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How do you identify the perfect wheel-and-tire setup to your automotive? Typically it’s essential to do some testing.
As we prepped for this yr’s One Lap of America, we wanted to make one key choice as early as doable: What tires ought to we run on our Honda CRX?
[One Lap of America: How competitive can a daily driver actually be?]
First, the foundations: The Tire Rack One Lap of America offered by Grassroots Motorsports requires a 200tw tire or higher that should be bought via Tire Rack to keep away from one-off ringers. Additional, there’s an inventory of eligible tires. And eventually, groups solely get one set of tires, and it’s gotta final the entire week. That’s 3500 freeway miles plus about 40 laps of observe use. Substitute is barely allowed for verifiable street hazard harm–which doesn’t embrace camber put on or overzealous driving.
Now add sizing to the equation. Regardless of its flared fenders that permit as much as a 275mm width, our Honda’s old-school inside wheel nicely dimensions restrict it to a couple of 23-inch-tall tire–which generally means a 15-inch wheel. As OE fitments have tended towards ever bigger diameters, nonetheless, the provision of appropriate tires assembly that exterior diameter has grow to be severely restricted.
Most rivals select a tire from Tire Rack’s Max Efficiency Summer season class, which supplies a very good stability of each dry and moist efficiency. The latter is necessary as a result of the occasion all the time features a moist skidpad competitors, and spring climate sometimes provides up rain different occasions in the course of the week. The Continental ExtremeContact Sport 02 and Michelin Pilot Sport 4S are standard selections, however neither is available in a CRX-friendly, 23-inch-tall tire.
In order that leaves Excessive Efficiency Summer season tires–aka Tremendous 200s. Inside that class, the one ones which have acceptable moist efficiency, at the least at full tread, are the Bridgestone Potenza RE–71RS and the Yokohama Advan A052. We efficiently ran the Bridgestones final yr on our GTI, and the model does provide a few appropriate sizes for the CRX, together with a 225/50R15.
However one thing else caught our eye this time: Yokohama provides its Advan A052 in a novel dimension. It’s marked as a 215/40R17 that’s 23.7 inches tall, but regardless of what it says on the sidewall, it’s even wider than the 225/50R15 Bridgestone.
One other risk from Yokohama: the identical mannequin in a shorter 205/40R17. Plus, the road additionally features a 205/50R15 and a 225/50R15, that are basically the same-diameter donuts because the 17s however with a smaller gap.
We have already got some 17×9-inch wheels for this automotive, however which setup will present the most effective mixture? Will the shorter gearing and decrease cg of the smaller-diameter tires ship a bonus? Will the broader tires outperform the narrower ones through higher cornering potential? Will the brief sidewalls of the 17s really feel extra responsive? Just one solution to discover out for positive: a take a look at.
After we final in contrast 15s and 17s, we ran the most recent Nankang CR-S on our Triple Threat ND Miata. In that take a look at, the shorter 15s had been considerably slower than the 17s, with more often than not differential being in nook exit energy up.
We additionally discovered that we might pinch a 245mm Nankang onto a 9-inch wheel. Actually, it outran a 235mm tire that was a theoretical higher match.
Miata Tire Take a look at Occasions
However each tire is totally different, and the A052 is often not joyful being pinched. After all, with the out there A052 tire sizes for our CRX, pinching was not going to be an element. Actually, the 205s had been pretty stretched on 9-inch-wide wheels, with the 215s and 225s being a standard straight-up match.
CRX Tire and Wheel Specs
Now to see which tires our CRX most popular. One logistical shortcut we took was to vary solely the entrance tires for every spherical of testing–the rears had been saved fixed at 205/50R15.
With our nose-heavy, front-drive utility, the fronts do many of the work anyway, so this shortcut has served us nicely prior to now. It did make for some moderately odd-looking combos, although.
From left to proper: 205/40R17, 215/40R17, 225/50R15, 205/50R15
As we all the time do, we heat-cycled our tires prior to check day. On this occasion, your complete operation was accomplished on the observe. We constructed warmth into them by doing a little skidpad circles in an empty paddock space earlier than working six laps on every set of tires. Tires had been then eliminated and allowed to chill for twenty-four hours, higher curing the rubber for optimum efficiency.
