The Way of the FiST – Part 4: Wheels, Tires, and Weight Savings

Our 2019 Ford Fiesta ST project car has been drag tested and autocross tested in bone-stock form. And when I say bone-stock, I mean absolutely bone-stock. The only modification added to the car thus far was a cell phone charger plugged into a 12-volt port. For the fourth installment of “The Way of the FiST,” we are going to start to dig down into the SCCA National Solo Rulebook and start making some modifications to go out and play in the H-Street class. And, if things go according to plan, we might win some races.

Here we have our 2019 Ford Fiesta ST in factory showroom stock form. Before we made any modifications to the car, we wanted to get a baseline weight.

When we purchased this car new from Ford, we chose a zero option Fiesta ST because we wanted the lightest possible version of the car. Since we knew the end goal was to attend the 2020 Tire Rack SCCA National Solo Championships in Lincoln, Nebraska, we wanted the car to have the best power-to-weight ratio possible. When the first model year Fiesta ST rolled out of the factory back in 2014, the specs on the car listed the curb weight at 2,720 pounds. It was time for us to find out if the 2019 version got porkier, as oftentimes occurs as cars move through manufacture years. Later year cars tend to get heavier due to add-ons and updates.

Get On the Scales

To get the baseline weight of the car and the corner weights, we used Proform wireless scales (which come from Proform in this super handy case).

At the Double Nickel Nine Motorsports shop, we used our wireless Proform racing scales to determine the weight of our project car. Before we put the Fiesta on the scales, we filled it absolutely full of gas. Gas does make a legitimate difference in weight. With a 12.4-gallon capacity fuel tank (with 87 octane weighing in at 6.216 pounds per gallon) that is 77 total pounds of fuel. We zeroed out the scales, rolled the Fiesta on the four platforms (one for each wheel) and saw good news. Our 2019 Fiesta came in at just 2,699 pounds, 21 pounds lighter than published weights from 2014. Awesome! We bought the right Fiesta ST.

With a full tank of gas, the Fiesta weighed in at 2,699 pounds. Like most front-wheel-drive platforms, the car had a front heavy weight distribution (with 60.4% of the weight on the nose).

With the car on the scales, we could see that 1,628 pounds of the 2,699 pounds of weight was on the front tires. That can be a good thing for acceleration (with a lot of weight on the drive tires) and it can be a bad thing during hard cornering (when the tire is saturated with weight and at the edge of the friction circle, trying to turn and accelerate out of a corner). To see what the car’s corner weights would look like with my butt behind the wheel, I jumped in and rechecked the scale data.

With my fat ass in the driver seat, the vehicle’s weight was up to 2,910 pounds. What was interesting was the amount of weight the left front tire was having to hold: 897 pounds.

One of the features I love about the battery-operated Proform wireless scales is that I can walk around the car, make adjustments, and see the readout without dragging wires from four different scales all over the shop. I can even sit in the car and see the scale numbers while holding the readout (just like the photo above).

The bad news about the listed corner weight is that the left front tire is doing a lot of the work (which makes sense with the driver in the left front seat). This will be something to remember when going through slaloms at autocrosses. The car may make better left turns than it does right turns due to the 897 pounds on that left front tire. Solution: get my lazy butt to the gym and lose some weight of my own!

SCCA rules in the Street classes allow for the removal of the spare tire and tools. We weighed our Fiesta spare tire and tools and they equaled 42 pounds of weight savings.

The rules for allowed modifications in SCCA’s Street Class are pretty tight. The idea of adding coilover shocks and corner weighting the car to help with getting some of the weight off the left front tire just wasn’t available to us. However, a deep dive into the rules found us a few things we could do to lighten things up. Pursuant to SCCA National Solo rules, section 13.2 F. “Spare tires, tools, and jacks may be removed.” Sweet! We can do that. We yanked out the spare, the jack and tools and put them on a scale. Result: 42 pounds of weight savings and it didn’t cost us a dime. Admittedly, that weight was pulled out of the back of the car, which was already light, but weight is weight. This is racing, so it all has to go.

New Rubber

The newly released Yokohama Advan A052s are Yokohama’s all-in effort in the war for the 200 treadwear racing classes like SCCA’s street class. We ordered a set of 215/40R17s, which are 10 millimeters wider than the OEM tires.

The biggest bang for our buck for improving the Fiesta ST and absolute hands-down, the best modification you can make to any car is upgrading the tires. Everything a car does, it transmits through its tires. Looking at the SCCA rulebook again, we delved into the type of tires we could use based on the information below:

SCCA National Solo Rule Section 13.3 Tires
1. Minimum UTQG Treadwear Grade of 200.
2. Minimum molded tread depth of 7/32” as specified by the manufacturer.
3. Listed in a current year or prior 2 years of the “Tire Guide®” and/or the “Tread Design Guide®” (www.tireguides.com).
4. US Department of Transportation (DOT) approval.

The 200 treadwear rule and DOT requirement kept us from using a true racing slick. So, the next thing to do was find the best 200 treadwear tire, and that is why we chose the new Yokohama Advan A052. These donuts were built to win races.

On the left we have the 215/40R17 Yokohama Advan A052s and on the right we have the stock OEM 205/40R17 Michelin Pilot Sports.

