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The Next Step Episode 18

The Next Step

 

 

Episode 18: Keeping Your Tires Happy

Dear Aaron,

I have a race question.  Do you anticipate certain times during a race when the tires you are running will start to go away? I know a lot depends on the tire, track, length of race. I ask simply because as a pretty new racer I would like to know what to look for and feel when the tires start to go. I know a slower lap will bring them back, but I'd like to be able to plan for it. It would suck to be in the lead and have to pull back to hold tires when I could have done so earlier in a race.
Tim Auger

Answer:

It’s not so much as anticipating when the tire will go away but more a matter of finding the limit, staying aware of where the limit is, and not overstepping it for too long.

 


 

The Next StepThe “limit” is a moving target.

There is a fine line between getting the most out of the available grip (i.e. filling the friction circle) and overworking the tires (i.e. overstepping the friction circle)  Overstepping the friction circle too much burns up tires, period. Being in touch with all the factors that envelope the “limit” and said boundaries of the friction circle is half the battle.

You are correct in saying it depends on the tire, track and length of race but it also depends on the car, the set up and how you are driving it. So let’s dive into each of these variables:

The Tire

Some tires can take a ton of abuse - other tires are much more delicate. For example, the Toyo RA1 that has been used in Spec Miata racing for many years is about as consistent as a tire comes. They remain uniform through many heat cycles and are thought to be at their best just before cording. Will this hold true with the new Hoosier tire that Spec Miata is adopting this year?  Good question!  Ask me mid-summer when I will have had some time on them. What I can say is that not many tires I have raced on are as consistent as an RA1. Heck when I think back to my Formula Ford 1600 days we had to be kinder to our tires over a 30-minute race – despite it being a single-seater weighing HALF of a Miata!

The Car

Another important factor concerning tire performance is the car itself - how much it weighs, how much power it has, and how well set up it is.

Let’s examine an interesting comparison from my recent Pirelli World Challenge racing experience. Take the two cars that had the closest fight all year: the Compass 360Racing Honda Civic Si Coupe vs. my K-PAX Racing Volvo C30.

Same Pirelli P Zero tires (including size), same class (Touring Car), both are front-wheel drive and both are within 20 hp and lb.-ft. torque of one other.

How do the same tires on relatively similar cars stack up after a 50-minute sprint?

Well, first let’s look a bit closer. The Civic is about 200 lbs. lighter, which is not the end of the world when talking about cars in the 3,000 lbs. range. But the Civic does gain some relevant advantages thanks to a lower centre of gravity and better overall weight distribution – the latter point is especially significant. The C30 is more top heavy, and because it’s a hatchback, its weight is less evenly distributed than the Civic’s is. The Volvo has a torquier engine but we paid for it – chiefly with a larger, heavier engine which put more weight over the front tires.  The Civic has a smaller, lighter engine and less overall mass around the front tires.

Drive both cars at 9.5/10th for 50 minutes and who do you think will have better front tires?

When you consider that front grip is everything in a front-wheel drive car, it starts to become REALLY important in the final 20 minutes of a race! I think back to the Mosport race last season when I was on pole in front of a slew of Civics by 0.05 sec, but on race pace I was 1.00 sec slower than the fastest Civic. I finished third behind two Civics simply drove away from me during the final stages of the race, and I had been looking after my tires all race long.

The point here is, when it comes to keeping your tires under you, even relatively minor things can make a big difference!

Most importantly – and getting back to your original question – how we drive the car and take care of the tires is the most relevant factor. Imagine if I had pushed 110% at Mosport in an effort to keep the Civics’ behind me, or had tried to stretch out a lead early in the race. Would we have finished third? No, not at all. Had I replicated a qualifying lap for 50 minutes, I’d have corded the poor tires by mid-race and dropped well below third!

The Driver

The biggest factor in keeping your tires at their best for the longest is how you drive them. The key is to drive real close to the limit, but not OVER that limit. Surpassing the limit too often for too long eats up the tires. Let’s segue for a moment and establish a very important thing:  The limit – what it is and where it lives.

Finding the limit

Speaking as pragmatically as possible here – the limit is the point where the tire starts to slide. It is loading the tire to the absolute max so that even a fraction more speed will cause the tire to slide. Examples: you are carrying so much speed that the front tires cannot get you to the apex and you push wide…or the rear end snaps out over…or you brake too late, too hard and lock up…or you brake too late, too hard and the ABS goes berserk and you miss your apex by a mile….or you stomp on the gas and spin tires…and on and on it goes.

