One thing thats bugged me for a little while is the locked diff issue in FWD cars.
Every decent setup I have used, or been given, has had a locked diff, and for some reason they give the best laptimes.
TBH, I can't figure out why this is, in my mind a locked diff shouldnt work anywhere other than on a drag strip, but they are being used everywhere.
Is there any reason for this?, or am I mistaken?,

Dan,

My guess is it's the low speed grip issue of the tyres (i.e. the difference in speed between the inside and outside tyres)

Locked diff is the best for traction under acceleration and braking stability and therefore gives you confidence in the car, but it should have significant disadvantages in the entry and exit phases of the corner... currently it doesn't.

Also currently the clutch pack behaves a little odd under trail braking, where there is often a sudden drop in RPM which causes unexpected moments (this doesn't instill great confidence in the car )

So when you've got a choice of clutch pack that has odd behaviour, or locked diff that doesn't have the disadvantages it should the choice is simple... but I don't think it will remain this way indefinately.

I also suspect this has something to do with the lacking tyre physics. And as Scawen is working on that, I have confidence this will be solved in the not too distant future.

Quote from Clownpaint :

I can't say I share that confidence! I know it will be fixed, just not soon I'd imagine.

Depends on how you define "not too distant future". I am kinda expecting a physics patch before the end of the year... But let's not get into that here.

I believe the tyres deform too much under load. That would explain the strange low speed grip and the performance of the locked diff. The tyres deform so much that they can compensate a good part of the difference in speed between inner and outer wheel.

Vain

Tyres deform alot in real life also try put chalk on your sidewalls then go do some auotcross

LFS is not realistic at all in this regard. IRL you could either not physically turn the wheel because it would be so heavy or even if you could the diff would simply rip itself apart.

Nah, there are lots of vehicles with locked diffs. Think of older jeeps (not those new fancy SU-can't-drive-over-a-patch-of-grass-Vs) where you can manually lock the diffs. It becomes noticable harder to turn the wheel and the tyres begin to make a scrubbing noise, just like in LFS, but no part rips itself apart.

Vain

Alot of drivers here in Aus (espicaly those P plater holden drivers!) run welded or spool diffs in their cars.

Yeah, but FWD or RWD?, a locked diff in a FWD is a different animal to one in a RWD.

Dan,

Oval racers over here use locked diffs - but they compensate for the Ackerman problem by running different rolling radius on each side of the car.

I have to say - the locked diff thing is very unrealistic in LFS. The cars would be virtually impossible to turn in real life.

simply put...if you chose to run a differential on LFS which transferred power to one wheel that loses grip...you would burn that tire flat through a hard corner...ie F9 temp turning red and then inner tire showing hollow black color...i use locked diff on XF Gti...but then im still dumfounded about the rest of the setup since i can only lap a 1:36...where ive seen others run a 1:33-32 on BL GP Road track...

i prefer the locked diff as when coming out of corners both wheels turn at same rate removing the inside wheel sitting in a burnout and goin nowere when entering a corner at speed, it gets the power down and i like that also there is a lot more control. in the rwd the inside wheel will spin as its not going as fast as the outside wheel thus creating a good controlable drift as you try to keep the car straight same as in my ascona as i have the diff welded.

Locked diffs are the way forward, rwd or fwd i recommend them

Locked diffs are terrible for me. So much understeer. Can't wait til preload is simulated (so I can let off the brakes without a wholly rear end) and the locked diff option is removed from some cars (or becomes track specific, i.e. drag lane only).

The trick with locked diffs (atleast for FWD) is that as soon as you want to turn you have to add a little throttle. When I'm driving the XFR I start braking for a corner, and just before I turn in I get on the throttle again, still braking but doing two things:

1) moving the brake balance to the rear (because I accellerate the fronts), thus increasing the tailbraking effect
2) "unload" the diff a bit, so not both tyres are trying to keep me straight, but they're kinda mixed

This seems to work ok for me. No idea if this works on RWD's though.

Yeah I noticed that too AndroidXP but I can't think as to WHY it should work. OK so when you add some throttle, most of this will be transfered to the outside wheel, which should help turn in... but the wheels are locked, force to turn at the same speed. So it shouldn't make any difference, that inner wheel is going to scrub unless (like in karting) you remove all the weight of it and get it to lift in the air.

Didn't Todd explain that quite believable some time ago? The outer tyre is heavily loaded and has much grip while the inner tyre is almost not loaded at all, having close to no grip, but still scrubbing a bit. That results in a rotational force, actually helping turning a bit. I think that's the same thing that can make FWD cars (somewhat) oversteer on throttle.

Hmm, I might of missed that, or was half asleep at the time.

I've got a front wheel drive road/track car that I can make oversteer under power. It has a Quaife ATB diff. Not locking - torque biasing. Provides a percentage of lockup which occurs gradually (unlike plate diffs that lock suddenly)

I have driven the car with locked diff.The bolt lock diff and clutchpack. It was 80hp fwd lada. It didnt have powersteer. It was hard, but possible to drive and it had great adwantage on snow. WHen the diff lockes it tryes to spin your wheel hardly and u have allways hold the wheel firmly during turns, especially on tarmac and slicks-style tyres.The behaviour was like lfs-but in chicanes the tires burns and all small radius turns was some sort of drifting. Clutchpack was quite comfortable-u almost doesnt notice it. I didnt use visco type diffs but i think if ull try to use it IRL like it is used in lfs i'll burn in a moment - in opel calibra or awd audi if your tire radius on one wheel is 5-10 mm smaller than on other - 100km and your visco is burned. The guy race with me on awd opel vectra changed about 5 diff boxes. And of cause the tyre damage...

But the other problem -how to mod AYC type system used in mitsubishi evo -6-8 and subaru ...The are used in rally- so must be in lfs - but the algorytm it works is complicated - it has accelerometrs in the center of the car - near hadbrake - and if car starts spinning- it locks the diffs.
I'm trying to make rb4 act exactly like my evo8 IRL -but it is not so easy .

I know its a bit early, but what is the general concensuss on the locked diff now?

I have found that in my FXO setups a locked diff give awesome power-on oversteer now, so am using the clutch pack instead.

Dan,

Quote from Sketch :

locked diffs in fwd rally cars are common as. I don't see what all the fuss is about. in rwd locked diffs are way more predictable handling wise, whilst less forgiving on tyres. but tyres are easy to replace right... :P i got a mechanical locker in my fourbie and will atest that it does make steering more heavy esp at low speeds but i have no idea how this would affect steering at 'higher' speeds. but i think locked FWD certainly adds predictability in LFS, whether its realistic is another matter.

if you have air lockers (or any other lockers ) in your 4x4 dont ever EVER drive on tarmac, or anything above 20 kmh, otherwise you WILL snap driveshafts, diffs and basically every part of your drive train is vunerable

in real life you wouldnt be able to use locked diff in a racing car because there would be way way too much pressure on drive parts and the car wouldnt make a lap driving hard, lfs dosent emulate this, and this is why we can get away with this

danowat:
I noticed this too when I was doing hotlaps in the XFG. When punching it at the apex it would start to oversteer

Same here.

On the XFG the locked differencial used to be killer. Grippy and smooth and all that. Now I'm getting massive oversteer at corner entry, even if I'm uber-careful with the throttle, and doing some very early braking, so it's a no-go.

I'm using the clutch pack now.

Oversteer in FWD car is good, no??