[bradleyland]

First I want to say that, while you (of course) don't need my approval for your opinions, I really enjoyed reading your post. You make some good points, and I agree with many of them. I do have some things to add that you might find interesting though.

Originally Posted by Dalko43

The GTLM weight you listed is the minimum weight, so theoretically cars could be somewhat higher than that. BMW lists their GTLM m6 at ~2756lbs, empty, so they aren't far off from that. My comment on that specific issue was a question more than anything else, so I now understand the weight and BoP issues which you brought up.

BTW, BMW themselves did an interesting writeup on both their GT3 and GTLM platforms: http://www.bmw-motorsport.com/en/cars/bmw-m6-gtlm.html

I appreciate that you've looked in to it and have a better understanding. I do get where you were coming from too. The M6 is a massive car compared to the Z4. It makes sense to question all aspects related to weight.

Originally Posted by Dalko43

Well, that's why I started this post: to discuss the decision behind using the M6 and whether certain commentary was hype or legitimate analysis. The longer wheel base of the M6 was noted as a possible issue in a previous race, not just Long Beach, because I remember the commentators mentioning it (I believe it was the 12 hours of Sebring). And I wouldn't be surprised if it was brought up again for Sahlen's 6 hours of the Glen and LimeRock. That's the thing about traditional road courses; they tend to have tight turns and corners.

Interestingly, I've heard it both ways in commentary. On Radio LeMans, I heard them say something along the lines of, "The longer wheelbase of the M6 should benefit stability around this circuit," at Sebring and Long Beach. Specifically at Long Beach, I heard Fox Sports commentators say the opposite. Ha! They remarked that the tight road circuit would be tough for BMW factory drivers who are used to the tiny (by comparison) Z4. I can see the benefit of the added stability, but it's a trade-off. The M4 would have been a nice in-between.

Originally Posted by Dalko43

1) Strategy and reliability and playing the "game" no doubt play a part, and BoP tries to emphasize driver and team performance and strategy over simply letting the richest, best supported team dominate the series (as is the case in certain other racing organizations). But the engines, transmissions, chassis setup and the overall vehicle design still play a huge role in determining how cars perform. BoP might make the performance seem nearly equal on paper, but do you really think that the M6 GTLM handles and drives the same, or even similarly, to the older Z4 GTLM? Or to the C7.R GTLM or 911 GTLM? All of the driver interviews and commentary I've seen and read suggests that despite the BoP regulations, there is quite a bit of difference between how the different cars actually perform and handle on the track. I remember watching video where the old Z4 GTLM's high-reving V8 had trouble keeping up with the C7.R on transitions from certain corners into straight-aways because its peaky power delivery was vastly different from that of C7.R's push-rod V8. Just one example, I know, but hopefully you see what I am getting at.

Couple of really good jumping points for discussion here. I think it's important to understand that part of "the game" is knowing when to go all out, and when to hold back. Remember the hubbub over the Huracans sandbagging prior to Daytona. I watched the GTLM M6 get passed no less than three times on the banking. That's just insane for a GTD car to be able to pass a GTLM car in that circumstance. It's not really relevant in the whole "why the M6 over the M4 discussion," but it's worth keeping in mind in the general sense. Porsche, for example, are notoriously good at this part of the game.

Next up is this: "BoP might make the performance seem nearly equal on paper, but do you really think that the M6 GTLM handles and drives the same, or even similarly, to the older Z4 GTLM? Or to the C7.R GTLM or 911 GTLM?"

No, I don't think they handle the same at all, and that's a great point! I know this is going to sound funny, but I've learned a great deal about racing from sim racing. Lately, I've been playing a lot of ProjectCARS. I have a decent quality force feedback wheel, and the game was developed with input from actual racing drivers. It's remarkable how different the cars feel. The developers really dedicated themselves to making each car distinct. So in addition to the interviews and comments from journalists who have spent some time behind the wheel of GT3 cars, I developed some of my own appreciation behind the wheel of a decent quality sim racing application.

You can see this reflected in the performance of the Z4 over its career. BMW tuned their platform to be strong in places where it was naturally strong. The Z4 was renowned for its performance in the twisty bits, but lost a little in the straights. The BMW teams favored downforce over straight line speed. I think there's some habit breaking that needs to happen in the BMW garage. I don't think the M6 is responding well to the teams' old strategies, so they're having to re-learn. Probably the hardest thing about the choice of the M6 is the huge difference between it and the Z4. An M4 would have been a nice middle-ground.

It's really, really difficult to get candid information about the M6. The drivers aren't going to say anything explicitly negative about the platform. They'd get roasted, and they are all dedicated to their team. The Motorsports team at BMW would never say anything negative, because they poured their heart and soul in to developing a car within the constraints of what their financiers allowed. In the remarks after Long Beach, some negative sentiment started to leak through from the drivers, but that's about the most harsh thing I've read/heard.

