How does a LSD work in a FWD car?

[Ex-User (19928)]

Can someone answer this?

For sake of argument, let's pretend you have 2 cars with the same box, but completely different ratios and FD. If you swapped the LSD from one to the other, would it affect the final drive? Or is it independent from that?

 

[imprezaworks]

@NorthloopCup

 

[alistairolsen]

The crownwheel bolts around the outside of the diff normally, so they are independent, you can install the diff with any number of different final drive ratios.
Diff looks like this with the crownwheel attached:

This is a rear drive one, but the principal is the same:

 

[McGherkin]

Should just bolt up to the crown, without changing that you aren't changing the ratio.

EDIT: yeah.

 

[Knuckles]

Everyone stfu and watch this!

Best. Video. Ever.

Info starts around 1:50



The highlight is the pronunciation of 'wheel'

 

[Crybert]

I would love to know how all that s**t works. All I know is my megane goes round bends like f**k and that's what it's all about

 

[masekwm]

Best mod on my Cup

 

[JohnnyE]

And mine

 

[Knuckles]

I would love to know how all that s**t works. All I know is my megane goes round bends like f**k and that's what it's all about

Watch the vid I posted.

I can follow it right up until they replace the sticks with gears.

 

[McGherkin]

I would love to know how all that s**t works. All I know is my megane goes round bends like f**k and that's what it's all about

Lego Technic is your friend.

That is the easiest way to understand how a diff works, and how it deals out the most power to the wheel with the least resistance (as an open diff).

 

[Crybert]

Watch the vid I posted.

I can follow it right up until they replace the sticks with gears.

It's a good video mate but that's just a standard diff, not LSD

 

[oreA]

Best. Video. Ever.

Best. Video. Ever. Agreed.

Thanks for posting :grinning:

 

[Knuckles]

It's a good video mate but that's just a standard diff, not LSD

Blast! My bad

 

[coverman]

There are several different types of LSD, at least one of which doesn't work too well from cold

 

[Cub.]

These are both good vids;





As others have said, it is by far the best mod I have done to mine in respect to track work. It made a difference on standard power, and since supercharging the difference made has only increased. I have a gripper.

 

[182Trophy]

Interesting stuff. So do performance 4wd cars have front and rear duffs (as in lsd).
Who can explain lsd's as I get confused by open/welded ect.

 

[Crybert]

Interesting stuff. So do performance 4wd cars have front and rear duffs (as in lsd).
Who can explain lsd's as I get confused by open/welded ect.

Yes all axles that drive wheels require a diff. If say it's FWD then both read wheels are independent of one another therefore don't require a diff. Without a diff driving the wheels you couldn't go round bends without the inside wheel skidding. LSD is different again and allows them to be completely free moving than a normal diff I believe.

I don't know what open and welded means, I'm sure someone will be along to help out

 

[Ex-User (19928)]

Yes all axles that drive wheels require a diff. If say it's FWD then both read wheels are independent of one another therefore don't require a diff. Without a diff driving the wheels you couldn't go round bends without the inside wheel skidding. LSD is different again and allows them to be completely free moving than a normal diff I believe.

I don't know what open and welded means, I'm sure someone will be along to help out:smile:

LSDs limit the slip

A differential by nature, will always apply the torque to the wheel with the least resistance. That's why with certain types of diff, if one of the drive wheels leaves the ground (hitting a curb on a track perhaps) then you will lose all drive until it touches the ground again.

Likewise, if one wheel is on ice and one is on grippy tarmac (mad scenario I know) then the wheel on ice will rotate as it's the path of least resistance for the torque.

Limited slip differential limits the slip, so lets say in the scenario with ice and tarmac, it will limit the amount of torque going to the wheel on ice to 50%, the other 50% going to the wheel on tarmac, meaning you actually end up moving.

 

[Crybert]

LSDs limit the slip :tongueout:

A differential by nature, will always apply the torque to the wheel with the least resistance. That's why with certain types of diff, if one of the drive wheels leaves the ground (hitting a curb on a track perhaps) then you will lose all drive until it touches the ground again.

Likewise, if one wheel is on ice and one is on grippy tarmac (mad scenario I know) then the wheel on ice will rotate as it's the path of least resistance for the torque.

Limited slip differential limits the slip, so lets say in the scenario with ice and tarmac, it will limit the amount of torque going to the wheel on ice to 50%, the other 50% going to the wheel on tarmac, meaning you actually end up moving.

Thanks mate

 

[coverman]

If say it's FWD then both read wheels are independent of one another therefore don't require a diff.

That would make for "interesting" driving I fear

 

[Crybert]

That would make for "interesting" driving I fear

???

I'm saying the rear axle on a FWD car doesn't have a diff

 

[coverman]

I interpreted your typo read as road wheel vice crown wheel rather than rear wheel.
Strictly speaking a car with selectable 4 wheel drive , does have a diff on the temporarily undriven axle.

 

[Crybert]

I interpreted your typo read as road wheel vice crown wheel rather than rear wheel.
Strictly speaking a car with selectable 4 wheel drive , does have a diff on the temporarily undriven axle.

I was referring to FWD which is front wheel drive..not 4WD

 

[coverman]

I have owned an fwd car, Berkely B105, with no CV joints on the drive shafts, just Hooke joints that required greasing every 100 miles, yes 100 miles. It was a pig to drive away from a tight parking space on a steeply cambered road, especially with its on-off motorcycle type clutch and its first gear good for 50mph! Unsurprisingly that advent of the Frogeye Sprite killed the sales dead of such a crude car even if it was much faster than the Sprite..

 

[NorthloopCup]

@NorthloopCup

In Germany currently.