- What a “pinch flat” really is (and why curb cuts cause them)
- 28 vs 32 vs 38 mm for city streets: what changes in the real world
- Before you copy a pressure number: 7 factors that change the answer
- Pressure targets by rider weight (city potholes + curb cuts)
- Two quick adjustments (most people need one of these)
- How to fine-tune in one short test ride (no guesswork)
- Setup choices that matter as much as pressure
- City riding technique that prevents pinch flats (even at the “right” pressure)
- If you can only change one thing, change this
- FAQ
- Referências
City streets have a special kind of rough to them, a square-edged rough that can hit your wheels like a square-edged step. Finding the right tire width and pressure is less about chasing a “fast feel” and more about preventing your tire from bottoming out on impacts, while still absorbing enough vibration for you to stay in control over rough asphalt.
TL;DR
- If your frame allows it, 32 mm is the best all-around city width for potholes: enough volume to cushion you from hits and keep you from losing control, without the size and weight penalty of bigger rubber.
- 38 mm is the comfort-and-control choice for truly broken pavement, frequent curb cut drops and a bag to carry—especially if you’re trying to reduce fatigue on your longer commutes.
- 28 mm / wider clearance limited works when the clearance is tight, but it’s the most pressure sensitive and most punishing if you make a mistake (low pressure = pinch flats; high pressure = harsh handling).
- Pinch flats (“snakebites”) occur when your tire compresses down enough that the tube itself gets pinched crushed against the rim—often a product of hitting curbs/potholes. (liveabout.com)
- Use the pressure tables below as starting points, then tune the pinches and twitches out in 1–2 psi increases on your worst local street.
What a “pinch flat” really is (and why curb cuts cause them)
With inner tubes, a classic pinch flat happens when you strike a sharp edge hard enough that the tire bottoms out. The tube gets pinched between the rim and tire casing and punctures—leaving two small holes like a snakebite. (liveabout.com) Curb cuts (especially the abrupt ones) can be worse than they look because they’re effectively a short drop onto a square edge. If your pressure is too low relative to your tire volume and load the rim takes the impact as the tire compresses instantly—that’s exactly what happens when pinch flats occur (and that practice also dings rims). (liveabout.com)
- With tubes, your best defense is: more tire volume (wider tire) and/or more pressure (inside safe limits).
- With tubeless, you eliminate the pinch mechanism, but can still damage the tire casing, dent a rim or burp air if the tire pressure is too low for the impact.
- If you’re wedded to tubes but want more pinch-flat resistance, tube material can matter; Schwalbe describes lab tests (including “snake bite” tests) where certain designs exhibit more resistance to pinch flats. (schwalbetires.com)
28 vs 32 vs 38 mm for city streets: what changes in the real world
Practical city differences (assuming similar tire construction and quality):
| Tire width | Pros in potholes/curb cuts | Cons / watch-outs | Best for |
|---|---|---|---|
| 28 mm | Quick handling; fits tight-clearance frames; can be efficient at appropriate pressure | Small margin of error: too low = rim strikes/pinch flats; too high = harsh + less grip on broken pavement | You have limited clearance and mostly decent pavement |
| 32 mm | Noticeably more air volume; easier to run “impact-safe” pressure without feeling like a jackhammer; better traction on rough patches | May need more frame/fender clearance; some aero-focused road wheels may not be optimized for it | Most commuters and “fast city” riders |
| 38 mm | Biggest comfort/control jump; easiest to survive surprise potholes; works well with lower pressures for vibration reduction | Heavier; may feel less snappy; clearance and fender fit become the main limiting factors | Broken pavement, frequent curb cut drops, carrying a bag, longer rides |
Why wider often feels faster in the city: on imperfect surfaces, vibration can cost energy and control. several tire researchers and manufacturers discuss how rough-surface vibration (“suspension losses”) can offset the benefits of very high pressure, which is one reason many riders move toward wider tires at lower pressures on real roads. (renehersecycles.com)
Before you copy a pressure number: 7 factors that change the answer
- Rider + cargo weight: A loaded backpack or panniers can add the equivalent of “one weight category” to your rear tire needs.
- Tube vs tubeless: Tubeless often tolerates lower pressures because there’s no tube to pinch, but it still needs enough pressure to avoid rim hits and burps.
- Rim internal width: Wider internal rims generally support the tire better and can let you run slightly less pressure for the same stability (but follow your wheel maker’s guidance).
- Actual measured tire width: A “32 mm” tire may measure 33–35 mm on a wide rim. Measure if you can—actual volume is what matters.
- Tire casing and puncture belt: Stiffer, heavier casings often need a touch less pressure to avoid harshness, but may feel less “supple” over chatter.
- Your speed and line choices: The faster you hit sharp edges, the more you need impact margin (i.e., a little more pressure or more volume).
