Tires, it’s said, are the most important parts of our vehicles. After all, they’re the only part that touches the road. It makes sense!i
But tires remain a nebulous thing. There are so many manufacturers, each with scores of different models, all of which perform just a little bit differently from each other, and all of which are continually refined from year-to-year. Keeping up with tire tech alone is a full-time job!
Some tires are optimised to particular cars but most are designed to fit a range of vehicles in a given category. In the world of performance driving, there are broadly speaking three types of tiresii – performance streets, R-compounds, and slicks.
“Performance streets” include the Michelin Pilot Sport 4S that I tracked this season in the GT-R.iii These tires are the best of the lot in terms of wet weather performance, so you needn’t worry about even a slightly heavier rainfall on your drive to and from the track, and they’re also the most durable in terms of treadwear.iv Unfortunately they’re not necessarily the most durable when it comes to high-temperature track runs as they also have relatively weak sidewalls and are prone to “rolling over” on their shoulders under heavy cornering with heavy cars on tight tracks when there’s insufficient negative camber dialed into the suspension, as I discovered first-hand recently.v But this is all part of the learning experience!
“R-compounds” include Michelin Pilot Sport Cup, Toyo Proxes R888R, and Nitto NT01, the latter two(!)vi of which are on the Elise at the moment.vii These tires are the most track-focused, highway-approved tires available. They have less-than-ideal-but-non-zero wet weather performance, though they really excel in the dry. Their treadwear ratings are lower but their sidewalls are stiffer and their tire compounds are “stickier” so you get markedly better lap times with these compared to performance streets, though slicks will still beat these handily around a circuit.
“Slicks” include Hoosiers, a brand practically synonymous with the segment, and are the “fastest” tire available. These are technically street legal tires but they shouldn’t be used on highways because they have approximately zero wet weather grip – they really don’t have any tread to speak of and therefore nothing to siphon water out and away from the tire with – and they degrade quickly at highway speeds. On the plus side, this lack of tread also means a maximisation of “contact patch,” or surface area of rubber in contact with the pavement at any given time. More contact = more speed, which brings us neatly to our first “driver aid” review on these pages.
Let’s review the results of my first track day with the handy dandy device known as APEX Pro, which markets itself as a “digital driving coach with real-time feedback” and which uses a very simple and easy-to-understand bar of twelve lights to tell the driver how close to “optimal” his driving is at-a-glance.viii These results were obtained in my Lotus Elise on R-Compound tires with brand new rears and mostly-worn-but-still-useable fronts on a drying track with air temperature of 13ºC. Note the percentages in the lower-righthand corners.
What we can see from these results behind the wheel of the Lotus is that, with scores of 76-77%, I’m squarely in the “B” grade range in only my third season of tracking. Not terrible! Especially keeping in mind two important differences between these times and previous times : 1) These laps were driven CW instead of the usual CCW,ix and 2) these laps were driven exclusively in third gear – no shifting!x The reasons for the latter certainly hinged on the former, and the former hinged on the fact that my right-front R888R tire was more worn than my left-front on account of all the CCW sessions, and I wanted to get as many laps out of the fronts as possible.xi Driven CW, the car only bogs down a bit in the northwest corner of the track but otherwise stays comfortably in the meat of the powerband. It’s a bit of a “drill” to stay in 3rd the whole way ’round but surely not significantly slower for it. For comparison, my best times CCW with shifting are a little more than a second faster.
Looking further at the APEX Pro readouts, what we can also tell quite clearly from the “rainbow” overlays is that I’m nowhere near maximising the tire’s potential grip in the straights, but as Ian Korf astutely points out, this has more to do with APEX Pro being broken than the car or the driver. Seriously, with the throttle pinned to the mat, what’s a guy supposed to “optimise” ? Even a little 2`000 lbs car with 300 hp can only generate so much mid-gear “shove.”