This may sound really simple, but 20 years of driver coaching tells me it’s not, and the reason is what I call “white noise”. White noise is a metaphor for all the meaningless inputs you receive from the steering wheel that can trick a driver into thinking the car is sliding. I’d be a rich man if I had a dollar every time a client described to me how the car was getting loose and sliding at every turn, while going five seconds a lap slower than the time I set in the same car ten minutes earlier. With 99% accuracy I can tell you that you are not sliding, or going over the limit in ANY corner when you are three seconds or more off the pace.

I always encourage people to try to establish a base line by getting a legitimate pro driver, or the fastest darn guy you know to drive your car for a session. If you are within a 1.5 seconds of a pro driver, that’s great. If not, you don’t need worry about abusing your tires but instead need to work on carrying more speed into and through corners. Loading the tire to the fullest extent at all times is the final step between amateur and pro.

Staying in tune with the limitThe Next Step

Step 2 – the limit is a moving target that we need to keep an eye on.

How do we know when the tire is starting to go away? Well, every tire has its own sign but generally it starts to slip more, it starts to feel greasy. Some common examples: you brake at the same point but now find it harder to get to the apex.  Or you go to full power exiting a slow corner and start to notice some wheel spin or oversteer. Or even more subtle, the slight rotation you normally get going into CRN “X” turns into no rotation at all, because your fronts are going off. It is a subtle thing, as if the track just got 5% greasier for some reason. Here comes the fun bit – sometimes the track DOES just get 5% greasier and your tires have absolutely nothing to do with it!  For example, the sun comes out from behind the clouds at Mid-Ohio in July and BAM – it’s a different game! How do you tell if it’s the track or the tires? It actually really doesn’t matter because at that point you need to adapt to the situation, whether it be tires or the track because missing apexes and spinning tires are slower than not. Period.

The thing we as drivers can control is NOT OVER DRIVING. By over driving, I am referring to sliding it around a little too much – as in filling the friction circle to the max and that little bit more. It's the difference between driving 10.5 tenths and 9.5 tenths. With most tires, after 4 or 5 laps of 10.5 tenths things start to feel greasy. Drive at 12 tenths and that greasy feeling will happen even sooner. The good news is the cure is simply backing off a little, not much though. Really all you have to do is stop grinding and or sliding the tire. Do this for a few laps and things should return to normal. It’s probably no more than a 1/2 sec per lap difference at most. I’d go so far as to say one of the defining attributes of a great driver is being able to feel that exact edge and stay where he/she need to get the most from the tires all race long.

Driving style has a say in this as well. Slow smooth hands and nice sweeping arcs tend to take care of tires much longer than abrupt late turn-ins! Think Alain Prost, Jenson Button. Turning in late requires more steering in less time. It is a recipe for creating understeer and taking a chunk out of your front tires, which is a direct link to how long your tires last, not to mention it forces you to slow down more. Racers that came up through DEs need to stop looking at the cones and start looking through the corner. Meaning, TURN IN SOONER WITH SLOWER HANDS!  The late turn that is taught by so many DE instructors is a hard habit to break but it’s a tire killer, end of story.

Putting it all into practice

In general, I try to set my race pace just a sliver below the tires sliding point - or just inside the bubble of the friction circle. If you stay true to this your tires should be consistent all race long and leave you with a bit more if you need to push for any reason. If you do find yourself locked in a battle and your tires are going off, drop back a little – give the tires a rest for a few laps then push on. The nice part about being the car behind is that you can use the lead car’s draft to stay close, and nurse the tires in the corners, whereas the lead car just has to push everywhere. It is something you sometimes have to factor in as a part of your strategy – which, of course, is relative to many other things. Be kind to your tires, not too kind, but kind enough. Fill the friction circle but don’t dance outside of it for too long.

Sometimes the best advice is the simplest. Something one of my mentors said many a moons ago comes to mind. The mentor I’m referring to is the great Richard Spenard, who back in 1998 was a central figure of the Player’s Racing Program, as well as the driver coach for the handful of us that were fortunate enough to be chosen to wear the blue suits. He told me at Trois-Rivieres to “drive the car, to the track”. What he meant was: drive your car to what the track, the conditions and the set up allow. Anything more is not sustainable, anything less is slow.  

Yours in Motoring,
Aaron

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