Thompson Speedway Track Guide
Every turn on the track (I believe; I have not seen the apex markers in some of the turn because I did not look for them at the time) has an apex marker. This is a red paint mark about a foot long and an inch wide which is perpendicular to the track center line, with half of it on the pavement and the other half on the curb. These marks are rather easy to spot when driving around the track at 30-40 mph - just follow the edge of the pavement where the apex curbs are.
Depending on the car one is driving these marks may not be exactly in the right places for all apexes, but they are good starting points.
Turn By Turn
The braking zone going into turn 1 is significantly uphill until the 2 brake marker. Between 2 and 1 brake markers the track is still going uphill but less so. From 1 brake marker the track starts to go downhill.
Because of the uphill, it is possible to brake for turn 1 very late. In the Miata I was braking at 250 and working toward 225, with the turn in point just past 100.
The surface in turn 1 is uneven. Outside half of the track is more banked than the inside half. There is a patch in the turn and most cars are supposed to place the left tires on that patch. However, the patch is bumpier than blacktop around it.
Turn 1 itself is a long, slow right hander. Because of how long the turn is most cars would run a late apex, with high power cars running a proportionally later apex. This turn is similar to VIR turn 1 or Summit Point Main turn 1 in this regard.
As with VIR and Summit Point, the car would reach the outside edge of the track at the end of turn 1 while the track continues to curve into turn 2 which immediately follows. A good track out reference point for turn 1 is the end of the exit curb. Using the flat part of the curb (first few inches width-wise) may be advantageous in softer cars, but going on the "square" part of the curbing is generally not advised.
Turn 1 transitions into turn 2 which is also a right hander, but a much more open one. This configuration again is similar to VIR and Summit Point. Most cars should be taking turn 2 under full power, and would not need to track out all the way left exiting turn 2.
There is a dip in the center line of the track between turns 1 and 2. What this dip does is it momentarily reduces grip as the car is crossing it, which happens twice: once when the car is tracking out in turn 1 and the second time when the car is turning into turn 2. The result is often momentary understeer.
Turn 2 has a bit of camber especially on the inside half of the track going into the turn. As the car crosses the center line exiting turn 2, this camber is lost and the result again is momentary understeer.
The track goes somewhat downhill between turns 1 and 2, and elevation drops quicker between turns 2 and 3.
There is a white X painted on the pavement approaching turn 3. This can be a useful reference point, but what it is a reference for is up to each individual driver to decide. Here is its location:
The track levels out right around where turn 3 begins, which effectively creates a compression zone. Turn 3 is also significantly banked. As a result, very little braking is necessary for turn 3.
Depending on how much power and grip the car has, apex point will vary quite a bit. A front wheel drive car with a welded differential will turn significantly earlier than a rear wheel drive car. High power rear wheel drive cars might be taaking this turn as a late apex one, even.
The exit of turn 3 is slightly uphill.
There is a dip in the track longitudinally between turns 3 and 4, and the braking zone into turn 4 is uphill again. The elevation change, just like in turn 1, means that braking can be done later than would otherwise be expected. Right at the point where the grass ends on the left and what looks like gravel begins the track begins to drop. End of the grass can be a good turn in point.
Once the car turns in, the track goes massively downhill. This drop typically manifests in strong understeer; people miss the apex a lot in this corner.
There is a patch in the turn that you can follow with your left tire.
What looks like gravel on the outside of turn 4 is actually asphalt - if you need to use the runoff, do not be afraid of it.
Turn 5 - Bridge Turn
The straight between turn 4 and turn 5 is all downhill, which makes turn 5 require earlier brake application than geometry alone would suggest.
The track map marks turns 5 and 6 as separate turns. On track they can be thought of as a single double apex turn - these turns are always taken as a combination. The track narrows at the second apex and goes off camber right past the second apex on the oval, as the oval is banked inward. Therefore in terms of car dynamics turn 6 can be treated as a decreasing radius turn, and turn 5 is therefore taken as an entry speed turn.
Braking into turn 5, especially in lower power cars, is likely to be done in the turn itself. This is reminiscient of VIR turn 4 or NjMP Lightning turn 3. I prefer starting most or all of the way on the right on the 4-5 straight and running a diagonal line toward the first apex of turn 5 while braking. An alternative is to run an arc.
Several lines are possible through turn 6. Low power cars can be on full throttle between the apexes of turns 5 and 6 - half way or 2/3 way between the apexes would be good. The line in these cars then can be thought of as a double apex through the turn 5-6 complex: touch the first apex, come out about mid track, turn more to hit the second apex and go full throttle.
Drivers of high horsepower cars would want to run a later apex for the apex of turn 6 as the exit is not that wide. These cars may come out further between apexes and possibly miss the apex in turn 5 completely to set up for turn 6, similarly to Summit Point Shenandoah loop turn.
Less experienced drivers, or drivers new to the track, would enter much further on the right - perhaps staying right of center through turn 5 - and then get on the high power line once they are between the apexes.
This is a right hander that does not use the banked oval, which explains why it looks the way it does on the track map. Approach and exit in this turn are on the oval, and are thus banked, but the turn itself is just inside the oval and hence is completely flat.
There is huge line variance in turn 7 depending on horsepower and grip level of the particular car. I ran a late braking, "entry speed" line in the Civic - a front wheel drive car that nonetheless turned eagerly thanks to its welded differential, and a much more conventional "exit speed" line in the Miata which is a balanced rear wheel drive car. In any event exit speed is important and time in the corner approach is quite significant. This turn demands excellent vision for best results.
This is an off-camber, decreasing radius, bumpy left hander. The entry, being on the oval, is very wide; the exit is easily half the width of the entry. Setup for turn 10 exit demands a very late apex in turn 9, but this means early braking and thus giving up the speed on turn 8-9 striaght. Put together, turn 9 is a tricky compromise corner that demands consistency and experimentation.
I liked mid-track to outside entry for turn 9 with a somewhat late apex mostly for reasons of safety.
If turn 9 is tricky, turn 10 can be outright fiendish. The spacing between turns 9 and 10 is just slightly bigger than would be ideal for an "esses" element, and the result is that the car typically needs to be straightened out for a moment between turns 9 and 10. The problem is that most cars do not just straighten out on demand.
If you can pull it off, cut the apex in turn 10 or use the curbing on the exit to flatten the turn.
An opening right hand sweeper. In lower power cars this turn can be easily taken under full throttle.
This is a kink on the main straight that also happens to crest a hill. My suggestion is to aim for the right edge of the track and cut the distance, although I have heard that letting the car track out reduces tire scrub and hence produces a lower lap time.
Great high power, late apex video