Revolutionary wheels: Why F1 going 18-inch will change everything


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Formula 1’s tyre rules are heading for their biggest change in a generation in 2021. The introduction of 18-inch wheels has implications that go far beyond their much-debated aesthetics, as Pirelli’s sporting director Mario Isola explains to Dieter Rencken.

During the French Grand Prix weekend an exclusive interview was requested with Pirelli’s Mario Isola, a man steeped in the (black) art of high-performance tyres, having spent the past 22 years with the company in various (mainly motorsport) positions.

The interview was requested in anticipation of Formula 1’s post-2019 tyre tender given that the current supply deal expires at the end of next year. A fact most teams had obviously overlooked given their surprise when the tender was subsequently announced during the German Grand Prix weekend.

Also foreseeable was the need to arrange the next deal around the timing of the current contract and F1’s regulations overhaul due to be introduced in 2021. If ever proof were needed that F1’s regulatory process is utterly dysfunctional, this provides it, but that is a story for another day.

We originally intended to publish the interview following the British Grand Prix. A number of crucial developments, such as the passing of Ferrari president Sergio Marchionne and Force India’s administration, forced a change of plan due to their immediate impact on F1, so publication of the interview was further delayed.

In the interim the FIA announced the 2020-23 tender, as revealed here by RaceFans, then revised certain provisions of the document last week. Isola’s incisive and comprehensive answers remain valid despite the passing of six weeks since our interview and the paddock noise created by the tender documents. Thus we have published the interview as per our chat in Paul Ricard.

Starting with the assumption that F1 will go for 18-inch rim sizes from 2021 – which the tender later confirmed – what does Pirelli require from F1 to make the switch?

“We need a test car for sure, but I would say that if you want to do something, you [can] do something,” he says. “Look at the wider sizes [on the current cars]: we didn’t have test cars, and then we had the three mule cars available, so we need to have something similar.

“But, it’s not easy. You cannot take a current car, fit 18-inch tyres, and test. [Going to] low profiles means you have to redesign the suspension; it’s a different behaviour of the car. In terms of aero you have a lot of differences; you have to redesign the brakes. There are a lot of impacts, but I believe if the target is to have an 18-inch tyre, we can do that.”

Mario Isola, 2017
Pirelli will need a test car for 2021, says Isola
What, though, are the implications?

“We have to work together with the teams and the FIA and [Formula One Management] to discuss possible solutions to that. It’s not something like that (clicks fingers), you cannot do that tomorrow.

“But if Formula 1 wants to do that, [we] can do it. It’s not just Pirelli, because a test car is not something we have, we don’t have a car and we don’t have a team, so we need obviously co-operation from the teams for our test car.”

At the time of our interview there was still talk that the contentious MGU-H would be dropped from 2021, resulting in a possible loss of engine power, in turn making the switch to 18-inch rubber easier, hence Isola’s next comment:

“I believe that [change] was very difficult in 2016 because the 2017 regulation was aiming to improve the performance. If the new target is 18-inch tyres, but with a car that is reducing the performance – I’m not saying it’s easy, but it’s a bit easier than what we did two years ago.

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“Because you can just downgrade and change and so on, and then you are close to the performance levels that are expected. Two years ago it was so difficult because obviously we were targeting to have five seconds per lap quicker cars in Barcelona; that’s a different story.”

All true contextually, but a little over two years remains to 2021, yet no definitive technical regulations exist. So what is Pirelli’s preferred solution?

“I know, I know,” Isola nods vigorously. “We need for sure to talk to the FIA and agree. It’s wrong, for example, to develop tyres with only one team, because you give the advantage to that team. In my opinion what we did two years ago with three teams, three mule cars, worked well. I believe it’s difficult for small teams to develop their current car, next year’s car, and a third car for the new (tyre) sizes.

Scott Dixon, Ganassi, IndyCar, Texas Motor Speedway, 2018
IndyCar uses 15-inch wheels
Why three cars, specifically?

“Three, four, it depends how many are available. Let’s say the three biggest teams: we can do something similar, if they are available, to what we did two years ago. With three mule cars, we are able to make a proper test plan. Time is running [out] quickly, so we need to find a solution quickly, on the other side we are in the process of renewing the contract.

“So first of all we need to renew the contract.”

