[Joe-BMW33]

Originally Posted by choppedliver

I stand corrected.

Personally I've never noticed understeer and neither did Motortrend.

According to MotorTrend (https://www.motortrend.com/news/bmw-5-series-2018-car-of-the-year-contender/)

So, according to MotorTrend, the M550i handles the best of the bunch. So, 530e is the worst, followed by 530i, with M550i and 540i doing the best for handling.

You’re forgetting, Larry knows more than motor trend. He drove an M550 for 5 minutes, couldn’t afford it, so he labeled it a pig to make himself feel better. Somehow he is the only one on the internet talking about excessive understeer on the M550.

[Knifeedge2k1]

Originally Posted by Joe-BMW33

You’re forgetting, Larry knows more than motor trend. He drove an M550 for 5 minutes, couldn’t afford it, so he labeled it a pig to make himself feel better. Somehow he is the only one on the internet talking about excessive understeer on the M550.

[Joe-BMW33]

Originally Posted by Knifeedge2k1

LOL, his favorite emojie to close with after he insulted half the members here.

[Knifeedge2k1]

After this thread i went about trying to find an M550 in the classifieds, unfortunately nothing available. Might be less than a dozen sold in my city.

[tsbrown]

Originally Posted by choppedliver

350Lbs seems excessive. That’s more than the weight of dry B58 motor and it would be illogical to think the N63 weighs twice the weight of a B58. Maybe 200lbs but even that seems excessive.

200lb weight difference is about right for the N63 (~500lb) vs the B58 (~300lb). The M550 also only comes only in Xdrive and more standard content so that’s where the rest of the weight is and roughly evenly distributed.

Comments about “on the limit handling” are a joke and entirely academic. If you’re driving a G30 on the limit you should be in jail because it will be on public roads because this isn’t a track car. The only place I’ve ever driven one of my cars on the limit is on the track, the only place it’s safe to do so.

[Neusser]

Originally Posted by Knifeedge2k1

With tire differences and spec differences I wouldn't put too much weight on those numbers

The M550 clearly has better tires here (to be fair they do come with those tires so fair enough)

Whether the car has 4ws, active away bars, xDrive or not, Lsd or not, etc will have huge impact

Regardless though I doubt the M550 would be wildly understeer-y and the 540 a drift monster simply because of the weight distribution. If that was true there would be an extreme shift in limit handling and balance every time I have a couple people in the back seat of my car which obviously doesn't happen. Does it have an impact, sure, is it noticeable, perhaps, will it be massive, I doubt it.

It's also something that can be remedied by tire choices and alignment

Perhaps the xDrive limits your choices somewhat as you really need to maintain the stock rolling circumference ratio been the front and rear axle but it's not a huge dealbreaker

You don't drive on the limit with people in the backseat. That said, there is a difference in handling when you have passengers in the back. This is basic physics.

A RWD car with a nice 50/50 weight distribution will actually benefit in some ways when loaded (in terms of balance). You get better traction and the front tires do less work. On the limit handling here is hardly a concern, however.

55% over the front axle (like on the 550) is quite understeery even at 6/10, and it is more typical of an Audi than a BMW. The balance of the 540 is enjoyable at any speed.

[Neusser]

Originally Posted by Thecastle

I've actually driven the M2 comp, M3 Comp, M4, M5 Comp and M8 all on the same track the M2 /M5 /M8 and M2/M3/M4 on the same days even, but in those groupings. I'lll also state there is a big difference in people desires for a track only car, vs a track car I drove the the track and daily.

My general impression on Circuit Of America's Track (COTA) and F1 track, is all of them are fine for general track use. Though the M5/M8 comps had the carbon ceramic brakes if I recall. I had no problems with any of them doing repeated hard stop from 140-160mph->50mph for the corner before entering the stands.

The AWD on the M5/M8 is an advantage for putting the power down earlier on corner exits, and allows throttle a bit earlier in a corner. But awd/stability control also tends to compensate for bad technique and the feedback is much more subtle your doing it wrong than the M2.

Personally, I find the M2 comp the most fun to drive on the track due to its tuning being perfect for track use, rwd, and immediate feedback your driving wrong. So its a good learner car.

I would think the M2 comp is a bit brutal on the road, and the brakes are hard to modulate when cold there isn't much difference between no stopping power and slamming your head in the dash at 20 mph. Just right for the track, not so great for the street.

I liked the M3 next best, more weight in the rear being a 4 door, but its close. the M3 is much better on the street with a softer ride and more nuance to the brake peddle.

The M5 (really M8 at north of 160K) the least for track use, its big and if you re-calibrate your driving techniques and tune into is far more subtle feedback its can dance too. But lets be realistic, people arn't buying the M5 generally for track use. Most owner's of an M5 don't want to see their front end chewed up with stone chips, tire chunks and damage from racing. Those sticky tires kick up a lot of sand/stones. These cars are about looking good with the potential to go fast, especially in the right hands. Only very rich people would race one, but then they'd probably choose a Porsche GT3, GT-R, Z06, etc for their dedicated track car. Yes I know people who have apartments at the track and keep their cars there.

The other things I do consider for a race car, is room for sitting with a helmet on. Ease of installing a seatbelt harness as 5/6 point harnesses are required for most racing, and location of a fire extinguisher. I had mine mounted under/front of the passenger seat for an easy reach on my 550i.

All of these cars are fast on a track, on an F1 track with a good driver, the M8 is probably the fastest. But for the average ammeter the M2 is a good choice.

Me if I was going to do more track racing on high speed tracks and wanted to keep it affordable, an M2 comp (not current gen), or a Civic Type-R would be high on my list. Or a nice used Z28 (I like my V8's).

Were I doing high-speed racing, I would not choose any of these cars, but if I had to choose between an M4 or M2 Comp, I would take the M4, as the Comp is a bit more nervous with the shorter wheel base.

That said, the short wheel base makes it more of a driver's car, like the M3s of old. There is a reason the M2 has scooped up so many awards for having exciting handling, but exciting handling is not always the fastest way from point A to B (particularly for the average Joe).

This Autocar piece sums things up nicely where driver's cars are concerned.

[choppedliver]

Originally Posted by tsbrown

200lb weight difference is about right for the N63 (~500lb) vs the B58 (~300lb). The M550 also only comes only in Xdrive and more standard content so that’s where the rest of the weight is and roughly evenly distributed.

It didn't even occur to me that the 540i in question was RWD.

[choppedliver]

Originally Posted by Neusser

55% over the front axle (like on the 550) is quite understeery even at 6/10, and it is more typical of an Audi than a BMW.

I went looking for reviews and there are couple of comments about the M550i understeering;
- A little understeer may be felt on turn-in to mountain hairpins, but grip levels remain high and traction from mid-corner is exceptional.
- So equipped, the M550i gunned through turns with mega grip and only a modest amount of understeer
- surprising amount of understeer in tighter turns and little evidence of the rear-biased xDrive system

All of which says yes it will understeer somewhat in tight turns, but the xDrive and power. I've had mine understeer on a skid pan but in practice on Pilot Sport 5 tyres in the rain I've tried at 90 degree street corners to get it to understeer and at the speed limit of 50km/h there is no understeer. BTW that is a lot of speed on a 2 lane suburban corner.

To say it understeers from 6/10 is plain ridiculous to the point of laughable. And even the mild understeer in tight corners is out balanced by the point and shoot of the V8 torque and AWD system from the mid point of the corner.

[Gautam]

Originally Posted by Neusser

M550 EU "Leergewicht" 1885 kg, with 55% over the front axle= 1036

540i EU "Leergewicht" of 1670 kg, with 52% over the front axle (wagon is 50/50, ofc)= 868 kg

A difference of 168 kg or 370 pounds.

Now consider (again) that both cars run the same track and tire sizes.

For the former: Do I hear the sound of understeer?

Originally Posted by choppedliver

I stand corrected.

