DSC intervening with square winter setup

[CanAutM3]

Originally Posted by RSXDC5

You are always so argumentative in your posts, I bet you are a real pleasure to be around in the real world...eeesh.

For what it’s worth the DSC does adapt, as for the time it takes to do so, it’s short enough and has never been an actual issue.

Seems like our experiences with DSC differ.

I am just posting my experiences for the collective knowledge. Having debates is the whole point of a forum. If my posts annoy you, just ignore them.

[CanAutM3]

Originally Posted by chetman7

I set them all at 32 psi.

BMW's recommended tire pressure for a square 255/35R19 M+S tire setup on the M3/4 is 34psi front and 37psi rear. In my 2019 owner's manual they even increased the recommended pressures for this setup to 35/38psi. You might want to try this out to see if it helps.

From the 2016 owner's manual found on-line:

[chetman7]

Originally Posted by tastes jigga

chetman7, what model of tire did you install? It may not be a diameter/DSC issue but a power/grip issue. Also, I believe BMW sells a square-tire winter setup with wider rear rims, so your varying wheel widths shouldn't be the issue.

Running ig52c

[chetman7]

Originally Posted by CanAutM3

BMW's recommended tire pressure for a square 255/35R19 M+S tire setup on the M3/4 is 34psi front and 37psi rear. In my 2019 owner's manual they even increased the recommended pressures for this setup to 35/38psi. You might want to try this out to see if it helps.

From the 2016 owner's manual found on-line:

Thanks..I will definitely give that a try!! I'm going to take the car out today as it is beautiful out in upstate ny..will report back

[wsccsw13]

http://www.ge39.com/files/dsc.pdf

DSC was a project by BMW and Bosch. This document is older but details the engineering of the current system (sensors, parameters used, placement, etc). I’d like to point out that DSC and DTC/Traction control are two different systems that work in conjunction. Traction control works longitudinally ie straight line speed/acceleration. DSC works about the vertical axis of the car ie rotation or spin. Also, per bimmerworld, bmwblog, tire rack, and various other publications as well as per general concensus a staggered setup is often used to enhance traction in high powered RWD cars as well as to enduce understeer for a margin of safety from a manufacturer. Pretty sure BMW is well aware that most people can’t and/or are no where ready to handle a vehicle like these without the nannies; they have no idea how much they’re doing behind the scene.

Having said all that, per the engineering document the DSC system relies on differences between each front wheel’s rotation relative to one another along with sensors in the car to determine if intervention is needed. The document also does not explicitly say changing square to stagger is ok nor does it say it’s not ok; it does however state that the system uses logic while monitoring what the vehicle is doing to determine if changes will upset the vehicles dynamics too much and thus warrant intervention. It continuously compares what the car is doing to the inputs by the driver, and if they deviate too much it will intervene. The systems are very complex and would be too restricted to be locked in to a set tire size/difference front to rear....switching brands with the same size would be problematic in that case.

Now, personal opinion with some physics. Switching from staggered to square, the car was noticeably different. I ran VIR stagger, then square. Same place, same car, same driver, same size in the back. Fronts went 255 to 275. Adding more rubber to the front increases grip and thus increases the likelihood of oversteer. The car will rotate easier. I noticed that I could break later and use more trail braking without running into push oversteer. I also noticed that when not carrying enough (ie more) speed though a turn that getting on the throttle too hard would tend to kick the rear out and MDM would intervene. This makes since as the front would not push out with the back at these lower speeds because it’s too planted (wouldn’t 4 wheel slide; 4 is good and 2 is bad). Once adjusting for this change/balance of the car and the new degree/ease of rotation of the car, I was able to be faster and MDM was no more intrusive. On my last couple sessions I was able to slide/move the car in a controlled manner just as I always have been able to, maybe even more since I was carrying more speed (both 4 wheel slide and just kicking the rear out). I also found regular DSC mode no different driving to and from the track/hotel each day. So once I became as smooth as before with the new balance of the car, I was faster and MDM was no more intrusive, in my experience.

Finally, I emailed Bosch and asked this specific question about adaptability and changing wheel size. I’ll post whatever they reply (assuming they reply). In the meantime, if you have anything that’s not hearsay or anecdotal stating it doesn’t adapt, I’d like to see that. From an engineering standpoint, it makes nose sense to restrict a system like this and not use logic based changing parameters.

