[Dalko43]

I watch IMSA racing quite a bit. With all the private and factory team involvement, it's quite interesting and fun to watch.

But, for the life of me, I can't figure out why BMW chose the M6 platform to base its new race vehicle off of. Both the GTLM (equivalent of GTE in European and Le Mans Racing) and GTD (roughly the equivalent of GT3 in Euro) BMW teams are using the M6. Why?

And what was wrong with the Z4 platform they were using previously? I do think it was kind of BS that BMW raced a NA V8 in a Z4, even though they really didn't make those models for road-going consumers, but still that car seemed to be a lot more nimble for racing applications than is the current M6.

And, why did they not use M4 platform instead? The M6 certainly looks cool, but it just seems way too big to be a true competitor.

Anyone have a guess on this?

[overcoil]

Without really knowing, is the M6 sillouhette and suspension points the dimensions that need to be retained for the race car and provide a better base for a race car then say the M4 having a too upright rear window and slightly too short wheelbase meaning engine set-back from front axle line and driver position didn't offer room as the M6 does

[Mywifes335]

I imagine a couple hypotheses:

1. Least modification necessary to race in the series
2. M6 might need to most "boost" from the factory to garner sales, whereas the M4 stands on its own already
3. It's BMWs flagship ///M car
4. Just because

[DieGrüneHölle]

Short answer...engine homolagation rules.

They had no plans to start a engine program based on the S55.

[3GFX]

BMW has offered explanation to a few magazines I read (PBMW etc.).

The M6 has a longer wheelbase ever so slightly; making it more stable in corners.

Mainly, the M6 has a smaller front area. The Z4 had excellent downforce but was limited to top speed on the long straights such as Daytona.

By switching the to M6 they were able to hone aerodynamics to allow for greater speed.

[DieGrüneHölle]

Originally Posted by 3GFX

BMW has offered explanation to a few magazines I read (PBMW etc.).

The M6 has a longer wheelbase ever so slightly; making it more stable in corners.

Mainly, the M6 has a smaller front area. The Z4 had excellent downforce but was limited to top speed on the long straights such as Daytona.

By switching the to M6 they were able to hone aerodynamics to allow for greater speed.

The question is more why not the M4? Not why did they replace the aging Z4.

[Dalko43]

Originally Posted by Blipit_

Short answer...engine homolagation rules.

They had no plans to start a engine program based on the S55.

I guess I need to read up on the homolagation rules. Their previous Z4 used a V8 derived from the S65, even though the S65 was never placed in the Z4 on the consumer side (at least not in mass production).

Still, it's kind of disappointing. The M6 traditionally never had a racing heritage whereas the M3 did. It would be much more awesome to see a M3/M4 racing in IMSA than the M6. Maybe the M6 has a slightly more optimal wheel base, but I got to believe that the M4 would be a better handling car overall just based on size alone, right? I mean the reason most car enthusiasts watch sports car racing is because they want to see their favorite street cars performing on the track. Corvette owners watch the C7R (which I honestly think is one the best looking cars out there), Porsche owners watch the 911, ect....how many M6 owners are really going to care about the M6 racing in IMSA? Not that it doesn't look cool, but the M4 is the enthusiast's car in the M lineup....it should be the one racing in IMSA.

[i8ur911]

They weren't going to use the M4 due to the car being in DTM. BMW doesn't want to have that chassis as the sole racing chassis.

The M6 has already shown to be a very competitive chassis, so I don't see any real need for concern.

I'm excited to see M235iR's in Pirelli World Challenge.

There's also a rumor of a team running at least 1, if not 2, 228's in CTSCC ST class. I'm very excited to see this.....if it happens 😊.

[DieGrüneHölle]

Originally Posted by Dalko43

I guess I need to read up on the homolagation rules. Their previous Z4 used a V8 derived from the S65, even though the S65 was never placed in the Z4 on the consumer side (at least not in mass production).

Using the P65 in the Z4 was not done under homolation rules, they had to ask for concessions. I don't think they were in the position to ask for more concessions with a brand new car. Plus using a S63 based engine in order to go GT racing with the M4 wouldn't look too good.

Originally Posted by i8ur911

They weren't going to use the M4 due to the car being in DTM. BMW doesn't want to have that chassis as the sole racing chassis.

A M4-look body on a series spec monocoque chassis, it isn't a M4.

Originally Posted by i8ur911

I'm excited to see M235iR's in Pirelli World Challenge.

There's also a rumor of a team running at least 1, if not 2, 228's in CTSCC ST class. I'm very excited to see this.....if it happens ��.

