M diff baffles me

M

mad4slalom

Senior member
Out in the mc for a blast last night on my own so a bit of spirited driving here and there on quiet open cornish roads, epic fun. I know i have posted this query before but again, am almost convinced that there is still some electronic wizardry afoot even with dsc off. surely others must have felt the same feeling that something is being reigned in when accelerating out of a corner.There are four possible scenarios that could :? cause this and would be interested in other "M" Owner's thoughts. 1,track mode is enabled (which afaik is'nt) . 2,the M diff is preventing slip electronically (which is its Job) and is therefore actually intervening so not really allowing the driver full control. 3, my dsc is not actually switching off even though the light is activated. (this is not the caseI'm sure, as with dsc on, it Really really interupts the speed and revs) 4, my new pilot supersports are sooo damn good that 338bhp just isnt enough to unstick them ! , or am I just not trying hard enough ? I am really aware when hard throttling out of a corner the diff engages and the back squats and grips. obviously I dont drive on the road as some people do on a track ,so maybe the revs just arent high enough to break it free , and when i think about it the rear wheels need to be spinning for something to slide , and with pss's the price they are I wont be doing that too often.
 
When DSC is off it's everything off in Z4M's. The reason you can't seem to be able to unstick the rear is due to the high traction of the Michelins. Especially with some heat in them (after a few miles of spirited driving for example).
My Yokohama AD08's are the same. Once they warm up you have to really be trying in order to slide them!
 
I'm pretty sure the diff is just very, very good at keeping the car going forwards instead of sideways. And good tyres will help. I still really want to go on an airfield high performance when I have the £, just to find out how far you can push it... And know what it feels like when it's going to let go.
 
Have you tried it in the damp or wet?

When the yellow dsc triangle is permanently displayed there are no aids / stability braking etc.
Probably your super sticky pss, but on damp roads they slip very easily.
 
It's the tyres - and they heat up quite quickly even in cold weather.

I had the same concerns when I went drifting with them.

Took so much more effort to unstick the PSS than the OE Contis or even the PS2s.

Probably the only downside to the PSS - less 'fun' to be had unless you're going very quickly :P

The Michelin tyre guys at my last Oulton Park track day (plus instruction by Tim Harvey) recommended taking 0.5 to 1 PSI out after I'd done a couple of laps in greasy conditions.
 
As a newbie to the M & the diff & I too am a little perplexed & have begun to wonder just what it takes to worry the back end into letting go :? .
I'm at ease now with the power delivery & the Sport button is on the whole time (DSC i have not disable as yet :cry: ) but whilst i can get the traction light to flicker accelerating out of certain bends it still feels nowhere near about to slide out from under me ?
I am also on Michelin rears
 
The M diff is great with DSC off..

Locks instantly and is controllable..... Try sticking some cheaper rubber on a set of old M3 wheels and go out for a blast and see how it feels..
 
Z4M-2006 said:
The M diff is great with DSC off..

Locks instantly and is controllable..... Try sticking some cheaper rubber on a set of old M3 wheels and go out for a blast and see how it feels..
Click to expand...

So next move is more miles with DSC off :?
Not that i'm wanting sideways action i just like to get a feel for a car's let go limit
 
I've got track mode coded , and with Michelins have had the rear end unstick in the dry once or twice without really trying :| Track mode keeps an element of stability control to try and reign it in past a certain yaw angle, but gives the car freedom in a straight line. The way it gets power down compared to the e-diff feels amazing though!
 
Silly question but have you switched the DSC fully off? The single press will give you a bit more play before pulling you in, but you won't get the back end really out until you've fully switched it off by pressing and holding the button...

Except for the wet it's very unlikely you'd be able to feel anything moving about with the TC left completely on either... It cuts power and applies the rear brakes to prevent a slide do you can have the throttle pinned and it won't let go...
 
Ed Doe said:
Silly question but have you switched the DSC fully off? The single press will give you a bit more play before pulling you in, but you won't get the back end really out until you've fully switched it off by pressing and holding the button...