[CanAutM3]

Originally Posted by wsccsw13

http://www.ge39.com/files/dsc.pdf

DSC was a project by BMW and Bosch. This document is older but details the engineering of the current system (sensors, parameters used, placement, etc). I’d like to point out that DSC and DTC/Traction control are two different systems that work in conjunction. Traction control works longitudinally ie straight line speed/acceleration. DSC works about the vertical axis of the car ie rotation or spin. Also, per bimmerworld, bmwblog, tire rack, and various other publications as well as per general concensus a staggered setup is often used to enhance traction in high powered RWD cars as well as to enduce understeer for a margin of safety from a manufacturer. Pretty sure BMW is well aware that most people can’t and/or are no where ready to handle a vehicle like these without the nannies; they have no idea how much they’re doing behind the scene.

Having said all that, per the engineering document the DSC system relies on differences between each front wheel’s rotation relative to one another along with sensors in the car to determine if intervention is needed. The document also does not explicitly say changing square to stagger is ok nor does it say it’s not ok; it does however state that the system uses logic while monitoring what the vehicle is doing to determine if changes will upset the vehicles dynamics too much and thus warrant intervention. It continuously compares what the car is doing to the inputs by the driver, and if they deviate too much it will intervene. The systems are very complex and would be too restricted to be locked in to a set tire size/difference front to rear....switching brands with the same size would be problematic in that case.

Now, personal opinion with some physics. Switching from staggered to square, the car was noticeably different. I ran VIR stagger, then square. Same place, same car, same driver, same size in the back. Fronts went 255 to 275. Adding more rubber to the front increases grip and thus increases the likelihood of oversteer. The car will rotate easier. I noticed that I could break later and use more trail braking without running into push oversteer. I also noticed that when not carrying enough (ie more) speed though a turn that getting on the throttle too hard would tend to kick the rear out and MDM would intervene. This makes since as the front would not push out with the back at these lower speeds because it’s too planted (wouldn’t 4 wheel slide; 4 is good and 2 is bad). Once adjusting for this change/balance of the car and the new degree/ease of rotation of the car, I was able to be faster and MDM was no more intrusive. On my last couple sessions I was able to slide/move the car in a controlled manner just as I always have been able to, maybe even more since I was carrying more speed (both 4 wheel slide and just kicking the rear out). I also found regular DSC mode no different driving to and from the track/hotel each day. So once I became as smooth as before with the new balance of the car, I was faster and MDM was no more intrusive, in my experience.

Finally, I emailed Bosch and asked this specific question about adaptability and changing wheel size. I’ll post whatever they reply (assuming they reply). In the meantime, if you have anything that’s not hearsay or anecdotal stating it doesn’t adapt, I’d like to see that. From an engineering standpoint, it makes nose sense to restrict a system like this and not use logic based changing parameters.

The term "DSC" has been used as all encompassing in this thread since modern systems do not differentiate between the traction control aspect and the cornering stability aspect of the system. Both are intimately linked. For instance, "DSC Off" in our cars disables both the traction control and the cornering stability system.

Also, there are two different variable when talking of a "staggered" setup: width and diameter. I agree that varying the stagger width ratio has very little to no incidence on the DSC tuning. You are correct in stating that the cornering stability aspect of the system monitors the speed difference between the two front wheels, amongst many other parameters, to assess the conditions. However, the traction control aspect of DSC does monitor the speed difference between the driven and non-driven wheels as a primary parameter. Hence, the traction control aspect of DSC is affected by a changing front-to-rear diameter stagger ratio. The DSC system is indeed unaffected by different types/brands of tires, as long as the diameter stagger is maintained. And BTW, the fact that it does not "adapt" does not "restrict" the system, it simply makes it more conservative and safer when on a square setup, therefore still meeting its primary design intent.

When simply going down the straight on a track with the throttle pinned to the floor and you get a flickering DSC light accompanied by a power cut, I am not sure how "driving smoothness" can make things better .

Lastly, I have never claimed that I have non-anecdotal evidence that the system does not adapt to changing diameter staggers, I have always been clear that this is based on my own experience, my own understanding of DSC systems in general and some engineering common sense. However, others, including yourself, have stated that they have actual BMW references to the fact that the system adapts to changing diameter staggers. Such bold statements need be based on more than hearsay or anecdotal evidence.

