McLaren MCL39

[gcdugas]

MCL39 rear tire cooling tricks... I've been thinking about tire alignment lately. Many may not know it but the front tires on road cars have a few degrees of "toe-in" and this produces a more stable feel as the front end doesn't tend to wander when going straight. Moreover in turns as the weight shifts to the outside tire, the front end rotates inward slightly more than the steering input. We tend to think of rear tires at perfectly parallel to the longitudinal axis, and in the case of solid rear axle vehicles it must be the case. But with independent rear suspension, as on F1 cars, the designers are not bound to this. They can have toe-in, perfect parallel, or even toe-out. Toe-in gets its stability much like a skier doing a "snowplow", but to a much lesser degree. The skier can turn very slightly simply by shifting his weight without changing the angle of his skis any. Theoretically this puts some heat in the tires relative to perfect parallel and slows the car nominally down the straights but the payoff in stability and feel far outweigh this.

But what about toe-out applied especially to the rear? It would help the car rotate in turns as the weight shifts towards the outside wheel. Moreover, a cleverly designed geometry could increase the toe-out of the outside wheel under compression while decreasing the toe-out on the inside wheel as it extends while the "car body rolls". This would add to the car rotation and have, to a VERY SLIGHT degree, the same effect as four-wheel steering. Moreover, this would put less energy (temperature) into the rear tires as the angles "cooperate" with the car rotation in corners whereas the traditional inclination of engineers is towards slight toe-in in the rear wheels (because that's the way we've always done it).

Separately but related, if the upper arm of the suspension is shorter than the lower arm, the wheel camber changes favorably under compression for the outside wheel and also changes favorably for the inside wheel under extension. So the inspectors can look all they want at the cooling ducts, the secret could be in relatively unobservable geometry and alignment settings that "cooperate".

I invite the experts to chime in.

[PhillipM]

I'd advise that this is stuff that has been known extensively and done for the past 100+ years of motor racing, there's nothing inherent in that which any other team wouldn't be doing.
Or even your local street racers are doing.

[mwillems]

MCL39 rear tire cooling tricks... I've been thinking about tire alignment lately. Many may not know it but the front tires on road cars have a few degrees of "toe-in" and this produces a more stable feel as the front end doesn't tend to wander when going straight. Moreover in turns as the weight shifts to the outside tire, the front end rotates inward slightly more than the steering input. We tend to think of rear tires at perfectly parallel to the longitudinal axis, and in the case of solid rear axle vehicles it must be the case. But with independent rear suspension, as on F1 cars, the designers are not bound to this. They can have toe-in, perfect parallel, or even toe-out. Toe-in gets its stability much like a skier doing a "snowplow", but to a much lesser degree. The skier can turn very slightly simply by shifting his weight without changing the angle of his skis any. Theoretically this puts some heat in the tires relative to perfect parallel and slows the car nominally down the straights but the payoff in stability and feel far outweigh this.

But what about toe-out applied especially to the rear? It would help the car rotate in turns as the weight shifts towards the outside wheel. Moreover, a cleverly designed geometry could increase the toe-out of the outside wheel under compression while decreasing the toe-out on the inside wheel as it extends while the "car body rolls". This would add to the car rotation and have, to a VERY SLIGHT degree, the same effect as four-wheel steering. Moreover, this would put less energy (temperature) into the rear tires as the angles "cooperate" with the car rotation in corners whereas the traditional inclination of engineers is towards slight toe-in in the rear wheels (because that's the way we've always done it).

Separately but related, if the upper arm of the suspension is shorter than the lower arm, the wheel camber changes favorably under compression for the outside wheel and also changes favorably for the inside wheel under extension. So the inspectors can look all they want at the cooling ducts, the secret could be in relatively unobservable geometry and alignment settings that "cooperate".

I invite the experts to chime in.

The team have worked on tyre interaction, traction/braking stability via the suspension (Though not wholly), essentially keep the car flatter and ride height tighter in by keeping the tyre flatter to the road with a bigger and more consistent contact patch, which in turn allows for better management of the tyres. The MCL39 suffers more in high speed corners and low speed kerbs, it seems on the face value that this may be because the kinematics are less able to deal with the stresses in these sections as well as the more "standard" angles would i.e the car is doing it's damnedest to keep the tyre flat and I'm sure there are times when this is not offering the most grip that another set of kinematics could in these corners.

There will have been an impact on how the team set the car up for Toe and Camber. Unfortunately the team are unlikely to discuss (Hence unlikely we will discover much) any time soon since this technology will almost certainly be on next years car and they will protect their IP.

[CjC]

Is this a new rear wing on the McLaren?

Don’t recall seeing anything like this from them this season so far.

[_cerber1]

Is this a new rear wing on the McLaren?

Don’t recall seeing anything like this from them this season so far.

[CjC]

Ah thanks. Good to know I’ve not lost it yet!

Same DF for less drag no doubt