LSD ramp angles

[prelit]

Hi Guys,

looking at the web sites of 2 manufacturers who make plate type LSD's they both quote a selection of alternative ramp angles and pre-loads.

Pre-load seems fairly straight forward, but I'm far from sure about the ramp angle figures.

Tran-X for example quote ramp angles 45/45, 55/90, 45/90 &

35/90.  (also pre-loads of 25/30 & 65/70 Ibs ft)

Is the first figure the drive ramp & the second figure for the anti-drive?

If so is a lower number on the drive more progressive than a higher number? and is this reversed on the anti-drive ramp?

I guess for a light car such as a Westie the LSD action would need to be fairly soft or understeer could occur.

Anyone care to recomend what angles would work best on a

sprint car that's running list 1a tyres with approx. 190bhp.

Thanks in advance,

Prelit.

[John Loudon - Sponsorship Liaison]

Simon,

You need a 35/90 Lotus Elan spec with a preload of 35ft/lb

John

[prelit]

Thanks John,

I've very kindly been offered the loan of 2 plate LSD's to try (both with the correct CWP ratio)

The first by Rob Navin (thanks Rob, top bloke) however Rob's is set up 'tight' as it's out of his Escort mk 2. Not unsure of the ramps angles or the pre-load.

The second off a friend (he lived just around the corner from you and has a yellow X flow Westie which he's been converting to a K Series for some time now) who had his specified new by Tran-X for 'road' use. My friend believes this has 55/90 ramps and a pre-load of 25/30 Ibs ft.

Is a 35/90 less progressive then? more suitable for competition perhaps.

Thanks,

Prelit.

[Jon Murray]

This might help.

Taken from here.

"The design of the cross pins and ramps in which they operate allow torque bias changes to be made. The closer to 90 degrees angle the ramp is made, the less action it has - so a 90 degree ramp effectively unlocks the diff making it behave like a standard diff. Conversely, the shallower the angle, the greater the locking action.

There are three basic types available. "90/55" for gentle Road use, 50/40 for rally & autocross use and 90/35 for full race!"

Jon

[prelit]

Thanks John M

Useful info.

Prelit.