Shading on Bob's Speed bar

[byegad]

A couple of my Bobs have some of their speed bar shaded black/white at the top end. One also has his Braking bar shaded similarly.
I've been A spec racing for a while and the main Bobs affected have 38 and 31 Exp and getting close to to the top of their capabilities. I've searched and can't find any explanation as to what this means.

Can someone help, please?

 

[PureHeavyMetal]

It means that they're aging and losing speed. My oldest bob has lost like 25% of his strength thus far. I think it's supposed to happen when their experience/career bar gets full, or close to full anyway.

 

[byegad]

Thanks for that I suspected it was the case but nice to have it confirmed.