I am eager to hear from your inquiry with Bosch

[wsccsw13]

Originally Posted by CanAutM3

The term "DSC" has been used as all encompassing in this thread since modern systems do not differentiate between the traction control aspect and the cornering stability aspect of the system. Both are intimately linked. For instance, "DSC Off" in our cars disables both the traction control and the cornering stability system.

Also, there are two different variable when talking of a "staggered" setup: width and diameter. I agree that varying the stagger width ratio has very little to no incidence on the DSC tuning. You are correct in stating that the cornering stability aspect of the system monitors the speed difference between the two front wheels, amongst many other parameters, to assess the conditions. However, the traction control aspect of DSC does monitor the speed difference between the driven and non-driven wheels as a primary parameter. Hence, the traction control aspect of DSC is affected by a changing front-to-rear diameter stagger ratio. The DSC system is indeed unaffected by different types/brands of tires, as long as the diameter stagger is maintained. And BTW, the fact that it does not "adapt" does not "restrict" the system, it simply makes it more conservative and safer when on a square setup, therefore still meeting its primary design intent.

When simply going down the straight on a track with the throttle pinned to the floor and you get a flickering DSC light accompanied by a power cut, I am not sure how "driving smoothness" can make things better .

Lastly, I have never claimed that I have non-anecdotal evidence that the system does not adapt to changing diameter staggers, I have always been clear that this is based on my own experience, my own understanding of DSC systems in general and some engineering common sense. However, others, including yourself, have stated that they have actual BMW references to the fact that the system adapts to changing diameter staggers. Such bold statements need be based on more than hearsay or anecdotal evidence.

I am eager to hear from your inquiry with Bosch

Yes, we agree changing width stagger doesn’t affect the system. And yes, we agree and both stated that DSC and TC are two systems intimately tied together and turning off DSC does turn off both (except the e-diff).

To what you referenced with TC intervening in a straight line at full throttle, I too have experienced that on the track with both my staggered and square setup. Same car, same track, same spots on the track. For example, Back straight at VIR just as you’re approaching halfway, the slope changes from downhill to uphill. The light will flicker just a couple times regardless of which setup I run. Always going 130+mph at that spot and my thought is the car obviously compresses/loads then unloads and there isn’t enough stock rear downforce to compensate for the momentary loss of weight on the rear. In my experience, nothing to do with the stagger vs square. I’ve personally not noticed a difference between stagger vs square on the street or track....ie intervention is the same if conditions are the same.

Bosch were quick with a response and not quite what either of us expected I’m guessing. They said:

“Dear Mr. _,
*
thank you for your question and interest in our mobility solutions.
All officially released tires for the specific vehicle model by the vehicle manufacturer can be used. Under these circumstances the dynamic stability control works without interferences. For tire / wheel combinations outside of this scope it is not possible to guarantee the usage.
*
Mit freundlichen Grüßen / Best regards”

I find this response interesting as BMW’s own winter setup for the f8x is a square setup for width and diameter, and the summer setups are staggered for both width and diameter. I have asked a follow up question about this because it would stand to reason then that either a)the system adapts or b) the tolerances are such that a 0 to +2.3% front to back stagger are the acceptable operating conditions for the system. Either way, they are saying the system works as designed with a stock staggered setup or square setup (since it’s a stock manufacturer setup).

[chetman7]

Originally Posted by CanAutM3

BMW's recommended tire pressure for a square 255/35R19 M+S tire setup on the M3/4 is 34psi front and 37psi rear. In my 2019 owner's manual they even increased the recommended pressures for this setup to 35/38psi. You might want to try this out to see if it helps.

From the 2016 owner's manual found on-line:

Tried this. Definitely less squishy during Light cornering. I can now at least now go partial throttle in level ground. Dsc lights up now on partial throttle going up a slight incline.

Dsc lights up anything over 50% throttle at minimum speeds of 40mph. No problems getting it up to highway speed as long as it's under 50% throttle input.

If I had to perform a passing maneuver on a single lane road..I'd be hesitant

I think this is as good as it is going get. As even with my summer contis I could feel the car pull away power during wot/kickdown switch with mdm

Car is still new to me...coming from a f32 435ix with super sports during the summer and WS80s during the winter so I've been spoiled for the past 5 years with awd where I could pin the throttle anywhere.

[Powerslide]

Originally Posted by danchee

I have the BMW approved 18" square set up and my DSC doesn't kick in regularly at all. It only kicked in once in the last month and that's when going up an on ramp raining heavily. The car started to slip when accelerating a little harder than I should and DSC kicked in.