Not quite. His numbers are accurate, but he’s comparing the weight of the rwd 540i against the weight of the (awd) m550. The 540i xdrive slots in the middle, 65kg or 143 lbs higher than the rwd. https://www.press.bmwgroup.com/deuts...67658DE/377421

The 540i xdrive touring has the best distribution, but that’s also because it weighs in at 1860 kg. https://www.press.bmwgroup.com/deuts...25535DE/471542

[Knifeedge2k1]

Originally Posted by Neusser

You don't drive on the limit with people in the backseat. That said, there is a difference in handling when you have passengers in the back. This is basic physics.

A RWD car with a nice 50/50 weight distribution will actually benefit in some ways when loaded (in terms of balance). You get better traction and the front tires do less work. On the limit handling here is hardly a concern, however.

55% over the front axle (like on the 550) is quite understeery even at 6/10, and it is more typical of an Audi than a BMW. The balance of the 540 is enjoyable at any speed.

If you can feel understeer at 6/10ths there's somethign wrong with your car dude

[Neusser]

Originally Posted by choppedliver

I went looking for reviews and there are couple of comments about the M550i understeering;
- A little understeer may be felt on turn-in to mountain hairpins, but grip levels remain high and traction from mid-corner is exceptional.
- So equipped, the M550i gunned through turns with mega grip and only a modest amount of understeer
- surprising amount of understeer in tighter turns and little evidence of the rear-biased xDrive system

All of which says yes it will understeer somewhat in tight turns, but the xDrive and power. I've had mine understeer on a skid pan but in practice on Pilot Sport 5 tyres in the rain I've tried at 90 degree street corners to get it to understeer and at the speed limit of 50km/h there is no understeer. BTW that is a lot of speed on a 2 lane suburban corner.

To say it understeers from 6/10 is plain ridiculous to the point of laughable. And even the mild understeer in tight corners is out balanced by the point and shoot of the V8 torque and AWD system from the mid point of the corner.

It understeers in both the wet and dry at 6/10. It is progressive and safe, but dull as dishwater to drive.

Part of this is due to geometry (all series BMWs have a bit built in), but the inherent balance is poor, just like an Audi. The AWD exacerbates the situation; although it is a rear-biased system, it still sends too much power to the front for this chassis, which overwhelms the tires far sooner than it would on a RWD model. The M AWD parameters on the M5 are better here, but the entire M5 was reengineered to have higher limits and, critially, to deal with anvil over the front axle.

A rapid cruiser yes, a driver's car no.

[G30M]

Originally Posted by Knifeedge2k1

If you can feel understeer at 6/10ths there's somethign wrong with your car dude

my M550i with DHP can achieve higher corner speeds with more stability than my M340i which is basically a go kart.

but it feels like it doesn't want to do it, but because you asked it reluctantly does it. like my teenager. no idea what it's like to take corners without DHP but i sold my M340i after comparing taking corners with the M550i and it got destroyed by the M550i. it is that good at corners.

DHP = magic.

i think the handicap in the M550i that can be easily fixed, is the soft springs making it floaty.

can't be easily fixed - front geometry. when i turn the steering like say 1 degree in the m340i it will instantly change direction to the point where if you don't have perfect steering hands your passengers will throw up. the M550i - you really have to turn past say 10 degrees before the car will even turn. i guess that's 'understeer' but a lot of it is the front end & steering geometry that the F90 M5 CS for example has completely fixed (well if you believe the reviewers anyway. i do. every single one says the same thing)

things that can't be fixed - heavy V8, long wheelbase.

[Knifeedge2k1]

Originally Posted by G30M

my M550i with DHP can achieve higher corner speeds with more stability than my M340i which is basically a go kart.

but it feels like it doesn't want to do it, but because you asked it reluctantly does it. like my teenager. no idea what it's like to take corners without DHP but i sold my M340i after comparing taking corners with the M550i and it got destroyed by the M550i. it is that good at corners.

DHP = magic.

i think the handicap in the M550i that can be easily fixed, is the soft springs making it floaty.

can't be easily fixed - front geometry. when i turn the steering like say 1 degree in the m340i it will instantly change direction to the point where if you don't have perfect steering hands your passengers will throw up. the M550i - you really have to turn past say 10 degrees before the car will even turn. i guess that's 'understeer' but a lot of it is the front end & steering geometry that the F90 M5 CS for example has completely fixed (well if you believe the reviewers anyway. i do. every single one says the same thing)

things that can't be fixed - heavy V8, long wheelbase.

