Oleg Goes To Barber
Last weekend I've driven Barber Motorsports Park and it immediately became one of my favorite tracks. It has a good mix of tight and open turns, massive elevation changes, plenty of width and good spacing between corners. The track is busy but in a challenging, positive way.
The track rewards mechanical as well as aero grip, well balanced cars, and a limited slip differential does not hurt either.
Turn By Turn
These thoughts are for my 1997 Miata with 133 crank hp, FM springs/Tokico shocks and Maxxis RC-1 245/40-15 tires (arguably the strongest point of the car).
This is a much faster turn than most DE drivers grant it. Because the exit is uphill, carrying momentum into turn 1 in a low powered car like a Miata is crucial. I've been braking at roughly the 1/2 marker, turning in somewhere between 1/4 and zero. Precision at the apex is key for a great segment time here - turning in too early results in the car cutting the curb which sets it airborne, whereas turning in too late creates a real danger of running out of track halfway between turns 1 and 2. Turning in early and cutting the curb is the safer choice.
There are two principal lines through turn 2 in a Miata: the "hugger" line and the "angle" line.
The "hugger" line follows the inside edge of the track through most of the turn. This is an easier line to drive, and it is quite quick. Apply full throttle somewhere around the apex and start tracking out to the exit curb on the left.
The "angle" line requires more grip and a car which is capable of both rotating on demand and staying planted. Come out 1/4 of the way toward track left between turns 1 and 2, the angle the line into turn 2 trying to make a straight line. This approach calls for a later braking point compared to the "hugger" line. Rotate the car with trailbraking at the end of the braking zone, rapidly changing direction toward the track out point, and immediately go to full power. If you have the car that can pull this line off, the reward is a later braking as well as earlier throttle application, saving maybe half a second in this turn. A car with insufficient grip likely will not rotate enough to make the angle line work or will be unable to plant the rear once power is applied, resulting in an extended slide under power. Both cost time and make the angle line as slow as the hugger line.
Regardless of car position and heading at the apex, use the entire track on the downhill up to and including the rumble strips in the left exit curb.
Continue the arc from the apex of turn 2 through the exit curb of turn 2 and it should put the car right at the apex of turn 3 just past the crest of the hill in turn 3. This section is taken under full throttle in low to medium power cars.
Low power cars will not be tracking out all the way as they are coming out of turn 3. Medium power cars will need more track width. There is enough distance between turns 3 and 4 to set up for turn 4 on the right edge of the track regardless.
This is a downhill transitioning into an off-camber transitioning into an uphill left. The off-camber nature of the turn limits grip, resulting in most cars staying in a relatively high gear through turn 4. I tried second in the Miata and it produced nothing but wheelspin. A limited slip differential should make a big difference in this corner.
The braking zone has surprisingly abundant grip considering it is downhill, permitting rather heavy brake application. It is critical to rotate the car with trailbraking - due to the off-camber nature of the middle of the turn, if the car is not rotated enough on turn in it becomes very difficult to come out of the turn without runinng out of pavement or lifting. Because the turn in is very slow, braking early is very noticeable in lap time. I was starting to brake at the 1/3 marker.
The exit curb is very usable in low power machinery, and should be used as it gives about 1/3 car width of additional track real estate.
A fast right, this turn calls for minimal braking just to stabilize the car between turns 5 and 6. I started to brake right before the turn in point.
A left-right chicane, this turn can be awesome if taken properly and I imagine miserable otherwise.
The correct line through turn 6 is to run the entire left curb over with the ieft side tires. Aim to have the left edge of the tires be at the left edge of the curb.
In a Miata I applied light braking starting from roughly the midpoint between turns 5 and 6, through the left curb as the car went up and down. Again there is a surprising amount of grip available in this turn considering the steepness of the curb. Obviously full effort braking will lock up the tires, hence I found that braking lightly the entire way is most consistent as well as smoothly transitions the car from the high speed right curve to straight line braking.
Come off the brake roughly half way between the left curb and the right curb and rotate the car with trailbraking into the turn. Trailbraking, like in turn 4, is again an absolute necessity to get the car quickly rotated the right way. The ideal line is to place right front tire in the transition between the pavement and the right apex curb; this will help rotate the car without upsetting it. Avoid running over the right side curb. A Miata should be full throttle just past this curb, aggressively tracking out. I was using the left side exit curb on most laps although it's just a hair too far from the apex to really use it like the pavement extension in Watkins Glen turn 7 exit.
This uphill chicane is taken flat out in low powered cars like Miatas. Medium powered cars should still take it flat out and use the exit curb on the left side between turns 7 and 8.
The second chicane on the back side of the track is more complicated. Even in my Miata I had to apply a bit of brake to settle the car going into the left turn, although a PTE Miata with a wing seemed to take this section without braking.
The critical part is positioning the car in the right place at the right side apex curb. I was going for about 2/3-3/4 way through that curb as my apex. Neither early nor late entries are good; an early entry requires cutting much of the apex curb to stay on track which upsets the car as the curb is very steep, resulting in the car understeering or oversteering when the right side tires finally land. A late entry (at the normal entry speed) results in rapidly running out of track past the apex as the car is cresting the hill, which is not pleasant at all. Like in turn 1, an early entry and cutting the curb is safer than a late/missed entry because there is time to lift and bleed some speed off, and hopefully adjust the car's trajectory.
This is virtually a pure confidence turn. Low power cars can maintain full power through it, using the entire apex curb. A car that oversteers in the steady state will probably go into a drift at some point in the turn, but this is not how road course vehicles should be configured. A well set up car will maintain a touch of understeer through turn 9 and be quite manageable.
This is perhaps the trickiest corner of the whole circuit. Assuming the car was quick through turn 9 it approaches turn 10 at a lot of lateral G under throttle; it then needs to brake while potentially still turning and nail the blind apex to set up ideally for turn 11.
The best strategy for turn 10 in my opinion is seat time - getting many laps through this section builds confidence in braking later as well as develops gauges for where the car needs to turn to hit the apex.
Hitting the apex in turn 10 is a prerequisite for a good lap time, as being off the apex in turn 10 means the car is way out of position between turns 10 and 11, compromising either the line through turn 11 or speed coming up to turn 11. Either way this affects exit speed out of turn 11 which is followed by the longest straight on the track.
This turn is primarily about vision - looking at the apex very early to dial the correct amount of steering into the car as well as turn in in the right spot, then looking at the track out point to be able to commit to throttle. In a Miata this turn can and should be taken under full power and the car should use all of the exit curb which is at least half a Miata wide.
Narrow Vs Wide Tires
I ran most of the event on 245/40-15 Maxxis RC-1s. As an experiment I switched to 205/50-15 Toyo RRs after lunch on Sunday.
Interestingly enough, the lap times of both tires were comparable. I was about a second slower on the RRs, and RRs felt a lot less grippy than the RC-1s. As the RRs were take-offs I assume they have been heat cycled out; with good condition RRs I imagine they would run roughly the same lap times as the wider RC-1s.
Given that the RRs were less grippy than RC-1s, I found it impossible to do the angle line through turn 2, and I was much less consistent in turn 4 with fast entries. The car exhibited strong understeer in turn 6 and was a little scary in turn 8. Turn 10 often became a drifting contest, and while the car was easily controllable most of the time drifting is not a quick way through that turn.