RE: BMW M340i xDrive prototype: Driven

RE: BMW M340i xDrive prototype: Driven

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Discussion

kambites

67,461 posts

220 months

Thursday 13th December 2018
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J4CKO said:
kambites said:
It's all a bit rubbish anyway really; manufacturers love spouting out ever great torsional rigidity figures for their cars but all modern tin-top cars are so far into diminishing returns that it's pretty much irrelevant IMO. On road tyres anything over about 15000nm/deg/tonne is enough that I can't feel any difference from going further.
Always impresses me how solid and stuff car bodies are now, I remember older cars that used to twist noticeably as you jacked them up, you noticed it upon opening doors, Mk2 Golfs were bad, 5 doors worse than 3 doors for obvious reasons, but the one that was worst was my 944 cab, scuttle shake was pretty bad.
Indeed, although I think it's been driven by safety more than dynamics. Modern safety cells are extremely strong.

nickfrog

20,871 posts

216 months

Friday 14th December 2018
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Ares said:
I agree. One of the reasons I walked past the M3 on favour of the Alfa was it was too stiff. Too uncompromising.
I think they were talking about the torsional rigidity of the chassis (as in how much nm it takes to get 1 degree of flex) not the how stiff the kinematics are set up.

Wills2

22,667 posts

174 months

Saturday 15th December 2018
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PorkInsider said:
C.MW said:
I understand that to defend your fond memories of a certain car, you can of course go as far as to say someone else's experience is nonsense. Yea, it's indeed PH here. May be you're right and your M3 is stiff as hell and all that, but everything is discussed in relative terms here so drive it back to back with its competitors and you will find out. If you don't bother to do so, do some google research and count how many reviewers criticised the car for not having enough feel. A fact remains a fact.

Wills2 said:
Huskyman said:
C.MW said:
I hope they fixed the weak chassis from the F30. Yes it was light, but it wasn't rigid enough to form the proper basis for the full-cream M variants and as a result the M3/M4 suffered numb steering and general lack of feedback through every touch point. The heavier competitors like the RC-F and AMG C63 were a lot better in that regard. If you can't make it light AND rigid, I suggest you make it rigid first and go from there; a rigid structure is a must for any true sports cars.

Edited by C.MW on Wednesday 12th December 04:43
Could you qualify this statement please? I cannot find any info on the AMG C63?
The figure F30 stands at 29300NM per degree and 40000 for the F80 M3, That’s more rigid than a carbon tubbed car like the Carrera GT.
I test drove an F80 and one thing it didn’t feel like was sloppy or imprecise.
He can't I've just sold My F80 m3 after 90,000 miles in 3 years it was the most rigid and stiff car I've had, the front end was as sharp as knife, he's talking nonsense but this is PH.

Edited by C.MW on Wednesday 12th December 23:18
Have you changed your mind about stiffness and moved onto something else now?

Anyone who thinks that an F8x has a ‘weak chassis’ and ‘[isn’t] rigid enough’ needs to lay off the crack pipe for a while. The C63 is absolutely nowhere near it, in terms of stiffness. Just absolutely nowhere near.

The F8x has plenty of faults but lack of rigidity is definitely not one of them.

https://www.youtube.com/watch?v=8CJ6IwVzV-A#t=10
Indeed, the M3 was a flawed car (but most could be solved) but to point to its chassis rigidity as one of them is laughable....



Julian Thompson

2,489 posts

237 months

Saturday 15th December 2018
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There seems to be a tremendous amount of confusion here - this is how I see it from my perspective:

First of all, electronic calibration of any form of stability control isn’t part of a chassis stiffness discussion. Switch that off because it’s put there by the insurance companies.

The actual physical chassis of the M3/4 is as rigid, corner to corner and back again, as any of its competitors and more rigid than many fine handling cars from the past. I shan’t attempt to put numbers on it because I don’t have them but each iteration of a car tends to boast that chassis rigidity has increased series on series.

The tuning of the suspension in the M3/4 is a decent compromise with some damping adjustment from the cockpit. The car wears rubber band tyres with little sidewall and you can tell.

As most have intimated, the front end is very pointy once you get it locked in to a turn.

The flaw with the M4 (assume the M3 is the same) is that around the centre the steering feels “sticky” - the car wants to keep going exactly in the direction it is already going. It doesn’t have fingertip delicacy for small corrections of the wheel. That means you have to put in a non linear effort to turn the wheel in the first place against that stiction. This is most noticeable and wearing, ironically, on motorways.

As an additional consequence/symptom, the steering feels quite dead at modest pace. This, I believe, has more to do with the PAS system than anything else. It’s a symptom I’ve felt before in some other cars that have eschewed hydraulic PAS.

I believe that it would be possible to garner an improvement by reprogramming the PAS system, and/or by taking a close look at the wheels and tyres and detail suspension geometry.

I don’t believe that you would need to take a look at any form of stiffness to eradicate these tuning issues.

anonymous-user

53 months

Saturday 15th December 2018
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Deficiencies in steering/suspension are highlighted in the M3/4 specifically, because the chassis is so rigid, there is no place for them to hide.

moffat

1,020 posts

224 months

Monday 17th December 2018
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It's disappointing the the PPF is robbing the M340i of 14hp and a lot of sound. Listen to a 40i with the M Power and Performance Sound Kit (remap to 360hp and a cat back switchable exhaust) and you will see what I mean. I'm also running MP4S's which most owners tend to move to, to get rid of the dreaded Pirelli Runflats!

For me running a 440i with MPPSK the xDrive is adding weight and a 14hp increase isn't enough. However, I'm encouraged by the improvements to the handling and steering so that will prove interesting.

I also eagerly await the new M440i and hope that there is an LSD RWD option.... and maybe the new 4 series will be a little better looking that the new 3er too.

HighwayStar

4,216 posts

143 months

Monday 17th December 2018
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moffat said:
It's disappointing the the PPF is robbing the M340i of 14hp and a lot of sound. Listen to a 40i with the M Power and Performance Sound Kit (remap to 360hp and a cat back switchable exhaust) and you will see what I mean. I'm also running MP4S's which most owners tend to move to, to get rid of the dreaded Pirelli Runflats!

For me running a 440i with MPPSK the xDrive is adding weight and a 14hp increase isn't enough. However, I'm encouraged by the improvements to the handling and steering so that will prove interesting.

I also eagerly await the new M440i and hope that there is an LSD RWD option.... and maybe the new 4 series will be a little better looking that the new 3er too.
When the 4 series arrived BMW said they would begin to move it away from the 3er, make it more individual. Not just a 3 series coupe. They are have said we should see more of that with the new 4er so it will be interesting to see what they serve up.