Contrary to popular belief stiff springs don't make you corner faster, soft springs are a good thing, soft = more mechanical grip. You want to run as soft as you can to handle bumps/ruts. Controlling roll via the heave springs is a losing proposition. Unfortunately with the M550i platform you can't easily change this without losing the compliance of the active sway bars, as far as I know no one makes an aftermarket upgrade that retains the adjustability (it's really complicated so I guess that's fair).

It's not geometry really that affects that turn-in effect you're talking about, it's the steering ratio. Important to note that steering ratio is also not handling, a fast rack will be sensitive but not neccesarily good handling. The deadspot in the middle when going dead straight is there deliberately to make it feel less jittery when cruising

The M5 has completely different hubs/suspension arms so yes the geometry is entirely different compared to the normal 5 series.

As far as I know though all the regular 5 series have identical front end suspension geometry, it will have different spring rates and stuff but the arms and hubs and what not are the same.

Changing the alignment and tire sizing will do a LOT to change turnin and limit handling characteristics

With X Drive changing tire sizing is a bit annoying though. You want to keep the front tire circumference between 100% - 101% of the rear tire circumference. All normal (non-m) 5 series xdrive are between 100.5% and 101% but on the 3 series some of them have square setups so 100%-101% is the "stock spec". You absolutely do NOT want to run front circumference smaller than rear circumference because that would basically mean you can't move any torque to the front*. No factory spec has a front which is greater than 101% of the rear but the higher this number is the more effective the xdrive will be at biasing torque to the front axle (at the expense of greater wear on the transfer clutches). I'd guess that going up to like 101.5% wouldn't be that bad but this isn't a parameter you can easily fine tune since tires come in specific set sizes.

275/35R19 Front
275/30R20 Rear
This would give 100.4% front/rear and a much bigger front contact patch (reduces understeer). This "should" fit but you might need different offset wheels for it. The M5 has 275 fronts and the wheel well is the same size but the steering axis might be slightly off so I can't really speak to how much or what needs to be done with regards to offset to make sure it is all kosher.

*xdrive has no center diff, it just uses a clutch linkage and the front/rear diffs run the same final drive so if you have a smaller front rolling circumference, when the clutches engage you're applying negative torque bias to the front and sending it to the rear, effectively engine braking the front and spinning up the rear even more

Add a bit of camber and take a bit of toe-in away from the front and you'll have a much more positive front end.

[G30M]

Originally Posted by Knifeedge2k1

Contrary to popular belief stiff springs don't make you corner faster, soft springs are a good thing, soft = more mechanical grip. You want to run as soft as you can to handle bumps/ruts. Controlling roll via the heave springs is a losing proposition. Unfortunately with the M550i platform you can't easily change this without losing the compliance of the active sway bars, as far as I know no one makes an aftermarket upgrade that retains the adjustability (it's really complicated so I guess that's fair).

It's not geometry really that affects that turn-in effect you're talking about, it's the steering ratio. Important to note that steering ratio is also not handling, a fast rack will be sensitive but not neccesarily good handling. The deadspot in the middle when going dead straight is there deliberately to make it feel less jittery when cruising

The M5 has completely different hubs/suspension arms so yes the geometry is entirely different compared to the normal 5 series.

As far as I know though all the regular 5 series have identical front end suspension geometry, it will have different spring rates and stuff but the arms and hubs and what not are the same.

Changing the alignment and tire sizing will do a LOT to change turnin and limit handling characteristics

With X Drive changing tire sizing is a bit annoying though. You want to keep the front tire circumference between 100% - 101% of the rear tire circumference. All normal (non-m) 5 series xdrive are between 100.5% and 101% but on the 3 series some of them have square setups so 100%-101% is the "stock spec". You absolutely do NOT want to run front circumference smaller than rear circumference because that would basically mean you can't move any torque to the front*. No factory spec has a front which is greater than 101% of the rear but the higher this number is the more effective the xdrive will be at biasing torque to the front axle (at the expense of greater wear on the transfer clutches). I'd guess that going up to like 101.5% wouldn't be that bad but this isn't a parameter you can easily fine tune since tires come in specific set sizes.

