The speed climbed gradually under controlled load. At fifty miles per hour the motor sounded healthy, at sixty it continued pulling smoothly, and around seventy Caleb began to see a change in the way the chassis moved. It was not dramatic yet, only a narrow, repeating tremor that seemed to pass through one section of the frame rather than coming equally from the engine. Caleb adjusted his observation position behind the barrier and watched closely.
At the speed Grip had described, everything changed. The engine stumbled, the sound breaking into irregular bursts, and the vibration became fierce enough that Caleb stopped the test at once. The motorcycle shuddered against its restraints, the tachometer showed the irregularity he had been looking for, and a final heavy cough died away into the shop's ringing silence. He did not need to see it a second time to understand that something was deeply wrong.
For several seconds he stood absolutely still. The failure was real; it had not been invented by a frightened rider or imagined by mechanics seeking an excuse. Caleb felt a grim satisfaction at having reproduced it and, beneath that satisfaction, the beginnings of real alarm. The motorcycle was more dangerous than Grip seemed to know.
He wrote down everything he had observed while the sequence remained fresh. Then he let the machine cool before approaching it, refusing to touch the hot engine despite the pressure of the wall clock. The temptation to repeat the test with a different adjustment was strong, but he knew another high-load run would be irresponsible until he understood what was moving. Aaron would have told him that proving a dangerous condition once was useful; proving it a second time without a plan could be stupidity wearing the costume of determination.
Caleb moved from the engine to the chassis. He examined the motor mounts, the alignment of the primary drive, the steering head, and the high-stress joints on the custom rigid frame. Most of the red paint was unbroken and glossy, although the machine had clearly seen years of hard riding. Nothing obvious explained a violent shudder, which made him more suspicious of the parts that could not easily be seen.
As the sun shifted across the shop floor, he lowered himself onto a creeper and rolled beneath the frame. The underside of the bike was a landscape of road grit, old oil stains, and carefully maintained hardware. Caleb followed the lines of the chassis with a flashlight, searching for evidence that the vibration had been rubbing two surfaces together. Under the rear portion of the engine, something caught the beam and flashed briefly silver.
It was a fine trace of fresh metallic powder in a place where he would have expected dirt and aged grease. He stopped moving. When he brought the light closer, he saw a narrow discolored band along the frame's red finish and a join whose appearance did not match the workmanship around it.