Same here - barely any difference for me either (I have ZCP - not sure whether or not that plays a factor vs. non-ZCP) - and I also drive in MDM mode pretty much all the time - I notice that even with the 18" BMW approved square setup I can still get a good amount of oversteer with the rear tires before DSC will kick in (while in MDM mode)...

OP - do you have ZCP, and either way - do you normally drive in MDM mode?

[ellipsis212]

Does TPMS talk to the DSC/TC systems?

Anecdotally: I recently changed a set of wheels/tires from the stock ZCP set to one with identical F/R diameter (255/35/20 and 305/25/20). Upon driving away on them for the first time I was in efficient mode with all the nannies and the dash was lighting up and I could feel the car braking. After about a half mile I parked and did the TPMS reset. During and after it finished calibration I have experienced no intervention in full nanny mode or MDM mode and have driven at least 50 miles now with no further issues.

Not sure what prompted the change but curious to hear ideas.

[chetman7]

Originally Posted by Powerslide

Same here - barely any difference for me either (I have ZCP - not sure whether or not that plays a factor vs. non-ZCP) - and I also drive in MDM mode pretty much all the time - I notice that even with the 18" BMW approved square setup I can still get a good amount of oversteer with the rear tires before DSC will kick in (while in MDM mode)...

OP - do you have ZCP, and either way - do you normally drive in MDM mode?

I do not have zcp.

I usually do drive in MDM mode and sport across the board with D2.

Since my snow tire wheel swap , I have been leaving dsc 100% on as i don't trust the car..

[CanAutM3]

Quite a few folks here reporting not feeling more DSC intervention when going with a square setup. I am starting to wonder if my own experience stems from my older 2015 M4 and that maybe BMW have improved the DSC programming since. I'll be installing the square winter setup on my 2019 M4cs this weekend. I am now eager to see the effect on DSC. I'll be reporting back.

[CanAutM3]

Originally Posted by wsccsw13

Yes, we agree changing width stagger doesn’t affect the system. And yes, we agree and both stated that DSC and TC are two systems intimately tied together and turning off DSC does turn off both (except the e-diff).

To what you referenced with TC intervening in a straight line at full throttle, I too have experienced that on the track with both my staggered and square setup. Same car, same track, same spots on the track. For example, Back straight at VIR just as you’re approaching halfway, the slope changes from downhill to uphill. The light will flicker just a couple times regardless of which setup I run. Always going 130+mph at that spot and my thought is the car obviously compresses/loads then unloads and there isn’t enough stock rear downforce to compensate for the momentary loss of weight on the rear. In my experience, nothing to do with the stagger vs square. I’ve personally not noticed a difference between stagger vs square on the street or track....ie intervention is the same if conditions are the same.

Bosch were quick with a response and not quite what either of us expected I’m guessing. They said:

“Dear Mr. _,
*
thank you for your question and interest in our mobility solutions.
All officially released tires for the specific vehicle model by the vehicle manufacturer can be used. Under these circumstances the dynamic stability control works without interferences. For tire / wheel combinations outside of this scope it is not possible to guarantee the usage.
*
Mit freundlichen Grüßen / Best regards”

I find this response interesting as BMW’s own winter setup for the f8x is a square setup for width and diameter, and the summer setups are staggered for both width and diameter. I have asked a follow up question about this because it would stand to reason then that either a)the system adapts or b) the tolerances are such that a 0 to +2.3% front to back stagger are the acceptable operating conditions for the system. Either way, they are saying the system works as designed with a stock staggered setup or square setup (since it’s a stock manufacturer setup).

Thanks for sharing their reply. Their answer can easily be interpreted that the system still works as intended with all BMW's recommended tire sizes. A system that is slightly more conservative when using a square winter setup can certainly be interpreted as working as intended.

I'd also like to point out that when I say I find the system to becomes more sensitive with a square setup, it remains a noticeable but subtle difference. The car does not become undriveable. For example I can feel DSC interventions on WOT highway pulls with a square setup that would yield no interventions with a staggered setup.

[wsccsw13]

OP-To your original question, a decreased rear width (275 to 255), cold roads/temps, and a less sticky/performance winter tire all decrease traction and the ability to put power down, thus DSC/TC will intervene more if driving habits don’t adjust. And even then, it will still intervene more (in my experience) because traction is so reduced for these high output motors. I think you notice it even more since your prior vehicle was AWD with 20-25% less power.

