redtopz

With the big HOD/Abel Chevrolet Hooked On Corvettes track day coming up I thought it would be fun to start a thread about Thunderhill with some videos and advice for corvette drivers getting around this track quickly and safely. I think I will bring my race car up for the day since it's something different than a street car and might be fun to see in the paddock and on track.

Thunderhill was the track where I learned how to drive. I really like that track although I almost never race there. Only did 1 or 2 events there last year and none this year. It has a nice flow to it and is the ideal track for corvettes.

Here's some simple advice to get started and is aimed mostly at beginner or intermediate drivers, although it could apply to anyone. I've been thinking about how it would be possible to drive at 8/10ths effort and still be one of the fastest cars on the track in hpde while being easy on your brakes. This is how I would do that in a corvette:

1. Brake relatively early, but with a smooth and light pedal engagement. Don't brake hard. Think of braking as simply a means to controlling your entry to the upcoming corner. The smoother the better.

2. Get eyes up ahead at the apex and smoothly release the pedal early and while still carrying a lot of momentum. The goal will be to smoothly scrub speed and carry maximum momentum into the corner in a controlled manner. Feel the weight transfer smoothly with brake pedal application and release. As you release the brake pedal, simultaneously turn into the corner. Don't suddenly release the brake. Squeeze it off slowly. You will continue to scrub speed as you approach the corner so don't over-brake.

With this technique if you are following a late braker you should seem them pull away slightly entering the brake zone as you hit the brakes first. But since you are braking lightly, as soon as they hammer the brakes you will see your distance close. As the late braker struggles to control their car and enter the corner, you are already releasing the brake and smoothly turning in getting ready to get back on throttle. The late braker will have upset the balance of his car more and will likely have understeer entering the corner, often times missing the apex. In addition, they will most likely over-slow the car and you will carry more speed through the corner.

4. After the initial turn in, get your eyes up ahead on the exit point. This will naturally tell you how much speed you can carry and when you can apply throttle. Since you entered the corner under control and maintaining good balance, you will be able to get on the throttle sooner and harder than the late braker. Aim to be full throttle at the apex. This will be a more advanced approach, so beginners will likely wait to go full throttle until after the apex, but still as early as possible. The key to going full throttle at the apex is to set the car up with enough yaw angle early. You want the nose of the car pointing inward so all 4 wheels are actively involved in getting the car though the corner. This takes practice and will likely be a "ah ha" moment once you figure it out and get it right. The other key to going full throttle early is preparing your hands to counter steer. As long as you can mostly straighten the steering wheel, you can go full throttle. You can still be cornering while this happens, limited slip diffs work wonders. Smooth hands and be quick to counter steer if you sense any oversteer starting.

The result of braking early, but lightly is you will probably turn faster laps, while being in better control of the car and not overheat your brakes. The key to making brakes last is keeping them cool. Late braking is fine for racers or time trialers, but isn't really necessary for hpde even when turning very fast laps. Remember, you are braking slightly early, but applying less brake pressure so you still have good entry speed. It will just be under more control allowing you to focus on carrying more momentum into the corner, getting the yaw angle set right, and then getting back to full throttle sooner than the late braker.

I guarantee if you do this and you are currently cooking your brakes and feeling like you are over-driving your car working hard to get faster, your car will be happy, your brakes will be happy, and you will wonder how you are turning faster laps with less effort. Hope this helps!

If anyone else has any videos, advice, questions, concerns, car setup questions, etc. please post them up! Looking forward to seeing a bunch of corvettes at Thunderhill next month!

DUMAN

Looking forward to this and thank you for the great advice!

RichieRichZ06

Excellent write up Bill. There will be a lot of us at the track to answer questions, give ride-a-longs or introduce people to experienced track guys.

Hooked On Driving is excellent at making people comfortable on track and more importantly, around other vehicles at high speeds. Their instructors are great and the focus they give to each and every newbie is better than the other local driving groups.

Hopefully Mike will come in a and post a few videos. He always has his camera on when we're up there.

