Negative scrub radius on the '17 Merc & Toro Rosso

[roon]

http://www.f1fanatic.co.uk/wp-content/u ... _HiRes.jpg

https://pbs.twimg.com/media/DIj1lLrXkAA1DQm.jpg
Via @ScarbsTech

The W08 & STR12 might have it, depending on where the lower suspension arm pivot is located within the wheel. In the image above, the green and yellow circles represent speculated locations for the wheel upright's lower pivot. The grey circle is the upper pivot. The vertical orange line is the wheel cover face. The pushrod axis is emphasized with a cyan line, and the lower suspension arm is emphasized with a purple line.

If so, the tire contact patch will rotate around the inside of the kingpin axis, rather than around the outside of it (positive scrub), or about itself (zero scrub radius). This will influence how the tire contact patch changes shape, steering forces, how the tire body is presented to airflow, etc. To what benefit?

Notice how long the interface is between the wheel cover and the lower suspension arm:

Via AMuS

This may suggest that the end of the arm is rather far inside the wheel.

[mep]

This is just the latest episode of a suspension being compromised for an aerodynamic gain. The high bracket can help a bit manage airflow around the tire. Also it allows to mount the lower wishbone even higher, which brings it out of the airflow around the bottom of the car. Note that hump on the rearward leg of the lower wishbone, it is another indication of flow management around the tire.

The pivot of the lower wishbone is most likely the further inboard one, so close to your green circle.

Notice how long the interface is between the wheel cover and the lower suspension arm:

I am not totally sure which interface you mean, but the wishbone shapes can be misleading. What you see is just an aerodynamic cover. The actual structure can be quite different. The lower wishbone pivot could even sit under the cover just close to the transition between wishbone and brake duct. The dark black section is flexible rubber or silicone; the extent of this can be taken as a reference of the required clearance for suspension movement. From the pictures you showed, the rubber area looks really small, indicating that the lower pivot must sit very close to it.

[roon]

If the steering arm connection is any indication, the lower control arm pivot may be well within the wheel hub as drawn in the OP.

Semi-related: if the car rides on its front tires' inner sidewalls due to camber, then pivoting off the sidewalls while steering, due to the apparent kingpin inclination and scrub radius, might reduce ride height. Said another way, the contact patch will be located nearer to the inner sidewall at zero-steer, and will shift toward the center of the tire as steering angle increases. I'm wondering if such a shifting off the inner sidewalls would reduce ride height due to tire shape and deformation.

[Greg Locock]

Once you've got PAS scrub radius is a detail. The only useful thing it does is help the driver to detect pull under braking, which may indicate he's on a split mu.

[gambler]

Easier to steer !, I would assume caster "rise and fall" would get less. It would make the car push and have less impact on the rear when it "steps out". Perhaps a narrower track and more caster than normal would fix it.It will wear the tires much more even especially on brake lock up with a lot of "turn" I am certain it will let more laps be run on soft tires. I think it will let the driver get on the wheel harder for longer periods of time.

[roon]

Once you've got PAS scrub radius is a detail. The only useful thing it does is help the driver to detect pull under braking, which may indicate he's on a split mu.

Beyond steering feel, I'm suggesting that having the center of the scrub radius inboard of the KP axis (negative-scrub) or near coincident to the KP axis (zero-scrub) will provide the rumored ride height drop while turning the wheels. Via "dropping off" the highly cambered tires inside shoulders i.e. the contact patch center shifts toward the center of the tire accordant to steering angle increase.

I'm assuming ride height increases with increased negative camber up until extreme angles are reached, beyond which ride height will be reduced. Consider the following image.




In this example, the components within the wheel (pivots, hub, lug nuts, etc.) will be slightly higher than if the wheel had reduced or zero camber, because it's riding on the tire shoulder.

F1 camber is not this extreme but it is still significant. Combined with in-wheel suspension pivots/connections, the same effect will be achieved.

Combined with KPI effects and resultant contact patch location shifting, I'm suggesting this is how ride height drop is achieved by the W08 and STR12.

[Tipo59/06]

Once you've got PAS scrub radius is a detail. The only useful thing it does is help the driver to detect pull under braking, which may indicate he's on a split mu.

Beyond steering feel, I'm suggesting that having the center of the scrub radius inboard of the KP axis (negative-scrub) or near coincident to the KP axis (zero-scrub) will provide the rumored ride height drop while turning the wheels. Via "dropping off" the highly cambered tires inside shoulders i.e. the contact patch center shifts toward the center of the tire accordant to steering angle increase.

I'm assuming ride height increases with increased negative camber up until extreme angles are reached, beyond which ride height will be reduced. Consider the following image.


https://d3vl3jxeh4ou3u.cloudfront.net/N ... 2BX0q7s%3D

In this example, the components within the wheel (pivots, hub, lug nuts, etc.) will be slightly higher than if the wheel had reduced or zero camber, because it's riding on the tire shoulder.

F1 camber is not this extreme but it is still significant. Combined with in-wheel suspension pivots/connections, the same effect will be achieved.

Combined with KPI effects and resultant contact patch location shifting, I'm suggesting this is how ride height drop is achieved by the W08 and STR12.

I think your correct and this area may become a bone of contention for stringent policing of rules....lets see if Toro Rosso runs the 17' design for the new car...edit they have indeed based on leaked images