Ah, the elephant in the room: The post-2020 contract. At the time we assumed that the FIA contract would be for three years – as per previous editions – meaning one year under 13-inch regulations, and two under low profile tyres. It later emerged a four-year deal is planned, but the crucial detail is that there will be one more year under the existing tyre size.

However, if Pirelli does not renew, then someone else will have one year under 13-inch tyres, and three under whatever is decided upon.

“Yeah, true, you are right. It is part of [it] when you are in Formula One; you need to be ready to change and develop your tyres every year. We change our product every year because we have to follow the development.”

Clearly Isola is downplaying Pirelli’s advantage, for any incoming supplier would need to develop two tyres within the next two years, without having the modelling data that Pirelli has accumulated. I let this point hang after putting it to him.

“When we came back to Formula One in 2011 we were learning. Now we have a lot more experience,” he says. “Obviously it is a challenge and very expensive…”

Start, Monaco Grand Prix, 2011
Pirelli has been F1’s tyre supplier since 2011
The implications of the tender and its timing were still four weeks away, yet even then it was clear the incumbent supplier would hold an advantage. In Germany the FIA’s head of technical, Charlie Whiting, admitted the governing body’s legal team had held discussions with Pirelli’s lawyers about extending the current deal by a year in order to start 2021 with a clean slate – but to no avail.

We’ll have to see how it eventually pans out, whether one or more interested parties – to wit, other tyre companies – legally challenge what is perceived in some quarters to be an ‘unfair commercial advantage’. But that lies outside Isola’s direct control.

Besides which, there are other significant areas of uncertainty, such as the matter of which three teams might supply test cars.

We don’t know whether Mercedes are going to be here in 2021. Or Ferrari – the late Marchionne had restated the team’s threat to leave F1 should the post-2020 landscape not suit Ferrari, which Isola acknowledges. So we can’t just assume that these teams will provide Pirelli with test cars, assuming the company is granted the tender…

“Yeah, there are a lot of question marks…” Isola laughs.

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We briefly discuss the timeline: Tender documents need to be issued (now done); the FIA needs to vet and technically approve the applicants; select one or more proficient candidates; provide candidate list to FOM to initiate commercial discussions; FOM nominates successful company and advises FIA, which then makes announcement. All this by the end of the year.

“That’s true,” Isola acknowledges. “There are a lot of unknown situations, or situations that this sport needs to clarify soon to have a proper development plan. At the moment there are no regulations for 2021, so we talk about an 18-inch tyre, but an 18-inch tyre has to work on a car, and we need to know the level of downforce, we need to know the speed of the engine, the torque.

“There are a lot of other elements that need to be clarified before designing a tyre. It’s a package, and at the moment it’s very difficult. I know they are working hard to find solutions, but we need to know all this [soon].

Why not go further than 18 inches, to 19 or even 20-inch tyres given that the latter sizes are increasingly fitted to supercars? One factor is that the lower the profile, the narrower the sidewall, and the smaller the branding area – which provides Pirelli with their largest visibility.

“We said also that we pay attention [to discussions], because if you go too high in diameter you reduce the sidewall a lot. OK, you can change the external diameter, but you can’t have a tyre…we need to find the right compromise. We always said 18, 19, but 18 is more now a size for supercars and is used in a lot of [mid-range] cars.”

Pirelli 18-inch tyre test, 2014
Isola presented a demonstration 18-inch Pirelli tyre in 2014
It’s a peculiarity of F1 that it has the highest sidewall to width ratios (profile) of any mainstream motorsport series, higher than rally or Formula E and substantially higher than WEC – indeed, so high are F1’s tyre profiles that they exceed even those of the tyres fitted to Pirelli’s trucks. Surely the time is ripe for some adventurous thinking, I suggest.

“We need to make a calculation, because also if you have a bigger rim, you reduce the volume of the air inside.

What about the weight of the rim for a given circumference – for alloy clearly weighs more than air?

“The weight of the rim also. But the volume of the air inside is important, because the tyre is supporting the car because of the air inside also. So the running pressure is important; there are a lot of numbers.

And the higher the sidewall profile, the more its elasticity affects wheel travel, which in turn affects suspension. “You have to redesign the suspension with bigger travel,” Isola acknowledges.

