Forza Horizon 3

This was so much easier after I tuned my car to perfection. I was able to complete 6 different PR Stunts with 3-star ratings. Just a "heads up", I have all festival locations upgraded to at least level 4 so if one of the places I mentioned isn't there for you, that's why. I used 2 different tunes for this achievement. For the Drift Zones I used my tune named "Throwing Weight" and the description says "Throw Your Weight Achievement." For the Danger Signs and Speed Zone I used my tune named "Clever Girl!" and the description says "Clever Girl! Achievement." You can also search for the tunes using my gamertag. As Calex dEUS noted below, you must be using the standard 2017 Ford F-150 Raptor to get these tunes and complete the achievement (thank you). All of the locations I chose were super easy and never took more than 1 try after using these tunes.

Locations:
Rainforest Reveal Danger Sign
Shipwreck Danger Sign
Byron’s Leap Danger Sign
Silver Sands Drift Zone
Kiewa Valley Drift Zone
Central Yarra Speed Zone
Gold Mine Danger Sign (AussieBigfoot)
Gold Mine Speed Trap (AussieBigfoot)
Hilltop Speed Trap (AussieBigfoot)
North Arid Plains Speed Zone (NMANOZ)
South Arid Plains Speed Zone (NMANOZ)

I hope I helped :)

EDIT: Thanks Calex dEUS, AussieBigfoot, and NMANOZ for the additions. I provided the best tunes and locations I have come across thus far to finish this achievement easily, but if you have a problem please reach out to me before downvoting.

The previous solutions are all solid, however, I did mine slightly differently. I managed to get 3 stars on all but a few speed zones. None of my fastest cars could stick to the road on these three in Byron Bay:

- Byron Plains Speed Zone
- Switchback Lakes Speed Zone
- Rough Terrain Speed Zone

If you search under my gamer tag I built three high quality tunes for this truck called 'OFF ROAD', 'DRIFT' and 'ROAD'

With the ROAD or OFF ROAD tune I managed to get my 3 stars on them and finish this achievement! As it turns out, this truck has enough power and weight to stick to the road better than a full upgraded Ariel Nomad and I finally got them. So after two easy 3 star achievements in this truck I got the Clever Girl and finished off three hard to complete Speed Zones.

Addition to v SATAN x's Guide:

Use v SATAN x's tunings. Search under Creator (v SATAN x). Throw Weight Around is for the drifts and Clever Girl! is for the 3 Star PR.

PR Stunts that have already been 3 Star can be used again, just once again pass the 3 Star Goal.

Also if you're having trouble with traffic, make a Private Online Freeroam session :) It reduces the traffic and gets rid of the Drivatars.

This is easier than it first seems and for those of you who can’t drift (like me) it can be done with 5 danger signs quite easily. I used Don Joewon Songs tune and did the following jumps.

Gold mine
Shipwreck
Byron’s leap
Rainforest reveal
And finally the only one that’s a bit tricky is Waterfall.
The first 4 are quite easy if you are having trouble there are a couple of relatively low speed traps. Gold mine is not a hard one.

Hi just another tip. I did this with the Horizon Edition version at first and then spotted it has to be the original Raptor truck. I thought I'd try one of the clever girl tunes and do the Danger signs. However I had trouble, couldn't tell if the tune was for drifts, jumps or speed.
So I did my own. I found it easiest to do speed traps and zones in and around the Byron bay area and towards the rainforest area. Just search for the ones with the lowest speed required for the 3 star achievement.

It is easier in a private session as there is less traffic.
For the speed traps try to have a straight run as possible to the speed camera. Approach from the side that has the the longest road or clear straight route to it, the map should show this.
You might need to start off road, on the grass or amongst the trees. So long as you have enough distance to get up to speed it should be easy.

For the speed zones again one way will have a straighter approach if you check the map. Generally if you can enter the speed zone a good 10-20mph above the average required you should average out ok. If there is a bend or 2 try lifting of the gas and then turn sharply rather than using the brake to keep your speed up. Just tap the brake a little if struggling to make the turn.... But you can still cut the corner a little bit if possible to keep your speed up.

Use my tune Clevergirl Speed for this as the acceleration and turning are better than usual and you should have it done in no time.