[Gianni Gentles]

Don't be too hasty in replacing your CPU, it's more of a GPU issue.
Try the same car/track combo offline with a full grid of AI, and start the race from the back of the pack. This should replicate the issue. Then turn down your graphics settings one by one starting with reflections, this is a major one. Anisotropic and anti aliasing are also big frame rate killers and shadows too.
What graphics card are you using?

This is exactly what I have been doing. I am now at a point with my settings that it doesn't happen with 24 cars but does happen with 25. 

Although it would still suggest I need to upgrade something.  I'm running a 1050ti

I would certainly replace the graphics card before the CPU. Your CPU is not the problem right now.
It very much depends on your budget but to give you an idea, here is a comparison website to see where your card perfroms against other cards on the market.
http://gpu.userbenchmark.com/Compare/Nvi...3646vs3649

If you want to future proof your PC then go for the GTX1070 upwards but they can be costly.

To put things into perspective, I'm using a GTX1080SC and when in VR I need to turn the ingame graphics down quite low to hit the necessary 90fps (for VR) although I do use super sampling to get a better image which is quite taxing on the GPU.