Additionally, I would recommend anybody new to the track to get on Youtube and just search for Thunderhill videos. It will give you an idea of the track layout and make for one less thing to try and remember that morning.

FredSM

Golden advice, Bill. After years of saying it to others, it hit me really hard last year when the west side opened just how important it is to keep your head up. If you look at the road immediately in front of you the west side is indeed a very twisty track. So for those of you who'll be there Friday as well, lift your head and you'll see that there is a straight line through every one of those chicanes.

A corollary to that is not to fixate on your corner entry mark. Make note of it because it helps you judge your brake zone, but lift your head early. See through the apex to the corner exit and imagine the line and the angle the car needs in order to hit those marks and like magic you'll turn in at the proper spot.

If you're missing your marks . . . SLOW DOWN until you can consistently put the car exactly where it should be lap after lap. I know that putting the hammer down feels good, but if you're not executing well, you won't be as fast (or as safe) as you could be.

For the more advanced folks (beginners, avert your eyes!), where is the end of your brake zone? At the point where the car needs to be at its lowest speed, right? And where is that? Where the car needs the most grip to rotate, right? And where is that? At the tightest radius in the corner, right? And is that always on entry? Well, at THill with sooooo many late apexes, the tightest radius is most frequently early in the corner and there isn't an enormous amount of trailing brake ... at least not for me. But, consider this . . . the HOD school line in T2, which if we were racing I'd call the qualifying line, calls for a single late apex. A more defensive racing line is the diamond or double apex. It is a very early, very shallow, and very fast entry. But you have to scrub speed in order to put in a second rotation between the two apexes. So where is the end of the brake zone on a line like that? You got it . . . BETWEEN the two apexes since that is the tightest radius. You dive into the corner early and hot and scrub speed all the way to that second rotation between the apexes! Cool, eh? Now think about those decreasing radius turns on the west side ... where is the end of your brake zone?

And finally, the most important advice I can give . . . don't do a late pass on a Miata unless you want to take one home in your boot! In fact, don't pass a Miata at all!

Robert R1

Long corners at Thill in a corvette (esp stock suspension) will require a focus on weight management. Let the car load and unload naturally and don't try to force it. I've seen corvettes snapping/moving around excessively due to aggressive inputs by the driver not letting the weight settle. Most of my corrections are mainly due to not managing this properly.

Bill's advice about smoothly coming off the brakes is a perfect example of letting the car naturally sit into the suspension which allows more speed to be carried thus faster times.

Also, stop obsessing over T8. It's just one turn on the track. More people lose more time coasting through 7 because they're obsessed with 8 coming up. In all, there are 15 turns on the track and each one is important.

RichieRichZ06

T8 does seem to intimidate everybody, but once you learn top trust the car and use every inch of track, it can be really fun. A Corvette on sticky tires can easily go through T8 at over 100 MPH. Even our heavy pig of a C7Z was entering at 105 and exiting at 110-112

redtopz

Great info guys! Yeah, I always hear people say the key to T-hill is Turn 1 and Turn 8. Not true at all. Those are the fastest turns and the ones that can get your car and yourself in the most trouble, so you can be cautious there and not lose much time. I would suggest building up to those turns by braking early and light, getting off the brake early, and getting on the throttle early. That will be safer and nearly as fast.

Here is throwback vid from my HPDE days in 2010 in my C5Z. I think I had just started doing time trials with nasa a few months earlier. Looking at this vid now I can see I'm going about 8/10ths and braking early, but I was carrying pretty good momentum through most of the turns. Notice I had zero drama in Turn 8. This would be a safe way to drive a street car at T-hill.

I can also tell you that a corvette handles better with a few simple mods. Poly bushings and T1 sway bars will work wonders at helping control the car. Slightly stiffer springs especially in front are also nice in controlling front squat in braking zones.

Robert R1

That's a flying time back in 2010 Bill. Do you recall what mods you had on the car at the time?

