Limited slip

[RDW67]

Edmunds said no mechanical limited slip due to cost, something about an auto braking diff.. Any speculation on if this will be replaceable by a mechanical limited slip diff.?

[gotgemini2000]

look here --> http://www.1addicts.com/forums/showthread.php?t=1960

"BMW will eventually offer a factory-replacement limited-slip differential under their performance products program recently announced. There are no plans to fit a limited-slip differential as a factory-fitted option."

[ttdmac]

I wonder what drives everyone's fascination with limited slip differentials.
Is it because they associate limited slip with high performance cars and believe that they will need it on a daily basis?

For 95%+ of potential 135i buyers, most wouldn't know what the limited slip would do for them.
Those who do know probably won't push the car to point where they need limited slip assistance more than 10% of the time.

I drove a high powered exotic for a while without limited slip and it performed perfectly fine in road conditions and rarely did I need it on track days that I attended.
If drivers are looking for better lap times, try better driving techniques and carrying more speed through corners rather than powering through them.
Power slides with limited slip may seem fun, but they don't improve your lap time.

[grant]

Originally Posted by ttdamc

I drove a high powered exotic for a while without limited slip and it performed perfectly fine in road conditions and rarely did I need it on track days that I attended.

I an unaware of any RWD true "Exotic" that does not have LSD included (or optional at least).

Please let me know what car you are referring to. Yes, only the Turbo and GT Porsches have LSD, but I wouldn't consider anything lower in their line to be "exotic". In fact, only the Carrera GT is exotic in that line, imho and it has LSD.

All M-series BMW's have it, Ferraris, Lambos, even Pontiac Solstice, RX8, 350Z, Miata, Corvette, WRX, STi, EVO, Pontiac GTO, etc. all have them...

[gbent]

Originally Posted by ttdamc

I wonder what drives everyone's fascination with limited slip differentials.
Is it because they associate limited slip with high performance cars and believe that they will need it on a daily basis?

For 95%+ of potential 135i buyers, most wouldn't know what the limited slip would do for them.
Those who do know probably won't push the car to point where they need limited slip assistance more than 10% of the time.

I drove a high powered exotic for a while without limited slip and it performed perfectly fine in road conditions and rarely did I need it on track days that I attended.
If drivers are looking for better lap times, try better driving techniques and carrying more speed through corners rather than powering through them.
Power slides with limited slip may seem fun, but they don't improve your lap time.

+1
The vast majority of these cars will never see anything other than daily commuting duty.

It's the same story with the brakes. When was the last time that the average BMW driver out drove the stock brakes on their car?

While I'm glad they're putting the 6 piston brakes on the 135i, I'm pretty sure most people who buy this car would'nt know a brake caliper (6 piston or otherwise) if it hit them in the head!

[grant]

Originally Posted by gbent

+1
The vast majority of these cars will never see anything other than daily commuting duty.

Then I recommend you save your money and buy a Daihatsu, otherwise you are just spending money to impress you friends:tongue:

[ttdmac]

All of the Lotus Esprit V8 did not have limited split diffs. The diff of choice who did the upgrade was Quaife, but I didn't want to drop 5k on the diff. I'd also upgrade the damn renault box before I'd even consider a LSD anyway.
My money went to fixing the quirks of Lotus cars, like cooling systems and fine tuning high wear areas like bushings.

[ttdmac]

Originally Posted by grant

Then I recommend you save your money and buy a Daihatsu, otherwise you are just spending money to impress you friends:tongue:

Who would buy a car to impress their friends? Who's friends would be truly impressed by a lowly 135i being driven on public roads?

Personally if the 135i fails to live up my expectations as a tight handling car with decent power it will go up for sale like the rest of my old toys.

[grant]

Originally Posted by ttdamc

All of the Lotus Esprit V8 did not have limited split diffs. The diff of choice who did the upgrade was Quaife, but I didn't want to drop 5k on the diff. I'd also upgrade the damn renault box before I'd even consider a LSD anyway.
My money went to fixing the quirks of Lotus cars, like cooling systems and fine tuning high wear areas like bushings.

