A case to go back to smaller wheels and tyres

[Sodemo]

Originally Posted by V8 Fireworks

It makes them go fast, what's wrong with going fast?

F1 cars (imo) are already fast enough in fast corners, I mean how fast do people really need F1 cars around fast corners? I would argue that actually F1 cars have too much grip in fast corners. Didn't JV once say that when F1 cars can take Eau Rouge flat out then thats when the cars have too much aero? I think we are already way passed that. 5000kg of downforce is ludicrous.

Where the cars have become so much slower is the in the slower corners and lets face it, its the slower corners where the spectators can get the closest to the cars. At nearly every fast corner the paying public are either banned from being anywhere near the corner(s) or they are so far away that its unspectacular. Whenever I look at F1 from decades ago, its not the high speed but the low speed performance that takes my breath away. That is what we have lost with today's cars.

Going back to that 5000kg figure. Whenever you build a tower so high, it falls with greater effect. This is what is happening with the current cars, they have so much downforce, that it only takes a relatively small exterior factor to disturb it and the whole thing is then out of spec. If they lowered the reliance on the aero wholesale, then if an exterior force intervened, the effect on the cars would be much less. I think colloquial evidence suggests that a mid-2000 car had about 2600kg of overall downforce, so roughly half what we have now?

[V8 Fireworks]

Originally Posted by Taxi645

"Drivers complain ride comfort is unacceptable in new generation cars".

This is changing the goal posts from whether 18" low profile tyres, despite the extra rotational mass, are better for (mainly lateral) performance in dry conditions though!

[V8 Fireworks]

Originally Posted by Sodemo

Whenever I look at F1 from decades ago, its not the high speed but the low speed performance that takes my breath away. That is what we have lost with today's cars.

I think colloquial evidence suggests that a mid-2000 car had about 2600kg of overall downforce, so roughly half what we have now?

This is true, but 2024 Formula 2 cars with 1500-2500kg of downforce also weigh 795kg, nearly the same as Formula One cars. The 2024 crash test regulations are tough, really tough! A tub weighs nearly 150kg now, compared to 60kg in 2005.

So F2 cars are also slow in slow corners, so dropping F1 cars to F2 downforce levels or less is not going to do much IMO. I'm guessing the superior low speed performance of 2021 F1 cars was due to the 50kg less weight (25kg of which in 2022 is safety stuff anyway), the much softer suspension and the more sophisticated suspension elements allowed.

I'm not sure how much was due to the flat floor and rake working better at low speed (obviously a car with rake could get the front wing really close to the ground to improve front wing ground effect and rotation and eliminate low speed understeer, then bleed that front downforce off at higher speed as the rear squats).

Everyone wanted to try venturi tunnel cars as the answer to close following and it worked somewhat in 2022.

[Richard C]

I would not have been "shocked" if they switched to 16" wheels, but I also am not shocked that they are remaining with the 18". A quote from the article posted above...

It would also create an additional challenge for the teams on top of everything else that they will have to deal with heading into the new era.

While the article calls out the marketing side and also pushback from Pirelli, I really suspect the real reason is teams just want to manage the amount of change going into 2026. And that adapting to a smaller diameter wheel is an area in which they would have to spend money and is likely not going to be a performance differentiator (i.e. spending money in that area doesn't give them a performance bonus when compared to the other teams). I think the teams just pushed back and said "we don't want to do this".

Originally Posted by Taxi645

With open wheel formula's drag becomes part of the equation much more than in touring classes. Especially now that they are focussing so much on efficiency. Sure one can reduce the tire height to get the same effect. I do think the drivers will love the effect that will have on their spines with the current and 2026 cars being already extremely stiff to keep the underside in the optimum flow regime. We can already predict the media topics, start 2026 seasons: "Drivers complain ride comfort is unacceptable in new generation cars".



https://www.motorsport.com/f1/news/n...sues/10588284/


And this is still with the current much higher tire height than what Pirelli is proposing for 2026.

I "think" you are saying that if they keep the wheel diameter the same, but slightly reduce the overall tire diameter that this results in a smaller sidewall. And with all things being equal, the smaller sidewalls should result in a the tire acting as a stiffer "spring". And that this will make the cars more harsh from a ride quality perspective? I agree with the basic logic (smaller sidewalls generally being stiffer), but disagree with the outcome (harsher ride level)

Overall motion of the car relative to the road is commonly expresses as the suspension movement (spring rates, motion ratio, suspension frequency, etc.) and to some degree act as if the wheel/tire combo are fixed. But (as I call out above) the tire is a spring (and damper) itself. So it is part of the overall suspension. So if the new tires have a slightly higher spring rate, they can reduce the spring rate of the suspension a bit to arrive at an overall spring rate that would match that of the prior tire/sidewall. The effect on a road car would a harsher ride as you not adjusting your car's spring rates to match the stiffer sidewalls. But race cars are not bound by those setup limits.

