Solved

Hold up! You can run two CDs?

When researching an area which is your CD's strength, you get 10% more design points from research, so if you have multiple CD's with different strengths and always activate the one with strength in the area you will research that race, you are indeed going to get more design points and a stronger car during the season. But at the cost of extra salary to be paid of course. For the next season your total points will remain the same, but more balanced, as Antonio mentioned.
There is an excellent guide explaining this and more, written by Kevin Bissell.

Antonio, not sure what you mean by CD's influence only applies after 6 races?

The old thread would have been at a time when:

• The design range was 1-100 (for Elite)


• A 5 star CD generated for next season start design 3.75 (Strength) / 2.50 (Standard) / 1.25 (Weakness)


• There was a start of season design cap of 50dp for each attribute


• Every season was fixed at 17 races.

It used to be possible to get three attributes to the level cap for next season start design by alternating CDs during the current season.

Multiple CDs can still be effective by using them to maximise research during the current season. However the benefit is now much reduced and costly in terms of wages so should only be considered if you're competing against managers who are ultra competitive and gaining a slight edge by doing this.

If you want to know more please read this... The Mechanics of Chassis Development

This no longer applies. The six race figure was a maximum (not a minimum) because this is how many races a CD needed to be active before the design cap was reached. Any more than six races and the dp were being wasted.

BTW, apologies for repeating what Gert said, I started writing the response then I had visitors to the house. When I came back and pressed the post button it became obvious that Gert had already given the reply.