There is a safety factor, too: the higher the sidewall ratio, the greater the chance of “jounce” of wayward wheels – although, to be fair to the FIA’s safety initiatives, the introduction of (beefed-up) wheel tethers has largely eliminated the dangers of flying wheels.

“Yeah, this is true,” agrees Isola, adding that kerbs present a problem with low profile tyres. “For example, consider the impact of kerbs, the impact you have on kerbs. That is different when the sidewall is like this,” he says, holding thumb and forefinger a few inches apart.

What would be the impact on brakes, I ask, given that they would need to be redesigned or appear lost within the larger rims.
“It’s not just the braking, also the lateral forces,” he says, adding, “This is more related to the footprint, the shape of the footprint, how you design a profile in order to have better braking, better…you have a tyre that is a lot more precise because obviously you have a lot less movement of the sidewall. So in terms of driving precision it’s a lot better.”

Are there, though, any potential directional issues, given that steering would be more direct with low profiles due to less flex in the sidewalls?

“Yeah, but we try to design a tyre in order to balance front and rear, and not to have a front that is too ready and making the driveability of the car difficult because you have snap oversteer or something like that.”

Pirelli 18 inch tyre, Monaco, 2015
GP2 almost raced on 18-inch wheels – F1 now will
Little known is that Pirelli was on the verge of introducing 18-inch tyres for GP2 back in 2015, at time when F1 seriously considered making the switch. Indeed, Pirelli showed off a Lotus fitted with 18-inch wheels. The F1 car didn’t, though, run in anger…

“No, but for example for GP2 the same year, because there was discussion about the possibility to introduce it in Formula One. So as usual GP2 wants to anticipate it, and we made a product for GP2 that was let’s say a final version…but then Formula 1 decided not to move to 18-inch, and GP2 said ‘OK, we stay on 13s’.”

Were there noticeable differences?

“I can tell you,” Isola says carefully, as though sharing a secret, “that the product we developed for GP2 at the time, in terms of performance, was in line with the 13-inch. Consider that it was a completely new product, so to have this, with the same performance as the 13-inch, that is a tyre that was developed since many years, it’s an encouraging result.

And anticipated performance gain after development?

“Maybe a couple of seconds. I would say maybe three. Three is a lot anyway. Three seconds per lap.”

So, Pirelli has 18-inch experience, the sport has the desire and the contract is about to expire. By when would Pirelli you need to know whether it has the gig for post-2020 and 18-inch tyres?

“End of this year we need to know more on technical regulations and the sizes, and the availability of a test car(s), concludes Isola. “We need to start making some vehicle models, then prototypes to test indoors, to run some indoor tests. We need to start as soon as possible, of course.”

The same, of course, applies to whichever tyre company is eventually granted F1’s tyre contract…

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46 comments on “Revolutionary wheels: Why F1 going 18-inch will change everything”

  1. Great article @dieterrencken, very informative.

    1. Thank you, yes I enjoyed the interview with Mario. A good guy.

      1. I really like the extra bits outside the question and answers quotes such as body language description. It really adds a lot of personality to the interview and add additional substance to it.

        Great read.

  2. What rim/tyre size is used by IndyCar?
    To be honest, this whole ‘business’ and the mismatch of contract/regulation duration seems typical of FIA/FOM.

    1. @nickwyatt Indycar uses 15″ rims.

  3. See picture above: 15-inch

    1. So @dieterrencken, what would the perceived advantage be of going up to 18 rims when a pretty comparable series uses 15 rims – and are the tyres of similar width and diameters?

      1. 15-inch would be a half measure – technology is moving towards +20-inch tyres for high performance, so if anything Indycar should go to 18 9or more) in the near future. All other series, including WEC and FE are already over 15″

        1. I reckon it’s mainly cosmetics. Anything above 18 does not generally benefit a road car, barring sports cars with very stiff suspension and lots of power. For example, the Porsche 911 RSR comes with 18s, and this is a race car.

          1. Shaun Robinson
            9th August 2018, 9:36

            Bigger rims = bigger brakes. I fear that if they go this way then braking distances reduce and we see less overtaking :(

          2. @Shaun The breaks are regulated. You’re not allowed to just put bigger breaks on.

          3. @Shaun I think it is more realistic that we’ll see greater reliability from the breaks. Meaning less laps where the drivers are forced to cool the breaks.