In short, what the driver feels shouldn't be any different. If you want to improve driver comfort, then overall less stiff cars would help. Of which teams could do today if they wanted, but don't as it would allow the underbody to get outside of it's optimal operating windows. So the teams make they as stiff as they can get away with. You just don't want them so stiff they skate across the really bumpy stuff.

Richard

[Sodemo]

Originally Posted by V8 Fireworks

This is true, but 2024 Formula 2 cars with 1500-2500kg of downforce also weigh 795kg, nearly the same as Formula One cars. The 2024 crash test regulations are tough, really tough! A tub weighs nearly 150kg now, compared to 60kg in 2005.

So F2 cars are also slow in slow corners, so dropping F1 cars to F2 downforce levels or less is not going to do much IMO. I'm guessing the superior low speed performance of 2021 F1 cars was due to the 50kg less weight (25kg of which in 2022 is safety stuff anyway), the much softer suspension and the more sophisticated suspension elements allowed.

I'm not sure how much was due to the flat floor and rake working better at low speed (obviously a car with rake could get the front wing really close to the ground to improve front wing ground effect and rotation and eliminate low speed understeer, then bleed that front downforce off at higher speed as the rear squats).

Everyone wanted to try venturi tunnel cars as the answer to close following and it worked somewhat in 2022.

Part of the problem is the amount of downforce, another part is how its generated. My guestimate is that 3000kg or so is generated by the floor of an F1 car and the other 2000kg is from the front and rear wings (plus any other upper surfaces). Single seaters generally have a 60/40 aero split, so for arguments sake the front wing would generate 800kg and the rear 1200kg. I think the reliance on these wing elements is what is causing the dirty air issues. They claim to have prioritised the cars ability to follow another car, but that flys in the face of being so reliant on the front wing to generate downforce. If the front wing was reduced in size and positioned closer to the ground, and made so that it only produced 200kg of downforce (and then 300kg for the rear wing) I would bet my house that the racing would be better, as when a car is following another, there is far less downforce to lose to start with. If we extrapolated this idea to having no wings at all then there would be no reliance on the wings at all in order to generate DF or to tweak handling.

[S griffin]

F1 did the right thing getting rid of unnecessary extra aero when the new regs came in, but unfortunately it seems it wasn't enough. But I think it will always be hard to get to a place where the dirty air problem is eradicated. As long as it doesn't get worse and aero is kept sensible, things should be relatively fine

[Sodemo]

Originally Posted by S griffin

F1 did the right thing getting rid of unnecessary extra aero when the new regs came in, but unfortunately it seems it wasn't enough. But I think it will always be hard to get to a place where the dirty air problem is eradicated. As long as it doesn't get worse and aero is kept sensible, things should be relatively fine

I hear what your saying and I gather for the F1 teams they dont want to paint themselves into a corner or give up any potential advantage, plus Turkeys dont vote for Christmas, no F1 team will want to shoot themselves in the foot.

[Taxi645]

Just to keep you up to date on the topic:
https://www.auto-motor-und-sport.de/...zoll-schmaler/

So talk is now to remain on 18'', but slightly lower profile and narrower.
Current:
Front: 305/720/18, rear: 405/720/18

Suggested: 275/705/18, rear: 375/710/18

With the introduction of the 405mm wide rears the width to height ratio was: 405/670= 60%

With the move to 18'' it became: 405/720=56%

Now with the narrower 18'' you'll end up with: 375/710=53%

That's not really a wide looking tire any more. Pirelli are so hung up on the side look of their beloved 18'', that they forget they will look pretty narrow from the rear (and like wagon wheels on the smaller 2026 cars).

For reference the initial hybrid era 13'' rears were 325mm wide and 660mm tall giving a width to diameter ratio of 49%. So this means with a 53% ratio, the now proposed 18'' rears will almost be as narrow looking as those narrow 13'' everyone hated so much.




Personally, I wished Bridgestone had won the bid. Then it would've been much more likely that we had tire and wheel sizes that made technical sense.

[Sodemo]

Lower profile meaning a poorer ride? Which means (potentially) more bottoming and more moaning from the drivers?

[Richard C]

Originally Posted by Sodemo

Lower profile meaning a poorer ride?

Why would they? See my earlier post regarding sidewall flex is a portion of overall suspension spring rate.