I saw the M235i Racings at COTA. A small team run by Classic BMW.

What is really telling is no privateer teams in CTSCC have chosen to run the M4. I thought Fall Line was developing a car, but they have gone silent. As it is now, no M3's in CTSCC. Sad really.

[Dalko43]

Originally Posted by i8ur911

They weren't going to use the M4 due to the car being in DTM. BMW doesn't want to have that chassis as the sole racing chassis.

The "M4" that you see in DTM is not really a M4, but rather a M4 body mounted on regulation chassis that is mostly common to what is used by all the other teams (kind of like NASCAR).

IMSA, LeMans, and the various regional GT racing series are the only ones that actually use homologated versions of the street cars.

Originally Posted by i8ur911

The M6 has already shown to be a very competitive chassis, so I don't see any real need for concern.

I'm excited to see M235iR's in Pirelli World Challenge.

One of the M6 cars has been doing all right in the GTLM class; we'll see how they finish at season's end. My question still stands though why a M4 wasn't used instead of a M6?

Originally Posted by Blipit_

Using the P65 in the Z4 was not done under homolation rules, they had to ask for concessions. I don't think they were in the position to ask for more concessions with a brand new car. Plus using a S63 based engine in order to go GT racing with the M4 wouldn't look too good.

So if they're willing to use a turbo V8 derived from the S63, why not just use the inline 6 turbo S55? I guess they prefer working with a larger displacement engine?

Originally Posted by Blipit_

What is really telling is no privateer teams in CTSCC have chosen to run the M4. I thought Fall Line was developing a car, but they have gone silent. As it is now, no M3's in CTSCC. Sad really.

Yeah it is sad. The M4 is marketed as a track-ready car. And certainly the reviews on the consumer side of things have indicated that it is....so you'd think BMW would race the damn thing to validate their whole marketing scheme.

I guess the racing season is still young, and the M6 race car hasn't been out for that long, so we'll see how things go. Still...it seems like BMW is racing everything in their lineup (Z4, M235i, M6) except for the one car that everyone considers a benchmark within the industry.... doesn't make sense.

[E9TOU]

I assume they use a similar model to what Mercedes and Audi use. DTM promotes the M4, C63, and RS5. Whereas their GT cars are based on their top tier road cars such as the AMG GT, R8, and M6 (although I wouldn't regard the M6 as on the same level as the other two cars). We're used to the M3 being BMW's go to car for all forms of racing but they've changed that philosophy and started promoting other models in different series. I do wish that BMW used the M4 instead of the M6 in IMSA though, stricly speaking of looks it just fits the profile better as the M6 looks like a tank compared to the other cars.

[i8ur911]

I understand exactly what the M4 DTM car is and isn't.

Being close with BMW Motorsport (closer than most) I can assure you that BMW isn't interested in backing an M4 in the US.

Also, when has anyone seen a brand new BMW "chassis" raced in a series in its first year? Probably not since the E36 and E46 days.

From what I understand, Fall Line is still working on M4 stuff, but it's not as simple as strip (edit: strong - typo) the car, installing a cage, a seat, some electronics and going racing.

Don't plan on seeing an M4 for another season.....or 2.

[FogCityM3]

Lots of weird things that BMW is doing these days...just chalk this up as one more in the "new world order"

[JackF]

I understand exactly what the M4 DTM car is and isn't.

[doogee]

Originally Posted by Dalko43

So if they're willing to use a turbo V8 derived from the S63, why not just use the inline 6 turbo S55? I guess they prefer working with a larger displacement engine?

Larger displacement = more torque and less stress.

The S55 wouldn't perform nearly as well, which is a perfectly good reason not to use the M4.

Originally Posted by Dalko43

Yeah it is sad. The M4 is marketed as a track-ready car. And certainly the reviews on the consumer side of things have indicated that it is....so you'd think BMW would race the damn thing to validate their whole marketing scheme.

Believe it or not, BMW races to win races too, it isn't all marketing...there isn't any point running an inferior car that will sit at the back of the field.

I'm sure they chose what would work best for them. It's racing, not a parade.


Seems like you are forgetting these :

[Law]

Originally Posted by Blipit_

Short answer...engine homolagation rules.

They had no plans to start a engine program based on the S55.

Originally Posted by doogee

Larger displacement = more torque and less stress.

The S55 wouldn't perform nearly as well, which is a perfectly good reason not to use the M4.

Believe it or not, BMW races to win races too, it isn't all marketing...there isn't any point running an inferior car that will sit at the back of the field.

I'm sure they chose what would work best for them. It's racing, not a parade.


