Aero grip vs. mechanical grip (and low profile tires)

[DaveW]

What can be achieved with 4 wheel steering?
I believe F1 need to get back to active suspension if we really are to see an improvement with following another car.
So these areas: 4 wheel steering, active suspension, (active aero maybe as well?) should be on the table.

https://www.youtube.com/watch?v=GvQh2ue--0g

Your youtube reference was interesting, I thought. I reminded me of the Prelude mechanical system devised by Honda. That provided some interesting reactions at the time (rather similar to Tim's remarks, above). The mechanical nature of the drive linkages was a limiting factor - I guess that the Porsche system could overcome those, I suppose.

I feel sure that the Porsche system would be integrated with its torque vectoring algorithm...

[ringo]

I think mazda also had 4 wheel steering in the 626.



The cars would be more stable and easier to drive of course, but this is in aid of following through corners.
There isn't a clear relationship between difficulty to drive, ability to overtake, and mechanical grip; might as well throw all the mechanical technology at the sport as we can to reduce the impact of loss of aero.

[bill shoe]

Moto GP bikes are surprisingly close to the lap times of top-tier Formula cars despite having no downforce. Moto GP bikes are much much quicker than any downforce-neutral car. And the bikes are definitely not too stable or easy to ride.

The bikes have monster mechanical grip. I don't know the numbers, but it seems like 2.0G + just based on simple observation of lean angles through slow turns. The power to weight is remarkable, but interestingly is roughly in line with F1 (2 or 3 lbs per hp). These bikes are very "racy", meaning they can be driven close to each other all race long with little influence on nearby bikes.

The connection to this aero vs mechanical thread might be that you can have quick and close racing with zero downforce, but once you start adding downforce, even a little, you drastically reduce the race-ability while going just slightly faster.

[Tim.Wright]

4WS doesn't add any grip, therefore it can't regain what's lost aerodynamically while following another car. It can only make trim changes which affect the apparent balance and stability.

Works perfect on road cars which lose stability and yaw damping at high speed and lack adequate downforce to regain it.

[Tim.Wright]

The connection to this aero vs mechanical thread might be that you can have quick and close racing with zero downforce, but once you start adding downforce, even a little, you drastically reduce the race-ability while going just slightly faster.

The downforce is responsible for about 20secs of laptime according to some lap sims by Willam Toet




Getting rid of its not an option if you want to keep the current performance levels.

[ringo]

4WS doesn't add any grip, therefore it can't regain what's lost aerodynamically while following another car. It can only make trim changes which affect the apparent balance and stability.

Works perfect on road cars which lose stability and yaw damping at high speed and lack adequate down force to regain it.

Well lets get into slip angles and grip for a moment. Wouldn't you say you should see an improvement in grip? (not an increase, but more usable grip for a certain yaw angle).
Also the effects of graining, degradation should be much different with 4WS.

[Tim.Wright]

Just to clear up terminology, when one speaks of grip performance this typically (well usually) means the peak lateral/longitudinal force capacity of the axle. By changing the slip angles it does very little to change the peak achieveable cornering force. To increase the grip performance of an axle you need to change either camber or vertical load.

The change in slip angle (not yaw angle) is not because the tyes are put in a different (better or worse) condition, they are working in basically identical conditions but they are rotated with respect to the chassis so the chassis sees a different axle slip angle. This has implications and possible advantages in stability and control (or driveability to use street speak). I assume this is what you meant by "more usable grip for a certain yaw angle"

However, like I mentioned before, the last thing F1 needs now is more stability/driveability.

The change in stability you get from 4WS will no doubt change the vehicle's transient behaviour but in my opinion it wont have a huge effect on grip performance. Tyre wear will also surely be quite different.

All in all, it wont make the cars much faster but it will make them significantly easier to drive.

Exactly the opposite of what we need from a spectator point of view in my opinion.

[bhall II]

What's it gonna be like in 2017 when, in addition to a wheelbase that's longer than that of most full-size SUVs, cars will have the track width of a Humvee?

[bill shoe]

Tim, interesting chart. But what happens if you use Moto GP levels of grip, around 2 to 2.5 G's with no downforce?

[DaveW]

The downforce is responsible for about 20secs of laptime according to some lap sims by Willam Toet

Getting rid of its not an option if you want to keep the current performance levels.

Forgive me, but I have a few questions about Toet's analyses. It looks to me that his simulations were executed with aero being the only change. Fine, but a real test of an aero-neutral car would require changes to springs, dampers, geometry, ride height, tyres, etc. Those changes would not recover the performance lost by (lack of) aero, but it would mitigate the loss and, perhaps, allow different lines to be driven through corners, etc.

[autogyro]

In any case, how do you equate sufficient performance.
Not from track design surely?

[Tim.Wright]

Tim, interesting chart. But what happens if you use Moto GP levels of grip, around 2 to 2.5 G's with no downforce?

I don't know, I didn't run the simulation so I can't check that case. Anyway, I have big doubt's over claims of >2g on any type of tyre without aero help. I haven't seen a lot of motorcycle tyre data but what I have seen is is comparable to equivalent car tyres in terms of peak friction i.e. a bit over mu=1 for a performance street tyre. Though if anyone has any roll corrected accelerometer data from a MotoGP bike, I'd happily stand corrected.

Even if it was true, these tyres with no aero help would only allow you to corner at GP2/3 levels.

Forgive me, but I have a few questions about Toet's analyses. It looks to me that his simulations were executed with aero being the only change. Fine, but a real test of an aero-neutral car would require changes to springs, dampers, geometry, ride height, tyres, etc. Those changes would not recover the performance lost by (lack of) aero, but it would mitigate the loss and, perhaps, allow different lines to be driven through corners, etc.

Yes, this is true but the performance change from setup tweaks are going to be much smaller than what you see from the massive aero changes. Moreover, what's to say that the setup wont need to go in the opposite (slower laptime) direction for the no downforce case in order to keep the car stable at high speed? I assume these simulations are done with a quasi steady state simulation. Their biggest weakness is that the driver "model" doesn't take into account instabilities.

[bill shoe]

Grip of motorcycle tires: A bit more research failed to produce hard info, but a more realistic estimate seems to be a lateral max of 1.8 to 2.0 G, less than my previous claim. But probably still more than any F1 tire with no downforce.

The last sentence probably relates to DaveW's recent point: If the tires don't have to stand up to the aero load and resulting cornering load of an F1 car then their construction can be quite different and more optimized for non-aero-enhanced grip. This probably partly explains why MotoGP has more zero-downforce grip than F1.

Interestingly, I can't think of any recent high-end formula car tire that was optimized for grip without aero load. Since all modern high-end formula cars have lots of aero downforce, the tire companies never have reason to go down the no-aero design path.

[ringo]

Can you say what are the differences in properties of a non aero designed tyre and an aero design?
and are these solely based on vertical load?

What improvement in overall grip can be had with 6 wheels, if 6 wheels were intended to shift the grip scale to the mechanical side?

[bill shoe]

If we're lucky a real tire designer will pipe in.

Part of high motorcycle grip comes from using camber thrust of tire. Conventional car suspension can't replicate this. Some attempts, but awkward (Renault and Michelin tried system on F1 car many years ago during testing).

F1 tires with no aero load could likely go in direction of larger contact patch and stickier compound, both would tend to help max lateral g.

6 wheels?-- Yea, I would like to see that allowed. Four contact patches on a flat surface is already statically indeterminate, so I see no intrinsic Engineering reason why 6 would be more weird.