Richard

[Sodemo]

Originally Posted by Richard C

Why would they? See my earlier post regarding sidewall flex is a portion of overall suspension spring rate.

Richard

A lower profile tyre can have a sidewall with more flex? How does that work?

[Richard C]

Originally Posted by Sodemo

A lower profile tyre can have a sidewall with more flex? How does that work?

Read my post from March 18th.

Short version, yes a factory road car that has fixed suspension components (no changes made to factory springs), then if you switch to lower profile tires (which should have stiffer sidewalls) then the overall spring rate goes up (total=tires as spring + suspension spring)

But in a car in which you can adjust spring, you can put in a softer spring to compensate for the high spring rate of the new tire.

Richard

[V8 Fireworks]

Originally Posted by Taxi645

Now with the narrower 18'' you'll end up with: 375/710=53%

That's not really a wide looking tire any more. Pirelli are so hung up on the side look of their beloved 18'', that they forget they will look pretty narrow from the rear (and like wagon wheels on the smaller 2026 cars).

This is still less square than an IRL/Indycar rear tyre, which is 720mm x 350mm (14" section x 29" diameter). It will look fine.



Of course it would look awesome if Indycar still used 425/720mm (or 18" section x 29" diameter), but oh well, times change.

I can't remember why IRL started using narrower tyres than CART.

[Sodemo]

Originally Posted by Richard C

Read my post from March 18th.

Short version, yes a factory road car that has fixed suspension components (no changes made to factory springs), then if you switch to lower profile tires (which should have stiffer sidewalls) then the overall spring rate goes up (total=tires as spring + suspension spring)

But in a car in which you can adjust spring, you can put in a softer spring to compensate for the high spring rate of the new tire.

Richard

But the teams won’t want to do that because it will upset their underbody aero platform. I am aware you can offset the tyre flex difference with a softer or harder spring.

[Richard C]

Originally Posted by Sodemo

But the teams won’t want to do that because it will upset their underbody aero platform. I am aware you can offset the tyre flex difference with a softer or harder spring.

I may be missing something, but I think if your overall spring rate is the same, the amount of movement between the bottom of the car and road surface will remain the same. The relative movement between wheel centerline and road will be less and relative movement between wheel centerline and bottom of car will be more. To make up an example of compression in a bump (note, numbers are made up, as I have no idea what might be typical static ride heights for these cars and relative compression between tires and sprung suspension)...

Current car...
Tire deformation (tire as spring) = 20mm
Sprung suspension compression = 10mm
Total movement of floor relative to road surface = 30mm

Future car..
Tire deformation (tire as spring) = 15mm (harder spring, so less movement)
Sprung suspension compression = 15mm (softer spring, so more movement)
Total movement of floor relative to road surface = 30mm (overall spring rate is unchanged so the overall movement for the same force is the same)

To be fair, I can't expect there to be zero impact of shorter sidewalls. This above view is a very simple view of suspension and there are other factors at play. But IMHO, I do not think classic issues of "short sidewalls means harsh ride" are probably not going to be a big factor. But as always I could be wrong. I think the bigger impact will be that teams will be moving yet again to another round of learning new tires and associated setup.

Richard

[Taxi645]

One of the reasons why the side wall is now higher than originally planned for the 18'' wheels was because the feedback from F1 teams was that the low side wall was going to have a too much of a negative effect on the suspension performance. Subsequently the side wall height was increased and together with the 18'' wheels we ended up with the very large 720mm diameter we have not

This negative effect on suspenson performance will propably relate to the following two consideration.

1 With the tire less able to respond to harsch impact the loads on the suspension parts will increase significantly requiring them to be beefed up resulting in more unsprung mass and perhaps more importantly a bigger disruption of the airflow to the rear as a result of these larger suspension parts.
2 Say the part of the tyre deflects during an impact with a kerb is about 1 kg. That is much lighter than the combination of the complete tyre, the wheel and part of the suspension which would have to move if the tire sidewall doesn't. This means that the ratio between sprung and unsprung mass deteriorates. If one likes to read up on it, see the wiki link:
https://en.wikipedia.org/wiki/Unsprung_mass

This link I shared earlier in the thread from James Allison in 2020 on his view to the move of lower side walls on a F1 car.
https://www.racefans.net/2020/06/04/...lower-allison/

That was for the current 720mm 18''. The current proposal for 2026 goes even a step further in this direction regarding lower side wall height.

He also reaffirms the whole marketing and "road relevance" angle of the 18'' tires.

