F1 tire sizes

[CapriRacer]

Just an FYI:

The new tire sizes for F1 starting in 2022 are 305/720R18 and 405/720R18. That's the equivalent (more or less) to 305/45R18 and 405/30R18.

The old sizes (2021) were 305/670R13 and 405/670R13 (305/55R13 and 405/40R13 - more or less).

I note with interest that the front tires in both cases have a significantly higher aspect ratios. I suspect that is done so the front has more compliance, but that also means the fronts will be more imprecise than the rears. Remember how some folks had trouble with the rear snapping into over steer?

So what do I think is going to change as a result of the new tire? More snap oversteer! Less damage due to curbs! The mechanical suspension will need to be softer - and that means more tuning opportunities! Getting brakes up to temperature is going to be harder, but you won't see as many on fire!

 

[Tifosi]

Just an FYI:

The new tire sizes for F1 starting in 2022 are 305/720R18 and 405/720R18. That's the equivalent (more or less) to 305/45R18 and 405/30R18.

The old sizes (2021) were 305/670R13 and 405/670R13 (305/55R13 and 405/40R13 - more or less).

I note with interest that the front tires in both cases have a significantly higher aspect ratios. I suspect that is done so the front has more compliance, but that also means the fronts will be more imprecise than the rears. Remember how some folks had trouble with the rear snapping into over steer?

So what do I think is going to change as a result of the new tire? More snap oversteer! Less damage due to curbs! The mechanical suspension will need to be softer - and that means more tuning opportunities! Getting brakes up to temperature is going to be harder, but you won't see as many on fire!

Strictly from the tire's POV and their impact, potentially will result in 2 second slower per lap.

 

[Davejam]

Interesting. I'm surprised that they made such a large change. But should make for an interesting first year of the new set-ups.
My biggest fear is that it seems that pole position may be at a disadvantage.

 

[B1974]

It's going to be interesting to see how running over the curbs is going to work out next year. The suspension staff is going to be very busy figuring this out.

 

[bdcardinal]

@CapriRacer I have a dumb tire question. How do the race tire sizes work? Like what would the 720 represent in place of the aspect ratio?

 

[Jimmy_Russells]

@CapriRacer I have a dumb tire question. How do the race tire sizes work? Like what would the 720 represent in place of the aspect ratio?

I believe it is the overall height of the tire

 

[930.engineering]

I note with interest that the front tires in both cases have a significantly higher aspect ratios.

I wouldn't call that 'significantly'. Both are 720, both mount on 18" rims, so the sidewalls are close to equal.

I suspect that is done so the front has more compliance, but that also means the fronts will be more imprecise than the rears.

Why do you think that? These tires are tailored to their purpose, meaning they're stiff as needed. Stiffness doesn't necessarly need to vary with sidewall height. These aren't passenger car tires.

So what do I think is going to change as a result of the new tire? More snap oversteer!

Not necessarily. It depends on so many variables that only the engineers know. We'll see.

Less damage due to curbs!

How is this going to happen?

The mechanical suspension will need to be softer - and that means more tuning opportunities!

Perhaps, but again not necessarily.

Getting brakes up to temperature is going to be harder, but you won't see as many on fire!

Why? Just because there's more space for bigger rotors? In fact it'll be easier, as the bigger size will probably reduce peak temps mostly and will go along with appropriate pad compounds and fine-tuning the ventilation.
.

 

[CapriRacer]

Strictly from the tire's POV and their impact, potentially will result in 2 second slower per lap.

The video attached to this post did a really good job - EXCEPT:

They didn't mention that the use of 13" tires in F1 and the 15" in NASCAR and IndyCar is largely historical. In all 3 cases, those were the wheel sizes popular in the post WW2 era.

When it became obvious that rules on tires and wheels were needed, the sanctioning bodies just froze everything in place.

@CapriRacer I have a dumb tire question. How do the race tire sizes work? Like what would the 720 represent in place of the aspect ratio?

720 is the diameter of the tire in mm.

Tire sizes is an interesting aspect of tire engineering. I go into more detail here: Barry's Tire Tech: Tire Sizing

Short version: The sizing format points to a tire standard - that is, load tables and dimension tables. Only 3 dimensions are needed, but the most important is rim diameter. Then you need a combination of 2 or 3 of the follwing: Aspect Ratio, Overall Diameter, Section Width. Any 2 will define the third.

