Thunderhill (East) — Race Line
Estimated from data not in trackdays.ai. The speeds and braking points come from cars lapping at a typical quick HPDE pace, checked against published brake markers. If you have data you would like to contribute, please send it to upload@trackdays.ai to help improve our estimates. It follows the East course with the Cyclone; some events run a bypass that takes a straighter strip of road over the hill. Turn numbers are our match of the 15-turn track map to the LiDAR corners, not a confirmed canon.
Heads up: This is an estimate of a typical quick HPDE line, not any one car's lap. Braking points are a starting point, not a target: start a little earlier and work later in small steps. The line goes straight from throttle to brake; amber only marks where you really lift or hold part throttle. The turn numbering is provisional; the Cyclone (T5) is three bends in one. Thunderhill climbs and falls 34 m a lap, so read the corner notes: crests and camber matter here as much as the line.
- Throttle
- Coast / partial
- Braking
- Apex
- T4Off-camber corner
Arrows show the direction of the lap. The grey basemap is USGS LiDAR: dark = asphalt, light = grass. Tap any map for the full-size image.
Thunderhill East is a hill track: the lap climbs and drops about 34 m, with two blind crests, at the Cyclone (T5) and at T9, and steep descents after each of them. The whole site falls gently to one side, so most left-handers are slightly banked and most right-handers are slightly off camber, which is why T3, the right after the Cyclone crest and the right after T9 feel looser than they look. Lap time comes from clean exits onto the long front and back straights, at T11 and at T14–T15, and from being patient and straight under braking on the downhill approaches to T10 and T14.
Sectors
Brake from the front straight on the right side of the road for T1, a slightly late left that leads straight into T2, a long, 180-degree left that you sit in for a long time while dropping into it. T3 is a right whose entry is downhill and off camber, so it has less grip than you expect, and T4 is a left whose exit starts the steep climb to the Cyclone.
The Cyclone (T5) climbs steeply to a blind left over a crest and drops straight into a downhill, off-camber right, so brake in a straight line on the way up and keep your inputs smooth. At the bottom, T6 is a long left at the lowest point of the lap that needs only a light brake, T7 is a bend in the curved run to T8, and T8 is one of the fastest corners on the lap, where you set up on the far right.
T9 is a banked, uphill left that crests a blind hill at the highest point of the lap, so have the wheel straight as you go over the top and down the other side. Brake earlier than you think for T10, a banked left on a descent where the rear goes light under braking, and then T11 is the tightest corner on the lap, where a late apex sets up the run onto the back straight.
T12 and T13 are fast kinks that most cars take near flat; straighten them out and keep the steering small, because T13 is the only off-camber left on the lap. Brake hard and straight at the end of the long straight for T14, a right of more than 90 degrees, and treat T14 and T15 as one long right that sets up the drive down the front straight.
Corners
Position the car on the right side of the road in the braking zone, brake hard early and then ease off so you can roll good speed into this left, trailing the brakes toward the apex. Aim for the middle of the inside curbing, since you will drift a little past it and end up with a slightly late apex, then track out to the right. The mistake to avoid is braking too long and too deep, which leaves you off the throttle on an exit that climbs.
From the survey: On camber (+2.6%), and the exit climbs about 3 m.
T2 is a long left that you are in for a long time, and the road drops into it, so do most of your braking in a straight line and a little earlier than the plan view suggests. Hold the car about a car width off the inside and tighten gradually to an apex about two-thirds of the way round, balancing the car on a light throttle. The mistake to avoid is an early apex, which runs you wide on the way out.
From the survey: A long 180° left that drops 5.3 m into it; on camber (+3.8%).
Come in from the middle or left side of the road at a slight angle and brake early, because the entry is downhill and off camber and there is not much grip. Be patient for a late apex on the right and let the car track out to the left only once it is settled. The mistake to avoid is braking and turning hard at the same time on the off-camber entry, which can send the rear wide.
From the survey: Off camber (−2.8%) and downhill.
T4 is a roughly 90-degree left that sets up the Cyclone, so give up a little entry speed for a clean exit. Let the car run out to the right edge of the road on exit, because that is where you want to be as the road starts to climb toward T5. The mistake to avoid is a wide, untidy exit that leaves you out of position for the Cyclone.
From the survey: On camber (+3.4%); the climb to the Cyclone starts on the exit.
