Three Suspension Questions Every Collision Shop Should Know the Right Answer To

A single collision can send force through a vehicle's suspension in ways that aren't always visible and aren't always intuitive. At a Collision Hub "Repair University Live" session focused on steering and suspension systems, experts dismantled three pervasive misconceptions — and the answers have direct implications for how shops estimate, inspect, and document suspension-related work.

Question 1: Does Drivetrain Type Affect Suspension Inspection?

The short answer from P&L Consultants co-owner Larry Montanez: "Yes and no."

The core inspection process is largely similar across two-wheel-drive, four-wheel-drive, and all-wheel-drive platforms. But four- and all-wheel-drive vehicles introduce additional inspection steps because of the added mechanical complexity of their drivetrains. Transmission type — whether CVT, automatic, or manual — also influences the inspection process, as do different rear suspension configurations.

Database Enhancement Gateway Administrator Danny Gredinberg added rear active steering to the list of variables. This feature, which essentially adds a second rack-and-pinion system to the rear axle, is rare but relevant when present — and demands its own inspection consideration.

I-CAR curriculum director Josh McFarlin raised another frequently overlooked point: estimators should ask whether four-wheel drive was engaged at the moment of impact. If it was, the damage may extend further into the drivetrain than a standard inspection would reveal.

A video case study shown during the session illustrated the principle clearly: a parked, unoccupied SUV sideswiped on the left side had its front wheels visibly reacting to the impact energy — rolling forward, stopping, and rolling back. On a four-wheel-drive vehicle, front wheels may be mechanically disconnected from the system and potentially undamaged. On an all-wheel-drive system, the outcome depends on the vehicle's speed at the time. On a front-wheel-drive vehicle, Montanez was direct: it's "definitely damaged."

Question 2: Is It True That Cast Components Either Break or Are Fine?

The collision repair industry has long repeated the idea that cast suspension components don't bend — they either survive intact or fracture. It's been treated as a dependable rule of thumb.

"That's false," Montanez said. "It's a lie."

Cast components do bend, and according to Montanez, they bend "more often than not." He has personally observed engine cradle mounting loads displaced significantly by collision energy. "This is a major, major issue that many people don't understand," he said.

This isn't just a theoretical concern. Several major European OEMs — Mercedes-Benz among them — have issued formal position statements addressing this exact scenario. Mercedes states explicitly that any impact to a wheel that requires replacement of a suspension component or tie rod also requires replacement of the rack and pinion steering gear.

The manufacturer's own language explains the reasoning: "A shock transmitted to the steering gear through the front axle or steering linkage may have caused damage not externally visible. A pressure test or crack test required for this is not possible in the workshops; therefore the steering gear is to be replaced in cases of doubt."

Importantly, Mercedes also advises that if an insurer disputes the need for this replacement, the shop should secure the insurer's signature — making the liability the insurer's, not the shop's.

The legal exposure here is serious. Both Montanez and Collision Hub CEO Kristen Felder have testified as expert witnesses in collision repair cases. Both confirmed that a "hold harmless" signed by a customer does not insulate a shop from liability for an improper repair. "The judge will laugh," Felder said.

Question 3: Are Recycled Suspension Components and Wheels Safe to Use?

The short answer: maybe, but the shop accepting responsibility for a part with an unknown history creates a liability problem that's difficult to justify.

"The parts may be good," Felder acknowledged. The problem is that the repairer has no way to verify the part's history — including what forces it absorbed in the collision that removed it from the donor vehicle, or how it was handled during the salvage process.

Montanez highlighted a front-end crash test video played during the session: the impact to the front of the car was clearly felt at the rear wheel and door, which visibly reacted even though they showed no external damage. "What happens to the back end of it?" he asked. Would you install that rear suspension in a customer vehicle and then discover it won't accept a wheel alignment because the components are subtly bent?

There are additional concerns about salvage yard handling practices. Felder described scenarios where parts are unbolted and dropped from a lifted vehicle during disassembly. "How it's cared for, stored, transported — there are all of these things that come into play," she said.

The same uncertainty applies to recycled wheels. Aluminum wheels can sustain invisible crack damage from impacts. No visual inspection reveals what the wheel absorbed during the accident that put it into salvage inventory. "You don't know what's been done to that wheel," Felder said.

What These Three Answers Mean in Practice

Each of these questions reflects a broader pattern in collision repair: the gap between what shops assume to be true based on old rules of thumb and what OEM documentation and engineering reality actually require.

Drivetrain type changes inspection scope. Cast components don't always break clean. Used parts carry unknown histories. In all three cases, the default approach — do less, assume less damage, use the cheaper part — transfers risk to the vehicle owner and legal liability to the shop.

The best protection for a shop is the same one that keeps customers safe: follow the OEM procedures, document the work, and ask the insurer to go on the record when they push for a less complete repair.