Not all exams go as deliberate. We sometimes do our work on weekday mornings when the observe is generally empty. This minimizes observe evolution past an preliminary dust-off, and in addition permits for uninterrupted lapping for evaluating heat-sensitive tires. However this weekday was totally different, as a slew of vehicles started to fill the paddock not lengthy after the observe opened. Nonetheless, we had been hopeful we might discover gaps within the circulation to make it work.
- dimension: 205/50R15
- finest lap: 1:24.3
After 20 minutes of lapping on some outdated scrubs to scrub the road and get our shifting and braking factors dialed in, we mounted up the 205/50R15s to set our baselines. With the A052 at full tread, the primary lap is often the quickest. Warmth soak units in quickly after, dropping the efficiency potential.
- dimension: 205/40R17
- finest lap: 1:23.9
Our subsequent dimension was just a little wider but additionally had a lot shorter sidewalls. In comparison with the 15s, these had been undoubtedly faster to reply to driver inputs, counteracting a few of the A052’s typical vagueness. The automotive additionally had much less torque steer and felt steadier over bumps, because the 17-inch wheels had 8mm much less offset. This reduces the scrub radius and is feasible as a result of the entrance suspension upright is curved, permitting for extra clearance the farther from the middle you go. In brief, the automotive felt extra pure and the occasions mirrored that.
- dimension: 215/40R17
- finest lap: 1:23.4
Add just a little extra tread width to all that 17-inch goodness and also you get the 215/40R17. Grip was up, and lap occasions dropped some extra.
- dimension: 225/50R15
- finest lap: 1:23.2
Our remaining comparability dimension was 225/50R15. By now, visitors was turning into a significant drawback, with gaps turning into few and much between. This session bought lower brief as a big group of vehicles entered the observe simply after our second sizzling lap.
Earlier than calling any take a look at remaining, we all the time retest the primary setup. Why? We wish to be sure observe evolution and driver enchancment haven’t contaminated the info.
So we once more mounted up our 205/50R15 baseline tires for that remaining bracket session. After which got here a dose of actuality: Site visitors wouldn’t die down sufficient for a clear session. We waited and waited–for two hours. After which, as rapidly as that they had arrived, everybody else left.
Heading again out, we had been greeted with a totally totally different observe floor. As a consequence of all the additional vehicles on observe, grip was clearly up in lots of key areas, with our lap time plummeting by a full second. This isn’t even near what we had been in search of in a affirmation bracket session.
Might our earlier information be trusted? Or was the tempo enhance development merely the observe getting quicker as we swapped to ever bigger tires? Our instinct stated we had been superb, however the science known as for a do-over.
So we did all of it once more.
Spherical 2
With restricted time readily available, we might solely do three extra classes. For the reason that 205/40R17 wasn’t as quick because the 215mm and 225mm tires, we skipped that one. Our new, quicker 205/50R15 occasions would function the baseline for this spherical, and the ultimate retest session on that tire duplicated the baseline properly. Success!
So What Did We Study?
Pictures Credit score: Anna Overman
For positive, we confirmed a lesson we’d already identified: A wider tire is all the time faster if correctly supported by a large sufficient wheel. Or, as we noticed with the Miata take a look at, had been the quicker laps from the taller diameter of our wider tires?
Given the restricted sizing availability, these two variables couldn’t be totally remoted. Both method, we now had two good selections for tire sizes for our One Lap of America journey. How will we determine between them? Yet another spherical of testing.
Having now verified match and performance, we headed again to the observe the next week with simply the 2 bigger candidates. This time, we actually centered on the subjective strengths and weaknesses of every mixture along with pure lap occasions. Right here’s that information:
Whereas the 17s once more felt a bit extra pure because of the stock-like offset of the wheel fitment, the brief sidewalls made the tires extra edgy on the restrict. Additional, the lowered quantity of rubber within the 17-inch setups contributed to earlier warmth soak. All that power generated throughout a sizzling lap has to go someplace, and the tire is that place.
