JA on F1 technical adviser Mark Gillan, formerly head of track operations at Williams and Toyota F1 teams has penned some thoughts on the test Pirelli carried out last week at Silverstone using low profile F1 tyres on 18 inch rims.
The exercise was for show only and to get people thinking about a change, which has been discussed between the teams, FIA and tyre companies for several years. Having sat in on many of the meetings and as an expert in aerodynamics and vehicle dynamics, here are Prof Gillan’s notes:
To my mind it’s a good time for F1 to go in this direction, it’s the right moment. The key to it is to agree now for two years ahead to give the teams plenty of time to revise the design of their cars and to add in the active suspension element that would be needed to make it work, for reasons I’ll explain further on.
The desire to move to larger diameter wheels in F1 has been discussed on an almost annual basis with the FIA for well over a decade. Tyre suppliers, despite what would effectively lead to reduced advertising space, are understandably keen to move away from the increasingly less relevant small wheel to larger wheels and associated lower profile tyres. With the large forces and moments that go through a F1 complete wheel assembly the tyre suppliers are clearly keen to ensure that the tyre’s profile is adequate to ensure that it is structurally sound i.e. we are unlikely to see very low profile tyres in the near future.
Up until recently every time this change has been mooted it has received only a cursory discussion and then rejected on the basis of the impact it would have on the design of a F1 car, primarily on the suspension and aerodynamics. It was always discussed as something for the short-term. As a significant amount of the ride height motion of a F1 car is supplied by the tyre (effectively a large spring) the move to much shallower profiles would require large changes in the suspension layout.
However if the sport is also moving potentially in the future to active suspension systems then a combination of a new active ride height control and more relevant tyre geometry would make sense. With reduced movement in the tyre the Teams will have more control of the car’s ride height through the suspension system.
The first thing many readers will think is: But won’t this add an extra cost for the teams when they are supposed to be cutting costs?
The answer is no. In fact all F1 teams have an active suspension system available already. The reason is that for the last few years whenever they have done their straight line aero testing (which used to be allowed four times per year, until it was phased out at the end of 2013; it’s what Maria de Vilotta was doing with Marussia when she had her accident) they always used active suspension to control the pitch and roll, so they always got more accurate data from the aero numbers. So the costs are not significant at all. Active suspension has been banned since 1994 for racing in F1, but it’s been developed very well by teams via the straight line aero testing ever since.
In FIA nomenclature the ‘wheel’ is defined in article 1.5 of the F1 Technical Regulations as ‘the flange and rim’ and the ‘complete wheel’ in 1.6 as the ‘wheel and inflated tyre’.
The Lotus ran last week at Silverstone an 18” wheel in order to collect vital data ahead of any possible future switch. It was a well done exercise; the car and its wheels looked right and Lotus did well to run the car
In the close up of the front complete wheel one can clearly see that Lotus retained the standard brake drum and internals which are dwarfed by the wheel.
As literally thousands of wind tunnel and computational fluid dynamic or CFD hours have gone into the intricate design of these drum and brake duct systems the loss in aerodynamic efficiency will be very large indeed with this update. Clearly if this change to the complete wheel was implemented from 2016/17, as is being mooted, then the Teams would have a big job to claw back the lost performance. Of course with the aerodynamic development process the current brake disc and caliper arrangement could be retained or one could alter it to allow it to fill the wheel but limit its performance to that of the current system.
Teams spend thousands of wind tunnel hours perfecting the aerodynamics for the four corners of the car around the wheels and tyres, so there would have to be a trade off in the rules whereby things were tightly controlled in that area, but the trade off would be the massive performance gain that would come with active suspension.
As for the impact this would have on lap times, that can all be controlled by the tyre supplier with the compounds selected, so the cars could remain roughly as fast as they were with passive suspension and fat tyres.
Finally, with a very different tyre construction (one would assume), a larger wheel and less air in the tyre to control the Teams would also have to revisit how to best optimise the tyre for qualifying and race conditions in order to ensure that it was at its optimal temperature at all times.
Their transient thermal tyre models which are used in the driver in the loop simulators will need revising to ensure that the Team’s virtual development tools remain as relevant as possible.
In conclusion, I think this is a real positive for the sport and it’s the right thing to do now. Provided that the teams are given clear rules for the 2016 or 2017 seasons, then they can work on it in the background and be ready to go when the rules come in.