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Guide
Tire pressure in the wet
On wet roads, grip matters more than anything else. A little less pressure helps noticeably, without making you measurably slower.
About 7% less pressure
That’s around 4–5 PSI less on a road bike and about 2 PSI on a gravel bike or MTB compared with dry conditions.
Dry vs. wet in numbers
| Dry | Wet | |
|---|---|---|
| Road, 28 mm | 58 / 67 | 54 / 62 |
| Gravel, 40 mm | 33 / 37 | 31 / 35 |
| MTB, 2.4″ | 22 / 24 | 20 / 22 |
Calculated with the TireDial model: 70 kg (154 lb) rider, tubeless, typical bike, default surface.
Why lower pressure helps in the wet
A tire with a little less pressure conforms better to the surface. It follows the small irregularities in the tarmac instead of skipping over them, so more rubber stays in contact with the road. On a wet surface, that’s the difference between holding and sliding.
Bike tires don’t aquaplane like car tires, by the way. At normal speeds hydroplaning is practically a non-issue on a bike, and road tires don’t need tread for it. What matters is the rubber compound, the contact patch and how you ride.
Does it cost speed?
Hardly. On real roads the optimal pressure is lower than many people think anyway, and in the rain you take corners and descents more carefully. A few percent less pressure is a very cheap price for much more safety.
Don’t go too low
With inner tubes, too little pressure raises the risk of pinch flats. Use the wet value as your target, not something lower still. Also, in the wet, glass and sharp grit cut into rubber more easily and stick to a wet tire. Tubeless with fresh sealant helps.
More grip in the rain: other tips
- Watch out for road paint, manhole covers, rails and wet leaves. Even the best tire doesn’t help much there.
- Brake earlier before corners and lean the bike less.
- Wider tires with a softer compound do more in the wet than any pressure tweak.
- Plan your braking: rim brakes bite much later when wet.
Rain starts mid-ride?
No need to stop and let air out. The difference is small, and without a gauge it’s easy to let out too much. Better to set your pressure before the ride based on the forecast. TireDial lets you save a ride profile like “Wet roads” and switch with a tap.
Your exact pressure in seconds. TireDial uses your weight, tires and rims, tubeless or tubes, surface and wet conditions, front and rear separately, and always respects your maximum pressure. Free for iPhone.
FAQ
How much lower tire pressure in the rain?
About 7% lower than in the dry. On a road bike with 28 mm tires that’s around 4–5 PSI; on a gravel bike or MTB about 2 PSI.
Can bike tires aquaplane?
At normal speeds, practically not. The narrow, rounded contact patch pushes water aside. Road tires don’t need tread for that.
Do I get more flats in the wet?
The risk is generally considered higher: water helps glass and grit cut into the rubber, and debris sticks to a wet tire. Tubeless with fresh sealant helps.
Keep reading
TireDial’s values and the ones on this page are well-founded starting points, not manufacturer specifications. Always stay within your tire and rim limits. See also the safety notice.