I don't have skills on mechanics and I don't understand why occours what I will say now but, in RL the rear suspensions on a street car works different than in LFS.

In a street car if you put reverse, move and pull hand brake the rear of car will move up, if you move forward (30kmh or something, without lock) the rear of car will move down.

I tried it with 7 diferent cars, (Opel Vectra '92, Citroen sXara picasso '06, peugeot partner '09, peugeot partner '05, peugeot 307 '07, opel astra '01, the most exagerated reaction is in the old/bad cars like Opel Vectra '92 and peugeot partner '05)

In LFS the reactions are completely opposite. In LFS if you move in reverse and pull handbrake the rear of car move down, I tried with XRT and FXO and XFG with hard_track setup

I don't know how affects to drive this in race. I think, and is just a guess because as I have no knowledge of mechanics, I think it has to do with modeling of the suspension or the way it is mounted in the car

It is solved on the next scirocco patch?

I think you're looking at something the wrong way, because it's done correctly in LFS. The 'lift' or what you want to call it, is weight transfer. When braking, weight transfers to the way you are travelling.
So when reversing the weight will shift to the front of the car which will push down on the front and pull up the back, and when braking it will shift to the back.

That's what we can think at the first moment, but please try it with your car and you will see the diference. I understand the weigth transfer, but in a street car 'ever' (at low speed) when braking (reverse of forward) the front will move down and rear will move up.

LFS is wrong. It's because the car in LFS that should have trailing arm rear suspension (or multi-link etc) just use the S1 suspension system, which was effectively a sliding pillar type suspension.

I'm sure, with the amount of work that's gone into the Scirocco, they'll have improved this.

Quote from RasmusL :

So when reversing the weight will shift to the front of the car which will push down on the front and pull up the back, and when braking it will shift to the back.

You're wrong Try it, Napalm Candy is right. I never noticed this and I don't think it's really a problem, either, but... he's right

Well, braking while going forward WILL result in what happens in LFS:
http://www.youtube.com/watch?v=xmdQgIGmZZo&NR=1

I don't see the problem?

I can't find a video in reverse, and I'm not about to go out and try it now ^^

Quote from RasmusL :

Well, braking while going forward WILL result in what happens in LFS:
http://www.youtube.com/watch?v=xmdQgIGmZZo&NR=1

I don't see the problem?

I can't find a video in reverse, and I'm not about to go out and try it now ^^

He was talking about braking with the handbrake.

I don't think it matters which brake you use in terms of weight transfer? AFAIK the hand brake is simply activating the rear brakes, whether they are drum or disc.

This is related to the way trailing arm suspension creates jacking forces which cause this unusual behaviour. I'm not sure if anti-dive or anti-squat geometry works in LFS at all.

So this happens only while braking in reverse, on cars with trailing-arm or multilink suspension on the rear axle??

The problem is best imagined with FWD cars doing hillstarts. In real life, if you put the handbrake on, the rear of the car goes up as the handbrake stops the car rolling backwards. As you try to accelerate, the rear of the car goes down. This is the jacking forces Bob mentions. In LFS this doesn't happen.

Quote from RasmusL :

I don't think it matters which brake you use in terms of weight transfer? AFAIK the hand brake is simply activating the rear brakes, whether they are drum or disc.

Look, if you're not willing to try it out for yourself then you shouldn't argue over this The rear of the car does go down when pulling the handbrake whilst moving forward, and vice versa.

I'm also not entirely sure if the handbrake just activates the rear brakes. It could be but somehow I would find it hard to believe in the case of brake discs.

I think, all questions should be answered via SusProg3D. Obviously, the program gives comprehensive solutions for all suspension types. Maybe, Scawen will check out this.

http://www.susprog.com/

Quote from obsolum :

I'm also not entirely sure if the handbrake just activates the rear brakes. It could be but somehow I would find it hard to believe in the case of brake discs.

On some rear disk cars, there's a small drum brake built into the hub that's cable operated for the handbrake, I heard before. But there's also disk brakes that can be cable operated as well as hydraulic. It's the law in this country for every post '79 car (cars are NCT exempt after 30 years, so they can be in any condition you like) to have a cable operated rear brake, at least. Look at bicycle disk brakes. The majority of these are cable operated, so it is possible

Surely when you reverse and pull the handbrake, the rear of the car will go down, not up, as it's the same effect as applying the normal brakes whilst moving forward? I never noticed LFS cars not dipping at the rear when handbraking going forward though, nice find

Quote from Bob Smith :

This is related to the way trailing arm suspension creates jacking forces which cause this unusual behaviour. I'm not sure if anti-dive or anti-squat geometry works in LFS at all.

Its not from what I know. When it is implemented it will help the UF handling loads

Yep the trailing arm should give anti-[dive|squat] but the old S1 pillar dones not give this.

