Lime Rock - Simon Kirkby's Track Walk
Published: June 17, 2014
Disclaimer: I took notes during the walk and wrote this page from my notes. Some inaccuracies may be present.
Most of the suggestions apply to advanced level drivers.
There are blue dots on the track indicating turn in, apex and track out points. They are about the size of a fist and are of darkish blue color. I never noticed any while driving, but they are there, and they are largely correct turn in and apex points.
Turn 1 Entry
Late to the party - missed it.
Stay tight to the apex curbing, this is worth 0.4 seconds in turn 1. Should be no more than a car width off the apex curbing until turn 2.
The track is cambered significantly more on the inside half width.
Tight line is better for understeering cars.
Turn 1 To Turn 2
Widen the line and lift to rotate the car into turn 2 - throttle steering. Doing this permits getting on power within a car length of the beginning of the apex curb in turn 2, and is worth 0.2 seconds between turns 2 and 3.
Turn 2 is cambered more on the inside half width, like turn 1. Going out to the outside half of the pavement means driving on the flat part of the pavement.
Can use the inside curb in a soft car, not in a race/stiffly sprung car.
Can use the first 1/3 of the exit curb in turn 2.
Three possible lines: inside, outside or middle. In turn 3, all three lines come out to take roughly the same time.
Inside line: stay left at the edge of the track. Very late braking is required to make the inside line work. Very light braking is required as well, as braking is done in the turn.
Outside line: entry from the right side, late apex. This line is easiest.
Middle line: entry from the middle. Drivers used to braking in a straight line then trailbraking can use the middle line.
Simon's own line is inside, but he generally recommends middle line.
Low powered cars that do not lift for turn 4, like Miatas, may benefit from the outside line because earlier throttle application produces higher exit speed out of turn 3.
Turn 3 is cambered more on the inside half.
Rain line in turn 3 is rimshot.
Put front tires on rumble strips, but not rear tires, at the exit of turn 3 - in dry conditions only. There is more grip over rumble strips actually.
Simon says he gets understeer in this turn in any car he drives, where understeer happens varies. This is because the inner half width is cambered more than outer - a car crossing mid point of the turn gets unsettled at some point.
Simon's suggestion is to turn in at full throttle and lift whenever understeer happens.
Early turn in is not as bad in this turn because the car gets into the more cambered inner half of the pavement quicker.
Do not use apex curb.
There is a lot of camber on the inside half of track width.
At track out the car crosses the camber change point again moving in the opposite direction - and loses grip/experiences understeer as it does at turn in. The correct solution is to straighten steering and allow the car to track out - grip will be regained once the car passes the crown.
Straightening when understeering at track out is counterintuitive and sketchy, need to practice.
1/3 of the exit curb can be used, same as with turn 2.
No Name Straight
It is possible to drive the no name straight without changing steering wheel angle given exit out of turn 4 at a specific point. This is worth 1 mph at the end of the straight due reduced to tire scrub.
There is a rise on the right side of the straight which can upset (high horsepower?) cars enough to where cars wreck toward the end of the straight. Driving straight per above helps, as does rain line which is on the left side of the track.
Rain line through this straight is left of the black line that follows the track approximately 1/3-1/2 from the right edge.
Blue dots on the left side of pavement and duplicated on the left curb indicate turn in points. The first set is for no chicane version, the second set is for the chicane.
These dots are approximately in the middle of the curb length-wise.
There is a blue dot on the edge of the pavement at the apex, indicating correct apex point.
Dry line up hill is just right of the white line indicating track limit on the left. Straightening steering should be done 2/3 of the way up, not when the car is about to crest, to give car time to settle and actually change direction to go straight. This also means the car should get to the left white line about 2/3 of the distance up the hill.
Rain line is left of the left white line. Nobody drives there ever (in dry) which means there is no oil etc. there.
There is a blue dot at the end of pavement extension on the uphill - not sure what this one is for (chicane exit maybe?).
Simon says this is the quickest turn where trailbraking makes sense. Faster corners should have braking finished before the turn in point.
There are two blue dots around turn in point, turn in at the second one which is the bigger of the two.
Timing of braking and trailbraking is critical. Need to trailbrake to turn in properly.
Spec Miatas can left foot brake without lifting off throttle.
There are blue dots for track point.
Rain line is to brake mid-track, cross dry line and then do a rimshot.
The track comes out left a little from the top of the hill to the turn in point. Don't follow the track - drive straight down hill and keep steering wheel straight until hitting the compression point, then turn.
There is a blue dot at the turn in point.
There is a blue dot at the apex.
Inside half width of the track is cambered more.
People do not unwind steering enough. Ture scrub holding steering at downhill exit is worth 2 mph by the end of main straight.
Rain line is a rimshot.
People overbrake at Lime Rock - there should be no threshold braking done anywhere. If a car gets squirrely under braking, solution is to reduce braking rather than braking harder.