Tubeless Tire Compatibility
This article reviews the different fit standards in tubeless bicycle tires.
Tubeless tires have become popular in mountain biking, fat tire biking, cyclocross, and to some extent road riding. The system can increase the contact area of the tire to the ground because they can be ridden at low relative air pressure, which can improve the ride feel and handling of MTB bikes, fat tire bikes, and cyclocross bikes.
Bicycle tubeless tire systems are similar to those used on cars and motorcycles. The concept is to have the tire is sealed airtight to the rim bead without an internal inner tube. The air pressure from the tire maintains internal pressure at the bead and keeps the tire inflated.
Depending upon the selection of tubeless system components, there are various degrees of reliability and consistency. It can be possible to manipulate non-compatible parts, but it should not be unexpected if the results are less than as desired.
Tires and rims
The most reliable tubeless systems are those marked UST (Uniform System Tubeless standard). Rims and tires must meet a certified standard to use the UST label. A UST tire will have a square shaped bead to match the UST rim. Inside the tire carcass will be a butyl liner, basically inner tube material formed into the inside carcass of the tire body. This extra material does make the tire heavier compared to non-UST tires.
UST rims will have either no nipple holes in the rim tire bed, or these holes will be completely sealed. The UST rim bead seat is designed to accept and hold the beads of the UST tires. UST tires can be used on a UST rim without tire sealants.
Another option is commonly known as “tubeless ready” or “tubeless compatible”. There is no set standard that a product must meet in order to use these labels. Each company decides what it considers to be “TR” or “TC”. The various “tubeless ready” components may or may not match between manufacturers.
A “tubeless ready” or similar wording on a tire indicates there are some design features to help get an air tight seal to the rim. The bead will generally have a square shape instead of the rounded shape commonly found on inner tube systems. The casing will be heavier than a normal tubed tire, as the liner in the tire needs to be air tight as well.
A tubeless ready rim will have a sidewall with a hooked design, which helps catch and hold the bead. Older rims will appear rounded without a hook shape. The shape of the rim will force the bead up snug against the outer hook, and will have a deep section in the middle to make it easier to remove.
Tape, Valves, and Sealant
The interior perimeter of the rim must also be correctly designed to work as tubeless. First, the rim channel must be airtight. This is typically done with different types of adhesive tapes.
Not all adhesive tapes are acceptable to seal the rim. The tape must be flexible enough to covers the uneven surface around nipple eyelets, and it must be resistant to the tire sealant. The tape can also be used to build up the inner diameter of the bead seat area. This is done especially for rims that were never intended for a tubeless tire. Typically heavier tapes such as Gorilla Tape are used to build up the rim.
Tubeless valves can vary in design. The base of the valve should create an air tight seal. The valve shaft is threaded and a nut is used to pull the head tight against the inside perimeter of the wheel well.
Tire sealant is also considered a part of the tubeless system. These sealants vary in chemical make up, and although latex is a common component, they are not necessarily compatible between brands. Clean out the tire carcass if changing brands, using the same techniques as if cleaning up after painting with latex paint.
For bicycles, tubeless tires are an evolving technology. It is a common assumption that the tire sealant will take care of any small air leaks or seepage. Although there is a large degree of truth in this, there are limits to using incompatible equipment.