When Riverton’s first freeze-thaw cycle opened up a jagged line of potholes along State Route 19, the calls started coming in: bent rims, shaken steering wheels and drivers who said their cars felt like they were “skipping” over rough patches. At Hemlock Auto & Tire, manager Luis Ortega said the damage is seasonal — but the complaints about ride and control reveal a year-round lesson about suspension.

Ortega pointed to a stack of scuffed alloy wheels behind the counter. “People think suspension is just comfort,” he said. “But it’s really about keeping the tire pressed to the pavement so you can steer and stop.”

At a roadside inspection Tuesday with city officials, transportation engineer Dana Hsu watched vehicles hit a patched section at 35 mph and noted how some cars “settled” quickly while others continued to bob.

“Two cars can hit the same bump and one stays composed,” Hsu said. “A big part of the difference is how much weight is moving with the wheel versus how much is supported by the springs.”

Sprung vs. unsprung mass, explained the way mechanics do

At Riverton Community College’s automotive lab, instructor Malik Garner uses a simple image for his first-year students.

“Think of a shopping cart,” Garner said, tapping the front caster wheel of a cart parked near the bay door. “If you bolt a heavy weight directly onto the caster, that wheel has a harder time following the floor. It wants to hop. If you put the weight up in the basket, the caster can flick up and down while the load stays steadier.”

In car terms, Garner said, the “basket” is the body and everything supported by the springs — the cabin, seats, engine mass carried by mounts, and the frame or unibody. That’s the sprung mass.

The “caster,” he said, is the wheel end: the tire and wheel, plus much of the hardware that moves with it — brake components and parts of the suspension links and hub. That’s the unsprung mass.

“The spring and damper are the bouncers at the door,” Garner said. “They try to keep the heavy crowd in the club calm, and they try to keep the wheel from getting wild outside.”

Why more unsprung mass can make traction harder

At a patch of broken asphalt near the Riverton water tower, patrol officer Janelle Rios described a common call after storms: a driver swerves to miss a hole, hits the edge anyway, then reports the car felt like it slid.

Hsu said the sensation often starts with what the tire is doing in the split-second after impact.

“When a tire meets a sharp bump, the wheel has to move up and then come back down fast enough to keep the tread pressing into the surface,” she said. “If there’s more weight attached to that wheel end, it’s tougher for the suspension to move it quickly and settle it.”

Ortega offered a shop-floor version. “A heavier wheel assembly doesn’t just go up — it wants to keep going up,” he said. “Then it comes down harder. If it’s still bouncing when the road changes again, the tire can lose its steady contact. That’s when you get that skipping, chattering feel through the steering.”

Riverton towing operator Beth McCann, who often arrives minutes after minor winter collisions, said she notices a pattern on certain washboarded side roads.

“You’ll see tracks where it looks like the tires were tapping the ground instead of rolling smooth,” McCann said. “People tell me, ‘I was braking and it felt like it wasn’t doing anything for a moment.’”

Garner said that moment can happen when the tire is lightly loaded because it’s still recovering from a bump.

“If the tire isn’t planted, it can’t do its job,” he said. “Steering, braking, acceleration — they all depend on that contact patch.”

The three body motions suspensions are hired to control

Drivers often describe ride problems with one word — “bouncy” — but Garner said suspensions are designed to manage several distinct motions.

Bounce is the whole car moving up and down.

Pitch is the nose and tail rocking opposite directions.

Roll is the body leaning side to side in a turn.

At the city’s fleet garage, supervisor Ellen Park said technicians look for these motions during test drives after replacing shocks, struts, or worn bushings.

“If a truck keeps rising and falling after a speed bump, that’s bounce,” Park said. “If the front drops hard under braking or the rear squats and then swings back, that’s pitch. If it leans and keeps leaning in a long corner, that’s roll.”

Park said each motion affects both comfort and control.

“A big pitch movement can shift weight forward or backward fast,” she said. “Too much roll can make the car feel delayed — like it takes a beat to respond.”

What you feel in the cabin

Drivers interviewed at a gas station near the worst stretch of Route 19 described sensations that Park said match those three motions.

• Bounce: “It feels like the whole car is on a pogo stick,” said commuter Aaron Delgado, who drives the route daily. Park said repeated bounce can make steering feel vague because the tires are cycling through heavier and lighter loading.

• Pitch: “When I brake, the nose dips and my head goes forward,” said nurse Kim Leary. Park said nose dive under braking is a common pitch sensation; some drivers also feel a rearward “squat” when accelerating from a stoplight.

• Roll: “On the on-ramp, it leans and I have to correct,” said delivery driver Suresh Nair. Park said noticeable roll can feel like a delay between turning the wheel and the car taking a set, especially in quick lane changes.

Hsu said these sensations are often more noticeable after pothole strikes because bent wheels, damaged tires, or worn dampers can add their own shake and oscillation.

“Once something is out of round or out of alignment, the suspension has to fight a problem it wasn’t designed to fix,” she said.

Sidebar: From simple springs to modern tuning

Older cars and light trucks, local historians say, often relied on simpler suspension layouts and fewer tuning options.

At the Riverton Classic Auto Club, member Stan Wilcox stood beside his restored 1978 sedan and described its straightforward setup.

“It’s springs, shocks, and not much else,” Wilcox said. “You feel the road. Sometimes that’s charming, sometimes it’s tiring.”

Garner said many older designs used basic springs and dampers with limited ways to tailor how quickly motions like bounce and pitch were controlled.

“Modern cars still use the same fundamentals — a spring to hold the vehicle up and a damper to calm movement,” he said. “But you’ll see more sophisticated linkages, better bushings, and different geometry that helps the tire track the road.”

Ortega said some newer models add suspension systems that can adjust damping as conditions change.

“Some cars can firm up for a corner and soften for a rough street,” he said. “It doesn’t change the laws of physics, but it can help the car settle faster and feel more controlled.”

A winter reminder at the tire counter

By late afternoon, Ortega said drivers were still arriving with sidewall bubbles and vibration complaints.

He offered the same advice he gives every January: check tire pressure, slow down on broken pavement, and pay attention to how the car behaves after bumps.

“If it keeps bouncing, if the front dives hard, if it leans more than it used to — those are clues,” Ortega said. “Suspension isn’t just a comfort feature. It’s the part that keeps the tire doing its one job: staying in touch with the road.”