Are big front wheels the real problem?

[henry]

It’s taken a long while, and some unnecessary squabbling, to get to the realisation that they might change the wheel size for non-engineering reasons. If we list the pros and cons so far....

Most of the pros and cons you mention are engineering reasons.

In my reading the discussion has centred round non engineering concepts of modernity or history.

From a historical context the cars being referred to had a much lower duty cycle in comparison to today’s F1. In crude terms today’s cars have twice the power, 50% more weight and their cornering and braking accelerations are much higher, I could research how much higher but it wouldn’t change my point.

Another difference, and germane to your original post, smaller diameter wheels ride bumps less well and today’s drivers treat the savage kerbs of today’s circuits as though they are the main carriageway of yesteryear. And small wheels with low profile tyres, with necessarily less scope for tyre deflection, would be worse than those with high profile.

Today’s engineers have more time, money, expertise, tools and data than their forebears and to date have resisted tyre changes, probably due to the last, data, but also the expertise and tools they have developed to exploit that. So not necessarily resisting for absolute, clean sheet engineering, but the reality of today’s incremental engineering. Who knows what the transient forces would be on the kerbs at the A1 Ring?

So my opinion is that smaller diameter front tyres which, to preserve space for brakes and suspension,would need to be lowish profile would likely be hard pressed to make the duty cycle of today’s cars. They would I would think be popular with the aerodynamicists, but I doubt they’d make the cars quicker overall.

[Slo Poke]

We can't be purists about a sport where if it was not banned, teams would literally thumble over eachother to create the best wheel cover.

Dangerous line to take. If it weren't banned, the teams would have ABS and full-on traction control (as opposed to clever maps to mimic the effect where possible). Would anyone want to see ABS and full-on TC back?

I know there's a difference between items to remove driver skill and those used to improve air flow, but if we take the view that we shouldn't be a purist about something the teams would have if allowed, we'll end up with LMP1-style cars equipped with fan-driven sealed ground effect aero, ABS, TC, dynamic slip control (steering automatically picking up any sliding, brakes being used to keep the car stable etc.). They'd be amazing machines but they sure as heck wouldn't be F1.

Having said all of that, I'd go for some sort of standardised wheel fairing to help wake control and thus aid closer racing.

That's an interesting thought. I might have been a bit "short around the corner" with my comment, but I always have felt the need for open wheels as unnecessary. If you want to keep a distinct difference with lmp1, I'd say just follow the example set out by Red Bull years ago, by only covering the wheel and not integrating suspension in overarching bodywork. That way you combine the best of both worlds: reducing turbulent wheel wake which will improve close racing, while you still have the appropiate aesthetics.

Are big front wheels the real problem? Well,.. they are and they aren’t! However, they could easily be the cure.
There’s a lot of debate about wheel wake. Inwash, outwash, upwash, downwash and all of it’s wishy-washy click bait as far as I’m concerned. These days there seems to be some kind of excitement surrounding those BTCC types. Apparently they’ve stumbled on something they’re calling Infinity Wings. Compressed atmospheric air is being accelerated around the front corners of their cars and being caught up in outlying winglets. So! Why not put front wings behind the front wheels where bargeboards used to be and call them infinity wings and treat them as such next year. You know! Turn a negative into a positive and all that. Plus, it may incorporate Tubof1’s final two words by putting that climbing frame come prison on top in a better light.

[MatsNorway]

Well.. Front wheels being smaller could reduce the chance of a car flipping over in a high speed accident.

If the front wheels are smaller than the rear they will in a crash have a wedging effect as the contact point is below the center line of the wheel. You could still flip. But you reduce that chance greatly.

[crbassassin]

Surely Tyrell and Mr. Stewart didn't used low-profile front tyres just for the sake of it (or to somehow match low-profile road cars tyres that weren't even available in the 1970s)?

Rather, it would seem there are benefits in front-end steering and handing precision from the lower-profile...

The size was necessary because the brake calipers available were at 15 inch.

[garygph]

Well.. Front wheels being smaller could reduce the chance of a car flipping over in a high speed accident.

If the front wheels are smaller than the rear they will in a crash have a wedging effect as the contact point is below the center line of the wheel. You could still flip. But you reduce that chance greatly.

I assume you are talking about when a car runs into the another and the front tyre is bumping into the rear? I would also assume that you are still taking the difference in directions of travel of the two surfaces that will make contact into account? Personally I can see that it would make a slight difference, but the forward momentum of the car doing the hitting is still going to drive it forward onto the rear and make it climb skywards

[MatsNorway]

All correct.

But making it climb skywards is entirely mechanical. We could go to the extremes and it would not get thrown up.

I will see if i can calculate any numbers on it. Been thinking about doing it before. say 5%-15% smaller wheel to see if it has any meaningful impact. or i can wait a bit and perhaps someone else or GruntGuru will. I'm sure he finds the idea interesting.