In consequence, the massive 15s had been simpler to constantly drive quick. And with One Lap time trials being a three-lap affair and each circuit being scored, consistency is essential.
Again to our unique query. How do you identify the most effective wheel-and-tire setup to your automotive? Ideally with some methodical testing.
Feedback
Ultimately plainly the driving force would make a much bigger distinction than the tires?🤷♂️
Keith Tanner stated:
“Get the widest one” 🙂
I used to be shocked, however apparently there are exceptions. 🙂 IIRC 949 did some testing of low-powered Miatas at large tracks and it was doable to go too broad on on the tires/wheels and decelerate. I believe the speculation was that diminishing returns on additional grip did not make up for the rise in drag.
This topic is ideal timing for me….large decession.
First yea yea not the primary and even fifth selection for a CAM T automotive. 1964 Mercury Comet.
Ive bought an OK match with 17 x8 with 5.5″ BS 255/40 tire. My “arduous restrict” is the within 5.5BS is most.
My plan is a sq. arrange.
Each entrance and rear would require some outer fender minor work for that arrange,however with extra work(chopping) ….. nicely you already know.
From studying GRM my 255 ought to work higher on a 9.5 to 10″ wheel , now if I’ve to do the work do I cease at a 275 with an 11″ wheel or bounce to a 3xx on an 18″?
My different restrict is 26″ tall.
All limits are structural .
Objective is minimal CAMT weight.
So largest tire or am I killing myself with a 275 on a17″?
Keith Tanner stated:
“Get the widest one” 🙂
Keith whereas I respect your accomplishments and enter right here you might be so fallacious on this one.
You need skinny tires so you are able to do wonderful 4 wheel drifts in all places.
Your large mistake right here is considering quicker lap occasions are an precise purpose……..like anyway cares about that.
codrus (Discussion board Supporter) stated:
Keith Tanner stated:
“Get the widest one” 🙂
I used to be shocked, however apparently there are exceptions. 🙂 IIRC 949 did some testing of low-powered Miatas at large tracks and it was doable to go too broad on on the tires/wheels and decelerate. I believe the speculation was that diminishing returns on additional grip did not make up for the rise in drag.
I am undecided that was 949, I believe it was accomplished earlier than they actually got here on the scene. Iirc it was with Spec Miatas and 205/50 vs 225/45 – and since SM makes use of 15×7 wheels, the 225s weren’t nicely supported. Might have been drag, might have been that the fatter rubber simply wasn’t getting used nicely. I am fairly positive that the SuperMiata race collection ran 225s on 15×9 wheels, and that was earlier than 245/40s had been actually out there.
I simply discovered it humorous that Andy did all this testing and ended up with “the widest that match” 🙂
My arm-chair considering on this comes up with “the widest tire that maintains correct temperature.”
Price range performs a big half within the setup of my observe automotive so the 16 x 8 E38 Model 5 wheels that nobody actually desires work nice (I’ve 10 at a mean worth of $40 CAD/wheel) together with 225/50R16 Hankook RS4 at $180 CAD/tire that by no means appear to die means I really get to be on a race observe pushing as arduous as I would like.
Would a light-weight 17 x 9 with round a 245 new hottness tire be quicker? After all however that is nicely over $2500. That buys me two full units of RS4’s (which ought to final 4+ years) and leaves $900 for entry charges, gasoline, and so forth.
kb58 stated:
My arm-chair considering on this comes up with “the widest tire that maintains correct temperature.”
Sure, this.
Not too sizzling, not too chilly – excellent. Kinda like porridge however black and actually chewy.
adam525i stated:
Price range performs a big half within the setup of my observe automotive so the 16 x 8 E38 Model 5 wheels that nobody actually desires work nice (I’ve 10 at a mean worth of $40 CAD/wheel) together with 225/50R16 Hankook RS4 at $180 CAD/tire that by no means appear to die means I really get to be on a race observe pushing as arduous as I would like.
I am jealous of that width. My automotive wears CLK Lightweights in 16×7 so my 225/50R16 race rubber is method ballooned out. I am shifting as much as 17x8s so I can get a 235 tire that matches nicely. However such as you had been mentioning, it is a $20 distinction per tire.
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