In this case, the diameter and the width are defined. Please note, that racing tires are generally defined by the tire manufacturer and not by the International tire standard organizations such and The Tire and Rim Association (US), ETRTO (European Tyre and Rim Technical Organization, or JATMA (Japanese Automobile Tire Manufacturers Association).

Racing tire manufacturers use a variety of formats to describe tire sizes. When I was racing Goodyears, the sizing looked like this: 30.5/10.5-13, which meant 30 1/2 inches in diameter, 10 1/2 inches wide, bias on 13" wheels.

Ah, you may be wondering why everyone uses inch diameter wheels instead of metric. Again, Historical! That's just what was popular when they set up these standardizing organizations and tire manufacturers went along with it.

 

[CapriRacer]

This post is a reply to 930.engineering's reply to my post. Unfortunately, the software won't do nested quotes, so this is going to appear a bit disjointed. Sorry!

I wouldn't call that 'significantly'. Both are 720, both mount on 18" rims, so the sidewalls are close to equal.

720 is the overall diameter, and while the section height is the same, the aspect ratios (section height/section width) are 3 sizes different.

Why is that significant? When tire engineers look at tires, they evaluate everything based on load carrying capacity. So a lower aspect ratio would need a wider width to get the same load carrying capacity.

So when looking at front tires on an F1 car, the higher aspect ratio results in a much more flexible sidewall. This means that the turn in will be more forgiving, but a bit delayed.

Why do you think that? These tires are tailored to their purpose, meaning they're stiff as needed. Stiffness doesn't necessarily need to vary with sidewall height. These aren't passenger car tires.

No, these aren't passenger car tires, but the engineering principals still apply. I am making the assumption that Pirelli isn't going to significantly change things in the tire and that is what everyone in the F1 community are commenting on.

Not necessarily. It depends on so many variables that only the engineers know. We'll see.

This was a reply about me predicting more snap oversteer. My prediction is based on the idea that a bit of sidewall flexibility helps absorb the forces and releases them back more gradually.

Yes, we will see.

How is this going to happen?

This was a response to my prediction that there is going to be less curb damage - and my prediction is based on the current higher ratio allowing more sideways flexure, which - IMHO - is why there have been tire failures. Reference the radio advisories to stay off the curbs.

The physics is that this sideways flex is exposing the sidewall to the curb.

Editorial comment: Racing needs to figure out how to get drivers from using the curbs. The curbs ought to be a penalty for going too far. No, I don't know how to do that and apparently neither does the FIA!

Perhaps, but again not necessarily.

This is a reply to my prediction that the mechanical suspension will be softer, allowing for more tuning opportunities. I agree, not necessarily.

Why? Just because there's more space for bigger rotors? In fact it'll be easier, as the bigger size will probably reduce peak temps mostly and will go along with appropriate pad compounds and fine-tuning the ventilation.

This was based on my comment about brakes being more difficult to heat up and sometime catching on fire.

I am thinking about the warm up lap just before the standing start. And in this case I think 930 is correct.

 

[edyvw]

I am interested to see how brakes are going to evolve? Those wheels leave more space for brakes.

 

[ragtoplvr]

F1 is so finely engineered (look t the front spoiler for example) the slightest change makes a big difference. Just the airflow over the bigger wheel dish is significant. Just the lug nut is worth many thousands of dollars.

 

[A_Harman]

I am interested to see how brakes are going to evolve? Those wheels leave more space for brakes.

F1 didn't have a big problem with brakes with the 13" wheels, so I wouldn't expect them to automatically go to the biggest rotors possible. The big negative about the larger diameter wheels is the increase in rotational moment of inertia, which engineers expect to add so much effective mass to the cars, they'll be 2 seconds per lap slower. Going to a maximum-sized brake rotor would add even more. But they may have to because the effective mass of the car has increased due to the larger wheels and tires.

Dagnab it! There is no such thing as a simple change.

 

[edyvw]

F1 didn't have a big problem with brakes with the 13" wheels, so I wouldn't expect them to automatically go to the biggest rotors possible. The big negative about the larger diameter wheels is the increase in rotational moment of inertia, which engineers expect to add so much effective mass to the cars, they'll be 2 seconds per lap slower. Going to a maximum-sized brake rotor would add even more. But they may have to because the effective mass of the car has increased due to the larger wheels and tires.

Dagnab it! There is no such thing as a simple change.

Sure, I get all that. But this leaves them space to experiment.