For the OP, also matters the wheel the handbrake is linked to. Some cars, my old BX for example, have handbrake linked to the front wheels.

Basically, Napalm Candy IS right.
I was having Practice in a Repair shop for buses (but they also had some cars there).
As they were Activating the handbrake on the DYNO (Dynamometer), the front lifted and the back went down.
But that only happened because the cars weren't moving,
so there were no G-Forces that could cause weight transfer.
This "reversed action" is caused by the Momentum of the Axle;
The Momentum is transferred to the brakes, and as the brakes a static, the Chassis moves in the opposite Angle of the Momentum.
Only cars Travelling on a veeeery slow speed will do that "reversed action"
(because weight transfer does not apply then).

http://en.wikipedia.org/wiki/Trailing_arm
http://en.wikipedia.org/wiki/Torsion_bar_suspension
http://en.wikipedia.org/wiki/S ... vehicle%29#Jacking_forces


Edit:

Quote from Niggo :

Only cars Travelling on a veeeery slow speed will do that "reversed action"
(because weight transfer does not apply then).

You can try that on the road, it works at any speed. As long as you don't pull the brake like mad locking the rear tyres it's relatively save to do as weight is transitioned to the rear.
Of course I'm not responsible for any of your actions.

Here's a drawing I just slapped together to explain the effect (excuse the crudeness, I hate drawing with a mouse):



The top is rear brakes while moving forward, the bottom in reverse.

When you apply the parking brakes in reverse the force on the wheel is towards the front of the vehicle. The trailing arm cannot become shorter, thus the trailing arm/body point moves up in a arc around the wheel, lifting the car body upwards. The reverse happens when you use just the rear brake when moving fowards.

In real life, if you attempt to reverse with the handbrake on, especially in a FWD car then the rear of the car will go upwards, and if you try and move forwards then it will go down.

I have just tried this in LFS using an XFG with a very soft suspension setup and it does do it a little bit, but moves up or down momentarily (depending weather you are reversing or going forward) before settling back to the original ride height, eventhough you stay on the power, so it kind of works, to a point.

Quote from Bob Smith :

This is related to the way trailing arm suspension creates jacking forces which cause this unusual behaviour. I'm not sure if anti-dive or anti-squat geometry works in LFS at all.

I'm pretty sure that the S2 suspension system was modelled in elevation only, so anti-roll and camber recovery are modelled but not anti-dive/squat. Could be wrong though.

Quote from Bob Smith :

I'm not sure if anti-dive or anti-squat geometry works in LFS at all.

im pretty sure that the lfs suspension model is entirely 2d
more than that i also think its 2d stricly in the xy plane of the car (i dont think thats the correct axis rotation for the system lfs uses but im an rf engineer and z is always forward for us)

a proper 3d model might change the way fwd cars handle considerably and also give scawen a lot more opportunity to get the suspension of the cars with more complicated geometry wrong

on a related topic after 8 years of driving an fwd car doing handbrake hillstarts with an rwd car feels very disconnected since you lack that sensation of when the clutch starts to bite as the car squats down

on another related topic has any of you got that video of a bmw squating down a lot under heavy braking? last time i treid to find it i ended up loooking at abs workout videos with a girl that was rather nice to look at (so the endeavour to find the video wasnt a complete disaster)

The same thing happens on a motorcycle when using the rear brake.

You apply a torque to the rear wheel while in contact with the ground and the wheel will apply a torque to the swingarm in the opposite direction.

Quote :

For the OP, also matters the wheel the handbrake is linked to. Some cars, my old BX for example, have handbrake linked to the front wheels.

Completely OT but yes Citroen's have front wheel handbrakes. A passenger in my old BX once descovered this after trying to get me to do a suprise handbrake turn. We almost crashed and there was punching involved!

Quote from Becky Rose :

Completely OT but yes Citroen's have front wheel handbrakes. A passenger in my old BX once descovered this after trying to get me to do a suprise handbrake turn. We almost crashed and there was punching involved!

A very similar thing happened to me too, my mate had somehow got an old citroen and as he pulled into a large gravel carpark, i had a feeling what was coming, but before i could stop him, he ripped the handbrake up and we skidded in a perfectly straight line.

The look on his face was priceless, as if to say, that shouldn't have happened, why didnt we spin around!?

Then when i told him, he then refused to accept that the handbrake was on the front wheels, and i in fact had to jack the front of the car up and actually show him before he would believe me.

iirc, 80's subaru's (brumby, leone, and the wagon...was it called a liberty at that stage?) have front wheel handbrake.

Re: handbrakes on cars with disc brakes, that utilize a seperate drum setup: Landcruiser 7x series have this, as does the toyota soarer iirc, thats the only ones i know off the top of my head.