At least all the modern Lotus cars offer them as options...

[ttdmac]

All the modern Lotus cars? Such as the Elise/Exige/Exige S? Yes they do have them either optional or standard.
However I would not trade the looks, sounds or huge kick in the rear at 3500rpm of the Esprit V8 TT for a "modern" Lotus.

[gotgemini2000]

If you drive a 335i aggressively at all on a windy road you are pretty much guaranteed to light up the inside wheel going around turns. If you drive a RWD car in snow, a LSD is always preferable to an electronic braking system. I disagree with the idea that an LSD is only required for the track. Any car with 300 HP and 300 ft/lbs of torque that weighs around 3400 pounds should have a LSD. The 335i certainly needs one. They make burnouts look great too, not that I would ever think of doing burnouts in a BMW:wink:.

[BForbes]

Originally Posted by grant

Then I recommend you save your money and buy a Daihatsu, otherwise you are just spending money to impress you friends:tongue:

I agree!

[gbent]

Originally Posted by grant

Then I recommend you save your money and buy a Daihatsu, otherwise you are just spending money to impress you friends:tongue:

Don't misunderstand me, I realize that a lot of the people on here are enthusiasts, & will drive their cars hard, but we only make up a small portion of the BMW buying public.

Three quarters of BMW owners buy their cars for exactly the reason you mentioned, to impress their freinds!

[ttdmac]

Originally Posted by gotgemini2000

If you drive a 335i aggressively at all on a windy road you are pretty much guaranteed to light up the inside wheel going around turns. If you drive a RWD car in snow, a LSD is always preferable to an electronic braking system. I disagree with the idea that an LSD is only required for the track. Any car with 300 HP and 300 ft/lbs of torque that weighs around 3400 pounds should have a LSD. The 335i certainly needs one. They make burnouts look great too, not that I would ever think of doing burnouts in a BMW:wink:.

Valid points, but here is my opinion

Point one, if you are on a public road and driving a 335i hard enough to create a traction issue, then you need your head checked.
I have no problems with spirited driving on an open public road, but I would not go to 9/10th and put other people at risk, that's just plain irresponsible.

Point two, if you are intending on driving a RWD in the snow, snow tires will cost less and improve your ability in snow 1000% over a LSD. If anything all the LSD will let you do is spin both your tires in a zero traction environment.

Point three, a 3200lb Lotus Esprit V8 TT with a great deal more power than the 135i doesn't "need" a LSD to be very quick. So there isn't a huge reason for a 335i to have one unless the owner is looking for that magic 1/10th of a second off their lap time and are driving at 10/10th of the car's envelope.

Point four, if a driver intends on getting a LSD to make "pretty" burn outs, then more power to them. I'm not paying for their tires or rear diff rebuilds so it matters not to me, however don't mask it with "I want to make my car faster". If you can truly think that the LSD will give you better return than spending that money at Skip Barber or something, then you are really delusional.

[larryn]

LSD doesn't make a difference on a lot of the tracks I go to. It's not like we're going to be lighting up tires at 70mph, unless you're a hamfisted moron, who has no business on the track to begin with. (Yes, I know there are certain tracks that do benefit from an LSD, but they are rare)

I will say that at autocross, you NEED that LSD, as you're making drastic maneuvers with the need for instant accelleration from slower speeds (inside rear tire slip territory).

[ttdmac]

Originally Posted by larryn

LSD doesn't make a difference on a lot of the tracks I go to. It's not like we're going to be lighting up tires at 70mph, unless you're a hamfisted moron, who has no business on the track to begin with. (Yes, I know there are certain tracks that do benefit from an LSD, but they are rare)

I will say that at autocross, you NEED that LSD, as you're making drastic maneuvers with the need for instant accelleration from slower speeds (inside rear tire slip territory).

I agree that most tracks that people attend don't have tight/low speed corners where LSD would make the most difference.

Also agree with your autocross comment, however who would be looking at the 135i as their preferred autocrosser? Pick up a Miata or a Super 7, mod it to hell and spank every 135i at the event.