Best I've managed on bypass is 1:53.9 with poly bushings and moderately used Cup 2's. I'm finally getting a front splitter with undertray on the car to hopefully match the full length spoiler that came on the car in hope to balance out the aero and help the high speed ABS engagement and general understeer. Might not make me any faster but atleast I'll feel more comfortable with the car.

Speaking of T1, can you talk me through how you take it? I tend to over brake and coast into it (mainly due to fear!) and it's costing me a fair amount of time. My exit is ok but entrance is a bit lazy if that makes sense. Are you clipping the inside curb to add further rotation so you can get on the gas earlier?

Here's a clip on a normal T1 line for me:

Start of the video and around the 2:00 min mark for the 2nd lap.

redtopz

Hi Robert, Turn 1 is one of the most challenging turns on the track because it's fast and it has a blind exit. The entry is slightly uphill. At your level of driving (which is very advanced), you should work on releasing the brake pedal sooner and allow the car to scrub speed as you turn in. You are slowing to roughly 90 and then turning. You should work on releasing the brake pedal while still over 100 and turn in using maintenance throttle. The car will scrub speed as you turn and go up the hill, then you can get to full throttle again as soon as you can see the exit. I sometimes hit the berm but it's more to widen the track than anything else. Those left side wheels are pretty light at that point and it doesn't seem to upset my car. I would recommend just touching that berm with your left tires as a goal.

I think in 2010 my C5Z had LG coilovers, T1 bars and hoosier scrubs. Also poly bushings and headers. I think it also had wilwood front brake calipers.

Robert R1

Thanks as always, Bill. I'll work on that next time out. I might even turn on the HUD so I can watch my speeds and make sure I'm doing it right. THat's a killer time with those mods and no aero.

As I'm sure you noticed in my videos, I tend to still brake in a straight line for the most part and then turn in with maint. throttle. One thing I'm going to start working on is picking a couple of turns and start trail braking. I think 14 with the run off and maybe T2 at Thill will be good for that. I'm hopeful that I pick it up quickly and can start applying it properly throughout my driving.

The next piece I want to work on in re-training muscle memory to heel toe towards end of the braking zone vs asap which when not done right, creates some issues.

Figured with no one else asking, I might as well take up the offer!

In terms of pure driving and nothing to do with car setups, what skillet(s) did you find most challenging to learn and incorporate?

DUMAN

I can not get the heel toe down. any tips?

RichieRichZ06

Practice, practice and more practice. It's hard to try and teach somebody without being in the car with them and demonstrating it, but once you get the hang of it you will be able to duplicate it easily. I remember going out in the country in my Camaro after my first track day and practicing it hundreds of times.

redtopz

You can tell a lot about your driving from the G-circle on your video. You are transitioning from braking to cornering very well but there's always room for improvement . Like you said, trailbraking in some corners can help accomplish that. The instructors at HOD will probably discuss the tire friction circle and that's what we are talking about. You want to keep the tires working to their limit at all times possible. In straight line braking you should be at the very limit of the tires, any more pressure and abs kicks in. However, then you have to turn into the corner. You don't want to release the brakes completely, unload the front tires, and then turn in. The key is to make this transition smooth and seamless to the tires. That is the art of racing at the limit that is so challenging. The same thing goes for transitioning from mid-corner peak grip to corner exit. At what point can or should you get back on the throttle? Basically as soon as your tires can handle the forward acceleration.

That leads into your second question about what I think are the most challenging skills to incorporate into driving at the limit. It's footwork. Keeping the car smooth with the hands and finding the correct line is pretty simple. Keeping the car at the limit and balanced from max braking to max cornering to max acceleration takes very skilled footwork. As someone who started this very late (40 years old), this was a huge challenge for me. Street car driving was fully engrained in my brain. Forcing my foot to lift off the brake and get on the gas while sliding into a corner at 100 mph is not a natural thing to do! Similarly, forcing yourself to push all the way down on the throttle while still cornering at 60 mph with 45 degree steering input is also not natural. But they are possible and necessary to turn your fastest laps.

