Intro

Thunderhill Park Raceway was opened by the SCCA  in 1994. It's located near I-5 west of Willows and 75 miles north of Sacramento. The original track consists of a 1.9 mile counterclockwise loop. There's an extension to the track opened in 1998 making the track 3 miles and 15 turns total. 

Turn 1

A very high speed turn. If you turn in too late you'll never make the apex--or you'll be heading sideways from trying to turn in too tightly. There's a slight rise near the apex that will lighten the car. Getting the braking correct here is most important.   There's lots of high speed spins that are fun to watch, but not so much fun if you're driving! If you hit the apex right (a little late) then it's full throttle rest of the way.

Common mistake:  Turning in too late then attempting to steer towards the apex and run out of traction.

Turn 2

This is a long, large radius sweeper. It's a good place to check out your suspension and tire adhesion. There's a downhill leading into the turn. Take a line about 1/2 to 2/3 of the way towards the outside. The apex is very late in the turn. After tracking out you have to immediately come back across to set up for Turn 3.

Common mistake:  Apex way too early.

Turn 3

This is a blind turn. There's a slight hill before the turn so do all your braking before or you'll find yourself sliding towards the outside because it becomes off camber after the crest. There's a flatter line about a third of the way from the inside.  Take a long arc to a late apex and you stay to the right for Turn 4. You have to memorize this turn since you can't really see it soon enough to be able to line up. Too much throttle out of Turn 3 can slide the car. This turn will take a while to master.

Common mistake:  Braking too late over the crest where your car is too light.

Turn 4

This is a flat, fairly fast turn leading to an uphill section. You want a good set up out of Turn 3 so you can really nail it in Turn 4. For this turn you want a fairly straight line through a late apex.

Common mistake: Coming out of Turn 3 where you can't set up for Turn 4 correctly.

Turn 5 & 5a

Turn 5 is a slow, blind corner. Finding the turn in for this corner takes practice since you can't really see where to apex. Immediately after the apex is an off camber downhill sweeper. The car is very light here so you should not try to steer or accelerate abruptly. Straighten the wheel and squeeze the throttle as the car settles heading down. You should be to the right on the way down so you have plenty of room to drift out.

Common mistake:  Hitting the throttle too soon and too abruptly after the apex of 5.  Be sure the steering wheel is straight before applying the gas.

Turn 6

Getting Turn 6 right is important because it leads into the back straight. Be all the way on the throttle as you hit a late apex. Some cars are flat out from 5 through 6.

Common mistake:  Waiting too long to put on the throttle. If you enter Turn 6 correctly you can be on the gas well before the apex.

Turn 7

This is a kink in the back straight. You should come out of 6 pointed to the apex of 7.

"Old" Turn 8 & 8a (on the original 1.9 mile track)

There are different theories as to how to take these turns. You can experiment with your own car. Most think you should take these corners as one. You have to use your brakes more coming into Turn 8 than anywhere else. Take a wide apex on 8 and start on the throttle as you apex 8a. If you try to apex 8 you can't set up for 8a so you're too slow exiting. You are giving up 8 in order to hit 8a correctly.  These are the second slowest turns after Turn 5.

Common mistake:  Not braking enough coming into 8. You'll miss the 8a apex and scrub speed while sliding through these turns (it's fun, but it's slow) and you won't be set up for the critical Turn 9.

Turn 8

A very high speed turn at the end of a straight. Very little braking is required because after the turn in you start up hill so gravity helps keep the car planted.  

Common mistake: Slowing too much before turn in.

Turn 9

This medium-speed turn has a blind turn out because the road rises then drops quickly after the apex.  Go slow into 9 so you can be squeezing on the throttle at the apex as you aim for the middle of the road at the top of the hill.  The steering wheel should be about straight here.  It's important to get the car straightened and back on the throttle as soon as possible so you can carry speed downhill into the straight.  Once you're familiar with this corner you can actually track out further into the blind turn keeping the wheel turned somewhat to the left. This will bring you over the top and pointed downhill without running out of road.

Common mistake: Being too far to the right at the rise after the apex.   You'll run out of road!

Turn 10

A "standard" 90 degree turn, but there's a long, downhill straight leading into Turn 10 so you need a lot of braking here.

Common mistake:  Not getting the braking right. Either braking too early or too late.  (You'll likely see the tracks in the weeds from the cars that braked too late)!

Turn 11

You should take 11 slower than you think.  You want to be set up for 12 & 13.  Apex late and don't track all the way out or you'll be offline for 12.

Common mistake:  Entering too fast and going too far out after apexing.

Turns 12/13 (sometimes called 12/12A)

You should be set up out of 11 to take these nearly straight. Use the apex of 12 as the turn in for 13.  If done correctly you'll be on the power well before the Turn 13 apex.

Common mistake:  Not being set up correctly out of 11 to be able to take 13 straight and fast enough.

Turn 14

Gradual, late turn in and a late apex.  The pavement is quite bumpy here.  If you apex too late you're not set up for the all-important Turn 15. If you apex too early you can easily run out of pavement or at least have to back off the throttle and lose valuable speed heading onto the main straight.

Common mistake: Wanting to turn in too early.

Turn 15

You want good exit speed here since it leads to the main straight. It's important to be lined up at the turn in. You shouldn't have to brake here, just a constant throttle. Squeeze on the power through the apex. The pavement between the apex and the turn out can upset the chassis so you may want to adjust your line.

Common mistake:  Hitting either the apex or exit berms which will upset the chassis.