Limited Slip Differential

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Page created by T May 14th 2007:

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Contents 1 Limited Slip Differential (LSD): 1.1 Why LSD's Were Developed: 1.2 What Happens Without LSD's: 1.3 What Happens With LSD: 1.4 Aquaplaning: 1.5 Visual References: 1.6 Wet Roads and LSD's: 1.7 LSD's in Under Powered Cars: 1.8 Links: 1.9 Terms:

[edit] Limited Slip Differential (LSD):

[edit] Why LSD's Were Developed:

Limited Slip Differentials were developed when engine capacities increased to extreme levels.

LSD's have been made in either Banjo or Salisbury form.

 

 

 

 

HQ SS' Shed

[edit] What Happens Without LSD's:

Without an LSD, large capacity engines can force the nearside (US) wheel airborne on departure as a result of torque reaction and invoke aquaplaning.

 

Steve McQueen floors it and the nearside (US) rear wheel breaks traction and spins freely.

 

Bullitt

 

The offside (US) rearwheel provides no forward traction at all. An LSD would provide a minimum of torque to each wheel to maximise traction and minimise tyre wear.

 

[edit] What Happens With LSD:

At 01:00

 

My Cousin Vinny.

[edit] Aquaplaning:

Aquaplaning is the process of producing molten rubber on the face of the tyre. The tyre no longer grips the road surface and soon begins to disintegrate.

It's also the reason why Antilock Braking Systems are fitted to some cars. ABS tries to prevent
one part of the tyre from being in constant contact with the road and melting. Cycling the
brake pedal on and off is a very effective braking method on a car without ABS.

Without an LSD fitted, the nearside wheel can break traction and begin to spin. Once it spins, molten rubber is produced on the face of the tyre reducing the tyre's ability to grip the road. The car tends to mark time on this spinning tyre and soon rip the tread down to the canvas.

Inside the differential, an LSD has a torque clutch for each axle. The clutches guarantee that
a minimum amount of torque will always be fed to each axle. In the departure case mentioned above, an LSD will guarantee that torque is fed to both the offside and the nearside rear wheels, propelling the car forward and minimising the aquaplaning that would otherwise destroy
the nearside tyre.

[edit] Visual References:

The issue is covered in the film My Cousin Vinnie, where the LSD is "the case cracker".

"Smash Palace (NZ)" is a film that shows a normal diff setting the nearside wheel into aquaplaning during the Ohakune (NZ town) chemist scene.

[edit] Wet Roads and LSD's:

LSD's can be a handful on wet roads because the rear wheels tend to stay locked together on corners.

[edit] LSD's in Under Powered Cars:

Certain model BMW's were fitted with LSD's. Many of these used to grind to a halt in inner city
carparks that had steep upward spiralling driveways. The engines did not have enough power to make
the axle clutches separate and and the car would become stuck on the spot (Torque, ABC TV).

LSD components. Click to Enlargen. Photo by HQ SS.	LSD components. Click to Enlargen. Photo by HQ SS.	LSD components. Click to Enlargen. Photo by HQ SS.	LSD components. Click to Enlargen. Photo by HQ SS.
Showing the Axle Clutch Springs in the centre of a Limited Slip Differential. Click to Enlargen. Photo by HQ SS.	LSD components. Click to Enlargen. Photo by HQ SS.	LSD components. Click to Enlargen. Photo by HQ SS.	LSD components. Click to Enlargen. Photo by HQ SS.
Showing the Axle Clutches in a Limited Slip Differential (large discs with spiral threads). Click to Enlargen. Photo by HQ SS.	LSD components. Click to Enlargen. Photo by HQ SS.	LSD components. Click to Enlargen. Photo by HQ SS.	LSD components. Click to Enlargen. Photo by HQ SS.
Large Salisbury LSD (left), Small Salisbury LSD (right). Click to Enlargen. Photo by HQ SS.	LSD components. Click to Enlargen. Photo by HQ SS.	LSD components. Click to Enlargen. Photo by HQ SS.

 

[edit] Links:

[edit] Terms:

Terms

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