Seems like you are forgetting these :

Yes & yes.
A 3.0L inline-six just wouldn't be competitive in the present day and BMW hasn't competed with its straight-sixes in this category of racing since before the E46 M3 GTR.
Not only is there a higher performance threshold with a larger engine, but also, different classes have different air-restrictor, horsepower, etc. regulations so having a 4.4L engine to work with makes for a more versatile and ultimately more reliable setup.

People want to talk about racing pedigree, but the "M6" & "6-series" moniker has more pedigree than the "M4", which has close to none.

Originally Posted by Dalko43

I guess I need to read up on the homolagation rules. Their previous Z4 used a V8 derived from the S65, even though the S65 was never placed in the Z4 on the consumer side (at least not in mass production).

Still, it's kind of disappointing. The M6 traditionally never had a racing heritage whereas the M3 did. It would be much more awesome to see a M3/M4 racing in IMSA than the M6. Maybe the M6 has a slightly more optimal wheel base, but I got to believe that the M4 would be a better handling car overall just based on size alone, right? I mean the reason most car enthusiasts watch sports car racing is because they want to see their favorite street cars performing on the track. Corvette owners watch the C7R (which I honestly think is one the best looking cars out there), Porsche owners watch the 911, ect....how many M6 owners are really going to care about the M6 racing in IMSA? Not that it doesn't look cool, but the M4 is the enthusiast's car in the M lineup....it should be the one racing in IMSA.

First of all, you're incorrect about the M6/6er.
The E24 M6(35CSi) had been chalking up victories since before the M3 even existed; European Touring Car Championship, Deutsche Tourenwagen Meisterschaft, Japanese Touring Car Championship, 24 Hours Nürburgring, just to name a few.
Here's the E24 DTM that won the 1984 championship:

Originally Posted by Blipit_

Using the P65 in the Z4 was not done under homolation rules, they had to ask for concessions. I don't think they were in the position to ask for more concessions with a brand new car. Plus using a S63 based engine in order to go GT racing with the M4 wouldn't look too good.

Regarding homologation, Blipit_ 's explanation is on the right track, but i'll elaborate.
While the E89 Z4 was never offered for sale with an S65, the homologation rules technically failed to directly state that the engine and chassis must be offered in the same road-going product (i.e., road-going Z4 with S65 engine).

To qualify, the regulations presented a quota for the engine and chassis that a car manufacturer must meet in road-going production, which the S65B40 for the P65B40 (and later S65B44 for the P65B44 via M3 GTS/CRT), and E89 Z4 chassis met.
But the rules fell short in specifying that the engine AND chassis must be the same product.
Obviously it was implied, because every other manufacturer was homologated with good faith. But BMW found a loophole where they could exploit the regulations to enter its then smallest chassis, the E89 Z4, installed with the E9X M3 engine in racing.

Now this isn't the first time in recent memory that BMW bent rules in racing.
Facing tough competition from Porsche, BMW prematurely retired the S54-homologated P54B32 and entered the V8-powered E46 M3 GTR. Per homologation rules, the car must have a street equivalent for sale on two continents within 12 months, so BMW literally did just that, put a few up "for sale" in Europe and N. America. Of course, Porsche wasn't oblivious to this loophole and neither was the FIA, so rules were amended the following season, raising the minimum to 50 units, and BMW pulled out. It was a great car and a great season, but BMW was borderline cheating & they knew it.
In fact, only 3 M3 GTRs are known to have been "sold", all of which were magically returned to BMW M's collection in Germany in the years following




This time around, perhaps under pressure, BMW is actually playing by the rules of homologation, entering a chassis and engine combo that one can actually buy as a street car.
And that is what homologation is all about.

[GuidoK]

Still an M6 in GT3 spec has little to do with a stock M6. Virtually everything is different.
Even things like complete different suspension arms that work on different principles.
The difference is not as big as in DTM but still..

[i8ur911]

Originally Posted by Law

Yes & yes.
A 3.0L inline-six just wouldn't be competitive in the present day and BMW hasn't competed with its straight-sixes in this category of racing since before the E46 M3 GTR.
Not only is there a higher performance threshold with a larger engine, but also, different classes have different air-restrictor, horsepower, etc. regulations so having a 4.4L engine to work with makes for a more versatile and ultimately more reliable setup.

People want to talk about racing pedigree, but the "M6" & "6-series" moniker has more pedigree than the "M4", which has close to none.



First of all, you're incorrect about the M6/6er.
The E24 M6(35CSi) had been chalking up victories since before the M3 even existed; European Touring Car Championship, Deutsche Tourenwagen Meisterschaft, Japanese Touring Car Championship, 24 Hours Nürburgring, just to name a few.
Here's the E24 DTM that won the 1984 championship:




Regarding homologation, Blipit_ 's explanation is on the right track, but i'll elaborate.
While the E89 Z4 was never offered for sale with an S65, the homologation rules technically failed to directly state that the engine and chassis must be offered in the same road-going product (i.e., road-going Z4 with S65 engine).

To qualify, the regulations presented a quota for the engine and chassis that a car manufacturer must meet in road-going production, which the S65B40 for the P65B40 (and later S65B44 for the P65B44 via M3 GTS/CRT), and E89 Z4 chassis met.
But the rules fell short in specifying that the engine AND chassis must be the same product.
Obviously it was implied, because every other manufacturer was homologated with good faith. But BMW found a loophole where they could exploit the regulations to enter its then smallest chassis, the E89 Z4, installed with the E9X M3 engine in racing.

Now this isn't the first time in recent memory that BMW bent rules in racing.
Facing tough competition from Porsche, BMW dropped the S54-homologated P54B32 and entered the V8-powered E46 M3 GTR. Per homologation rules, the car must have a street equivalent for sale on two continents within 12 months, so BMW literally did just that, put a few up "for sale" in Europe and N. America. Of course, Porsche wasn't oblivious to this loophole and neither was the FIA, so rules were amended the following season, raising the minimum to 50 units, and BMW pulled out.




This time around, BMW is actually playing by the rules of homologation, entering a chassis and engine combo that one can actually buy as a street car.
And that is what homologation is all about.

Mic drop

[Dalko43]

Originally Posted by i8ur911

I understand exactly what the M4 DTM car is and isn't.

Based on the way you referred to how the "M4" is raced in DTM, it didn't sound like you did, but fine, I'll chalk it up to miscommunication.

Originally Posted by doogee

Larger displacement = more torque and less stress.

The S55 wouldn't perform nearly as well, which is a perfectly good reason not to use the M4.


Believe it or not, BMW races to win races too, it isn't all marketing...there isn't any point running an inferior car that will sit at the back of the field.

I'm sure they chose what would work best for them. It's racing, not a parade.

Well I suspected that displacement had something to do with it. And for the record, I wasn't advocating that BMW race the M4 simply for appearances' sake. I thought that the M4's smaller profile and footprint would make it a more nimble platform (relative to the M6) on the track.

Originally Posted by Law

Yes & yes.
First of all, you're incorrect about the M6/6er.
The E24 M6(35CSi) had been chalking up victories since before the M3 even existed; European Touring Car Championship, Deutsche Tourenwagen Meisterschaft, Japanese Touring Car Championship, 24 Hours Nürburgring, just to name a few.
Here's the E24 DTM that won the 1984 championship:

I didn't say the M6 lacked a racing pedigree. My point was that the M3 is the car that built BMW's reputation on the circuits and on the street....and yes, I realize that is all entirely subjective.


Your points on racing homologation were very interesting.

[DC-T]

So many correct answers here I don't even need to bother *sips tea

[Law]

Originally Posted by Dalko43

I didn't say the M6 lacked a racing pedigree. My point was that the M3 is the car that built BMW's reputation on the circuits and on the street....and yes, I realize that is all entirely subjective.


Your points on racing homologation were very interesting.

When you say "the M6 traditionally never had a racing heritage whereas the M3 did", that's exactly what you're saying.
The words came out of your own mouth, not mine.

BMW's reputation on the circuit in touring car racing & in Formula One, was established before the existence of the M3. One could argue that the M3 represented a peak in the touring car story, but it is not what built BMW's reputation. As far as the "street", BMW has been building reputable, agile, fun, and sporty daily drivers long before the M3.

It is not a matter of subjectivity, it is a matter of fact.

[GuidoK]

Originally Posted by Dalko43

My point was that the M3 is the car that built BMW's reputation on the circuits and on the street....and yes, I realize that is all entirely subjective.

Not only subjective but also very limited.
The m3 only came around in the mid 80's and bmw is far far older than that.
The've raced the 2002 extensively, the e9 (Csl) was very succesful etc etc
The 'm3' only made the reputation because they call certain cars m3 over and over again; it's now the fifth generation, but all those cars have nothing in common except the name. So if a car built the reputation, which M3 specifically do you mean?
The interweb tales probably say the e30 was the most succesful, but in which class etc? probably a fact copied out of some old book because the production numbers of the e30 m3 were very low.