Except for the wet it's very unlikely you'd be able to feel anything moving about with the TC left completely on either... It cuts power and applies the rear brakes to prevent a slide do you can have the throttle pinned and it won't let go...
Click to expand...

only 1 press needed in the m :thumbsup:
 
I think DSC manages all four brakes, not just the rears...though I could be wrong.
 
thanks for those opinions re the grippyness of the tyres, thinking about it, i could have a nice controllable, slightly out of line,moment easily, in the dry, up mawgan porth hill with the older goodyear eagles :driving: only everhave dsc on if its really greasy.otherwise its always off. cant see why anyone would use it as so over nannying. some say they are afraid of loosing the back end but the diff seems more than adequate at keeping things under control. :thumbsup:
 
mr wilks said:
As a newbie to the M & the diff & I too am a little perplexed & have begun to wonder just what it takes to worry the back end into letting go :? .
I'm at ease now with the power delivery & the Sport button is on the whole time (DSC i have not disable as yet :cry: ) but whilst i can get the traction light to flicker accelerating out of certain bends it still feels nowhere near about to slide out from under me ?
I am also on Michelin rears
Click to expand...
switch it off mr wilks, it really comes alive and shows how over nannying the dsc is, surprising that bmw M devision for all their expertise fall short on aspects of the z4m. such as the dsc , the suspension and the over servo'd brake pedal when initially pressed. :headbang:
 
mad4slalom said:
mr wilks said:
As a newbie to the M & the diff & I too am a little perplexed & have begun to wonder just what it takes to worry the back end into letting go :? .
I'm at ease now with the power delivery & the Sport button is on the whole time (DSC i have not disable as yet :cry: ) but whilst i can get the traction light to flicker accelerating out of certain bends it still feels nowhere near about to slide out from under me ?
I am also on Michelin rears
Click to expand...
switch it off mr wilks, it really comes alive and shows how over nannying the dsc is, surprising that bmw M devision for all their expertise fall short on aspects of the z4m. such as the dsc , the suspension and the over servo'd brake pedal when initially pressed. :headbang:
Click to expand...

ps, dont get me wrong, I still absolutely love this car !!!
 
I don't think the brakes are too bad actually, though they do still take me by surprise sometimes when I lift off quickly whilst accelerating hard and go to brake, as they're primed in those circumstances to speed up the response. Logical as if you are in that situation it's likely something unexpected has caused you to lift and brake. At other times it's just about having a feel for them, at least in my case.

The suspension I can't really comment on as I've probably not pushed it hard enough, but I guess if I make changes I'll notice it and I know from many posts it isn't ace.

As for the DSC, a large proportion of drivers of the cars won't be driving them as they can (and should ?) be - it's very deliberate I reckon, to make the car more usable every day, as the M division know exactly what they are doing. Which is proven when you switch it off and you're being given everything they've magically created, but you still stay on the road :D
 
mad4slalom said:
Out in the mc for a blast last night on my own so a bit of spirited driving here and there on quiet open cornish roads, epic fun. I know i have posted this query before but again, am almost convinced that there is still some electronic wizardry afoot even with dsc off. surely others must have felt the same feeling that something is being reigned in when accelerating out of a corner.There are four possible scenarios that could :? cause this and would be interested in other "M" Owner's thoughts. 1,track mode is enabled (which afaik is'nt) . 2,the M diff is preventing slip electronically (which is its Job) and is therefore actually intervening so not really allowing the driver full control. 3, my dsc is not actually switching off even though the light is activated. (this is not the caseI'm sure, as with dsc on, it Really really interupts the speed and revs) 4, my new pilot supersports are sooo damn good that 338bhp just isnt enough to unstick them ! , or am I just not trying hard enough ? I am really aware when hard throttling out of a corner the diff engages and the back squats and grips. obviously I dont drive on the road as some people do on a track ,so maybe the revs just arent high enough to break it free , and when i think about it the rear wheels need to be spinning for something to slide , and with pss's the price they are I wont be doing that too often.
Click to expand...


Watch this https://www.youtube.com/watch?v=CIH0V8pg8jk to see the difference in performance between an open diff, one with 25% LSD and the BMW M differential. The video showing the M diff pulling away on the rollers uphill is particularly impressive, especially when the right rear tyre suddenly gets its share of the grip once the tyre gets on tarmac. The high grip levels from your PSSs just add to the overall mechanical grip.

If you're wanting more rear end "action" you should've kept your Z3M. :P If you like a lot of sideways action, get a kart and take it on track with slick tyres in the wet; that's what I do. :thumbsup:
 
thanks exdos , epic video. the z3 mr looks to be about 3 to 4 k more now than when i sold it two years ago :headbang: but was time for a change,no regrets but yes had a v hairy moment in that when i went in to a corner too fast and lifted quickly :cry: !! much better when i learned slow in fast out ! great fun. have done a couple of kart gp,s won the first one with tight overalls 5 days after a vasectomy :rofl: sore ! second one came 8th out of 24 but couldnt get my head round how a friends 16 yo daughter was 6th , wondered if she knew about racing lines, apexes and trail braking which i am sure she didnt, or if she was just lighter or in a better kart or was she just a natural driving god :cry: :thumbsup:
 
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