One of the reasons I get a bit frustrated by people on here criticising the FIA while often letting the FOM of the hook. To me the FIA has proven to be a better guardian of the sport in a pure sense. They are certainly not without fault, however the FOM, the manufacturers and Pirelli with there silly insistence on 18'', if left alone, I believe would go quite far to compromise the integrity of the sport to suit their commercial and business interests. For example the entity pushing for lower weight has been the FIA, the trio above does not care much.


I probably won't go into it much further.

[V8 Fireworks]

Originally Posted by Taxi645

One of the reasons why the side wall is now higher than originally planned for the 18'' wheels was because the feedback from F1 teams was that the low side wall was going to have a too much of a negative effect on the suspension performance.

But that's because F1 cars have piddly torsion bar springs and not proper springs. We don't have such issues on WRC cars with their 500mm of coil sprung strut suspension travel, even on 18"tarmac tyres.

Originally Posted by Taxi645

This link I shared earlier in the thread from James Allison in 2020 on his view to the move of lower side walls on a F1 car.
https://www.racefans.net/2020/06/04/...lower-allison/

1969 March 15" front tyre:


Looks low profile to me...

So it should be Allison on the return to low profile tyres, no?

13" was only ever due to the rules. Who says F1 tyre suppliers would not have gone to increasing larger diameter wheels & lower profile tyres than 15" of the late 1960's, if they had been allowed to?

Yes, the constructors used the balloonish 13"tyres as an opportunity to design more compact suspension systems with minimal travel, but who says that was inevitable if tyre development had run its course? That didn't happen in sportscar prototype racing after all -- they went to larger and larger wheels up to 18", while using comparatively long travel suspension systems.

[Sodemo]

Originally Posted by V8 Fireworks

But that's because F1 cars have piddly torsion bar springs and not proper springs. We don't have such issues on WRC cars with their 500mm of coil sprung strut suspension travel, even on 18"tarmac tyres.




1969 March 15" front tyre:


Looks low profile to me...

So it should be Allison on the return to low profile tyres, no?

13" was only ever due to the rules. Who says F1 tyre suppliers would not have gone to increasing larger diameter wheels & lower profile tyres than 15" of the late 1960's, if they had been allowed to?

Yes, the constructors used the balloonish 13"tyres as an opportunity to design more compact suspension systems with minimal travel, but who says that was inevitable if tyre development had run its course? That didn't happen in sportscar prototype racing after all -- they went to larger and larger wheels up to 18", while using comparatively long travel suspension systems.

But surely in tarmac spec a WRC car only has, what about 3-5cm of effective suspension travel?

[Greem]

Personally I don't think bringing the WRC in any spec is relevant.

Mainly because the concept of "grip" at that level of rallying is about 1 millionth that of F1 cars. WRC cars don't have measurable grip, they just have velocity and direction!

[V8 Fireworks]

Originally Posted by Sodemo

But surely in tarmac spec a WRC car only has, what about 3-5cm of effective suspension travel?

In the early 90's maybe, nowadays they have outrageous amounts of travel even on tarmac specification:
https://www.youtube.com/watch?v=uijwob-DpoU

Petter Solberg described the Rally1 cars as like riding along in a sofa! As you can see even in tarmac 18" specification, they are very soft and glide over the road.

Look at that full droop! Rally1 cars sure are a lot of fun, it's a shame the WRC is quite niche nowadays.
https://youtu.be/uijwob-DpoU?si=G9nKibEm4Gz-ICTm&t=432

It looks like they have at least 150mm (6") of travel, if not a little more. They are much softer than most sporty road cars like a Ferrari 488 or Porsche 911 GT3 or something, the very long front and rear strut suspension allows for a lot of travel, of course.

Originally Posted by Greem

Personally I don't think bringing the WRC in any spec is relevant.

Mainly because the concept of "grip" at that level of rallying is about 1 millionth that of F1 cars. WRC cars don't have measurable grip, they just have velocity and direction!

They have a darn sight more grip than a F1 car on such a muddy undulating tarmac special stage at least!

The point was just that because you have a stiff 18" tyre, doesn't mean you can't have soft suspension to compensate. The total wheel rate is the sum total of the tyre's contribution and suspension's contribution after all.

They run 15" tyres on gravel and snow, obviously gravel and snow tyres are narrow and have a tall sidewall so the tyre can try to conform as best as it can to the very uneven and soft road surface.

If 15" tyres high profile tyres also generated more grip or increased performance on tarmac (as seems to be implied in this thread), if Pirelli supplied them with the appropriate compound and width, then WRC teams would run them on tarmac, but they do not as they do not.

[Greem]

There is a tiny chance I may not have been entirely serious