WTCC rear toe alignment

[Belatti]

In the last WTCC race at Termas de Rio Hondo I took a look arround the cars and noticed they use the front ARB attached to the upright. In a FWD car that may help to transfer weight to the rear inner wheel proportionally with steering.

What I could not see is how do they align rear toe.

Rear toe out is obvious for a FWD car with a "normal" layout, but not when you are transferring weight to the inner wheel as steer is turned... what do you think?

[marcush.]

In the last WTCC race at Termas de Rio Hondo I took a look arround the cars and noticed they use the front ARB attached to the upright. In a FWD car that may help to transfer weight to the rear inner wheel proportionally with steering.

What I could not see is how do they align rear toe.

Rear toe out is obvious for a FWD car with a "normal" layout, but not when you are transferring weight to the inner wheel as steer is turned... what do you think?

in which ways is there a difference to the arb being attached to the upright or the A-arm(?) I assume your point is the steering of the upright does change the angle of the link to the arb leading to arb movement (twist) ..but that´s something you design into the application -it could be adding or releaving cross weight with steering effort -or am i wrong here ?

[Belatti]

-it could be adding or releaving cross weight with steering effort -or am i wrong here ?

that

[Belatti]

More adding that releaving I may add. Its a feature that seems to work well in many type of cars (FWD or RWD, front or central engine) but mostly with tyres that have low load sensitivity coeficient.

[Jersey Tom]

Rear toe out is obvious for a FWD car with a "normal" layout

Why is that?

[Belatti]

At least in my experence, both with national tyres or brazilian pirellis, fwd cars in the range of 200 to 300 hp need rear toe out if you dont want to understeer like hell.

[MadMatt]

Toe out at the rear is good if you have lot of corner entry understeer, but that will deffo make your car more unstable. As Belatti said, it make sense on a FWD car.

[Belatti]

Toe out at the rear is good if you have lot of corner entry understeer, but that will deffo make your car more unstable. As Belatti said, it make sense on a FWD car.

As I said, I have seen FWD cars with no "front upright attached ARB" use rear toe out but I guess its NOT because the corner entry indersteer as you state.

Allow me to separate corners in 2 simplified groups: fast and slow.
a) slow: more braking required, more weight tranferred to the front at corner entry, less contribution of rear toe out to make the car unstable
b) fast: with not much braking, the rears are somehow more loaded so here it can get tricky. As "FWD drivers" use to apply throttle with oversteer, in the particular case where you have way too much rear toe out, the "throttle" loaded rear can contribute to increase the O/S the driver suposedly wants to correct...

In every FWD case I have seen with "no front upright attached ARB" rear toe out is used.

The question is, that with upright attached ARB I have seen both cases...

[Jersey Tom]

Interesting stuff, particularly given that I don't have really any experience with FWD cars.

[Luke]

Toe out at the rear is good if you have lot of corner entry understeer, but that will deffo make your car more unstable. As Belatti said, it make sense on a FWD car.

As I said, I have seen FWD cars with no "front upright attached ARB" use rear toe out but I guess its NOT because the corner entry indersteer as you state.

Allow me to separate corners in 2 simplified groups: fast and slow.
a) slow: more braking required, more weight tranferred to the front at corner entry, less contribution of rear toe out to make the car unstable
b) fast: with not much braking, the rears are somehow more loaded so here it can get tricky. As "FWD drivers" use to apply throttle with oversteer, in the particular case where you have way too much rear toe out, the "throttle" loaded rear can contribute to increase the O/S the driver suposedly wants to correct...

In every FWD case I have seen with "no front upright attached ARB" rear toe out is used.

The question is, that with upright attached ARB I have seen both cases...

My first thought would be if the rear toe is predominantly to tune high speed corner entry/mid balance, then whether or not the ARB is attached to the upright in this situation is less of a factor as high speed generally means less steering, so less effect of the upright attached ARB than in slow corners with lots of lock?