When the new BMW M5 debuted last week, its immense output from the plug-in hybrid V-8 was overshadowed by the car's hefty curb weight. At 5,390 pounds, the seventh generation of the super sedan is a little over 1,000 pounds heavier than its predecessor. No doubt, that's a massive difference, but it was to be expected. Allow us to explain.

First of all, the M5 "G90" is much larger than its predecessor. At 200.6 inches long, 77.6 inches wide, and 59.4 inches tall, the speedy luxobarge is 4.2 inches longer, 2.7 inches wider, and 1.6 inches taller than the "F90" model before it. Concomitantly, it's also slightly bigger than the regular 5 Series upon which it's based. It's the first M5 to have wider tracks than the lesser 5er. In addition, its wheelbase is longer to accommodate a different suspension geometry.

That brings us to another sign we had all along about the new M5 putting on weight. The 550e xDrive is also a plug-in hybrid with AWD but with a smaller inline-six engine instead. Curious to know how much that weighs? It tips the scales at 4,751 pounds in European specification. The US-spec 550e's curb weight has not been disclosed yet, but it can't be significantly different.

<p>2025 BMW M5</p>

2025 BMW M5

At the heart of the partially electrified 550e xDrive is a "B58" engine with a 3.0-liter displacement and a single turbocharger. The "S68" that goes inside the new M5 is a significantly larger 4.4-liter unit with an extra turbo. Shoving a much bigger engine underneath the hood partially explains the weigh penalty between the M5 and the 550e. Their batteries are almost the same capacity, 18.6 kWh for the former and 19.4 kWh for the latter.

We're not trying to play the devil's advocate here but that 5,390-pound curb weight largely was predictable. There's no denying that it's unusual for a car with a combustion engine to be heavier than its fully electric counterpart. We're talking about the i5 M60, a dual-motor EV that weighs 5,247 pounds. Yes, the new M5 is 143 pounds heavier than the electric M Performance model.

<p>BMW i5 M60</p>

2024 BMW i5 M60

That's despite the fact the i5 M60 has a much larger battery pack, at 81.2 kWh vs just 18.6 kWh for the M5. Weight distribution is also important since it impacts the fun factor. BMW quotes 50.1 percent front and 49.9 percent rear for the hot EV. As for the M5, it's an "almost perfect 50:50" but we’re certain the car is more nose-heavy due to its big V-8.

If weight is a concern, it's about to get worse. The new M5 Touring is coming soon, and it'll be even heavier since wagons tend to be slightly fatter than the sedans upon which they're based. That said, what's another few more pounds when the car already weighs well over 5,000 pounds? The silver lining here is that BMW is bringing the "G99" to America.

<p>2025 BMW M5 Touring</p>

2025 BMW M5 Touring

Could BMW M have gone a different way? It's hard to say. Ideally, it would've kept the pure V-8 setup without adding the plug-in hybrid bits. M boss Frank van Meel told Top Gear the PHEV setup has added about 882 pounds of weight. As to why the new M5 had to be electrified, the German luxury brand has yet to provide an explanation.

One plausible scenario is that without going the plug-in hybrid route, BMW would've had a hard time meeting increasingly stringent emissions regulations, especially in Europe. In addition, having higher emissions typically comes along with higher taxes the owner must pay. That's why the new M5 is actually cheaper than an M3 in Ireland since it has a less-polluting powertrain. Well, at least in theory.

Downsizing was ruled out because an inline-six would've made the front end too long, per the M division's head honcho. In addition, the new M5 needed a different gearbox than what the six-cylinder M3 is using since it must cope with the immense 737 pound-feet of torque of the electrified V-8 setup.

The M5 is the only 5 Series of this generation to have eight cylinders since the old M550i is gone. Perhaps electrification was a necessary evil...

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