  4. ‘Also foreseeable was the need to arrange the next deal around the timing of the current contract and F1’s regulations overhaul due to be introduced in 2021. If ever proof were needed that F1’s regulatory process is utterly dysfunctional, this provides it, but that is a story for another day.’

    That I await with anticipation!

    I have personally said for a few seasons that the FIA is no longer fit for purpose.

  5. Why 13 inch or 18 inch? Why not 15 inch like in Indycar?

    1. See reply to @nickwyatt above

    2. My guess would be that 15” rims are still small compared to most other racing series and most domestic cars these days, so if they’re going to make a switch, it might as well be a relevant and a noticeable one. 2” increase doesn’t seem worth the bother.

    3. 15″ is smaller than most modern road cars, this is the driver behind bigger wheels. So that they can show off big(er) rims and look a tiny bit road car-ish. It’s not for performance, it’s fully the thinking of the grey hair’d FIA trying to connect with the youth. Pure marketing.

      1. I think your right, to me it seems like a fashion statement that only serves the tire/wheel manufacturers – also those large sidewalls do act as a bit of a suspension component – they will add bigger brakes – shorter stoping distances

  6. Thanks @dieterrencken. Is this change for changes sake, change because F1 is an outlier with smaller rims, or change for some anticipated performance/racing benefit?

    1. And change perhaps because the likes of Michelin for example have expressed an interest in coming back to F1 only if they go to larger rims?

      1. @robbie Cheers, that might help explain it.

  7. Very informative and insightful interview.

  8. 15, 18, 20… I don’t think it makes any difference in fan interest. Low profile 20″ tires may negatively impact the cars handling over the kurbs. Why redesign the entire suspension just to change your tire size? Pirelli has their name on the tire and gets their exposure regardless of a little short term news on tire sizes.

    1. No Don, but it could well mean that there will be more Tyre suppliers interested in supplying tyres for F1.

  9. I still think this is mostly pointless. It’s a change to make it look closer to what we have in road cars, not a performance gain. “Technology is moving forwards” I hear you say but it’s just about looks, they could well keep this high sidewall design and be just as quick without redesigning the whole car. It’s going to be a really expensive change, again… and for no reason other than to “look modern”. Who cares if road cars use lower profile tyres? why are we only considering road relevance in the profile of tyres? road cars don’t have huge wings and carbon fibre bodies normally… and it’s just fine!

    1. @fer-no65 But it is obviously not pointless as Michelin has said they are only interested in entering F1 if F1 goes this route, and now F1 is going that route, so obviously they have solid enough reasons to do this that they are proceeding. So who cares? The tire makers and F1.

      As far as expense, the perfect time to do this is when they will be redesigning the cars anyway. So the added expense will be minimal. The teams have plenty of advance notice now, that their 2021 cars will have 18” rims on them.

      1. @robbie pointless from the technical and sporting POV. Of course it has political implications and if they really want Michelin in, they’d do it.

  10. Those rims look ridiculous. The tiny brakes make it seem like it’s a bike’s wheel.
    Ridiculous on road cars. Ridiculous on race cars.

    Which is not a problem. The cars are ridiculous as it is, they sound like mopeds.

    1. +1. Better call it Formula 1 Ricer, Formula 1 Detroit Edition, Formula 1 Fast and Furious. We just need some NOS and neon lights.

    2. For the real wheels, expect bigger brakes than you see on the mockup.

      1. I think that a natural limit on braking performance is an advantage of the current wheels. I’m not sure we want to have the same brakes but with 30 percent larger rotors. I think that would hurt passing, other things equal. Passing a car that can brake for a corner from 180kph in 150 meters is hard enough now. It’s like target shooting.

        1. Michael Brown (@)
          8th August 2018, 19:55

          If the FIA can notice that braking distances are too short they can make the brakes smaller or make them a different material, like steel.

      2. If they make the brakes bigger, then I think they’ll look good. Small brakes are ridiculous on big rims.

        1. I feel like a lot of people didn’t bother reading the article – or at least didn’t pay attention to it.

  11. Dieter Rencken… asking the right questions!

  12. Story of my life, developing software to unknown future specification, that needs to work at unknown speed with unspecified data.

