The web is filled with motorsports keyboard warriors who will debate endlessly concerning the theoretical superiority of their favourite elements or setup. Specs and physics equations are wielded like swords on the battlefield of paper builds.
Achieved nicely, this strategy can yield some helpful data. In spite of everything, simulation works on the identical ideas and has proved its worth. However on the finish of the day, back-to-back testing is the gold normal, particularly in the case of tires.
When testing, isolating variables is vital to getting good information and deriving applicable conclusions. Nonetheless, affirmation bias can creep into the combo, as typically we get outcomes that we simply don’t fairly imagine.
What to do? Repeat the take a look at, looking for uncontrolled variables. Driver consistency, observe evolution, ambient temps, prior warmth cycles, order of working and even manufacturing batches can have an influence.
Two current GRM tire assessments left us very excited, as the mix of their outcomes produced the quickest lap occasions our Triple Threat ND2-chassis Miata had ever turned at Harris Hill Raceway. One was the introduction of the 2023 revision of the Nankang Sportnex CR-S, the brand new 200tw high canine for observe use. The opposite was a long-term case research on the consequences of heat cycling and tread depth.
Road tires sometimes get faster and extra constant as they’re used on observe, with warmth cycles curing the rubber and the decrease tread depth higher controlling squirm and warmth buildup. Much less tread additionally makes for a lighter tire and shorter gearing, each of which assist in acceleration.
As Nankang ramped up manufacturing of the brand new tire, we noticed two new sizes that would probably carry out even higher than the 245/40R17 we’d been working on our 17×9-inch Flyin’ Miata wheels. The primary was a 235/40R17, which supplies a smaller general diameter and lighter weight, much like a well-worn (or shaved) 245. Theoretically, that ought to assist it speed up faster–and the Miata wants all the assistance it could possibly get in that division.
The opposite new measurement that appeared attractive was a 245/40R15, which might ship a fair shorter, lighter tire. If some is sweet, extra is best, proper?
Nankang Sportnex CR-S
We nonetheless had a set of the 245/40R17 tires mounted up on our Flyin’ Miata Kogeki alloys from that earlier tread depth story, and so they sported minimal put on. The opposite two contemporary units have been every mounted up and given our normal warmth cycle prep: a 45-minute drive to the observe, six laps of accelerating depth, after which the drive dwelling. After cooling for twenty-four hours, our new tires have been prepared.
Summer time just isn’t our favourite season to check, as ambient temps rise rapidly within the morning, and the afternoons are just too scorching. Happily, take a look at day dawned cloudy, which helped average the temperature swing of the observe floor–although ambients have been already within the mid-80s. We did a session on the 245/40R17 tires to heat up and clear the observe floor, then took a break to permit the automotive and tires to chill.
With the lap timer now working, we went again out on those self same tires to set a baseline. Whereas feeling acquainted, they didn’t appear fairly as constant as they did throughout our winter testing–again when the temps have been 40 levels cooler. Nonetheless, all six laps have been inside six-tenths, with a better of 1:26.7.
Shifting to the 235/40R17, we discovered a noticeably extra elastic and skreechier-sounding tire. And whereas all of the laps have been inside an analogous unfold because the baseline passes, the quickest–a 1:26.9–got here earlier within the session. The tire gave the impression to be warmth soaking pretty rapidly. Including to the combo, the clouds had now disappeared, permitting the solar to rapidly heat the observe floor.
For the subsequent spherical, the 245/40R15–fitted on 15×9-inch Kogeki wheels–delivered the identical really feel and sounds because the 235s however recorded a fair slower tempo with a finest lap of 1:27.4. On the plus facet, they felt extra nimble and responsive, however they couldn’t carry out as nicely when requested to mix hundreds throughout trail-braking and nook exit power-up. The latter counteracted any gearing profit on acceleration from the shorter tire.
Whereas most 15-inch wheels won’t clear the brakes on an ND-chassis Miata–particularly with the Brembo possibility–the Kogeki line from Flyin’ Miata will.
We at all times bracket our assessments by going again to the unique tire to see if we had correctly managed variables. With temps now 10 levels hotter and the observe floor getting very popular from the solar, we anticipated slower occasions. As an alternative, the 245/40R17 tires cranked out three constant laps–all a pair tenths quicker than earlier than and with a quickest of 1:26.4. Shocked, we went to the info logger for an evidence: The enhancements got here in two areas the place each driver confidence and a cleaner observe offered a profit.
Confronted with the specter of flawed information from observe evolution and driver enchancment, we saved the take a look at rotation going by once more mounting up the 235/40R17s. In addition they picked up time over their earlier iteration with a finest lap of 1:26.6, however they remained the identical two-tenths slower than the 245s within the back-to-back periods. This confirmed our comparability of these two tires.
Lastly, we ran the 15s once more, discovering no enhancements there in any respect, with a finest lap of 1:27.5. Whereas sounding good on paper, the shorter, lighter tire was merely not the appropriate reply as soon as the rubber met the street.
Check Day 1
All the best way dwelling, one factor was bugging us: the distinct distinction in really feel and audible suggestions of the brand new tires versus the set that we carried over from earlier testing. They nearly appeared like a special tire. We even contacted Nankang to confirm that nothing had modified within the tire’s manufacturing.
our information, we discovered that whereas our 245/40R17s have been nonetheless at almost-new tread depth, that they had a number of extra warmth cycles on them. Was that the trigger? Just one method to discover out.
Over the subsequent a number of days, we made two extra journeys to the observe so as to add to the 235s’ lap depend. Halfway by way of that course of, the screechiness went away and the tire turned extra constant, just like the older 245s. Having now eliminated that variable, we went again for an additional back-to-back take a look at. We additionally switched the working order to verify it wasn’t a contributing issue.
Check Day 2
Conclusion
So what did we study? In each back-to-back comparability, the 245/40R17 ran a number of tenths faster than the 235/40R17. Drilling down into the info for extra readability, we discovered that the 245/40R17 tire carried out higher beneath trail-braking and corner-exit acceleration, that means it might merely multitask higher–with out giving up something wherever else. (Just like the 235/40R17, the 15-inch tire additionally didn’t multitask in addition to the 245/40R17.)
To a point, this consequence flies within the face of different tire- and wheel-width assessments we’ve performed. For road tires utilized in motorsports, we’ve beforehand discovered that there is no such thing as a profit to working a tire that has tread width any wider than the wheel width. With the brand new Nankang, the 235 suits the rim width higher than the 245, the previous having a slight stretch and the latter being extra sq.. But the 245 was persistently faster.
So we dug out our copy of Paul Haney’s high-performance tire e-book and located an evidence. Simply as a wider wheel-and-tire mixture shapes the contact patch to profit lateral grip, a bigger diameter shapes it to help grip within the longitudinal course. Whether or not this outweighs the advantages of shorter gearing, decrease weight and decrease cg may be very depending on tire mannequin and automobile software. On this specific case, although, it did.
Paul Haney’s e-book “The Racing & Excessive-Efficiency Tire” is a improbable useful resource for understanding the black artwork of motorsports tires. We reference it usually. Whereas lengthy out of print, you will discover used copies on-line.
For this reason we take a look at empirically quite than utilizing web knowledge or theories. The latter are good beginning factors for concepts, however finally we’re higher off with a real-life comparability. Ultimately, we didn’t discover any new velocity, however we did have enjoyable attempting–and we discovered a number of classes alongside the best way.
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