Tire pressure: the real-world chart, not the sidewall max
Sidewall max is for tire safety, not your comfort. The Silca-derived chart for road, gravel, and MTB by rider weight and surface.
The number printed on the sidewall of your tire is the maximum pressure the tire can safely hold. It is not the optimal pressure to ride. For most riders, on most roads, the optimal pressure is 15-25 psi below the sidewall max — and that one change makes the bike faster, more comfortable, and grip better.
This article uses pressure data from Silca's lab testing and on-road rolling resistance studies. The conclusions are not opinion — they're physics that's been measured.
The two physics that matter
Tires roll faster when they deflect appropriately into the road surface. Too hard = the tire bounces over imperfections instead of conforming, transferring shock to the rider and losing speed through micro-vibrations. Too soft = the casing flexes too much per rotation, wasting energy in deformation.
The optimal pressure is where these two losses are equal. That pressure depends on tire width, rider weight, surface roughness, and tire construction.
The chart (road bike, 700c tires)
| Rider weight | 25c | 28c | 32c |
|---|---|---|---|
| 120 lbs | 75 / 70 psi | 62 / 58 psi | 52 / 48 psi |
| 140 lbs | 82 / 76 psi | 68 / 63 psi | 57 / 52 psi |
| 160 lbs | 90 / 83 psi | 75 / 69 psi | 62 / 57 psi |
| 180 lbs | 98 / 90 psi | 82 / 76 psi | 68 / 62 psi |
| 200 lbs | 105 / 96 psi | 89 / 82 psi | 73 / 67 psi |
Front pressure listed first, then rear. The rear carries about 60% of weight; the front about 40%. Equalizing pressures makes the bike feel unbalanced.
Gravel and mixed surface
| Rider weight | 38c | 42c | 47c |
|---|---|---|---|
| 140 lbs | 42 / 38 psi | 36 / 32 psi | 30 / 27 psi |
| 160 lbs | 46 / 42 psi | 40 / 36 psi | 33 / 30 psi |
| 180 lbs | 50 / 46 psi | 43 / 39 psi | 36 / 33 psi |
| 200 lbs | 54 / 50 psi | 46 / 42 psi | 39 / 36 psi |
Gravel pressures are dramatically lower than road. The wider tire deflects more naturally and the rougher surface needs that deflection. Underinflated road pressures on gravel make pinch flats and slow rolling.
Mountain bike
| Rider weight | 2.4" XC | 2.5" Trail | 2.6" Enduro |
|---|---|---|---|
| 140 lbs | 26 / 23 psi | 23 / 20 psi | 21 / 18 psi |
| 160 lbs | 28 / 25 psi | 25 / 22 psi | 23 / 20 psi |
| 180 lbs | 30 / 27 psi | 27 / 24 psi | 25 / 22 psi |
| 200 lbs | 32 / 29 psi | 29 / 26 psi | 27 / 24 psi |
What the chart doesn't say (and matters)
- Tubeless tires can run 5-8 psi lower than tubed at the same width. The casing supports the tire shape instead of relying on tube pressure.
- Tire casing matters. Supple casings (high TPI cotton or 3T-construction) run lower pressures than stiff casings (60 TPI nylon). The chart above assumes mid-quality casings.
- Surface roughness matters. Smooth asphalt: use top of the range. Chipseal or weathered asphalt: drop 5 psi. Wet roads: drop another 5 psi.
The honest test
If you can't determine your "optimal" pressure from a chart, do this:
- Start at the chart number for your weight and tire width.
- Ride 5 miles on your usual route.
- Drop 5 psi front and rear. Ride the same route.
- If it feels faster and more comfortable: drop another 5 psi.
- If it feels squishy in corners or starts pinch flatting: go back up.
The first point where the ride starts feeling vague in turns is 3-5 psi below optimal. Add 5 psi back and you're there.
What sidewall max is for
Sidewall max pressure is the safety limit the tire was tested to without failure. It's not the limit for use — it's the limit for survival. Manufacturers print it because legal liability requires it.
If you run sidewall max, you're trading rolling resistance for a margin you don't need. The optimal pressure is below the sidewall max for every realistic rider weight.
