[bradleyland]

Originally Posted by Dalko43

We are talking about GTLM as well, not just GT3 spec cars (GT3 falls within IMSA's GT-D semi-amateur class). But yes, I understand what you are saying about teams stripping out the weight. But if you are starting with a lighter platform to begin with (like the 911 or Corvette), then by comparison won't the M6 still be a bit heavier on the circuit even after the weight reduction?

It doesn't matter if we're talking about GTLM, GTE, GTD, or GT3. They're all homologation race cars with minimum weight requirements. I lump them together as "GT cars", because GTLM, GTE, GTD, GT3, whatever all use conceptually similar regulations. You can get all pedantic about which regulations we're referring to, but none of that refutes the actual fact, which I will restate again below.

The weight of the production car is irrelevant, because they manufacturers are easily able to hit the weight targets using composite components. These days, GT cars contain massive amounts of carbon fiber.

Fire up a search engine some time. It's elucidating.

IMSA "Classes" page states:

GTLM WEIGHT: 2,745 minimum
GTD WEIGHT: 2,700 pounds

From there, BoP may add mass to cars based on their performance relative to competitors.

There is no problem at all getting a race version of the M6 down to those weight targets, and even if the cars don't hit those targets, BoP makes up the difference. Even if BMW started with an i3, they'd have to meet weight minimums, and BoP would be applied to bring it in line with the rest of the cars in that spec. So again, the production car weight is irrelevant.

Originally Posted by Dalko43

I'm not following you on the dimensions aspect. I've heard that dimensions (wheel base, physical size/footprint, center of gravity, ect.) play a huge role especially in the technical, twisty road courses. If dimensions play no role, then what's to prevent a team from racing a heavily modified crossover SUV or a station wagon?

Dimensions do play a role, but if you listen to all the hype, commentary during races, etc, they all play up the longer wheelbase of the M6 as an advantage because it's more stable. The only race where it was a "concern" was at Long Beach, because the course is kind of tight in areas. It's all hype to me though, because none of it makes that much of a difference.

The cars are all regulated and BoP'd to within a few tenths of each other. Winning and losing on race day comes down to strategy (fuel, pitting, etc), reliability, and gaming the system (knowing when to put on your best performance, and when not to). The best teams are the teams that balance all these equally. BMW is currently failing (primarily) at reliability and strategy. Tangentially, I'm not sure the M4 would have fixed either of these.

Think of it this way, if the car you started with mattered, the Ferrari teams would be wiping the floor with the M6 by wide margins on every lap, because the 488 is such a vastly superior car in stock form, yet the top M6 qualified better than the top 488 at Daytona, Sebring, and Long Beach.

Originally Posted by Dalko43

Where is your source for this (that the M4's engine development would have cost a lot more)? I agree that the M6's turbo v8 has its own advantages for racing, but have we seen anyone even attempt to make a racing-version of the S55? How do we know anything about its cost and/or reliability on the track?

I don't need a citation, it's simple thermodynamics. The larger the displacement, the more power you can make (all things being equal). The displacement of the S55 is 15% smaller than any other car in the series, and is 46% smaller than the P63. It costs money to make up that deficit. When you stress components more, you have to use more expensive materials. I also didn't say "a lot" more; I only said more, because obviously we don't have any real world examples to work from.

Originally Posted by Dalko43

I'm not surprised that the M6 platform costs less than the Z4 GT3; the Z4 was basically hodge-podge of components and had to built from scratch as they were not mass-producing Z4's (with the S65) for consumer sales (it was basically a unique custom built M-variant of the Z4). The real question is how much does the M6 cost relative to the E92 M3 GT3 GTLM or a notional M4 GT3 GTLM?

That's a great question. Why don't you fire up a search engine for once and provide some answers. Be sure to adjust for inflation. Please also share any methodology you use to arrive at a hypothetical M4 GT3/GTLM price.

Originally Posted by Dalko43

Where did you find some of these answers and facts? I've asked why the M6 was used in place of the M4. The answers you provided deal more with the inherent characteristics of the M6; much of what you say about the M4 is speculation and opinion, because, as stated before, we don't have a M4 racing platform to compare the M6 to.

I've provided two core facts, both of which stand on their own.

1) The weight of the production car is irrelevant.
2) The M6 platform has a larger engine displacement from which BMW Motorsport can build from.

It is from this that we can draw very reasonable conclusions, but ultimately, it is speculation. The only people who can really answer your question are BMW, and they won't go on record (for obvious reasons). But you don't seem to want an answer to your question. You want to make an assertion. I wish you would just come out and say it:

"I think the M4 would have made a better racing platform."

To which I would say, " OK." Outside of the displacement issue, I don't disagree with you. I've already said once that I'd have rather seen an M4 GT car than an M6, but that's not what we got.