The recent announcement that, from next year, there will be no stopping for rain in premier-class racing has resulted in considerable debate throughout the MotoGP world - not least among the participants of the Crash.net MotoGP forum - with a great deal of uncertainty raised by the following brief statement released by the FIM:
"In the MotoGP class only, in case of rain, the race will not be interrupted."
It remains to be seen exactly how the riders will be able to continue racing regardless of the weather, but it appears most likely that they will be offered the chance to make some sort of pit stop which will end – one way or another – in the rider rejoining the circuit on a bike better suited to the new conditions.
When to pit?
How this set-up change (from dry to wet) will be achieved is a matter for the rule makers, and still to be announced, but regardless of the method (ranging from a tyre change to a whole bike swap) the key to the rule's success is likely to involve making the 'changeover time' - the total time lost entering the pits on a dry set-up bike and getting back up to full speed with a wet set-up - as small as possible.
The biggest criticism the new rule faces is that 50-minute MotoGP races are too short, proportion wise, to encourage riders to make a pit stop – which even in its shortest form would be equivalent to a ride through penalty (the pit lane speed limit is 85km/h) – unless the rain is very heavy, or falls early in the race.
As an illustration, consider the following simple formula, the type of which could be used to determine if and when a rider should pit in the case of rain:
Pit for rain set-up when:
(Time lost per lap with dry set-up x number of laps remaining) > (changeover time lost)
In other words, pull into the pits only when the time lost by staying out on a dry set-up exceeds the time lost in changeover, by the end of the race.
Clearly, this is a simplistic view – factors such as race position and time advantage/disadvantage, the rider's wet weather ability, an assessment of risk, how much time will be lost overtaking slower riders after a pit stop and not least the likelihood of the weather changing – would also be taken into account.
Meanwhile, estimating the time lost per lap by staying on slicks is also more difficult than its sounds; the tyre suppliers are likely to provide an estimate, but an accurate indication will only be found when a rival - or ideally a team-mate - makes the change from dry to wet set-up.
Nevertheless, the laps remaining and changeover time are easily found - in the latter case, once the rules are finalised - and the fact remains that to help prevent riders taking risks on slicks (by encouraging them to pit as soon as possible) the rule makers will have to come up with a system that makes the time lost during changeover as short as possible.
Unless...
The changeover time becomes irrelevant if all riders chose to make a pit stop - or if they are forced to do so, perhaps by some 'pit stop flags', instead of red flags, waved by race control... but that raises more questions than answers.
Some thoughts on bike swapping...
The quickest way to reduce the changeover time (outside of altering the pit lane speed limit, unlikely for safety reasons) would be for a rider to jump off a dry bike and straight onto a waiting wet bike.
In order to check that the wet bike was working correctly, it would need to complete an installation lap (one lap then back into the pits) – just as the normal race bike does before taking its position on the grid.
But bike swapping also raises the issue of how fuel limits will be checked - the consumption of each bike would need to be combined - but the main problem with post race fuel checks is that the machines don't stop as soon as they cross the finish line.
A more time consuming solution would be to swap the fuel tank onto the wet bike during the changeover - or to pump the remaining fuel from the dry bike into the wet one - but both will raise safety concerns and extend the changeover time.
Indeed, it may be easier to scrap the fuel limit in the case of rain – with power delivery softened and riders using less throttle in slick conditions, the wet bike fuel usage should be significantly lower anyway.
Plenty for the grand prix commission to think about...