Why a team introduces a different chassis for a driver

Sebastian Vettel played down the significance of his new chassis here in Spain, pointing out that it isn't brand new - it was used for pre-season testing - but it's new to him this season replacing one that he said, "Isn't talking to me."

Vettel has struggled this season, twice being asked to move over to let his team mate Daniel Ricciardo through during races.

So what goes on behind the scenes with these chassis and why does a team introduce a new one for a driver in a situation like this?

JA on F1 technical adviser Mark Gillan offers this insight:

"Typically a team makes 4 to 5 chassis a year and sometimes the better funded teams will make 6. The lead time to manufacture a new chassis from scratch is between 60 to 90 days. With modern manufacturing techniques and testing process there is very little between each chassis in terms of mass and stiffness, assuming that they are made to the same design.

"Going to Australia the teams will have 3 chassis made and should have run at least two on track. These two tend to be the race chassis. One may chose to adopt a new chassis for the first race but this is not necessarily the norm and depends what has happened to the other two chassis.

"For instance if there have been incidents in the FIA crash tests or on track which has necessitated modifications and/or local repairs to the first two chassis which add mass and can compromise stiffness one may chose to use chassis no 3 and put no 1 or 2 in the box as a spare tub. Moreover newer chassis may have updates to reduce mass etc which is clearly beneficial, especially this season when everyone is pushing hard to reduce mass as much as possible.

"Some drivers also tends to get 'attached', in an almost superstitious manner, to their particular chassis, especially if things are going well, although the opposite is true too. When performances are not as expected then doubts can arise over the chassis, although these are usually unfounded.

"The positive aspect of moving to a new chassis is that it removes uncertainty (the last thing that you want is the driver believing that there may be an issue with their chassis) and the driver will also benefit from any improvements that can be included in the design to reduce mass, whilst not compromising on safety."

As for Vettel's explanation of why he changed chassis and what he is looking for from the change, here is what he said in the FIA press conference this afternoon in Barcelona, admitting that he has been struggling with the car's rear end stability issues and cannot feel the car as he wishes to,

"We all have our own style to how we like to drive the car, how to set up the car. I think in general I don’t mind when the rear’s moving so I don’t mind suffering or having oversteer in the car. But if it is too much obviously if it starts to bother you when the car slides too much, then you find yourself correcting more than actually being able to push or get the maximum out of the car. And, yeah, it slows you down. I think that has been part of the problem so far.

"We concluded after China, where we were quite a little bit behind, to change the chassis, so actually it’s not a new chassis, it’s an old one that we used in testing in the winter, and we have some experience with it.

"It’s more a sanity check rather than a real problem with the other chassis. So it’s just to try everything we can and basically reset and start again. Obviously there is still a lot of work ahead of us, as I mentioned after the first couple of races, maybe I’m not as happy as I want to be but it’s a long process, a lot of things have changed and I think we need to be patient."