Hug the right edge as you climb the hill, brake smoothly in a straight line, and wait for a slightly late turn-in to the blind left at the top, aiming for the inside curbing. Have the car straight and settled with a little throttle as it goes over the crest, then let it fall into the downhill, off-camber right on the other side and flow out to the edge of the road. The mistake to avoid is turning or braking hard over the crest, where the car goes light; build up to it over several laps.
From the survey: Climbs at +14% to a blind crest, then drops at −15%. The left over the crest is banked (+3.6%); the right after it is off camber (−3.1%).
T6 is a long left at the bottom of the hill that needs only a light brake to settle the car before you turn in. Take a slightly late apex and get back to full throttle just after it, letting the car run out to the right. The mistake to avoid is carrying too much speed into the long middle of the corner and having to wait for the throttle.
From the survey: Sits at the lowest point of the lap (84.6 m), banked +3.1%.
T7 is really just a bend in the curved run from T6 to T8, and most cars are on full throttle through it. Keep the steering smooth and use the exit to place the car on the far right of the road for T8. The mistake to avoid is drifting to the left here, which ruins the setup for T8.
From the survey: On camber (+2.8%), gently uphill.
T8 is one of the fastest corners on the lap, and it looks tighter than it is, with good grip and extra room on the exit. Come in from the far right, make any small speed correction early, and be at or near full throttle by the apex as the road begins to climb. The mistake to avoid is an abrupt lift at this speed, which can unsettle the car.
From the survey: On camber (+2.3%), climbing at up to +5%.
Brake uphill toward this banked, roughly 90-degree left, turn in a little early and use the inside curbing as your apex; the banking lets you roll more speed than it looks. The exit crests a blind hill at the highest point of the lap and then drops away, so have the wheel straight as you go over the top and stay parallel to the edge of the road. The mistake to avoid is still turning when the road falls away, which can unload the car mid-corner.
From the survey: The most banked corner on the lap (+7.7%), climbing to the high point (119 m); the right that follows is off camber and drops at −13.5%.
The road is already descending, so brake earlier than you think and do most of it before you turn in, watching for the rear to go light under heavy braking. Turn in a little early with a light trail of the brakes, apex in the middle of the inside curbing and use all of the road on the exit, out to the right. The mistake to avoid is braking too late downhill and overshooting the turn-in.
From the survey: Banked +7.9% and downhill at −5.8%.
T11 is the tightest corner on the lap, and it leads onto the long back straight, so exit speed is everything. Turn in late, take a late apex and roll onto the throttle smoothly, setting the car up for a straight run through the T12–T13 kinks. The mistake to avoid is an early apex that forces you to lift on the exit.
From the survey: The tightest corner on the lap; on camber (+3.0%) and slightly uphill.
T12 is a slight right and T13 a slight left, and most cars take them flat or nearly flat, so straighten them out as much as the road allows. Keep the steering small and the car settled, especially through T13, which is the only off-camber left on the lap. The mistake to avoid is a late, untidy T11 exit that leaves you correcting the car through the kinks.
From the survey: T12 is banked (+3.0%); T13 is the only off-camber left on the lap (−2.9%).
Brake hard and straight at the end of the back straight, where the road runs slightly downhill and the braking zone is bumpy, and trail the brakes into T14, a right of more than 90 degrees. Hold a long, late apex, then feed in the throttle and take a slightly late apex at T15, tracking all the way out to the left onto the front straight. The mistake to avoid is the high, abrupt apex curbing at T15; if you run out of room, straighten the wheel and use the runoff rather than snapping the car back.
From the survey: T15 is slightly off camber (−0.8%) and downhill onto the front straight.
Version history
- v1.2 · 2026-10-01 — T4 is now drawn as throttle: the car gains speed through it, so it is not a lift. The T2 exit goes green about 45 m sooner for the same reason.
- v1.1 · 2026-10-01 — Speeds rebuilt from cars at a typical quick HPDE pace on the Cyclone layout: about 20 km/h lower at the end of the straights and up to about 10 km/h lower at corner minimums. Braking points were checked against published markers: T1 moved 15 m later, the rest by 5 m or less. The line now goes straight from throttle to brake, with no coasting in between.
- v1.0 · 2026-10-01 — First version.
Feedback contributors
Drivers and instructors whose feedback has improved this line. Thank you.
- Mike M — no coasting between throttle and brake; braking points (v1.1)
- Brian L — corners where the car gains speed are throttle, not a lift (v1.2)