275/35R19 Front
275/30R20 Rear
This would give 100.4% front/rear and a much bigger front contact patch (reduces understeer). This "should" fit but you might need different offset wheels for it. The M5 has 275 fronts and the wheel well is the same size but the steering axis might be slightly off so I can't really speak to how much or what needs to be done with regards to offset to make sure it is all kosher.

*xdrive has no center diff, it just uses a clutch linkage and the front/rear diffs run the same final drive so if you have a smaller front rolling circumference, when the clutches engage you're applying negative torque bias to the front and sending it to the rear, effectively engine braking the front and spinning up the rear even more

Add a bit of camber and take a bit of toe-in away from the front and you'll have a much more positive front end.

That makes sense, I have no plans to dismantle the car to for firmer springs so that's good.

I'm not sure what alignment can be changed out of the box. Afaik only front toe and rear toe and camber can be adjusted.

I am now running 255 40 19 fronts stretched onto 9.5" rims so plenty of sidewall support and contact patch.

[Knifeedge2k1]

I'm surprised you didn't get a drive train error

What rear size are you running

[Knifeedge2k1]

Camber, toe and caster are all adjustable in the G30

[G30M]

Originally Posted by Knifeedge2k1

I'm surprised you didn't get a drive train error

What rear size are you running

255 40 19

[Knifeedge2k1]

Originally Posted by G30M

255 40 19

How have you not got a drivetrain error with such a big difference between your front/rear ?

[G30M]

Originally Posted by Knifeedge2k1

How have you not got a drivetrain error with such a big difference between your front/rear ?

sorry i typed wrong

they are 255 40 19 all round

did that because i didnt want the to have the fronts 1.1% larger with the 20" rft staggered, plus it was very bumpy

these tires have made the ride more compliant, less noisy, the downside is the rear end is now "loose". used to be super stable back end but now it moves around - eg when accelerating hard while turning, when driving straight on loose surface.

[Knifeedge2k1]

Originally Posted by G30M

sorry i typed wrong

they are 255 40 19 all round

did that because i didnt want the to have the fronts 1.1% larger with the 20" rft staggered, plus it was very bumpy

these tires have made the ride more compliant, less noisy, the downside is the rear end is now "loose". used to be super stable back end but now it moves around - eg when accelerating hard while turning, when driving straight on loose surface.

ah ok

Yeah a square setup will certainly kill off a lot of that factory built in understeer

[G30M]

Originally Posted by Knifeedge2k1

With tire differences and spec differences I wouldn't put too much weight on those numbers

The M550 clearly has better tires here (to be fair they do come with those tires so fair enough)

Whether the car has 4ws, active away bars, xDrive or not, Lsd or not, etc will have huge impact

Regardless though I doubt the M550 would be wildly understeer-y and the 540 a drift monster simply because of the weight distribution. If that was true there would be an extreme shift in limit handling and balance every time I have a couple people in the back seat of my car which obviously doesn't happen. Does it have an impact, sure, is it noticeable, perhaps, will it be massive, I doubt it.

It's also something that can be remedied by tire choices and alignment

Perhaps the xDrive limits your choices somewhat as you really need to maintain the stock rolling circumference ratio been the front and rear axle but it's not a huge dealbreaker

people do realise that weight distribution is a myth.
sure you can build a car exactly 50:50.

the moment you accelerate the car, depending on how hard you gas it, it's going to become lighter in front and heavier in the rear. which is why the american classic FR V8s will smoke the tires all the time.

in corners it's even more complex. pressing the brake or lifting off the throttle will change the weight distribution not only front to back but also side to side. that's how Max Verstappen gets his cars turned. he uses the steering wheel less than he uses his feet to turn his cars.

the moment you stomp on the brakes, it's going to move the weight to the front. it is this action that lightens the rear a lot, to the point where even FF cars will produce oversteer if you stomp on the brakes in corners.

according to Porsche, the ideal weight distribution is 40:60 for racing. for drifting, it's anywhere between 60:40 to 40:60. FR can drift. RR can drift. even FF can drift.