[spool twice]

my reasoning to ask the question is more to find out what is the true reason behind limiting it?

Heat?

Battery depletion reasons?

Motor RPM limitations?

I don't necessarily intend to get anywhere near the 140mph limit, nor do I care that it's limited there, it was to find the reasoning behind it.

[techwhiz1]

Originally Posted by spool twice

my reasoning to ask the question is more to find out what is the true reason behind limiting it?

Heat?

Battery depletion reasons?

Motor RPM limitations?

I don't necessarily intend to get anywhere near the 140mph limit, nor do I care that it's limited there, it was to find the reasoning behind it.

Probably a combination of motor RPM limitations (single speed) and energy consumption.

[spool twice]

Originally Posted by techwhiz1

Probably a combination of motor RPM limitations (single speed) and energy consumption.

Hopefully BMW will release more technical video's/specs like they did with the M3/M4's and highlight why they did this.

At any rate, I can't wait to pick mine up this is going to be a long 6-9 months...

[techwhiz1]

Originally Posted by spool twice

Hopefully BMW will release more technical video's/specs like they did with the M3/M4's and highlight why they did this.

At any rate, I can't wait to pick mine up this is going to be a long 6-9 months...

I can't wait either.
It's going to be a slow, painful and arduous wait....

[hotrod182]

Pretty impressive the i4 was just rated as one of the most efficient UK EVs available, especially with it's weight handicap.

https://insideevs.com/news/549870/uk...efficient-evs/

[spool twice]

Originally Posted by hotrod182

Pretty impressive the i4 was just rated as one of the most efficient UK EVs available, especially with it's weight handicap.

https://insideevs.com/news/549870/uk...efficient-evs/

I need to figure out how to calculate miles per kWh now

**edit** looks like it's just miles / total usable kWh of the battery = miles per kWh, so in this case 3.72 miles / kWh.

[Ken7]

Originally Posted by hotrod182

Pretty impressive the i4 was just rated as one of the most efficient UK EVs available, especially with it's weight handicap.

https://insideevs.com/news/549870/uk...efficient-evs/

I wonder if this was the 50 or e40 series. I’m pleasantly surprised at how well it did.

[Accident]

Originally Posted by spool twice

I need to figure out how to calculate miles per kWh now

**edit** looks like it's just miles / total usable kWh of the battery = miles per kWh, so in this case 3.72 miles / kWh.

It will get confusing when you hear someone with a Tesla talking about Wh/mi and someone in Europe with Wh/100km and you are trying to compare the units with your car showing mi/kWh

[bavarianride]

Originally Posted by Accident

It will get confusing when you hear someone with a Tesla talking about Wh/mi and someone in Europe with Wh/100km and you are trying to compare the units with your car showing mi/kWh

No worries, miles/kWh = 1/(kWh/mile), so it is an easy conversion.

And miles/kWh = (km/kWh)/1.6.

[spool twice]

Originally Posted by Ken7

I wonder if this was the 50 or e40 series. I’m pleasantly surprised at how well it did.

Likely the e40 since the M50 mile per kWh is less.

Originally Posted by bavarianride

No worries, miles/kWh = 1/(kWh/mile), so it is an easy conversion.

And miles/kWh = (km/kWh)/1.6.

mind blown

[techwhiz1]

i4 listed as one of the most efficient EV's

https://www.bmwblog.com/2021/11/23/bmw-i4-efficiency/

[spool twice]

I wonder what the weight difference are between the standard 19" vs 20"? And also the tire.

That reduction in range would also lead me to believe there would be a reduction in acceleration during the course of wide-open pedaling. In other words, as speed increases, so would the time to speed gap between a 19" vs 20" equipped car at 100% pedal.

Only time will tell.

[Sportstick]

Originally Posted by spool twice

I wonder what the weight difference are between the standard 19" vs 20"? And also the tire.

That reduction in range would also lead me to believe there would be a reduction in acceleration during the course of wide-open pedaling. In other words, as speed increases, so would the time to speed gap between a 19" vs 20" equipped car at 100% pedal.

Only time will tell.

Assuming the 20s do weigh more than the 19s, a reasonable assumption, they deteriorate range, acceleration, braking distance, and ride harshness...all the factors of trying to manage a rotating mass. OTOH, some people think they look better.

[techwhiz1]

Originally Posted by Sportstick

Assuming the 20s do weigh more than the 19s, a reasonable assumption, they deteriorate range, acceleration, braking distance, and ride harshness...all the factors of trying to manage a rotating mass. OTOH, some people think they look better.

They (20") would not increase braking distance. The larger contact patch would allow more grip at the edge where the ABS kicks in. The 20" is less likely to cause the ABS to activate

Also for acceleration, if the 19" tire slips that means you are wasting power.

It is more complicated than just the 20" weight is greater.

[Sportstick]

Originally Posted by techwhiz1

They (20") would not increase braking distance. The larger contact patch would allow more grip at the edge where the ABS kicks in. The 20" is less likely to cause the ABS to activate

Also for acceleration, if the 19" tire slips that means you are wasting power.

It is more complicated than just the 20" weight is greater.