[roon]

It’s taken a long while, and some unnecessary squabbling, to get to the realisation that they might change the wheel size for non-engineering reasons. If we list the pros and cons so far.

Pros
The tyre contact patch is less variable - easier to manage the suspension
The tyre sidewall is less variable in shape - making aero more predictable
There is more space for the brakes (although using this might add to the cons of more weight and higher inertial
There is more space for the hubs and suspension components.
They are “modern”
They might help marketing

Cons
They’re heavier - less acceleration both linearly and laterally (slower round corners)
- more unstrung mass
They have higher rotational inertia - less linear acceleration and higher precession forces
The contact patch is less compliant reducing the ability to deal with distortions in the road surface
They are potentially taller and so making visibility worse

I think there are sound engineering reasons for the change. Some already discussed here and in other threads. I'm not sure the wheel-tire assembly will be heavier. The wheel spokes get longer but their thickness isn't necessarily constant radiating from the hub. The barrel wall increases in surface area but may get thinner. Same for the lip/bead.

Regardless, consider how lightweight these forged magnesium parts are. A used 2016 rear wheel for sale has a shipping weight listed as 2.5kg. https://chequeredflagcollectables.com/s ... 3i9u77pi10

There is some obscurity online regarding the weight of the Pirelli tires. Tire weight and assembled wheel-tire weight are used seemingly interchangeably. I find 9-12 kilos in these references for front and rear tires from the past decade. In either case, it would seem the tire vastly outweighs the wheel by a factor of 2 - 5, depending upon how the definition is interpreted.

[henry]

I think there are sound engineering reasons for the change. Some already discussed here and in other threads. I'm not sure the wheel-tire assembly will be heavier. The wheel spokes get longer but their thickness isn't necessarily constant radiating from the hub. The barrel wall increases in surface area but may get thinner. Same for the lip/bead.

Regardless, consider how lightweight these forged magnesium parts are. A used 2016 rear wheel for sale has a shipping weight listed as 2.5kg. https://chequeredflagcollectables.com/s ... 3i9u77pi10

There is some obscurity online regarding the weight of the Pirelli tires. Tire weight and assembled wheel-tire weight are used seemingly interchangeably. I find 9-12 kilos in these references for front and rear tires from the past decade. In either case, it would seem the tire vastly outweighs the wheel by a factor of 2 - 5, depending upon how the definition is interpreted.

All of the major thicknesses and rim shapes are fixed by regulation. The barrel wall will be 40% larger at the rear and 36% at the front where they’ve reduced width. Similarly the bead, a heavy part of the tyre will increase by 40%. These heavier parts will be replacing tyre wall which is very thin and light. Also at the rear the tyres will be 10% larger in diameter increasing the mass of the tyre tread. So I still think the assumption that these wheel assemblies will be heavier and higher inertia is valid.

All of these increased mass elements are further from the rotational axis of the wheel and so the polar moment of inertia will increase even more than the mass. This will slow down linear acceleration just as the increased mass will slow down linear and lateral.

Back in 2014 when 18” wheels were first proposed I modelled the wheels and tyres in a spreadsheet, I don’t have a solid modeller. I’ll see if I can find it. If I can I’ll calibrate against the masses you have noted and the currently proposed dimensions and see what the numbers look like.

As an aside, as a result of the numbers I got back then I add 60kg to the car mass when calculating linear accelerations to account for the rotational inertias.

For interest here are the current regulations:

12.3 Wheel material :
Wheels must be made from AZ70 or AZ80 magnesium alloys.
12.4 Wheel dimensions :
12.4.1 Complete wheel width must lie between 370mm and 385mm when fitted to the front of the
car and between 455mm and 470 mm when fitted to the rear.
12.4.2 Complete wheel diameter must not exceed 670mm when fitted with dry-weather tyres or 680mm when fitted with wet weather tyres.
12.4.3 Complete wheel width and diameter will be measured horizontally at axle height, with the wheel held in a vertical position and when fitted with new tyres inflated to 1.4 bar.
12.4.4 Wheel dimensions and geometry must comply with the following specifications :
a) The minimum wheel thickness is 2.5mm.
b) The minimum bead thickness is 4.0mm (measured from hump to outer edge of the lip).
c) The ETRTO standard bead profile is prescribed.
d) The tyre mounting widths are 13.7” (348.0mm +/-0.5mm) front; 16.9” (429.3mm +/- 0.5mm) rear.
e) The wheel lip thickness is 9mm (+/-1mm).
f) The outer lip diameter is 358mm (+/-1mm).
g) A lip recess of maximum 1.0mm depth between a radius of 165mm and a radius of 173mm from wheel axis is permitted (for wheel branding, logo, part number, etc.).
h) With the exception of the wheel lip, only a single turned profile with a maximum thickness of 8mm is allowed radially outboard of the exclusion zones specified in Article 12.4.5.
i) The design of the wheel must meet the general requirements of the tyre supplier for the mounting and dismounting of tyres including allowance for sensors and valves.
j) The wheel design cannot be handed between left and right designs.