There are 5 Silver Race Badges to earn over the course of the game. Your progress can be checked anytime by heading to RiderNet at the Main Menu by pressing the 'Back' buttonand selecting 'Badges' then 'Race'.
The Badges are:
Achieve a speed of over 200km/h
This should not be difficult to achieve. After a few runs once you get the controls a bit more down pat when using the Boost earnt in Uber Tricky mode this should send you to this speed on a strech.
Maintain 100 km/h for 20 seconds
This is also quite simple. Your rider will want to keep above 100 km/h anyway, you just have to keep on the ground to let them. Avoid jumping .and just give it a good boost on a strech and this should be yours
Pushing the Limits
Maintain 130 km/h for 20 seconds
Similar to the above but more difficult. To get this you will need a Tricky Boost and a solid downwards slope and just keep forging ahead. Avoid jumping again and it should be yours.
I Can't Stop!
Boost for more than 30 minutes total
This is cumulative and will take you a while to earn. Most races you will have roughly 20-30 seconds of boost throughout untill you get the hang of it. Just remember Boost does not get eaten away while in Tricky mode so make the most of that and stick to the ground as you cannot use Boost in the air. You will more than likley have this after completing World Tour though.
Ride a total of 50 Kms in Race Events
Again this is cumulative. Most larger mountains are about 2000m so a large race on a larger run will mean 25 runs. The only thing to note is that it must be in Race events so a Trick/Deadly Descent do not count towards this. You will more than likley have this after completing World Tour though.
My recommended run is Himilaya's - Makalu - Serenity
At the top of the run you will encounter many good long grind spots and then flat surfaces before and after. If you can land on one of these with a Tricky boost and a quick board many of these will come easy.
A good trick to get the 'Pushing the Limit' and 'Speeding Ticket' badge is to find a long rail and grind it using boost while ensuring you are over 100 km/h or 130km/h, once you reach then end rewind to the begining of the rail/whenever you hit over 100 km/h or 130km/h then continue doing this untill the badge pops.