As far as the square diameter, I asked Bosch for you and all of us directly. Their reply is posted above. It’s states the system works like it should regardless of staggered diameter or square diameter.

[yayaya]

Originally Posted by chetman7

I do not have zcp.

I usually do drive in MDM mode and sport across the board with D2.

Since my snow tire wheel swap , I have been leaving dsc 100% on as i don't trust the car..

You ever figure this out? I just put the same tires on my zcp with 19x9.5 wheels square and am having the same issue.


Edit: my dealer suggested 34 psi front 37 psi rear this was done and TPSM reset, no more DSC issues for me.

[chetman7]

Originally Posted by yayaya

You ever figure this out? I just put the same tires on my zcp with 19x9.5 wheels square and am having the same issue.


Edit: my dealer suggested 34 psi front 37 psi rear this was done and TPSM reset, no more DSC issues for me.

I haven't driven the car much as it is not my DD. I did wash it the other day but before I did I drove it around the block and did a tpms reset..for some reason this time it took a lot longer to fully reset so maybe that is what I forgot to do when I swapped them. Only time will tell..but i did up the pressure to 34/37 as recommended above

[yayaya]

Originally Posted by chetman7

I haven't driven the car much as it is not my DD. I did wash it the other day but before I did I drove it around the block and did a tpms reset..for some reason this time it took a lot longer to fully reset so maybe that is what I forgot to do when I swapped them. Only time will tell..but i did up the pressure to 34/37 as recommended above

I think it just needs to be driven. I went about 50 miles today with the tires and the issue only got better, now nonexistent. Also, I forget about all power the rear 285s do a better job at grounding the car than I thought.

[OhioRiderAaron]

I ran 255/40/19s hankook winters on a set of stock wheels last year. No issues whatsoever unless I was acting like a hooligan. Any aggressive throttle inputs would try to light up the skinny rears, but otherwise no problems for me.

[hoppes-no9]

Originally Posted by danchee

I have the BMW approved 18" square set up and my DSC doesn't kick in regularly at all. It only kicked in once in the last month and that's when going up an on ramp raining heavily. The car started to slip when accelerating a little harder than I should and DSC kicked in.

This is my experience as well.

[scott13]

Originally Posted by CanAutM3

Quite a few folks here reporting not feeling more DSC intervention when going with a square setup. I am starting to wonder if my own experience stems from my older 2015 M4 and that maybe BMW have improved the DSC programming since. I'll be installing the square winter setup on my 2019 M4cs this weekend. I am now eager to see the effect on DSC. I'll be reporting back.

FWIW, on my 2015 M4, I definitely experience a bit more DSC intervention on my winter tires (square setup on 18"s). I've always assumed/attributed that to the fact that they're winter tires (i.e., skinnier and less grip) and DSC is just acting accordingly, not "adapting" per se. But nothing dramatic like the OP is experiencing.

Originally Posted by ellipsis212

Does TPMS talk to the DSC/TC systems

I'll freely admit that I don't *know*, but I would guess not since you're not technically required (as far as I know) to have TPMS installed. Since I'm admitting that I get a bit more DSC intervention on my winters in the post above, I guess I should also mention that they do not have TPMS installed.

[wsccsw13]

Originally Posted by CanAutM3

Thanks for sharing their reply. Their answer can easily be interpreted that the system still works as intended with all BMW's recommended tire sizes. A system that is slightly more conservative when using a square winter setup can certainly be interpreted as working as intended.

I'd also like to point out that when I say I find the system to becomes more sensitive with a square setup, it remains a noticeable but subtle difference. The car does not become undriveable. For example I can feel DSC interventions on WOT highway pulls with a square setup that would yield no interventions with a staggered setup.

Finally heard back from Bosch on my follow up question:

Dear Mr. _,

Thank you for your question and interest in our mobility solutions.

The dynamic stability control is very robust, which means that it can cope with all approved tire combinations. Any measurable differences in the tire circumference are detected and compensated by the system. The angular speed of the wheel is corrected without any changes in the application parameter.
Mit freundlichen Grüßen / Best regards

James Lavar
Robert Bosch GmbH
Bosch Service Center
Postfach 300220
70442 Stuttgart

The system detects and compensates. It adapts to changes.