M40i Handling

[Boyo]

Overall I am delighted with my M40i, however, under hard acceleration the rear feels like it's about to let go. The car is on its factory supplied Michelin Pilot Super Sports with only £3K on the clock and running exactly on the recommended pressures. Even in warm dry conditions things feel a unstable. I appreciate I was a little spoilt with regard to handling with my Caymans, but I wonder if anyone who has/had an M40i can share their thoughts on the matter.

[tomscott]

When you say let go do you mean loose traction? Oversteer? Or that the ride is uneven/twitchy

If oversteer then its standard BMW M/Mlite behaviour?

Thing I really dislike with the cay/box is that there is no movement at all, it sticks and I found it super predictable and a bit boring. My dad has a 981 GTS and its lovely but so predictable I dont really enjoy driving it as much as the Z.

Depends I suppose on personal preference on driving dynamics.

I put PS4S on my Z4M and honestly its ruined the experience for me because it just sticks all the time have to press it pretty hard for it to break traction even with traction control off. Then I suppose PS4S are designed with cars that have twice the power of the Z4M so PS4S is probably overtyred.

[Boyo]

When you say let go do you mean loose traction? Oversteer? Or that the ride is uneven/twitchy

If oversteer then its standard BMW M/Mlite behaviour?

Thing I really dislike with the cay/box is that there is no movement at all, it sticks and I found it super predictable and a bit boring. My dad has a 981 GTS and its lovely but so predictable I dont really enjoy driving it as much as the Z.

Depends I suppose on personal preference on driving dynamics.

I put PS4S on my Z4M and honestly its ruined the experience for me because it just sticks all the time have to press it pretty hard for it to break traction even with traction control off. Then I suppose PS4S are designed with cars that have twice the power of the Z4M so PS4S is probably overtyred.

It loses traction and feels like the tail end is going to step out, very similar feeling to the M140i which I owned. Personal preference but I found the 718 Cayman handling sublime and suited my limited driving skills.

[B21]

Factory supplied variant of MP4S not noted as the best ..Conti SC7s are a better tyre..

A very torquey B58 engine will cause difficulties to any rear wheel drive car..

I assume the electronically controlled LSD is behaving itself…?

[Boyo]

Factory supplied variant of MP4S not noted as the best ..Conti SC7s are a better tyre..

A very torquey B58 engine will cause difficulties to any rear wheel drive car..

I assume the electronically controlled LSD is behaving itself…?

Yep LSD is fine. Have read Conti SC7's are a better package but at this stage don't really want to incur the cost of a new set of boots.

[B21]

Factory supplied variant of MP4S not noted as the best ..Conti SC7s are a better tyre..

A very torquey B58 engine will cause difficulties to any rear wheel drive car..

I assume the electronically controlled LSD is behaving itself…?

Yep LSD is fine. Have read Conti SC7's are a better package but at this stage don't really want to incur the cost of a new set of boots.

No problem…I think it’s generally acknowledged that the European version of the B58 fitted to the G29 is very ‘healthy’ for its numbers..

My 400 BHP version of my 35is could easily over power the MP4S if provoked..the SC7s are markedly better for the more powerful RWD cars..

[Nanu]

Enjoy pushing it to it's limits. That will burn a few thousand miles off the rears and then replace them with the tyre of your choice

[PSQ777]

Factory supplied variant of MP4S not noted as the best ..Conti SC7s are a better tyre..

A very torquey B58 engine will cause difficulties to any rear wheel drive car..

I assume the electronically controlled LSD is behaving itself…?

My car is the same. I want the back to be a little less lively. Don't get me wrong, it's really well controlled but I would like a little more traction in day to day driving in less than perfect conditions. Tyre choice I suspect is the main factor.

[q96169we]

My answer might be irrelevant here as it's my experience and my analysis on track. When I exercised the tyres (star marked MPSS from factory) to reach 40+ degree or even higher, I found the tail extremely stable. I can confidently increase the throttle input when exiting corners. But, our B58 has 500NM of torque which can break the tracking easily if my throttle only have two positions (on and off). One thing I noticed is about the E-Diff. It behaves more like a electronically controlled diff lock than a limited slip diff. Maybe to preserve the fraction material or heat management, its control logic locks up the diff more aggresively, which means less slip between two wheel is allowed. When it locks up, the inside rear wheel may jump a little bit (basically, break the grip then regain the grip then lost again) to keep the same rotational speed as the outside wheel. Translate this to subjective feelings, it's like the tail wants to jump out in a pulse maner especially when exiting slow corners. For me, once I understand and get used to this behaviour, I try to modulate the throttle input based on the grip feeling on the outside wheel (when outside wheel starts to slide, it's real slide and feels totally different than the pulse jump of the inside wheel), the rear can put down much more power than I expected and it's quite stable and predictable.

But, on the other hand, I find the MPSS is almost useless when it's only like 30 degree or below, if compared to its full capability when temp is 40+ degree. I had multiple moments when I began the afternoon section after lunch and the tyres were cooled down, I slided out at the first corner on track despite I've been very careful and slow, knowing the tyres were cold.

[buzyg]

Good to read comments on the M40I handling.

[PSQ777]

Very useful information. Thanks. I'll pay more attention now to the slip behaviour to see if I can feel the diff working as you describe it.

[ori]

The standard tyres in the m40i are the first tyres that I have experienced that require so much warmth to have full grip. Pulling away fast is almost impossible until they are proper heated. Will look at changing them next round.

[q96169we]

The standard tyres in the m40i are the first tyres that I have experienced that require so much warmth to have full grip. Pulling away fast is almost impossible until they are proper heated. Will look at changing them next round.

Exactly. MPSS is useless when below 30 degree. Between 30-40 degree, you can feel the tyres are waking up and above 40, its grip level is actually quite amazing for a non-slick non-track focused tyre. Also, the heat degradation is also quite low. In contrast, I did a trackday last year using the p-zero (PZ4-LS) on the z4 m40i. The overall grip level is much lower and the heat degradation is very noticable after 60 degree, and it actually heat up much quicker than the MPSS.