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      01-03-2013, 03:59 AM   #23
wisesoul
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I knew the M6 would be faster, but all in all a very close race. Jethro is a great reviewer and an even better driver. You can't make a mistake buying an M5 or M6
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      01-03-2013, 08:47 AM   #24
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Quote:
Originally Posted by mlhj83 View Post
If the M5 had 20" and the same PSS* tyres, it would be a bit quicker (lap time) than being on 19", but obviously still slightly slower than the M6.

In general, on a smooth surface, lower profile tyres will generate more grip in a corner due to less sidewall flex. Thus, if you compare the same tyre model with the same section width, but with different profiles, the lower profile tyre will be quicker round a track. The overall weight difference between the BMW M 18" and 19" with tyres on, or 19" and 20' with tyres on, isn't significant enough to make as much of a difference in lap times as sidewall flexing does. Straight line acceleration, however, should favour the lighter smaller diameter wheel, but cars spend more time in corners than they do on straights on most circuits.

I've tested my oem 219M 18s and 359M 19s with the same tyres with similar wear on the same track and the 19s generated a much better lap time and significantly less roll with improved steering response. Many people put track biased tyres on their 18s for practical reasons, which are obviously going to be quicker than 19s on the best road tyres.
exactly - and I would argue the 0-60 times would have favored the tire with the bigger contact patch in a car with as much torque as these. Either way, in order to compare apples to oranges in this comparo, I would have suggested they have the same size wheels and the same tires.
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      01-03-2013, 09:46 AM   #25
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      01-03-2013, 10:04 AM   #26
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Stealth - take some pics and I'd be interested in your thoughts of the two cars after some track time.

Thanks for posting and thanks to C&D for doing the piece. The outcome was a foregone conclusion but it was interesting to see how the differences in the two cars actually play out on the track.

The M6 is a great car but IMHO it under performs my expectations for a GT car while the M5 although slower than the M6, far exceeds my expectations for big heavy Saloon/Sedan. I guess I'm one of those people that really enjoys the "sheep in wolf's clothing" sleeper factor of the M5. In short, like the 6, love the 5! To each his own eh?
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      01-03-2013, 11:45 AM   #27
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The looks of the M6 alone make it worth the price difference. The M5 is nice, but somewhat boring looking. That said, I think there are better options in that price range.
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      01-03-2013, 02:35 PM   #28
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Quote:
Originally Posted by mlhj83
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Originally Posted by doug_999 View Post
check me if I'm wrong Sandy, but the M6 appears to have 20" wheels vs. the 19s on the M5.
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Originally Posted by SleepyE90 View Post
So you're saying that the m5 is at a disadvantage?
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Originally Posted by Adriansideways View Post
Bigger rims and wheels are not always a advantage! My E90 M3 is quicker on 18" than on the standard 19" on any track
If the M5 had 20" and the same PSS* tyres, it would be a bit quicker (lap time) than being on 19", but obviously still slightly slower than the M6.

In general, on a smooth surface, lower profile tyres will generate more grip in a corner due to less sidewall flex. Thus, if you compare the same tyre model with the same section width, but with different profiles, the lower profile tyre will be quicker round a track. The overall weight difference between the BMW M 18" and 19" with tyres on, or 19" and 20' with tyres on, isn't significant enough to make as much of a difference in lap times as sidewall flexing does. Straight line acceleration, however, should favour the lighter smaller diameter wheel, but cars spend more time in corners than they do on straights on most circuits.

I've tested my oem 219M 18s and 359M 19s with the same tyres with similar wear on the same track and the 19s generated a much better lap time and significantly less roll with improved steering response. Many people put track biased tyres on their 18s for practical reasons, which are obviously going to be quicker than 19s on the best road tyres.
Then please tell me why has all M vehicles have a normal tyre and not run-flats? Run flats has a stiff sidewall ? And why do formula one tyres have such soft sidewalls?
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      01-03-2013, 03:09 PM   #29
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Then please tell me why has all M vehicles have a normal tyre and not run-flats? Run flats has a stiff sidewall ? And why do formula one tyres have such soft sidewalls?
Because, like everything, it's a compromise. BMW M probably preferred the way the non-run flats works with their suspension setup. Regardless, the debate isn't about run-flats vs non run-flats, it's about the same model tyre with the same section width but with different profiles. The same argument would also apply if M decided to use run-flats; the lower profile run-flat would generate more grip than a taller profile run-flat, all other things being equal.

F1 use tyres with taller profiles as the car has been designed to use the sidewall flex as a significant part of the suspension travel. If F1 cars used low profile tyres, the cars would effectively have insufficient suspension movement. This is completely different to the suspension design of a road car where there is a lot more suspension travel (excluding sidewall flex) than a F1 car, therefore, increasing stiffness with lower profile tyres for a road car can generate more grip on a sufficiently smooth surface, all other things being equal. Google F1 tyre design and suspension travel if you don't believe me.

