IndyCar IR-28 Explained: The New 2028 Car, in Plain English
Welcome to the Happy Hour Racing IndyCar Tech Breakdown - where we take one confusing part of IndyCar and make it make sense. No engineering degree required.
The Short Version
On July 28, IndyCar pulled the cover off the Dallara IR-28, the first all-new IndyCar chassis since the DW12 arrived in 2012. Four days later it turned its first laps, with Alexander Rossi driving it on the Indianapolis Motor Speedway road course. The headline numbers: about 100 pounds lighter, a new 2.4-liter twin-turbo V6 making up to 760 horsepower, and a hybrid battery holding roughly 14 times the energy of today's setup. It races in 2028. Here is what all of that actually does.
Why a New Car at All
IndyCar is a spec series, which means every team runs the same chassis from the same builder. That keeps costs down and puts the racing on the driver and the crew. The tradeoff is that when the car gets old, everyone's car gets old at the same time.
The DW12 has been that car since 2012. It has been improved along the way - the aeroscreen in 2020, the hybrid unit in the middle of 2024 - but every addition bolted more weight onto a tub designed in 2011. The IR-28 is a clean sheet. Dallara builds it again, Chevrolet and Honda still supply the engines, and Firestone still supplies the tires. What changes is everything underneath.
Lighter Is the Whole Point
Weight is the enemy of a race car. A lighter car turns quicker, stops shorter, uses less fuel and is easier on its tires. When IndyCar added the hybrid unit partway through 2024, the minimum weight went up by roughly 105 pounds, and drivers felt it immediately in the way the car changed direction.
The IR-28 claws that back. The whole package is about 100 pounds lighter than the current car. The savings come from a few places at once: a lighter monocoque, a new Xtrac gearbox that sheds about 25 pounds, a hybrid power unit about 20 pounds lighter than the one it replaces, and a slimmer aeroscreen built into the body instead of bolted on top of it. Pair that with more power and you get a better power-to-weight ratio, which is the number that decides how hard a car accelerates.
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The Hybrid Goes From a Sprint to a Marathon
Today's hybrid stores its electricity in supercapacitors. A supercapacitor is a bucket you can fill and dump extremely fast, but it is a small bucket. That is why the current system is good for short, sharp shots of about 60 extra horsepower rather than long pulls.
The IR-28 swaps that for a proper battery built by BOLD Technology, with the hybrid package engineered by Helix. IndyCar says it holds roughly 14 times the energy of the supercapacitor setup. Same idea, much bigger bucket. Strategists can then use electric power over a whole lap instead of one corner at a time, which opens the door to real energy management, where a driver decides when to spend and when to save.
The Aero Change That Matters Most
Here is the fan-facing one. When a race car cuts through air, it throws a messy, turbulent wake behind it. Part of that mess is outwash, air that gets shoved sideways out past the front tires. Outwash helps the car in front and hurts the car behind, because the trailing car's wings end up working in disturbed air and lose downforce. That is the "I could catch him but I could not pass him" problem.
IndyCar says the IR-28's body was purpose-built to manage that wake and cut outwash, including new bodywork behind the front tires. The goal is simple: keep more grip on the car that is following so it can stay close enough to actually try a move.
The Suspension Trick Nobody Else Allows
The IR-28 also gets a series-wide suspension package called the Custom AXIS Inertance Control Suspension System. Buried in that mouthful is a part most fans have never heard of: the inerter.
A spring resists being squashed. A damper resists being moved quickly. An inerter resists being accelerated, and it does it with a small spinning flywheel geared to the suspension. Think of stirring a thick pot of chili: slow stirs are easy, but try to change direction fast and the mass fights you. That is what an inerter does to sudden suspension movements, which helps a car settle over bumps and curbs without having to run brutally stiff springs.
IndyCar will be the only major championship allowing this kind of third-element inertance system at both the front and the rear. The practical payoff is mechanical grip - grip that comes from the suspension instead of from the wings - and mechanical grip does not disappear when you are following another car.
Safer, and Roomier
IndyCar calls the IR-28 the safest monocoque in series history. The monocoque is the carbon fiber tub the driver sits in, the survival cell. This one has stronger side-impact structures that absorb more energy, an aeroscreen and roll hoop designed into the core structure rather than added to it, and shapes tuned so the car is more likely to stay on the ground in a spin.
The cockpit is also wider, with better airflow and cooling. Fitting into a spec car has been a real problem for taller drivers, and Felix Rosenqvist said the first thing that struck him was how much more room it has. Even the anti-roll bars changed: they are now electronically adjustable from the cockpit, which removes hard knobs and levers from the space around the driver.
What the First Test Actually Told Us
On Saturday, August 1, Rossi ran the IR-28 for the first time on the 2.439-mile IMS road course. Weather cut the day to about 50 minutes and roughly 40 laps, and the car ran a lower-power 2.4-liter mule engine with no hybrid fitted, so the lap times mean very little yet. What matters is that a brand-new car ran a full session and the only thing that needed replacing was a sensor. Rossi said he had never been part of a new car launch that went as smoothly. Alex Palou took over the next day.
What You Will Actually See on Track
Not in 2026 and not in 2027. The DW12 finishes out those two seasons, so this year's championship runs on the car you already know. Starting in 2028 you should expect quicker lap times, a real run at the Indianapolis qualifying records that have stood since 1996, longer hybrid deployment instead of short bursts, and, if the aero work does its job, cars that can run nose-to-tail without the chaser falling away in the corners.
The Bottom Line
The IR-28 is not a facelift. It is 100 pounds lighter, has a bigger engine, a battery instead of a capacitor, and a body shaped around the car behind it instead of just the car in front. IndyCar had one shot to fix everything the DW12 could not, and it swung at all of it.
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