    I feel Pirelli pain. And they don’t even know if they will be the only ones developing a solution.

    It also makes Michellin entry less likeley. One year 13″ then two plus one for 18″.

    What does F1 do if Pirelli abandon them? They are out of contract next year right? What if they do a Ricciardo?

  13. I really don’t see the need for this. Yes, 18s are more commercially relevant, but only nominally. You will not be able to buy a tire for your road car in anything like the spec of an F1 tire. And the lack of 18s in F1 does not now limit Pirelli’s ability to market its P Zeros or whatever to consumers by saying, look, F1 cars have them too. (Also, I find the comment that 18s are for “supercars” to be laughable. The wheels on a base model Corvette are 19/20. 18s are for VW GTIs now.) With the turmoil in design issues to address performance and following, not to mention cost and trying to reduce staffing, why are we doing something that will cause a complete redesign of the suspension concept of the cars?

  14. All this ruminating over wheel size.
    If the teams got to decide and source their own tyre supply, likely 15 or 16 fronts and 18+ at the rear. Who knows and it ain’t gonna happen.
    One problem that the FIA has to deal with, apart from all the new ones they create, is finding a credible supplier that actually wants the job. Michelin has indicated they won’t do 13 inch wheels and it is looking like Pirelli doesn’t want to extend their current contract for the same size.
    That white blur was Bib running down the road as fast as possible.
    How much is the FIA prepared to pay to have a supplier sign up for one season of 13s and two seasons of 18s.? My guess is not enough.

  15. Peter Scandlyn
    8th August 2018, 19:56

    So many questions raised there by Isola, brief is clearly beyond Pirelli.
    Best pass the ball to another tyre manufacturer…..

  16. What is even more interesting than the tyres is the comment on MGU-H—– ‘At the time of our interview there was still talk that the contentious MGU-H would be dropped from 2021, resulting in a possible loss of engine power, in turn making the switch to 18-inch rubber easier.’—this would seem to indicate that it is almost a foregone conclusion that with the lack of new engine makers in F1 then the existing engines will be retained unaltered!

  17. Would the specification be written in inches or centimeters?
    Curiosity got me reading & I guess the tender at least must have to be in metric.

  18. What kind of tyres did F1 use in the past? When did they switch to the current 13″ tyres?

    1. The size became 13” by default: Goodyear used 13s while some others supplied 15s over the years, then when Pirelli and Michelin left during the 80s, Goodyear had the grid to itself, so continued on 13s. When Bridgestone came in in 1997 they suggested 15 (or more) but Goodyear, got not wanting to develop a new range at great cost, threatened to leave unless 13s were retained. Then Goodyear left and Michelin returned – same threat from Bridgestone…

      When Michelin left at end-2006, a year ahead of a 2008-10 three-year sole tyre supply deal that went to Bridgestone, 13s we’re retained on costs grounds.

      When Bridgestone gave 1 year notice of exit at end-2009 (for end 2010), F1 messed about until June 2010 before announcing Pirelli as successful tenderer. They had little over 6 months to develop a range so everyone agreed to keep 13s on cost/expediency/engineering grounds.

      That was the size retained through Pirelli’s three contract, the last of which expires at end-2019.

  19. Generally I really don’t like the bling look with enormous wheels, but F1 should have moved to larger wheels years ago in my opinion. I don’t care about the exact sizes of the wheels as long as it makes sense for a performance racing car. If any engineer was asked to design a race car from scratch today they would definitely not use 13 inch wheels for 660mm tall tires if they didn’t have to. That is why F1 should move to larger wheels – not because it would look different or give the manufacturer more or less advertisement space.

    The biggest impact of a slimmer sidewall tire would be that more control of the movement of the car would be put in the hands of the teams engineers rather than the tire manufacturer. That sounds like a good thing to me. With the current 13 inch wheels some 60% of the suspension travel is just a rubber balloon bouncing around. What the teams can do is developing complicated suspension systems that navigate around stupidly strict rules just to control the remaining 40, or so, percent of the suspension travel that isn’t in the tire sidewall. Letting that development have a larger impact on performance would only be fair, wouldn’t it?

  20. That is nice that 18-inch wheels will change everything. Maybe it would be good for some racers to get wheels like these. That is something I would want if I were a race car driver.

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