Why doesn't the M4 have 12in wide rears?

[Sae]

Caught a bmw m4 vs 911 video the other day, at one section the 911 shows more high speed grip, where the M4 starts to breaks into a slide and hence loses time... but isn't this just a lack of grip.

The porsches are legendary for handling so the marketing goes, but from BMWs perspective, why doesnt the M3/M4 not have 12in/300 section rear rubber? It surely has enough power to burn and probably enough smart suspension tech to give it decent handling with bigger rubber and therefore more grip?

Not sure if already been discussed, but thought it be worth throwing it out into the auto-ether?

 

[StevenH72]

Not a bad point. One frustration with mine is that it's breaks traction very easily. Fun, but frustrating at times.

40-45mph, WOT in 3rd will spin up the rears significantly. It does struggle to put the power down at times. This is still during my running in period, I've not experienced upchanges from 7k yet!!

 

[Bing]

Bet it's a fuel economy thing... Ridiculous, I know...

 

[sars]

It may be a pressure/contact patch thing, the 911 maybe has greater mass at the back, overall it's lighter but the M4 will have 50/50 balance.

 

[StevenH72]

Sars, do you think slightly lower pressure would make an improvement?

 

[Sae]

It may be a pressure/contact patch thing, the 911 maybe has greater mass at the back, overall it's lighter but the M4 will have 50/50 balance.

Not quite sure what you mean, yes the 911 is rear weighted so requires more contact patch for the respective same rear tyre pressure, however, if you increased the m4 rear contact patch, I would have thought even more grip/friction at the rear, yes slightly less economical but enhanced grip levels - but we're talking wrt grip and performance

 

[Sae]

Sars, do you think slightly lower pressure would make an improvement?

We're the Michelin sport cup 2 tyres an option on the M4 at time of purchase?

 

[sars]

It may be a pressure/contact patch thing, the 911 maybe has greater mass at the back, overall it's lighter but the M4 will have 50/50 balance.

Not quite sure what you mean, yes the 911 is rear weighted so requires more contact patch for the respective same rear tyre pressure, however, if you increased the m4 rear contact patch, I would have thought even more grip/friction at the rear, yes slightly less economical but enhanced grip levels - but we're talking wrt grip and performance

Not that it requires a greater contact patch, rather it makes better use of a larger contact patch because it has more mass over the rear wheels, so if you put wider tyres on the M4 the force exerted over the contact area (Pressure) would be reduced which wouldn't necessarily give you extra mechanical grip.

and Steve, you could try dropping the pressures down to their bottom setting and see if that helps, just look what 1.5 Psi did to F1 tyres

 

[Sae]

Right oh, So for example you'd need extra rear downforce to take advantage of the extra contact patch...

 

[StevenH72]

Sars, do you think slightly lower pressure would make an improvement?

We're the Michelin sport cup 2 tyres an option on the M4 at time of purchase?

No, and frustratingly UK spec M4's are no longer clad with Michelin Pilot SuperSports, but rather Conti's.

I'll try to reduce tyre pressures slightly and will report back.

 

[sars]

Right oh, So for example you'd need extra rear downforce to take advantage of the extra contact patch...

Of course, again look at F1, if you don't go fast enough the aero doesn't work and you have no grip

 

[hopz121]

Sars, do you think slightly lower pressure would make an improvement?

We're the Michelin sport cup 2 tyres an option on the M4 at time of purchase?

No, and frustratingly UK spec M4's are no longer clad with Michelin Pilot SuperSports, but rather Conti's.

I'll try to reduce tyre pressures slightly and will report back.

The one we tested when the car was first released had Supersports on it, what tyres are they currently fitting StevenH72?

 

[MrPT]

It'll be as much about chassis/suspension dynamics as mechanical grip from the tyres. This is where the 911 has decades of refinement. Just look how widely it is praised for turn-in sharpness and adjustability - doesn't make any sense when you take the fundamental concept of the car. The M4 has a ludicrous amount of power for a 1400kg, RWD saloon, and I'm sure others are right when they say that refinement/fuel economy/packaging seriously complicate things for BMW.

 

[Sae]

The thing is, it's well accepted that semi slick track tyre upgrade will help the same car grip better and hence faster on say a track, so whether you put cup2 tyres on the m4 or any other big m car, or put wider cup 2 tyres on same car that has the potential to need the extra grip, ie has enough power to overcome the associated rolling resistance at the higher speeds, surely it would benefit but yes balance has to be taken into account, don't know what a 265 section front cup2 tyre would do to handling feel - probably none because it's electric anyways...

 

[StevenH72]

We're the Michelin sport cup 2 tyres an option on the M4 at time of purchase?

No, and frustratingly UK spec M4's are no longer clad with Michelin Pilot SuperSports, but rather Conti's.

I'll try to reduce tyre pressures slightly and will report back.

The one we tested when the car was first released had Supersports on it, what tyres are they currently fitting StevenH72?

As I understand due to Michelin struggling to meet demand Conti Sport Contact 5's have been used in lieu. Not sure if all cars come with Contis or whether it's hit and miss. I might speak with BMW to query, would much rather have MPSS's.

 

[Paulwirral]

Because if it had loads of grip it would be called an audi rs5 , bmws have always been about the drive . Stick big tyres on almost anything and it will grip but still be crap to drive .

 

[LeeZ4MR]

The M4 has a ludicrous amount of power for a 1400kg, RWD saloon,

That would be very nice if the M4 only weighed 1400kg its 1500kg plus but still lighter than the previous model though which does make a nice change.

When Autocar road tested it they weighed it in at 1610kg which is still a little lighter than the E92 M3.

 

[MrPT]

The M4 has a ludicrous amount of power for a 1400kg, RWD saloon,

That would be very nice if the M4 only weighed 1400kg its 1500kg plus but still lighter than the previous model though which does make a nice change.

When Autocar road tested it they weighed it in at 1610kg which is still a little lighter than the E92 M3.

You are right. I'll revise my statement... it has a ludicrous amount of power for a land-based vehicle.

 

[LeeZ4MR]

The M4 has a ludicrous amount of power for a 1400kg, RWD saloon,

That would be very nice if the M4 only weighed 1400kg its 1500kg plus but still lighter than the previous model though which does make a nice change.

When Autocar road tested it they weighed it in at 1610kg which is still a little lighter than the E92 M3.

You are right. I'll revise my statement... it has a ludicrous amount of power for a land-based vehicle.

:lol: