Think of it as Yoga for the brain, we are going to stretch a bit.
The Tallest Tires for Comfort
Every Crossfire owner has the same thought, usually about forty minutes into a long drive on a bad road: this car rides like the tires are made of wood. They are not made of wood. They are made of almost nothing — that is the problem. The factory fitment is a low-profile staggered set, 225/40ZR18 in front and 255/35ZR19 in back, which means the sidewall — the part of the tire that actually cushions you — is about three and a half inches tall in front and not much more in back. Great for steering response. Terrible for potholes, expansion joints, and your spine.
So the question is a fair one, and it comes up in the owner groups again and again: how tall a tire can you fit on a Crossfire coupe if what you want is comfort? Taller tire, more sidewall, softer ride. Simple idea. The limits are not simple, so let’s work through them honestly.
First, What the Car Came With
The factory sizes are already in this book, in the Alignment, Brakes, Tires & Wheels chapter, exactly as the manual prints them: front 225/40ZR18, overall diameter about 25.1 inches; rear 255/35ZR19, overall diameter about 26.0 inches. One size pair for the whole line. The manual does not list one size for the base and Limited cars and another for the SRT-6 — the brakes differ between those cars, the tires do not.
That matters because owners compare cars side by side and get confused by the letters. One car wears 225/40R18 and 255/35R19, another wears 225/40ZR18 and 255/35ZR19, and it looks like two different factory setups. It is not. It is the same size, wearing two different markings. The R simply means radial construction. The Z is an old high-speed rating mark — 149 mph and up — that used to be built into the size itself; on modern tires the speed rating usually rides at the end of the full designation instead, as a letter like W or Y after the load index. So a tire marked 225/40R18 92Y and a tire marked 225/40ZR18 can be the same size and the same speed capability, described two different ways by two different makers in two different decades. Same dimensions, fully interchangeable as sizes. Do not let the letters talk you into thinking one car came with something the other did not.
Why Taller Helps, and Where It Stops Helping
Sidewall is suspension you can buy. A taller tire flexes more, takes the sharp edge off broken pavement, and is kinder to the wheels themselves — a low-profile tire on a twenty-year-old rim and a deep pothole is how rims get bent. The bill for that comfort arrives in four places. Clearance: a taller, wider tire can rub the fender liner or suspension at full lock or full bump. Speedometer: the car counts wheel revolutions, so a taller tire makes the car travel farther per revolution than the speedometer thinks — it reads low. Electronics: the ABS, traction systems, and the tire-pressure monitoring thresholds were all established around the original tire size. And handling: more sidewall flex means a little less of that sharp Crossfire steering feel. None of that forbids going taller. All of it says go taller in small steps.
The usual working limit owners use is about a 3 percent increase in overall diameter. That is not a law of physics, it is the line past which the speedometer error, the gearing change, and the clearance questions stop being rounding errors and start being real.
The Sensible Comfort Step
One profile step up, same widths, same wheels:
Front: 225/45R18 — about 25.97 inches overall, +3.5 percent over stock. Rear: 255/40R19 — about 27.03 inches overall, +3.9 percent over stock.
That buys you roughly half an inch more sidewall at each end and raises the car about half an inch. Owners feel this one — it is the difference between flinching at every bridge seam and not. It sits just over the 3 percent guideline rather than under it, so be honest about what comes with it: at an indicated 60 mph on the taller rears you are actually doing about 62 to 63. Clearance on a stock-height coupe in good shape is normally workable at these sizes, but “normally” is doing some lifting in that sentence — a car with sagging or lowered suspension is a different car, and the check is yours to make, at full lock, before you commit.
The Upper End — Handle With Care
You will see bigger combinations quoted: 235/45R18 in front (about 26.33 inches, +4.9 percent) and 265/40R19 in back (about 27.35 inches, +5.1 percent). Those numbers are arithmetic, not a promise. At five percent over stock you are well past the guideline, the speedometer is reading a full 5 percent low, and clearance at the front on full lock and at the rear over bumps is genuinely in question from car to car. Some owners may run them. This book is not going to tell you yours will clear, because nobody who has not put a hand inside your wheel wells can know that. If you go there, you are in test-fit territory: one axle at a time, full lock both ways, and a careful first drive over the worst road you know.
The Tire Matters as Much as the Size
Here is the part people skip: a touring tire in the stock size will ride softer than a max-performance tire in the taller size. The stiff, sticky, ultra-high-performance compounds the SRT crowd loves are built for response, not mercy. If comfort is truly the goal, the recipe is both halves — the one-step-taller sizes above, in a grand-touring tire rather than an ultra-high-performance one. Keep the same make and model front and rear; mixing families changes the balance of the car in ways that are hard to predict and easy to regret. And whatever you fit, keep the pressures at the door-label values as your starting point and the lug bolts at the factory 110 N·m (81 ft. lbs.).
The Bottom Line
Stock is 225/40ZR18 and 255/35ZR19, for every Crossfire, whatever letters your current tires happen to wear. For comfort, go one step taller — 225/45R18 and 255/40R19 — in a touring tire, accept a speedometer that reads about 4 percent low, and check your clearances like an adult. Anything taller than that is an experiment, and experiments on a twenty-year-old car should be run one careful step at a time.
