I remember rear wheel drive "posi-traction" or rear ends using clutches that apply nearly equal drive to each wheel. Newer "Limited slip" would stall the spinning wheel and drive the other. This was a conventional differential design for years.

We wanted the posi style to hook-up and go fast in a straight line so Posi's and Ford 9" lockers were trick. 4-wheel hardcores want locking power driving all wheels. I have driven both styles in winter snow conditions and liked the posi way better than limited slip. Often you can drive out of a situation where the LSD gives it up.

This was rear wheel drive world so I'm not sure if it even applys to MC. Guys racing these buggers may get a treat from the option but can the basic street driver tell? When it comes to winter driving will LSD be a blast from the past? ... carry traction sand in the boot mates.

 

>>
>>I remember rear wheel drive "posi-traction" or rear ends using clutches that apply nearly equal drive to each wheel. Newer "Limited slip" would stall the spinning wheel and drive the other. This was a conventional differential design for years.
>>
>>We wanted the posi style to hook-up and go fast in a straight line so Posi's and Ford 9" lockers were trick. 4-wheel hardcores want locking power driving all wheels. I have driven both styles in winter snow conditions and liked the posi way better than limited slip. Often you can drive out of a situation where the LSD gives it up.
>>
>>This was rear wheel drive world so I'm not sure if it even applys to MC. Guys racing these buggers may get a treat from the option but can the basic street driver tell? When it comes to winter driving will LSD be a blast from the past? ... carry traction sand in the boot mates.
>>
>>

When using the Quaife LSD in a MINI (different parts for a MC and MCS) it should help for everyday street driving by providing more traction (reduces torque steer & reduces smoking of tires) to the two front driving wheels under all conditions whether going straight or turning except under conditions where your tires are on a surface that provide little or no traction such as non snowtires on ice, or if on sand/ very loose gravel. As long as one wheel has some traction the Quaife will help to restore traction.

Some notes from http://baysho.milleredp.com/tech/quaife/quaife.asp
Quote-
The Quaife is a helical gear, torque-sensing differential, meaning that as it sees a torque difference between the driving wheels, it smoothly transfers torque to the wheel on the higher mu surface. The Quaife cannot produce a locked condition between the wheels, and therefore is a very safe diff for a front drive application. The Quaife does not contain any clutch plates or similar wear items like conventional limited-slip diffs, such as the Chevy Posi-Traction, Ford Traction-Lock, Auburn, or Torsen 2 diffs, and as such, should be highly reliable. The Quaife is similar in design to the Torsen 1, as found in the latest generation RX-7 twin-turbo, and the Tochigi Fugi helical gear diff as supplied in the Acura Integra GS-R.

Editor's Experiences
My SHO has been Quaifed for almost a year now. The Quaife has proven to be pretty much everything I'd wanted - probably the best $1200 I've spent on the car. In street use, when I stand on the gas in a corner I get acceleration instead of wheelspin. On cloverleafs, more throttle means a tighter line. If you're abrupt about your throttle motions you can provoke some steering-wheel fight, but other than the lack of wheelspin you'll mostly never know it's there.

In track use the Quaife is even more impressive. Stock, the SHO is predictable and stable but frustratingly traction-limited. The Quaife changes the character of the car completely. The car can now be throttle-steered - as the differential transfers torque to the outside front wheel, it does progressively more work, pulling the nose of the car around the CG and causing the car to rotate into the corner.

With the Quaife, Eibachs, Konis, and stock anti-roll bars, the end result was a beautifully safe and stable track car, tremendously easy to drive hard. Turn down and stomp the gas and the car bites straight for the apex in a fairly neutral attitude. Lift off the gas in a corner, and both ends move out more or less evenly - the tendency toward lift-throttle oversteer being (mostly) balanced by the reduction in angular force from the drive wheels in front. Wheelspin is still possible in slow-speed turns, but now you pretty much have to spin both wheels.
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I have the Quaife LSD in my MCS and I find it works really well with a strong even pull in every gear and throughout the full rpm range. Couldn't ask for more. Downside is the high cost of install- $900-$1400+, slightly heavier weight, slightly more heat generated and voids your transmission warranty. Quaife has a lifetime warranty on the part which for the MCS is about $1100.

Many vendors do sell it including Webbmotorsports.com, Helix13.com, Outmotoring.com and others.
It's pretty heavy so shipping by air is expensive, by ground not bad. Works well in an MC or MCS.

 

Good info minihune.

My confusion is if "the Quaife does not contain any clutch plates or similar wear items like conventional limited-slip diffs, such as the Chevy Posi-Traction, Ford Traction-Lock..."
then the term limited slip means Posi type performance - great but what was the following generation of differentials after Posi in rear wheel drive cars? Those were terrible.

I thought (old school) early Posi - good, later generation LSD - bad. '69 Chevy 12 bolt Posi - good, '78 Chevy non-clutched yet still refered to as LSD - not good. The later flavor would not apply power to both wheels in a spin situation ever.

So how does the current (stock) MINI differential compare? Is it direct drive or what?

 

the stock is called an open diffrential, if that help clears the old school mind, meaning power goes to the easiest route, in case of wheel spin that would be the easiest route........................

 

For straight-line traction, I've found the stock open diff to be pretty good at evenly distributing torque between the front wheels. The equal length driveshafts no doubt contribute by eliminating torque changes due to suspension travel.



That said, I've driven LSD-equipped MCS and they offer much better acceleration when coming out of a corner. There was a great article in last month's GRM that compared the different types and brands of differentials in detail.

 

andy, your car is so pretty! what is GRM? i am interested in the article you mention on the different limited slip differentials. do you know which one BMW is using on the 2005?
thanks

 

GRM is Grassroots Motorsports, a very good magazine for autocross/open track/normal human affordable racing.

Not sure about your data there Andy, but prior to my quaife install straight line acceleration was strictly a one wheel peel. Since the LSD I find I have a much better start off the line, and can apply a greater amount of throttle, especially with the sticky Azenis.

 

My logging agreed with the black stripes on the road.

If the mu split (difference in coefficient of friction between left and right tires) gets big enough, then one wheel definitely spins. But in my experience in most straight line conditions on both street and strip, both wheels spin about the same amount.

 

>> in most straight line conditions on both street and strip, both wheels spin about the same amount.

Would that be with the stock differential? mu split, friction coefficient and I thought this was an easy question.

 

Yep, stock differential.

http://auto.howstuffworks.com/differential.htm

 

>>Yep, stock differential.
>>
>>http://auto.howstuffworks.com/differential.htm

Thanks Andy, the link cleared up the cob webs.

 

So andy, do you have data on an LSD equipped MINI you could share? I am getting ready to make the big spend on the quaiffe........

 

Nope, I haven't done any logging in LSD-equipped MINI's.