I can’t give you proof on a forum and I’m not a vehicle development engineer. But, when we were doing vehicle evaluations for new programs at the proving grounds, I learned from the development engineer experts who do know the actual cause and effect. We were in a decision meeting regarding 20s for a new program application and they laid out all the facts as to the effect of a larger mass and how they are dynamically negative. They had responsibility for meeting fuel economy goals as well and showed the deteriorating effect by wheel size. I consider them as qualified experts on the matter. The bottom line quote from them I still remember was, “Design Office loves large wheels. Engineers don’t.”

[techwhiz1]

Originally Posted by Sportstick

I can’t give you proof on a forum and I’m not a vehicle development engineer. But, when we were doing vehicle evaluations for new programs at the proving grounds, I learned from the development engineer experts who do know the actual cause and effect. We were in a decision meeting regarding 20s for a new program application and they laid out all the facts as to the effect of a larger mass and how they are dynamically negative. They had responsibility for meeting fuel economy goals as well and showed the deteriorating effect by wheel size. I consider them as qualified experts on the matter. The bottom line quote from them I still remember was, “Design Office loves large wheels. Engineers don’t.”

There are plenty of reasons where 20" wheels with nothing else changed can; but not will have a negative effect.

Unsprung weight can be greater on the 20".
That translates into more rotating mass.
But you will also have a larger contact patch if the 20" is wider as is this case.

The swept area is greater on the brakes because a larger disk is used on the 20".

There are plenty of variables that we don't know and a blanket statement saying the 20" wheels will have poorer performance just isn't accurate

We will see when the actual numbers come out. Until then it's speculation.

I can tell you my stock 335i with factory brakes and 18" wheels didn't come close to the 19" wheels an inch wider, with 4 piston Brembos and a rotor that was an inch larger in diameter. Couple that with an E90 M3 brake master cylinder and my 335 modded would launch your eyeballs before we got impeding lockup with ABS.

Too many variables to call it on the M50 without real numbers.

[bavarianride]

Originally Posted by techwhiz1

Unsprung weight can be greater on the 20".
That translates into more rotating mass.
But you will also have a larger contact patch if the 20" is wider as is this case.

The swept area is greater on the brakes because a larger disk is used on the 20".

Do note bigger rims + bigger rotors/disks = more rotating mass, which affects both acceleration and deceleration.

Wider (rear) tires usually come as staggered, and then tends to induce understeer.

Track folks usually go with small rim + square/neutral setup to maximize performance.

[techwhiz1]

Originally Posted by bavarianride

Do note bigger rims + bigger rotors/disks = more rotating mass, which affects both acceleration and deceleration.

Wider (rear) tires usually come as staggered, and then tends to induce understeer.

Track folks usually go with small rim + square/neutral setup to maximize performance.

Larger rims are needed to cover larger brakes.

Rule number one in cars is that brakes must stall the motor at any speed. The majority of braking force is at the front. Ask Toyota about that failure.

So you go with the smallest wheel that will fit over the brakes and a wide enough tire to guarantee you won't burn the tires up. A 370mm rotor is 14.5" in diameter before you add caliper. you need an 18 or 19 inch wheel clear

Square setups work fine on street cars that are tracked, but I haven't see a square setup on anything racing in F1, ALMS, European Touring Car, or any other series I follow.

Even with a staggered setup you can dial out understeer.

It's more complicated that just rotating mass.
You need to take into swept area for brakes, heat capacity, rotating mass, etc.... Just because you make the wheel larger does not mean lower performance is all I'm saying.

[spool twice]

On the MY3 perf, some guys switch over to the smaller wheels/tires and see a rather good amount of range.

Isn't the Dual Motor version with the Acceleration Boost quicker as speed rises as compared to the Performance as well? Because of the smaller brakes and tires and probably other factors.

Either way, can't wait to see comparisons and get definitive answers.

[bavarianride]

Originally Posted by techwhiz1

Square setups work fine on street cars that are tracked, but I haven't see a square setup on anything racing in F1, ALMS, European Touring Car, or any other series I follow.

I think in F1 and the likes the staggered wide tires also have low psi (say, 10-15) to maximize contact patches,while street cars + tires (like BMWs) do not run that low per factory spec.

From my understanding, bigger rims + staggered wider tires on street cars are mainly aesthetics. You are correct that bigger rotors have higher heat capacity, but bigger rotors require bigger rims, so there are tradeoffs.

[hotrod182]

The good news is that Matt Watson's 3.62 sec 0-60 time was with 20" wheels I believe. (And possibly his travel gear in the back, as he was in the middle of a road trip). So hopefully with 19" wheels, we will see even quicker numbers.

[spool twice]

Originally Posted by hotrod182

The good news is that Matt Watson's 3.62 sec 0-60 time was with 20" wheels I believe. (And possibly his travel gear in the back, as he was in the middle of a road trip). So hopefully with 19" wheels, we will see even quicker numbers.

Yes, and his street surface may not have been the best either due to the rain in the area previously. I think with a 1 ft rollout and 19" wheels it may trim it down .3-.4 seconds once it hits official test results.

It's too bad he couldn't do the test again with a smaller SOC, but given the video you posted of the i4 accelerating 120+ kph, it seems to be rather strong still.

I'm going to predict:

0-60 3.2
1/4 mile 11.4@123-124mph

Probably being optimistic, but perhaps not? BMW historically has sandbagged their acceleration time and I'm thinking this car will align itself right between the RWD M3/M4 and x-drive M3/M4 in acceleration #'s.