PSI to Bar

Bike Tyre Numbers in PSI, Pump Gauge Marked in Bar

Cycling grew up bilingual about pressure. Tyre sidewalls printed for the US market carry psi, most pressure calculators and forum threads quote psi, yet a large share of floor pumps, shock pumps and workshop gauges sold outside North America are graduated in bar. Somebody hands you a recommendation of 65 psi for a 28 mm tubeless setup and the only marks on the dial run 0 to 11 in half-bar steps.

The factor: 1 psi = 0.068947573 bar, so multiply psi by roughly 0.0689. That 65 psi recommendation becomes 65 × 0.068947573 = 4.48 bar — a hair under the four-and-a-half mark on the dial.

Why the Two Scales Keep Crossing Paths

Dual-scale dials mislead

Many floor pumps print both scales on one face, but the bar ring is usually the fine one and the psi ring the coarse one. On a 0–11 bar dial a single psi is barely a needle width, which is why riders read the bar side and convert once.

Wider tyres, smaller numbers

A 23 mm tyre at 100 psi and a 45 mm gravel tyre at 30 psi can carry the same rider. Air volume rises fast with width, so the pressure needed to keep the casing off the rim falls just as fast.

Tubeless moved the floor down

With no inner tube to pinch, riders now run pressures that would have been reckless on tubes. The limiting factor became the bead unseating or the rim striking the ground, not a snakebite puncture.

System weight, not body weight

Charts are driven by the load reaching each wheel: rider plus bike, bottles, bags and kit, split roughly 45/55 front to rear on a road bike and closer to even on a loaded gravel bike.

Getting From a Recommendation to a Dial Reading

Do the conversion once for your setup, write the two bar figures on a strip of tape beside the pump, and stop doing arithmetic in the garage every Saturday morning.

Put the psi target in the left box

Enter the number a chart, a sidewall or a riding partner gave you — 30, 55, 72.5, anything. The bar value appears while you type, and the field takes a comma just as happily as a dot for the decimal mark.

Convert front and rear separately

The rear wheel carries more load, so most riders run two to four psi more behind. Do both ends rather than pumping one figure into both tyres — on a 45 mm gravel tyre those few psi separate a planted front end from a vague one.

Grab the bare figure for your notes

Each field carries its own copy button, and it hands over the number alone — no unit, no spacing — which drops cleanly into a training log, a spreadsheet or a message to a mechanic. Pressing Ctrl + C inside a field does exactly the same.

Turn a bar reading back into psi

Tap the swap arrows (↔) and the page runs bar → psi instead, for when a European sidewall says 8.5 bar maximum and you want to know how close your 110 psi habit sits to it. That direction multiplies by 14.5037738, so 8.5 bar is 123.3 psi.

Obey the lower of the two limits: a tyre can be rated higher than the rim it is mounted on. Hookless carbon rims in particular are commonly capped near 5 bar (72.5 psi) whatever the tyre says, and that ceiling is not a suggestion.

Working Pressures by Discipline and Tyre Width

Representative starting points for a rider and bike totalling around 85 kg on flat-to-rolling terrain. Read them as the middle of a range: lighter riders and smoother surfaces sit below, heavier riders and rougher ground sit above.

Setup	Tyre width	Pressure (psi)	Pressure (bar)
Road, inner tube	25 mm	90 psi	6.21 bar
Road, tubeless	28 mm	70 psi	4.83 bar
Endurance road, tubeless	32 mm	55 psi	3.79 bar
All-road / light gravel	38 mm	40 psi	2.76 bar
Gravel, tubeless	45 mm	30 psi	2.07 bar
Cross-country mountain bike	2.25 in (57 mm)	24 psi	1.65 bar
Trail / enduro mountain bike	2.4 in (61 mm)	22 psi	1.52 bar
Fat bike on packed snow	4.0 in (102 mm)	8 psi	0.55 bar

Notice how compressed the bar column is. Everything from a skinny road tyre to a fat bike fits between 0.55 and 6.21 bar, which is why a dial graduated in half-bar steps is fine for gravel and mountain work but frustratingly coarse for the road — one graduation there covers more than 7 psi.

What the Two Fields Give You in the Workshop

Walk a whole pressure range

Both boxes stay editable and recalculate on every keystroke, so you can step through 28, 30, 32, 34 psi and watch the bar figure move without clearing anything or pressing a button.

Flip it when the sidewall speaks bar

The swap arrows reverse the pair to bar → psi, the direction wanted when a tyre or rim prints its maximum in bar and your riding habits are stored in psi.

Every pressure unit is one search away

Searchable dropdowns on both sides carry all 26 units the app knows, so a suspension chart quoting kPa or an old shop gauge marked kg/cm² lands on this same page.

Fine enough that one psi still shows

Answers carry up to eight decimals, so a single psi of difference reads as 0.069 bar instead of rounding into nothing, and the copy button passes on that plain number.

Tyre Pressure Questions From the Saddle

How much does rider weight shift the pressure I should run?

Roughly in proportion, because the tyre exists to support a load. A common workshop rule of thumb moves about one psi per kilogram of system weight away from a chart's reference rider on a road tyre, and far less on a wide mountain bike tyre where the air volume is enormous by comparison. A 60 kg rider on 28 mm tubeless might settle near 55 psi (3.79 bar) where a 95 kg rider needs 75 psi (5.17 bar) on the same wheels.

How low can a tubeless tyre go before it burps air?

Burping happens when a hard side load momentarily lifts the bead off the rim shelf and a puff of air escapes. There is no universal floor — it depends on bead fit, rim profile and how aggressively you corner. Most riders find their limit by dropping two psi (0.14 bar) at a time on familiar ground until the tyre feels vague or squirms mid-corner, then adding two back. Tight beads and hookless profiles hold on at lower pressures than a loose fit on a hooked rim.

Does internal rim width change what the tyre needs?

Yes, in two ways. A wider internal rim spreads the same casing into a rounder, higher-volume shape that measures wider than its printed label, so it supports the load at lower pressure. It also braces the sidewalls, cutting the squirm that used to push riders towards over-inflation. Moving a 28 mm tyre from a 17 mm to a 23 mm internal rim typically buys several psi of headroom for the same handling.

Is a rock-hard tyre actually faster?

Only on glass-smooth surfaces. On a laboratory drum, rolling resistance keeps falling as pressure climbs. On real tarmac, past a certain point the casing stops absorbing surface texture and starts throwing bike and rider up and down instead — impedance losses — and total drag rises again. That break point is why fast riders on rough roads have gone wider and softer rather than narrower and harder.

Should I let air out for wet tarmac or loose gravel?

A modest drop helps, because a longer contact patch finds more grip on a slick or loose surface. Two to four psi off a road tyre in the wet, and around five off a gravel tyre in deep loose material, is a typical adjustment — 30 psi down to 25 psi is 2.07 bar down to 1.72 bar. Overdo it and you trade that traction back for casing roll in corners and a much higher chance of striking the rim on a hidden rock.