Last edited by mlhj83; 01-03-2013 at 03:21 PM.
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      01-03-2013, 03:51 PM   #30
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Great review!
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      01-04-2013, 02:41 AM   #31
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Quote:
Originally Posted by mlhj83
Because, like everything, it's a compromise. BMW M probably preferred the way the non-run flats works with their suspension setup. Regardless, the debate isn't about run-flats vs non run-flats, it's about the same model tyre with the same section width but with different profiles. The same argument would also apply if M decided to use run-flats; the lower profile run-flat would generate more grip than a taller profile run-flat, all other things being equal.

F1 use tyres with taller profiles as the car has been designed to use the sidewall flex as a significant part of the suspension travel. If F1 cars used low profile tyres, the cars would effectively have insufficient suspension movement. This is completely different to the suspension design of a road car where there is a lot more suspension travel (excluding sidewall flex) than a F1 car, therefore, increasing stiffness with lower profile tyres for a road car can generate more grip on a sufficiently smooth surface, all other things being equal. Google F1 tyre design and suspension travel if you don't believe me.
Overall idea is correct, but as you also stated, there are reasons that a softer sidewall will also help grip.

Certain tires benefit more than others in outside tread shoulder loading, based off its design. These tires will start to include more of the shoulder area as they flex, increasing the contact patch.


Best way to determine is how the tire wears at the track. If the tire is wearing in the off shoulder area of the tread that is ineffective, you need stiffer sidewalls, more tread grip (footprint or compound) or higher pressures.

Also, it's rare to have any track buttery smooth. Low profiles will cause harsher impacts that will unsettle the suspension and cause momentary loss of grip.

Low profile doesn't always = more grip.
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      01-04-2013, 03:32 AM   #32
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Quote:
Originally Posted by anerbe
Quote:
Originally Posted by mlhj83
Because, like everything, it's a compromise. BMW M probably preferred the way the non-run flats works with their suspension setup. Regardless, the debate isn't about run-flats vs non run-flats, it's about the same model tyre with the same section width but with different profiles. The same argument would also apply if M decided to use run-flats; the lower profile run-flat would generate more grip than a taller profile run-flat, all other things being equal.

F1 use tyres with taller profiles as the car has been designed to use the sidewall flex as a significant part of the suspension travel. If F1 cars used low profile tyres, the cars would effectively have insufficient suspension movement. This is completely different to the suspension design of a road car where there is a lot more suspension travel (excluding sidewall flex) than a F1 car, therefore, increasing stiffness with lower profile tyres for a road car can generate more grip on a sufficiently smooth surface, all other things being equal. Google F1 tyre design and suspension travel if you don't believe me.
Overall idea is correct, but as you also stated, there are reasons that a softer sidewall will also help grip.

Certain tires benefit more than others in outside tread shoulder loading, based off its design. These tires will start to include more of the shoulder area as they flex, increasing the contact patch.


Best way to determine is how the tire wears at the track. If the tire is wearing in the off shoulder area of the tread that is ineffective, you need stiffer sidewalls, more tread grip (footprint or compound) or higher pressures.

Also, it's rare to have any track buttery smooth. Low profiles will cause harsher impacts that will unsettle the suspension and cause momentary loss of grip.

Low profile doesn't always = more grip.
I agree, lower profile doesn't always generate more grip as it very much depends on the setup of the car, however, given that BMW M cars have road suspension which has softer spring rates than a track focused car, a lower profile tyre on BMW M cars will not increase stiffness to a point that the tyre starts skipping over surface irregularities on most tracks, so in this case a lower profile road tyre will improve lap times.

Track biased tyres have much stiffer sidewalls than road tyres, therefore aren't normally available in low profile dimensions.
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      01-04-2013, 03:17 PM   #33
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great video. i'd love to have either as a DD.
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      01-05-2013, 12:08 PM   #34
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I am not so sure if I agree with you all the way.

I am with you on the bandwagon that M6 should be lighter and not so large or if it is going to be so large then at least offer more use able rear seat room.

On the other hand I disagree that M6 has no purpose in the market segment. I think it compares real well with fast stylish & sporty GT cars and not pure sports cars/exotics.

M6 compares very well against likes of Aston Martins, Jaguar XKR and XKR-S, MB CL63 AMG, Bentley GT coupe, and Bentley super sport.

It was not intended to be all out performance sports car and was never intended to compete with the likes of Audi R8 or 911 GT3 or GT-R. The R8 is an exotic mid-engine with no rear seats, 911 GT3 is a track machine focus less on luxury and style and ditto for GT-R with its inferior interior fit and finish, luxury and style.

I think M6 can improve in more areas no doubt but take it for what it is a larger, stylish, luxury, sports GT.

I am hoping for all us performance hungry folks BMW gives us an awesome M4.
I agree. Astonished by those that personally don't care for it and think they speak for the universe.
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      01-07-2013, 12:41 PM   #35
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tiny bit quicker but imo better looking than the M5..you can't go wrong with either...white M6 PLEASE!! nice review
How's this? http://www.6post.com/forums/showthread.php?t=788159
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      01-08-2013, 05:26 AM   #36
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I wonder if the M6 GC can beat the M5

Probably a very close call.....
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      01-31-2013, 12:32 AM   #37
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Car and Driver Video: BMW M6 and M5 comparo

Not sure if this was posted before:

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