Since I’m still, at best, at the “intermediate” level of driving skill, although APEX Pro isn’t perfect, there’s no improving art without engaging science. At the very least, I need to give the device a go in the GT-R and in the more familiar CCW track direction. Besides, it’s kinda fun to get a percentage grade and this is currently the only “data” that I’m using other than TrackAddict, which is its own ball of inconsistent yarn.
While there are a nearly infinite number of variables when driving, ranging from ambient humidity to the driver’s blood glucose levels, tire selection and grip maximisation are absolutely fundamental to driving faster.xii So here’s to next year in the 80s!
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- In the same way, the golf ball is the most important piece of equipment for golfers because it’s the only piece that’s consistent between every shot. When I was winning club championships a decade ago, I always intuitively understood this. Unlike many a “club ho,” I never changed my clubs that much but I was always at the cutting edge of ball tech. Heh “ball tech.” Not Viagra! But I was definitely the first to play the Callaway HX Tour and the Taylormade Penta back in the day, several years before anyone else caught on. ↩
- Or “tyres” if you’re British and drive on the wrong side of the road from the wrong side of the car. ↩
- Other performance streets include the Pirelli P Zero and Continental ExtremeContact Sport. Feel free to chime in below in the comments if you’ve used either and prefer them to the PS4S. ↩
- Treadwear ratings for the Performance streets category are in the 200-300 range. For comparison, your standard all-season tire is 500-600, and a doubling (halving) of the rating roughly corresponds to a doubling (halving) of durability in terms of miles/laps. ↩
- I’m planning to rectify the inadequacies of the stock GT-R suspension’s range of camber with a few new parts for spring 2020. The front upper control arms absolutely need replacing ; -1.5 degrees up front just isn’t enough for a handling-centric track like SCR. I’m currently eyeing Top Secret’s products, which are designed to use adjustment shims instead of screws (à la SPL, etc.) for greater “lock-in” of a suspension set-up, and also have mid-arm adjustments so that my mechanic doesn’t have to spend three hours removing and replacing underbody panels every time I want to make an alignment tweak (the stock control arm adjustments hide at the inboard ends of the control arms). While I’m doing the front, I might as well do the rear toe, camber, and tension arms, right ? ↩
- The little Elise has a staggered wheel set-up with 16″ up front and 17″ in the rear. This late in the Canadian track driving season, that means that the R888Rs I had at all four corners previously are no longer for sale anywhere in the country. They’re sold out for 2019 and will be restocked for 2020. That leaves the Nitto NT01, of which there were four 17″ tires left in the country last week when I replaced the roasted rears, but none in 16″ because Nitto flat-out doesn’t make that size. ↩
- Treadwear ratings for the R-compunds category are in the 60-180 range. ↩
- For those interested in tech specs, the Apex Pro has :
– High-brightness RGB LED display (400 mcd)
– N42 magnetic alignment/mounting clip
– ARM Cortex Microprocessor
– 9-axis Inertial Measurement Unit
– 12-bit precision accelerometer (+/- 4 G)
– 16-bit precision gyroscope (+/- 250 deg/s)
– Self-calibrating FIR and IIR filtering on all sensors
– 10 Hz, satellite augmented GPS+GLONASS receiver
– Temperature-compensated gyroscope and GPS clock ↩
- I have 10x more experience in the CCW direction than the CW direction. ↩
- Apparently, according to Ian Korf, staying in 3rd for an entire lap is a “drill” of sorts. The things I stumble upon accidentally, yet fruitfully, beggar belief! ↩
- After two more sessions, “Dreidel” was earning her nickname again, and indeed the fronts are now due to be replaced, but this too will have to wait until spring 2020. ↩
- Maximising grip is also why I’m upgrading the GT-R’s stock brake pads to Endless CC-Rg pads this week, because it’s hard for the tires to grip when the brakes are cooked! Just in time for one more session this season ? Here’s hoping for a mild Alberta fall! ↩