We went with a 215-millimeter wide tire to provide a bigger footprint for the Fiesta (10 millimeters wider than the stock 205-millimeter tires). The Yokohama Advan A052s are meaty and have an excellent tread design for dry weather racing. Instead of mounting them on our stock Ford Fiesta ST wheels, which weigh 22.5 pounds, we decided to purchase some lighter wheels to try and save more weight. And not just curb weight, but actual rotational mass. Rotational mass is anything the engine has to spin or the brakes have to stop spinning, making more work for the car. So, if we could find some lightweight wheels, we would not only make the car overall lighter, but we could make it accelerate faster and brake shorter. A win-win.

The 17×7 OZ Racing Ultraleggera wheels wrapped in Yokohama Advan A052 tires (35 pounds total) was a whopping 8 pounds lighter than the stock Fiesta ST 17×7 OEM wheel and tire combination (43 pounds total).

When ordering wheels, there is more to think about than just the diameter of the wheel and the number of studs the wheel is mounted on. One of the most important things to think about is offset. The stock Ford wheel had an offset of 47.5 millimeters. In the SCCA rule book regarding upgraded wheels, section 13.4 states: “same width as standard and as installed it does not have an offset more than ±7.00 mm (±0.275 inches) from a standard wheel for the car. The resultant change in track dimensions is allowed.

We searched for a wheel with less offset which, once installed, equals an overall wider track width for the car. The idea is that the wider the track (lateral distance between left-side and right-side wheels) the wider the car, thus a more stable vehicle in the corners. We found a wheel that would meet our criteria in the OZ Racing Ultraleggera, which had a 42-millimeter offset (5.5mm less than stock). With the left and right side wheels installed, that would provide a track width that is 11-millimeters wider than stock, and still legal per SCCA’s rules.

The other great thing about the OZ Racing Ultraleggera wheel was that it came in at a svelte 15.7 pounds each, whereas the stock Fiesta ST wheels were a hefty 22.5 pounds. Once we mounted our Yokohama Advan A052s, we put the OZ Racing/Yokohama wheel/tire combo on the scales and compared it to a stock wheel/tire weight. The OZ/Yoko combo weighed in at 35 pounds while the stock wheel/tire was 43 pounds. With eight pounds per wheel saved, multiplied by four wheels, that would be a total of 32 pounds of rotating mass lost on the car once we bolted on the wheels. And that reminds me, bolting on those wheels brings us to the type of lug nuts we used.

WE WENT NUTS ABOUT WEIGHT

Using a metric bolt gauge, I was able to determine the thread pitch for the stock Ford lug nut was 12×1.50 fine thread.

The Fiesta ST came from the factory with heavy steel lug nuts. This is great for putting 100,000 miles on a car taking trips to the store to buy diapers, but not what we needed for an autocross car that we will race and continually check the torque on the lug nuts. I used a metric bolt gauge to determine the thread pitch for the lug nuts and found that they were 12×1.50, which just so happened to be the exact same size as our Honda Challenge race cars. This was good news because I had an extra set of Skunk2 Racing forged aluminum lug nuts that we tested over many years while road racing in NASA Honda Challenge.

Using our little scale at the shop, we measured the stock steel lug nuts (four of them for one wheel) and they weighed 0.414 pounds. The Skunk2 Racing forged aluminum lug nuts weighed less than half of the weight of the stock lugs with four of the Skunk2 units at 0.201 pounds, earning a total saving at each wheel of 0.213 pounds.

The Skunk2 Racing lugs are not “import-racing style” all show and no go. They are forged aluminum, which makes them strong and super light. With the weight savings of 0.213 of a pound at each wheel from the updated lug nuts, multiplied by four wheels, that was another 0.852 pounds of rotating mass saved. We were shaving weight like crazy! The Fiesta should be the new spokesperson for Weight Watchers.

Here is the full package on the Fiesta: lightweight 17-inch OZ Racing Ultraleggera wheels, lightweight Skunk2 Racing forged aluminum lug nuts, and sticky Yokohama Advan A052 tires. Things are looking light and sticky.

From our base weight of 2,699 pounds and staying within the SCCA rulebook for modifications, we were able to save 42 pounds by removing the spare tire and tools, 32 pounds of rotating mass by installing OZ Racing wheels and Yokohama Advan A052 tires, and nearly a pound by switching to Skunk2 Racing forged aluminum lug nuts. That makes for a total weight savings of 75 pounds, bringing the Fiesta’s weight down to a respectable 2,624 pounds.

Once we had the lightweight wheels and Yokohama Advan A052 tires mounted up, it was time to thrash.

Pulling out of the shop on the Yokohama Advan A052s for the first time, our Fiesta ST, known as “The FiST,” was a completely different car. The turn-in, responsiveness, and adhesion of the tires was night and day better compared to the stock Michelin Pilot Sports (and those aren’t bad tires).

The new Yokos made the car want to be driven hard. The sticky tires, in combination with the super light wheels, made the car feel like it accelerated quicker. It was time to take it back to the autocross, where the tires could be put through their paces in a safe environment. But that is a story for another day.

Next time on “The Way of the FiST,” we take the car back to the autocross to see how fast the Yokohamas can take us, and then start thinking about our next mods for the car.

About the author

Rob Krider

Rob Krider will race absolutely anything. He is a multi-national champion racing driver and is also the author of the novel, Cadet Blues.
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