I would say those are the most difficult things to learn. Learning to smoothly transition into corners without overbraking and getting back to full throttle without the fear of uncontrollable oversteer. This is where a good coach saves tons of time. I will never be as good as I'd like and that's what makes this fun. The day I stop improving will be the day I lose interest.

Yes, heel/toe is essential for smooth corner entry. Like Rich said, this is a difficult technique to master and will take a lot of practice. First of all, find a technique that works for you. I like to turn my right knee inward with my foot at a roughly 45 degree angle (toes pointed at 10 o-clock) and use the ball of my foot on the brake. Then with my heel planted as a pivot point on the floor I roll my leg to the right which pushes the right side of my foot on the throttle. I do this all the time on the street and all the time on the track. Really focus on maintaining constant pressure on the brake pedal while blipping the throttle.

This is a video of a miata racer who is very fast and has excellent foot coordination. He uses a more traditional approach to heel/toe different from my technique but it works well for him.

Robert R1

I hope more people pay attention to these points.

For the first point, my personal example of this is T9 at Thill in which you can come into the corner fast, get oversteer but catch the car with the throttle. For me, it's the only way to catch the car outside of running wide. Catching the car with the throttle is an absolute must skill to learn and very difficult as it forces you to go against your survival instincts. Back to the example: once I've caught the car with the throttle a positive side effect leads to the car's weight being ideally distirubted which in turn means I'm more stable to go WOT over the crest and down the hill where most people are tip toe'ing over the crest with an unweighted car. It's not that I'm any brave than the next driver, it's just that my car is more ready to put down the power than the other driver.

The 2nd point described here is the one we all do all too often. It's the feeling you have at the exit of a corner where you think "why didn't I get on the gas sooner." It's easily my biggest area of improvement. For me, the problem here isn't exit oversteer, it's mid corner snap oversteer which is much more difficult to recover from. I'm sure it'll become more comfortable with experience.

Lastly, you can ignore all this, buy a C7Z, keep the nannies and "GO FLAT OUT IN THIS M'FER!!!" as our great hero put it.

Delta Jim

Thanks for the tips and vids, guys. I'm not able to attend the HOD Corvette event this year but will add this info to my NCRC THill day on Oct 9th.

Rich hooked my GS up with new Michelin PSS a few weeks ago and based on the limited seat time I am expecting improved lap times on that upgrade alone. Still a long ways off from the lap times you all are running but am definitely getting smoother and faster at each event.

I also cannot heel toe but am practicing in the garage (car off) and normal driving where no cars are ahead. I find acheiving consistent/smooth braking modulation during throttle blip is the hardest part. Should the outside of my right foot be making throttle pedal contact or more toward the mid sole/heel area?

RichieRichZ06

If you guys/gals want another perspective of a fast lap at Thunderhill, below is a video of Addison Lee driving a customer's 2011 Carbon Z06 that we just wrapped up. The car features all LG suspension (mono *****, coil overs, sways, bump steer kits and camber kit) along with their GT2 front splitter and GT2 rear wing. We slapped my Finspeed wheels on with R7's and took a few hot laps.

Needless to say this combo is potent and has a huge amount of mechanical grip. 3:01 on the 5 mile course with west side bypass in a stock powered car is a fantastic time, just look at the corner speeds.

Delta Jim

Thanks Rich. Had not seen the west bypass on video... I like it.

I noticed you fast folk driving straight through rumble strip on Turn 12. Is there a bonafide course demarc on that turn or is all pavement fair game? During a NCRC day last year, they had encouraged us to use the rumble as a course demarc.

DUMAN

wow

RichieRichZ06

All paved surfaces are fair game and you paid for the whole track, so might as well use it. If you use that area at exit of T12, it gives you a better line (less turning) into T13 and more of a run down the straight.

The west bypass is fun and takes about 15 seconds out of the backside.

carefulnow

That's incredible... I feel like I'm going through 1 and 8 a solid 10 mph slower ... do you absolutely have to have splitter/wing to do this?