As to whether this situation would be any different with the M4, I find it really hard to say, but it certainly would have been more similar (dimensionally) to the Z4, which I can't help but believe would be a benefit.

Originally Posted by Dalko43

2) I'm not sure that the M4 platform would have solved any of BMW's current issues either. My only reason for questioning the use of the M6, was because, engine aside, it seems like a lot more work is required to get such a big car ready for GTLM and GT3 use.

I really do think the engine situation is a major factor. Have a look at this speculation from Road & Track (which is pretty racing focused).

http://www.roadandtrack.com/motorspo...is-the-m6-gt3/

They think it has to do with the engine as well. They also asked BMW directly and didn't get an answer. Him. Kind of dubious if you ask me.

Originally Posted by Dalko43

I agree that BoP equalizes some things, but I still think the inherent characteristics and pro's/con's of each car/setup play some measurable role in determining how the different teams and manufacturers perform. It's not purely about the strategy and driver skill, in the same way that something like NASCAR or DTM are.

I'm not sure if the a notional M4 GTLM would cost more than a comparable M6 GTLM; I'm asking the questions because I haven't seen much if any commentary on that subject. In general, I agree with what you are saying on this issue though; a larger displacement turbo V8 seems like a better starting point for building a race car.

Agree completely. All these things have to be balanced, but some challenges are greater than others.

Originally Posted by Dalko43

Hasn't F1 paved the way for using small displacement turbo engines in racing applications? I thought they were employing that kind of technology back in the 80's, if not earlier?

Sure. BMW, rather famously, made 1500 HP from a tiny four-cylinder. A single F1 engine unit costs $7.7 million though. Check out this quote from Car and Driver:

Meet the M6 GT3, fitted with a tweaked version of the 4.4-liter turbo V-8 that’s offered in series production cars. In the GT3, it’s rated at up to 585 horsepower and mated to a sequential six-speed racing gearbox. BMW says it trounces its predecessor in terms of driveability and efficiency; the cost of operating the powertrain is said to be about 30 percent lower than that of the Z4 GT3.

So, set aside the cheerleading about the drivability of the car (of course they'll say that), and have a look at the reduction in driveline cost. Clearly cost was a big priority. How many series have died because costs have run out of control? Many!

Pulling big power out of small engines costs money. F1 is a great example. I think the engine was a significant factor, and so do a lot of credible journalists.

Originally Posted by Dalko43

Like I said earlier, I can only guess and speculate as to whether the M4 would make a better racing platform. I'm trying to understand if BMW's decision to use the M6 was purely because of the better performance potential it offered or if there was some cost/marketing issues taken into account.

I agree that the M6's engine offers a better starting platform to work with (even though we have no direct comparison with a racing version of the S55).

I understand that the M6's weight can be reduced to make it at least comparable to other cars in the series.

Those 2 issues aside, what did BMW really see in the M6 that made them decide to use that as the foundation for their GT3 and GTLM cars? It just didn't seem like the obvious choice to me when they first came out with those cars.

I think it was a mix of both. Like you pointed out, there are some positive attributes of the M6 that can't be ignored, but there are also some negatives. The weight issue is moot, but the M6 is still a big ass car, and that has consequences around a race track. At the end of the day, I think that the marketing guys at BMW had a lot of influence over the decision. I don't think that automatically makes the M6 a bad race car, but the platform hasn't exactly been a strong performer so far. I think that in the total context — considering the body of experience that teams have with the Z4 — the M6 was a risky choice. Personally, I'd rather have seen them go with the M4.

This got really long, so I'll shut up now and see if anyone actually reads all this garbage lol.

[RSBro]

Considering this thread is for some reason still going... lol, I found this article pretty interesting.

http://nasportscar.com/gtlm-vs-gt3-vs-gtd-version-2-0/

[bradleyland]

Originally Posted by RSBro

Considering this thread is for some reason still going... lol, I found this article pretty interesting.

http://nasportscar.com/gtlm-vs-gt3-vs-gtd-version-2-0/

That's a great guide, and contains what is probably the most succinct summary of why base-vehicle choice is a relatively minor consideration from a performance standpoint:

So in theory, a manufacture can show up with damn near anything, but if it doesn’t fit in the performance envelop of the rest of class the sanctioning body reserves the right to require modifications.

Doesn't matter what you pick for the base car, because they're going to BoP your car in to the lap time envelope.

[RSBro]

Originally Posted by bradleyland

That's a great guide, and contains what is probably the most succinct summary of why base-vehicle choice is a relatively minor consideration from a performance standpoint:

So in theory, a manufacture can show up with damn near anything, but if it doesn’t fit in the performance envelop of the rest of class the sanctioning body reserves the right to require modifications.

Doesn't matter what you pick for the base car, because they're going to BoP your car in to the lap time envelope.

Exactly. When you put it in those terms, it's not as complicated as you'd initially think!

[Flying Ace]

1 reason - MARKETING