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View Full Version : Why are the cars attracted outside on kerbs.



tomaprice
22-05-2018, 07:29
This is particularly true at lesmo2 (turn 7 at Monza), La source and les Combes (turn 1 and 9 at Spa). Generally I noticed this behaviour when the outside wheels are on the kerb. I don't know if this behaviour is realistic or not but it's very annoying.
Do you have a "scientific" explanation for that ?

Thank you.

Sankyo
22-05-2018, 07:40
I believe it's a real effect. A quick websearch didn't get me anything useful, but I guess there can be different effects.
If the kerbs have less grip than the asphalt (either because they're more slippery or because they are serrated and the tyres will lose contact going over the edges), basically the tyres on the asphalt push the car forward but the tyres on the kerbs cannot, which would mean that the car will start turning towards the kerb.
If the kerbs are slanted w.r.t. the road surface, going over them will tilt the car and that will change the loading of the tyres that are still on the asphalt. This could also result in a force towards the kerbs, but not sure how that would work.

It may also depend on the tyre pressures, as was found in the discussion thread about the Radical SR8 tyres. So you could try and increase tyre pressures and see if that changes the behaviour.

WellRED Barron
22-05-2018, 07:51
In short, friction.

If the side of the car that hits a kerb requires more energy to maintain speed than the side that is not on it, the side that requires more energy will slow down faster than the other, thus causing the car to turn towards it. Same goes for puddles, or soft turf. Like aerodynamics and drag, ground friction, if uneven, can pull you towards the source of the friction unless you counteract with some steering input. When you ride a kerb, those wheels on the kerb are at the very least, going uphill at a higher grade than the wheels not on the kerb, and that is enough to change the balance of friction on your tires, as half your car has to do more work to keep going in the direction you intend than the other.

Hope that helps.

blankfile
22-05-2018, 08:03
Could also be that your inside tirewall is hitting the outside of the kerb.

tomaprice
22-05-2018, 08:09
Ok, so it depends of the amount of grip on the kerb.
In spa and monza, kerbs have less grip than in Watkins glen for example, because in Watkins glen, this phenomena is absent.
maybe it's due to the presence of grass or gravels at the outside of kerb.

hkraft300
22-05-2018, 08:52
Ok, so it depends of the amount of grip on the kerb.
In spa and monza, kerbs have less grip than in Watkins glen for example, because in Watkins glen, this phenomena is absent.
maybe it's due to the presence of grass or gravels at the outside of kerb.

Some kerbs are just painted, and without VR it's hard to see.
Serrated/ flat.
Banked Kerbs.
Narrow or wide.
Speed/ loading of the corner...

Keena
22-05-2018, 10:03
Could be the floor bottoming out- Ive experience this. Makes steering a bit interesting as if you have input on when you come of the kerb its a bit whoah..


Remember when everyone was getting punctures one year in F1 because of the kerbs? (hint hint for the devs)..

Franco Ferrari
22-05-2018, 10:31
It does that only if you're accelerating on a RWD car... and to a minor extent on a FWD car. *
If you coast, you shouldn't feel any particular attraction.
The reason is that the wheel on the track has traction while the one on the kerb/grass has less or has not.
And if only the wheel on one side can provide traction, it "pushes the car ahead" on that side only, hence makes it rotate toward the "outside".

In theory you need a limited slip differential to suffer from this effect (or the TC activated), but all racing cars have one. **

It also works the other way around: if you brake with only the wheels on one side on the track and no ABS, you'll get pushed "inside" the track... into a spin.



* and **: I haven't checked it in game yet... it's the reason that told me so.

Scott Coffey
22-05-2018, 12:05
I've noticed being "sucked in" by the curbs since the last patch.

ELAhrairah
22-05-2018, 12:18
In my opinion the real question should be: is this realistic behaviour?

I noticed it too, especially with RWD Formula R3.5 cars. It doesn't happen at every corner, at any speed or over every kerb. So my guess is that the effect of the kerb is non-linear.

Any reallife racedrivers here that can confirm that this effect is realistic?

Zaskarspants
22-05-2018, 12:19
When a car goes around a corner it will experience a force that throws it to the outside of the corner. It is only the four small patches of rubber that prevents the car from doing so. Reduce the grip and the force stopping the car from going wide is reduced, so the car will run wide.

There is no sucking but the movement is a natural result of the forces acting. Like cutting the string on a ball being spun round, the ball stops following a circular path and will travel in a straight line.

As stated above the kerbs have less friction, and lifting a tyre may also reduce the corrective force.

MaximusN
22-05-2018, 12:25
Also try playing with 'tone' (or maybe FX). FFB is very different going from left to right. I have mine at 10-ish, and I do notice kerb pulling. But I alwas thought that was because of my choice. I like the low tone feeling a LOT better than standard(halfway) or even worse full, so I didn't bother to test my theory. :)

Sankyo
22-05-2018, 12:37
When a car goes around a corner it will experience a force that throws it to the outside of the corner.
As a physicist I have to jump in here :) There is no force throwing it to the outside, it's really a fictitious force (commonly known as the centrifugal force) as there is no initiator of the force. What's happening is that there is a force (exerted by the tyres) on the car pushing it away from the outside of the corner. Since the car's natural tendency is to continue its movement in a straight line (inertia), it feels as if the car is pushed outward while in reality the real force is inward. What the car (and the person inside the car) really feels is inertia.

[/pedantry]

Keena
22-05-2018, 13:53
Just tried some kerb running on the Formula C. No effect noted as described in this thread unless I put the outside tyre actually off the kerb on the off track side. All as expected in that scenario also. Hope that helps potentially narrow down any actual observed anomalies.

Keena
22-05-2018, 13:54
As a physicist I have to jump in here :) There is no force throwing it to the outside, it's really a fictitious force (commonly known as the centrifugal force) as there is no initiator of the force. What's happening is that there is a force (exerted by the tyres) on the car pushing it away from the outside of the corner. Since the car's natural tendency is to continue its movement in a straight line (inertia), it feels as if the car is pushed outward while in reality the real force is inward. What the car (and the person inside the car) really feels is inertia.

[/pedantry]

Shurely centripedal hic..? ;)

superpedantry

ATSS
22-05-2018, 14:09
Could be the floor bottoming out- Ive experience this. Makes steering a bit interesting as if you have input on when you come of the kerb its a bit whoah..


Remember when everyone was getting punctures one year in F1 because of the kerbs? (hint hint for the devs)..

Pirelli was not on top of their game though.

Keena
22-05-2018, 16:09
Pirelli was not on top of their game though.

Yeah for that race in the States definitely. I was thinking of one somewhere else though were a sharp edged kerb was shredding the sidewalls and causing tyre failures on cars that were running wide on that particular corner. Sorry I cant remember which one. It might even have been pre Pirelli..

WGIstation6a
27-05-2018, 03:36
Road America is ruthless with this. Just stay off them.