[gotgemini2000]

Originally Posted by ttdamc

Valid points, but here is my opinion

Point one, if you are on a public road and driving a 335i hard enough to create a traction issue, then you need your head checked.

I actually really disagree with this statement. I have not driven my younger brother's 335i very aggressively, but a simple rev matched down shift going up a hill with a little too much exuberance on the throttle will easily light up the wheels and result in some pretty scary and very unpredictable oversteer. An LSD will not entirely solve this but will certainly make the vehicle much safer.

As for driving in the snow, I really do think a LSD will improve traction a lot (snow tires are a big DUH, you can't drive a RWD in the winter without snow tires period). My 96 328i does not have a LSD but it does have a great set of blizzaks. With the traction control on, the vehicle refuses to allow for any wheel spin whatsoever by cutting power directly from the engine. With the traction control off, one wheel just spins. With an LSD and traction control off, as long as you have snow tires and you sustain your momentum, winter driving should be improved.

[inTgr8r]

Oh gawd.....
Do we really have to do this again?????

[gotgemini2000]

Originally Posted by inTgr8r

Oh gawd.....
Do we really have to do this again?????

Good point. People who want an LSD, buy it from BMW, people who don't, don't buy an LSD from BMW.

[ttdmac]

Originally Posted by gotgemini2000

I actually really disagree with this statement. I have not driven my younger brother's 335i very aggressively, but a simple rev matched down shift going up a hill with a little too much exuberance on the throttle will easily light up the wheels and result in some pretty scary and very unpredictable oversteer. An LSD will not entirely solve this but will certainly make the vehicle much safer.

As for driving in the snow, I really do think a LSD will improve traction a lot (snow tires are a big DUH, you can't drive a RWD in the winter without snow tires period). My 96 328i does not have a LSD but it does have a great set of blizzaks. With the traction control on, the vehicle refuses to allow for any wheel spin whatsoever by cutting power directly from the engine. With the traction control off, one wheel just spins. With an LSD and traction control off, as long as you have snow tires and you sustain your momentum, winter driving should be improved.

Ok I agree with the snow thing to an extent, however you have to agree that many folks completely ignore snow tires, hence my comment on that part.

Oh the "over exuberance" on the throttle, I'd rather work on throttle technique than spend the money on the LSD, but that's just me.

I'd take a well trained/practiced driver with non-LSD 335i over a 335i with LSD driven by a driver who might know some driving basics.

I'm going to make some assumptions about your particular incident with as well, so don't flame me on this, but I would say that you probably entered the curve/corner with too much speed, you may have either lifted or hit the brakes and downshifted as you approached the apex or during the apex, you hit the gas which then resulted in a bit of a wild ride with the tail stepping out slightly.
Am I close?

If that's how it happened, then you were victim of lift off oversteer, which a LSD wouldn't have helped due to the weight shift forward under breaking/lift off.

I am wondering however how you managed to get power to generate the oversteer, if you are going up hill and it's likely that the inside/spinning wheel was not providing you power.

Feel free to better describe your oversteer situation.

[ttdmac]

Originally Posted by gotgemini2000

Good point. People who want an LSD, buy it from BMW, people who don't, don't buy an LSD from BMW.

If you don't want to partake in this discussion, then don't partake.
However this thread I hope has evolved into a best practice discussion of cornering, rather than "Should I get LSD or not".

I was originally just curious as to what was the motivation was for most people who opt to go for the LSD.
Obviously people will do whatever makes them happy, but it's genuine interest in the handling aspects of the 135i that is driving this thread.
If the LSD will truly make the car, then I'd get one too however there has not been much detail on whether or not the LSD will give me better lap times or feel of the car.

[grant]

Originally Posted by ttdamc

All the modern Lotus cars? Such as the Elise/Exige/Exige S? Yes they do have them either optional or standard.
However I would not trade the looks, sounds or huge kick in the rear at 3500rpm of the Esprit V8 TT for a "modern" Lotus.

That is a valid choice, but that car would be even more fun if it had an LSD...