Can a 150 tire be replaced with a 180 tire on a motorcycle?

[McSophie]

Motorcycle 150 tires cannot be replaced with 180 tires. Motorcycles are also classified as motor vehicles, and traffic laws prohibit the modification of motor vehicle tires. Unauthorized modifications are considered illegal. Notes on motorcycle modification registration: For motorcycle modification registration, you must first apply at the local vehicle management office. Otherwise, the vehicle will not pass the annual inspection. Modifications such as changing tires or rims, adding spoilers, altering lights or exhaust pipes are considered illegal modifications. These must be restored to their original condition to pass inspection, and penalties such as fines and license suspension may be imposed. Introduction to illegal motorcycle modifications: Illegal vehicle modifications refer to alterations to the vehicle's appearance, power system, transmission system, or braking system that exceed the original design load capacity and functionality, and are not permitted by national laws or the manufacturer. This includes replacing key components. If the body color, body, or frame is changed, the owner must register the changes at the vehicle management department within 10 days.

[LeLilah]

As a veteran with ten years of motorcycle experience, I personally tested the modification from 150 to 180 and advise caution. Wider tires do offer better grip, but widening the front tire can easily cause it to rub against the fender and make steering sluggish, like steering a boat. If you force a 180 tire onto the rear wheel without upgrading to a wider rim, the tire surface may deform, negatively affecting braking. I've seen cases where the speedometer showed a 5 km/h discrepancy after modification, causing issues during annual inspections. It's recommended to first check if the frame can handle the 180 width, whether the chain will rub against the tire sidewall, and if there's enough clearance in the rear swingarm. If you decide to proceed, have a professional adjust the suspension and axle—never attempt it yourself.

[DelJune]

A mechanic with 15 years of motorcycle repair experience told me that upgrading from 150 to 180 tires largely depends on the frame structure. Street bikes can barely fit 180 tires, but doing so on an ADV or sportbike may disrupt balance. Last week, a young guy forced the modification and nearly crashed while leaning in the rain—the wider tire didn't increase the contact patch; instead, it arched in the middle, worsening water drainage. Insufficient rim width also accelerates tire wear, requiring replacement within months. Annual inspections become a headache too, as mismatched registration photos and actual tires may force you to remove and reinstall them. If you must modify, a 170 tire is a recommended compromise, avoiding the need to change rims and chains.

[VanLuke]

A motorcycle modification specialist warns that increasing tire width by 20% causes three major issues: First, rim mismatch leads to insufficient sidewall support, causing tread wrinkling and skidding during cornering. Second, altered crown curvature reduces contact area, impairing braking performance. Lastly, changed tire circumference disrupts ABS and odometer functions. Experts recommend using a tire calculator to ensure the diameter difference between old and new tires stays within 3%. For such modifications, always upgrade to J-value matched rims and reprogram the ECU.