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    May 4, 2012 3:05:50 PM

    Porker
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    40% locking differential - smooth driving still possible?

    Hi all,

    As my M3 is being overhauled, my LSD will also be changed for a new one. Now the question is, do I retain the stock 25%, or will I go for a 40% locking differential.

    I do enjoy a little 'dirty' driving now and then, and I don't mind a car being a little more tricky but I would find it a shame if a 40% LSD would make smooth and quick track-driving impossible.

    Should you have any experience on this, I'd happily hear your thoughts! Smiley

    May 6, 2012 12:11:57 AM

    JimFlat6
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    JimFlat6
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    Reply to: Porker

    Re: 40% locking differential - smooth driving still possible?

    This is free advice so take it for what its worth.indecision

    For a BMW a 40% Locker is great for street and occaisional track and hooligan use. If its a track car only you would want a 75% locking diff. Your standard 25% really only gives very minimal help on the street. A 40% locker wont be "tricky" for street use. I dont know wich M3 you have and what mods and what final drive ratio, but you also might want to think about corner balancing the car and to rebalance the drive shaft(or switch to a carbon fiber one) and have the half shafts balanced so that they match in weight. I used to vintage race a BMW 1602 wich had a BMW 1800cc engine from their factory Pikes Peak hillclimb car with a 40% LSD and also drove it on the street and it never bothered me. And then a E30 M3 with a modfied 40% LSD, Whatever you do on planet BMW, get bigger brakes(!) and check into rebalancing the drive shaft and matching the halfshafts. You will be amazed at how smoother the car will be.

    May 6, 2012 5:57:23 AM

    RCA
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    RC
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    Reply to: JimFlat6

    Re: 40% locking differential - smooth driving still possible?

    I would stick with 40% at max, 75% is insane for street usage and it also makes the car trickier to drive on the track.


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    May 6, 2012 10:45:21 AM

    Porsche-Jeck
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    Reply to: Porker

    Re: 40% locking differential - smooth driving still possible?

    Hi Porker, I have no own experiences with the BMW but I will do a quick poll with some of the experienced BMW drivers at the 'Ring next weekend and will let you know Smiley With the GT3 (which is a completely different package of course) I never regretted changing to a 75% locking diff - pure bliss at Exmühle Smiley


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    May 6, 2012 10:51:15 AM

    Porker
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    Loc: SZ , Switzerland
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    Registered on: Jan 17, 2005
    Reply to: JimFlat6

    Re: 40% locking differential - smooth driving still possible?

    JimFlat6:

    This is free advice so take it for what its worth.indecision

    For a BMW a 40% Locker is great for street and occaisional track and hooligan use. If its a track car only you would want a 75% locking diff. Your standard 25% really only gives very minimal help on the street. A 40% locker wont be "tricky" for street use. I dont know wich M3 you have and what mods and what final drive ratio, but you also might want to think about corner balancing the car and to rebalance the drive shaft(or switch to a carbon fiber one) and have the half shafts balanced so that they match in weight. I used to vintage race a BMW 1602 wich had a BMW 1800cc engine from their factory Pikes Peak hillclimb car with a 40% LSD and also drove it on the street and it never bothered me. And then a E30 M3 with a modfied 40% LSD, Whatever you do on planet BMW, get bigger brakes(!) and check into rebalancing the drive shaft and matching the halfshafts. You will be amazed at how smoother the car will be.

    Hi Jim, thank you for the advice, the M3 is an E36 GT, heavily modified towards track usage (brakes included, single best upgrade on an M-car indeed Smiley). I'll consider your advice regarding the drive shaft, never actually thought of that..

    Regarding the 75% locking diff, I doubt that will still be driveable on the road, I would consider that on a car with more mass on the rear axle, but given that isn't the case, I think 40% is the maximum. Smiley

    May 6, 2012 10:54:34 AM

    Porker
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    Registered on: Jan 17, 2005
    Reply to: Porsche-Jeck

    Re: 40% locking differential - smooth driving still possible?

    Porsche-Jeck:

    Hi Porker, I have no own experiences with the BMW but I will do a quick poll with some of the experienced BMW drivers at the 'Ring next weekend and will let you know Smiley With the GT3 (which is a completely different package of course) I never regretted changing to a 75% locking diff - pure bliss at Exmühle Smiley

    That would be very kind P-J, thanks! Indeed on a GT3 it's a different story altogether, all the weight removed from the M3 was located on the back axle, creating a very mobile rear-end indeed. Couple that to a 75% locker and I'll be staring to my side window more often than not. Smiley

    May 15, 2012 9:45:03 AM

    Porker
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    Re: 40% locking differential - smooth driving still possible?

    Porker:
    Porsche-Jeck:

    Hi Porker, I have no own experiences with the BMW but I will do a quick poll with some of the experienced BMW drivers at the 'Ring next weekend and will let you know Smiley With the GT3 (which is a completely different package of course) I never regretted changing to a 75% locking diff - pure bliss at Exmühle Smiley

    That would be very kind P-J, thanks! Indeed on a GT3 it's a different story altogether, all the weight removed from the M3 was located on the back axle, creating a very mobile rear-end indeed. Couple that to a 75% locker and I'll be staring to my side window more often than not. Smiley

    I went for a fresh 25% locker eventually, I was informed that anything more would only create understeer in slower corners, which I'd absolutely want to avoid..

     
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