Hookless vs hooked MTB rims: the 5 bar ceiling you don't negotiate
A hooked rim has a lip that retains the tire bead; a hookless rim has a straight wall and the bead is held by interference. So hookless imposes two hard conditions: tire compatibility (not every tire is approved) and a safety ceiling of 5 bar (72.5 PSI) per the ETRTO standard, which you don't exceed. You'll almost never touch that ceiling in MTB; the limit that really matters is the lower one, set by burping. Your running pressure is closed by the calculator.
"Hookless" is not a marketing fad or a budget version of the rim. It's a different geometry with its own rules, and one of those rules — the pressure ceiling — is a physical limit, not a suggestion.
The upper ceiling is ETRTO; your running pressure is something else. The PSI Pressure Calculator gives your real range by weight, width and rim. ▶ Open the PSI calculator
What changes between hooked and hookless
In a hooked rim, the inner edge ends in a small lip curved inward. That hook physically catches the tire bead and retains it against the pressure pushing outward. In a hookless rim, that wall is straight: the bead is not caught but held by interference — squeezed against the wall because its diameter is slightly smaller than the rim seat. Less material at the edge means a rim that tolerates flank impacts better, which is exactly where a hooked rim tends to crack.
The hook retains by shape; the straight wall retains by fit. Switching from one to the other changes the rules of the mount, not just the label on the rim.
The 5 bar / 72.5 PSI (ETRTO) ceiling you don't negotiate
Because nothing catches the bead on hookless, the ETRTO standard sets a safety ceiling of 5 bar (72.5 PSI) for hookless tubeless rims. Above that value, pressure can overcome the interference and walk the bead off the straight wall. That number is a hard limit: not "recommended," but the ceiling by design. The good news is that in MTB you rarely get near it — working pressures sit well below — but if you ever inflate to seat the bead, that 5 bar is the line you don't cross.
Tire compatibility: mandatory, not optional
On a hooked rim you can mount almost any tubeless-ready tire without drama. On hookless you can't: the tire must be declared hookless-approved by the manufacturer, with a bead dimensioned and stiff enough to seat by interference. A non-approved tire may not seat safely, or may seat unevenly. Before mounting, confirm that both parts — rim and tire — declare hookless compatibility. Don't infer it: find it in writing.
The limit you actually use is at the bottom, not the top
The 5 bar ceiling is real, but in MTB practice it's never your problem. Your daily decision lives at the low end: how far you can drop before the bead momentarily releases air on a side hit — burping. That floor depends on your weight, tire width, rim inner width and terrain, and doesn't come from a chart. Hookless or hooked, the standard sets the ceiling; you set the floor with judgment, and the calculator refines it.
FAQ
Maximum pressure on hookless?
5 bar (72.5 PSI) per ETRTO. A safety ceiling you don't exceed, not the running pressure.
Hooked vs hookless?
The hook retains the bead with a lip; hookless holds it by interference against the straight wall.
Any tire on hookless?
No. The tire must be declared hookless-approved by the manufacturer. Compatibility is mandatory.
Should I ride near 5 bar?
No. In MTB you ride well below it. The limit you use is the lower one, set by burping.
The ceiling is ETRTO; your working pressure is closed by the PSI Pressure Calculator per wheel by width, rim and discipline. ▶ Open the PSI calculator
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