RE: Ask the expert: All you want to know about differentials

RE: Ask the expert: All you want to know about differentials

Author
Discussion

roger.daltrey

114 posts

194 months

Thursday 23rd February 2012
quotequote all
How about a bluffers guide to differentials - including the pros/cons of

Standard (whatever that really means)
Limited Slip Diff
ESP Diff's
Torsen Diff
Viscous Couplings ? (I think I'm out of my comfort zone now, but I'm sure you can add to the list)

And what parameters you can introduce on each type - so with an LSD how you can limit the slip and the control behind this.

All of the above is generally available on t'interweb but great to have all in one place on this site.

Rog

RenesisEvo

3,615 posts

220 months

Thursday 23rd February 2012
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What is your view on the impact of the increasing complexity of such devices on issues such as reliability, servicing and maintenance? Do you think the new technology is contributing meaningfully to a significant level, or just another feature that could go wrong?

Affalterbach

48 posts

156 months

Thursday 23rd February 2012
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What are the advantages of fitting a Drexler LSD to my SL55 AMG. At the moment it does pull to one side slightly when you floor it.

ratty6464

628 posts

211 months

Thursday 23rd February 2012
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I've read that in the case of the M-Differential (M3/Z4M) that one of the draw backs can be less stability at speed on straight roads i.e. Dual Carridgeways.

Is this in fact true? If so, why? and does it apply to all the types of LSD?

GTiFrank

625 posts

185 months

Thursday 23rd February 2012
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1. What is the different between a mechanical LSD and a Torsion LSD?

2. Can a LSD help with FWD on turn in under left foot braking?

CDP

7,461 posts

255 months

Thursday 23rd February 2012
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Kawasicki said:
Is it always the case that a lsd will induce corner entry understeer?

Surely partially locking the rear tyres together can also induce (non power) corner entry oversteer, as the total grip of the rear axle will be reduced because each tyre is not independently free rolling, and therefore not capable of producing maximum lateral grip.



Edited by Kawasicki on Thursday 23 February 10:42
A couple of questions I was going to ask too.

Also what sort of difference in reaction times is there between a mechanical limited slip diff verses an electronically controlled device?

jimbro1000

1,619 posts

285 months

Thursday 23rd February 2012
quotequote all
clarkey said:
Yes, an LSD can induce understeer. If you are going round a bend, the inside wheel needs to turn more slowly than the outside wheel. An LSD will limit the difference in turning speed between the two wheels, which could cause the car to push on in the bend rather than turn (ie understeer)
Think of it like a kart, which has no differential. To avoid understeer in a kart you have to get the inside rear wheel to lift.
Once an LSD starts to "lock" under acceleration it will promote understeer, the idea is that you should be winding off the steering and adding power when it happens. If you get on the power too early the result can be quite embarrassing...possibly even expensive just in a different way to a car without an LSD.

Different types of LSD show different behaviour though. Some give up if you lose traction completely on one wheel - that really does give big understeer.

Stuart

11,635 posts

252 months

Thursday 23rd February 2012
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Please could someone explain the offside rule. Ideally with (not too complicated) diagrams.

Once I've understood this and how a diff works, I'll get some sort of badge which confirms that I've qualified as a bloke, right?

nsa

1,683 posts

229 months

Thursday 23rd February 2012
quotequote all
BMW M-cars sliding sideways in clouds of tyre smoke:

http://www.nurburgring.org.uk/ringtaxi/taxi.php

CDP

7,461 posts

255 months

Thursday 23rd February 2012
quotequote all
doogz said:
Stuart said:
Please could someone explain the offside rule. Ideally with (not too complicated) diagrams.

Once I've understood this and how a diff works, I'll get some sort of badge which confirms that I've qualified as a bloke, right?
Only as long as you reverse with your left arm around the back of the passenger seat.
Don't they teach you the reversing trick when learning to drive?

Setch993

195 posts

231 months

Thursday 23rd February 2012
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Steff said:
2) How does a geared LSD like the quaife work compares to a conventional plate LSD?
+1 and effects in a rallying context (rear wheel drive)

BarnatosGhost

31,608 posts

254 months

Thursday 23rd February 2012
quotequote all
clarkey said:
Yes, an LSD can induce understeer. If you are going round a bend, the inside wheel needs to turn more slowly than the outside wheel. An LSD will limit the difference in turning speed between the two wheels, which could cause the car to push on in the bend rather than turn (ie understeer)
Think of it like a kart, which has no differential. To avoid understeer in a kart you have to get the inside rear wheel to lift.
Surely the delta between the inside and outside wheels will be below the threshold at which an LSD begins to intervene?

Otherwise you'll get one wheel dragging like a truck in a tight turn.

Ognyan

3 posts

186 months

Thursday 23rd February 2012
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Why are the older generation BMW "sper" limited slip differentials so popular and sought after? How do they work?

BarnatosGhost

31,608 posts

254 months

Thursday 23rd February 2012
quotequote all
Stuart said:
Please could someone explain the offside rule. Ideally with (not too complicated) diagrams.

Once I've understood this and how a diff works, I'll get some sort of badge which confirms that I've qualified as a bloke, right?
The basics:
A player is offside if there aren't two opposition players closer to their goal line than he, at the moment the ball is played.

A few details:
The offside law only applies to an attacking player, who is 'interfering with play', whilst in the opposition's half. It only applies to a ball played forwards. You can't be offside from a corner or other ball played backwards. Nor a throw-in. In too-close-to-call circumstances, the referee is to give the benefit of the doubt to the attacking player. To be level with the 2nd to last opposition player is to be onside.

To explain it in proper bloke style I will need 4 or 5 items from a normal dinner table, and you will need to be much more attractive.

_g_

741 posts

202 months

Thursday 23rd February 2012
quotequote all
BarnatosGhost said:
Surely the delta between the inside and outside wheels will be below the threshold at which an LSD begins to intervene?

Otherwise you'll get one wheel dragging like a truck in a tight turn.
Indeed, I always presumed this was why they were 'limited slip', rather than 'locked'!

Triumph Man

8,699 posts

169 months

Thursday 23rd February 2012
quotequote all
Stuart said:
Please could someone explain the offside rule. Ideally with (not too complicated) diagrams.

Once I've understood this and how a diff works, I'll get some sort of badge which confirms that I've qualified as a bloke, right?
Here you go, courtesy of Chrysler in the 1930s. http://www.youtube.com/watch?v=K4JhruinbWc

Kozy

3,169 posts

219 months

Thursday 23rd February 2012
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For a FWD racing car, is a helical or plate diff a better option?

Do Quaifes/Torsens/helicals work under braking?

Dagnut

3,515 posts

194 months

Thursday 23rd February 2012
quotequote all
Stuart said:
Please could someone explain the offside rule. Ideally with (not too complicated) diagrams.

Once I've understood this and how a diff works, I'll get some sort of badge which confirms that I've qualified as a bloke, right?
http://www.youtube.com/watch?v=QxSpovGp65w

Dan Trent

1,866 posts

169 months

Thursday 23rd February 2012
quotequote all
Thank you all for your questions; the floor is now closed and Herr Trommer is being sent his list of questions. Hope he wasn't planning on a quiet afternoon!

Cheers!

Dan

PhillipM

6,524 posts

190 months

Thursday 23rd February 2012
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Yeah, can you ask him if he's got a plate diff stashed away that'd fit the buggy....biggrin