Rear End Twitch - Any Ideas?

Discussion in 'F80 M3 Saloon / F82 M4 Coupe / F83 M4 Convertible (2014-present)' started by lindorez, Dec 7, 2017.

  1. 7 Dec 2017 at 7:30 AM #1
    lindorez

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    I've been having this intermittent issue with my car and wanted to know if anybody else has had this before.

    At lower speeds 30mph or less (usually on a round about) the backend will kick side to side and then regain traction. The only way I can describe it is that it feels like the brakes were slammed on the rear at one side of the car it kicks the car out and then its released again and drives fine.

    - There is no traction control light on when it happens, sometimes this does come on afterwards as the car is unsettled but not every time.
    - I initially thought it was when in automatic mode and unexpected change of gear unsettled the rear but it happened to me in manual mode a couple of times now.
    - I checked the rear brakes and doesn't look to be anything touching that could knock against the discs unnecessarily.
    - It's always at a reasonable speed and not under heavy acceleration. Its happened mainly in efficient mode but also a couple of times in sports mode. So its not me pushing the car to the limits and an actual drift. I've done this before and its a very different feeling.
    - I've been back and checked the road surface afterwards a few times and never any issue so its not a spillage, cold weather etc
    - Its happened with both my Michelin MPSS and Michelin Alpines which have loads of tread so its not the tyres.

    As this is intermittent and I can't show the garage and I doubt it would happen to them on a test drive. It has happened maybe 10 times in my 2 years ownership.

    The car generally performs great but I always have this concern it is going to do this at either a higher speed or when another car is around. It happened just turning on a roundabout yesterday and an Audi was right up my arse, it got a fright and so did I as it was almost into the back of me.

    Anybody had this issue before or any ideas?
     
  2. 7 Dec 2017 at 8:15 AM #2
    caterham7

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    just sounds like the rear is losing traction slightly, could be due to too much throttle, or too much steering angle (or both).

    You dont have to have your foot anywhere near the floor to break traction (even with traction control fully on), just the right (or wrong depending on your point of view) combination of camber of surface, road temperature,throttle and steering input.

    Roundabouts are usually where this will happen for me, on the transition where the road camber changes where you exit a roundabout, slightly too much throttle in combination with a bit too much steering angle will see the back slide at less than 30 mph even with the TC on.
     
  3. 7 Dec 2017 at 8:45 AM #3
    Muu

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    What are the tyre pressures at?
     
  4. 7 Dec 2017 at 9:12 AM #4
    lindorez

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    Thanks for the advice. It is possible but 90% of the time it is on roads I know and drive every day.

    I am very good at regulating the throttle - in the last incident I was at most 20% throttle in efficient mode when it happened.

    I have experience in powerful rear wheel drive cars and I only mash the throttle in proper conditions so.

    I have the 20" comp pack wheels - 2.3psi front and 2.1psi rear. Fluctuates with the cold weather plus or minus 0.1 psi
     
  5. 7 Dec 2017 at 9:46 AM #5
    Billyali86

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    Alingment maybe ? I recently had my m4 returned to stock with springs included. Didn't get a chance get alignment sorted before it was being traded in.

    Felt like a totally different car, to the point I was actually scared to drive the damn thing
     
  6. 7 Dec 2017 at 11:47 AM #6
    lindorez

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    I had thought that myself but had an alignment done on a hunter system and car is straight as an arrow. It has happened since then.
     
  7. 7 Dec 2017 at 11:53 AM #7
    Melvyn

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    What depth are the tyre tread
     
  8. 7 Dec 2017 at 12:29 PM #8
    lindorez

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    MPSS are 7mm front 6mm rear
    Alpine are 7mm front 6.5mm rear
     
  9. 7 Dec 2017 at 1:00 PM #9
    Schuey

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    Why are you running higher pressures on the front? Typically the rears should be 0.1 more than the fronts.

    I run 2.1 bar fronts, 2.2 bar rears.
     
  10. 7 Dec 2017 at 1:34 PM #10
    lindorez

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    Well I personally thought that but BMW recommend 2.4 front and 2.1 rear for the comp pack wheels on the door sticker. The 19's are recommended as a 2.2 square setup.
     
  11. 7 Dec 2017 at 4:20 PM #11
    antych

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    It was always 2.2-2.4 bar depending on the load, CP or not.
     
  12. 7 Dec 2017 at 5:26 PM #12
    lindorez

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    [​IMG]

    Had a look at my sticker

    2.2 - 2.2 for 19"
    2.4 - 2.1 for 20"
     
  13. 7 Dec 2017 at 5:29 PM #13
    Melvyn

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    Not that then buddy, reason I asked was that these M cars start to let go at around 4 mill :thumbsup:
     
  14. 7 Dec 2017 at 5:48 PM #14
    Singh21

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    I had this exact same thing. I thought it may be my diff as it was pulling over every little bump at low speed and in the wet was pulling all over the place.

    What sorted it for me was an alignment. Get it done at a good place and then see after.
     
  15. 7 Dec 2017 at 7:13 PM #15
    E46CoupeM3

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    If it's dry less tread is better as less block flex. Only worse if insufficient to clear water, so better in damp too.
     
  16. 7 Dec 2017 at 7:30 PM #16
    Melvyn

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    Not according to my flashing yellow gremlin :muttley:


    Your right of course , putting heat into them will make them stick, just wrong season to do so :D
     
  17. 7 Dec 2017 at 7:34 PM #17
    antych

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    That looks different than mine. I have 2.2 - 2.2 for 20"
     
  18. 7 Dec 2017 at 7:40 PM #18
    E46CoupeM3

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    Nope, less block flex = better grip heat regardless, unless too much standing water to clear. Block flex actually generates heat too and is one of the reasons treads aren't deeper
     
  19. 7 Dec 2017 at 8:23 PM #19
    jpf

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    Managed to get good heat into my crazy Atom's nearly worn out (2.5 - 2.9mm) Yokohama AD08 tyres yesterday. Those tyres are truly amazing once warmed up. Went out today for a short blast, completely different story spinning tyres everywhere which is of course highly amusing.
     
  20. 7 Dec 2017 at 9:32 PM #20
    lindorez

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    That is very strange. I have no idea why they would differ - Perhaps that could be part of the issue.

    Might try set the pressure to 2.2 - 2.2.
     

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