being lighter
• Power was kept the same despite FWD vehicles having less driveline loss
• Tire pressures and suspension settings were kept the same despite having more weight on the front tires
• Alignment wasn’t changed because I don’t know how to optimize that for FWD vs RWD

The FWD cars had no advantages, and I think you could argue had some disadvantages. A racer would normally tune their suspension and tire pressures to match their weight distribution. This is not exactly a fair fight.

Lap Times

I conducted the test by driving 20 laps in a row at Brands Hatch Indy and then selecting the 10 best for further analysis.

OK, so this came as a bit of a surprise, but FWD can be faster than RWD. When FWD is at 60/40 weight distribution, it is very similar to RWD at 51.5/48.5. But when the FWD balance is 55/45 it is faster than RWD. Also, at 65/35 it is slower than RWD. You might argue that I’m a better FWD driver than RWD and that’s the reason for this. But I don’t think so. In simulators, I spend much more time driving RWD than FWD. The 55/45 FWD wasn’t just a little faster than RWD. The slowest lap I did in the 55/45 was a 1:02.920. This is faster than every RWD lap.

Squiggles

In the graph below:

• Red is RWD (because all Miatas should be red)
• Blue is FWD 65/35 (because my Yaris is blue and is probably ~65/35)
• Black is FWD 60/40
• Green is FWD 55/45

The difficulty in driving 65/35 is that it understeers and has low mid-corner speed. To compensate for the lack of grip, I took a slightly different line starting at 2500 feet, sacrificing the exit so I could get well set up for the critical downhill corner. This is why the blue line deviates a bit from the others. What was really surprising was how much faster the FWD cars were in Surtees. I usually think of Graham Hill Bend as the most important corner on the track.

Conclusions and Thoughts

Can you imagine a FWD Miata with a 55/45 balance? It would be faster, lighter, and cheaper than its RWD counterpart. On the other hand, it probably wouldn’t do so great in the 0-60 tests, and nobody in their right mind would buy a FWD roadster. Well, I’m not your usual car enthusiast, so please make mine in British Racing Green.

I’ve actually fantasized about making a FWD for Lemons racing. Not because I thought it would be any better, but because it’s such a stupid idea. Nobody swaps a RWD car to FWD, and the last car you would do that with would be a Miata. Now it’s starting to make some actual sense.

Since my Yaris has such a forward weight distribution, I’m wondering if it would be faster if I added ballast to the rear. In a drag race, it would go slower, but on a skid pad it would go faster. Is a race track more like a drag strip or a skid pad? Certainly it depends on the track. This kind of experiment is easy enough to do in Assetto Corsa. Maybe that’s my next experiment? Check back and find out.