Here is the pattern owners describe. New belt goes in, the machine runs fine for a while, and then the first inspection shows one sidewall worn bright and smooth while the other still looks close to new. Sometimes there is a chirp or a squeal at engagement. The belt is not defective. It is being asked to run through two clutches that are not lined up with each other.
What Alignment Actually Means in a CVT
A CVT belt only lives a long life if it enters and leaves both clutches straight. The primary and the secondary have to sit in the same plane, so the belt travels a flat path between them rather than being pulled sideways at one end.
When the secondary sits slightly inboard or outboard of where it should be, the belt has to twist to bridge the gap. That twist concentrates load on one sidewall. That side takes the heat, polishes over, and hardens, while the other side barely does any work. What you end up with is a belt doing the job of a half belt, and it will not last the interval you expect.
Reading the Belt Instead of Guessing
Pull the belt and lay it on the bench. Compare the two sidewalls side by side. Even wear looks the same on both faces, with a uniform matte texture. Misalignment looks lopsided: one face glassy and slick, the other still showing its original finish. Fine black dust concentrated on one side of the CVT housing is another tell.
It is worth checking this at the first belt change on a new machine, not after the third belt. Alignment tolerance stacks up from manufacturing, and a machine that left the factory a little offset stays that way until somebody corrects it.
Correcting It on the U10 Pro
On the CF Moto U10 Pro, the correction happens at the secondary. Our CF Moto U10 Pro Clutch Alignment Shims install on the back half of the secondary clutch and move it into the correct plane so the belt sits evenly between the primary sheaves. The set includes two shims, and depending on how far off your machine is, you may need only one or you may need both. They fit both the 2 seat and 4 seat U10 Pro.
This is a fifteen dollar part solving a problem that otherwise shows up as a belt bill every few hundred miles. Start with one shim, reassemble, run the machine, and read the belt again. If the wear evens out, you are done. If it is still one-sided, add the second.
While You Have It Apart
Wipe both sets of sheave faces down with brake cleaner and a clean rag so you are reading a clean baseline, and check that the sheaves are not scored. A belt that has been running crooked and hot can leave rubber deposits behind, and those deposits change the friction surface for the next belt too.
Also confirm the belt itself is the correct part for the U10 Pro. It is a different machine from the older CF Moto UForce 1000, and the belts are not interchangeable. Installing the wrong length belt produces its own wear pattern and will send you chasing an alignment problem that is not there.
The Point
Uneven sidewall wear is one of the few CVT symptoms that tells you exactly what is wrong. It is a geometry problem, not a belt quality problem, and no brand of belt will out-live a crooked clutch stack. Shim it right once and the next belt does full duty on both sides.