- Front vs rear load: The rear carries more weight, so it generally needs more pressure; many pressure calculators explicitly output different front/rear numbers. (sram.com)
Pressure targets by rider weight (city potholes + curb cuts)
Pressure units: bar ≈ psi × 0.069 (and psi ≈ bar × 14.5). For hookless setups, confirm your rim/tire pressure limits first—some guidance identifies ~72.5 psi / 5 bar as a key max for hookless road systems. (cadex-cycling.com)
| Weight | 28 mm tubeless | 32 mm tubeless | 38 mm tubeless |
|---|---|---|---|
| 120 lb (54 kg) | 52 / 56 | 45 / 48 | 32 / 35 |
| 150 lb (68 kg) | 58 / 63 | 50 / 54 | 36 / 39 |
| 180 lb (82 kg) | 64 / 69 | 55 / 59 | 40 / 43 |
| 210 lb (95 kg) | 70 / 75 | 60 / 64 | 44 / 47 |
| 240 lb (109 kg) | 75 / 80 | 65 / 69 | 48 / 51 |
| Weight | 28 mm (tubes) | 32 mm (tubes) | 38 mm (tubes) |
|---|---|---|---|
| 120 lb (54 kg) | 60 / 64 | 51 / 54 | 37 / 40 |
| 150 lb (68 kg) | 66 / 71 | 56 / 60 | 41 / 44 |
| 180 lb (82 kg) | 72 / 77 | 61 / 65 | 45 / 48 |
| 210 lb (95 kg) | 77 / 82 | 66 / 70 | 49 / 52 |
| 240 lb (109 kg) | 83 / 88 | 72 / 75 | 53 / 56 |
Two quick adjustments (most people need one of these)
- Carrying cargo (laptop, groceries, panniers): add +2 to +6 psi to the rear depending on how heavy the load is and how often you hit sharp edges.
- Lots of curb cut drops or surprise potholes: add +2 to 4 psi front and rear, or (better) consider the next wider tire size so you don’t have to run a harsh pressure to gain impact safety.
How to fine-tune in one short test ride (no guesswork)
- Pick one rough, repeatable loop (include a couple of the worst patches you actually ride).
- Start at the chart pressure for your weight and tire width.
- Ride the loop and pay attention to: (a) grip in turns, (b) harsh “buzz” through hands/feet, (c) any rim strikes, (d) tire squirm in fast corners.
- If the bike feels harsh, skittery, or you’re losing traction on broken pavement: drop 1–2 psi and re-test.
- If you feel rim strikes, hear a sharp “clack,” or you dented a rim before: add 2–4 psi (or move up to a wider tire).
When you find that ultimate combination, make it your “City Rough” preset, then make a second preset for “City Smooth” (+2–4 psi).
Setup choices that matter as much as pressure
1) Tire construction: don’t go “race-day fragile” for daily city abuse
For city potholes you want something that can take blam-impact after blam-impact without cuts to the sidewall. Slightly more robust casing (or just tire they’re making for endurance/commuting) often wins vs chasing the lightest thing. Especially if you’re already on tubes, trying to avoid snakebites.
2) Tubeless vs tubes: pick your failure mode
Tubeless advantages in the city: no too-low pinch flats (no tube), small puncture seals with sealant. Tubeless tradeoffs: setup etc etc is a faff; too low pressure can still munge the rim??? Can still blam and even burp out sealant if too low.
Tubes advantages: messing about roadside is easier/faster. Mess. More likely to keep it as “known quantity.”
Tubes tradeoffs: more likely pinch-flat with square-edge hits, pressure becomes more critical if 28 mm size.
3) Rim type (hooked vs hookless): pressure limits can cause you to choose different tire-width
If your system has a hard stop on pressures (the sort of things people discuss around 72.5 psi / 5 bar on the road hookless systems), you might be forced too near the limit to have adequate support for impacts if using a narrower tire. 28 mm bike + heavier lighter rider/freight, moving to allow 32 mm is usually simplest. – (@cadex-cycling.com)
City riding technique that prevents pinch flats (even at the “right” pressure)
- Square edges = unweight: as you come upon the edge of a pothole or curb cut drop, slightly unweight the saddle and get the front wheel lighter. You set yourself up for a rim strike and a possible flatting of the sidewall rimming instead of pushing through.
- Hit curb cuts as close to perpendicular as practical: glancing hits teach you up. Go straight for the joys rather than glancing off to the side of the edges adjacent to the curb cut. It gets worse during a strike.
- Look farther ahead than you think: go a little faster if you must; the easiest “pressure fix” is simply not running into the worst edges at speed.
- Don’t run equal front/rear by default: the rear usually needs more support because it’s taken the most weight on it; a calculator I ran treated front and rear differently. (sram.com)
- Common mistakes (and the quick fix):
- Mistake: running 28 mm tires at “max sidewall pressure” because safety. Fix: use enough to avoid bottoming out, but don’t automatically assume that max is the best for those rough streets—I get out with my pump and try out 1 or 2psi low/less, then keep notes on those changes. (Also never exceed the max displacement shown.). (cycling.hutchinson.com)
- Mistake: treating tire pressure as a set and forget number. Fix: don’t forget that and don’t be so voluminous and broadabout, just re-check it from time to time. Remind yourself however, that it is already summery.
- Mistake: Getting pinch flats, over and over tires, and just adding in increased pressure. Fix: go wider and learn better technique or dig tubeless.
- Isn’t it fun treating rim/tire system rules as irrelevant on hookless! Fix it: believe that you can go by your rim+tire guidance/level rules if you want. Go play within that envelope of room. (enve.com)
If you can only change one thing, change this
For most city riders trying to survive potholes and curb cuts without pinch flats, the biggest improvement per dollar is usually moving from 28 mm to 32 mm (if you have clearance), then re-tuning pressure. It widens the “safe zone” where you get impact protection and comfort without living right on the edge of rim strikes.
FAQ
Q: Do wider tires automatically mean lower pressure?
Q: Why do I still get pinch flats even when my tire feels “hard” by hand?
Q: Should I run the same pressure front and rear for simplicity?
Q: What if my calculated/target pressure is above my system’s max (especially hookless)?
Q: Is 38 mm overkill for the city?
Referências
- SRAM/Zipp — How to Calculate Tire Pressure
- Hutchinson — Recommended Pressure (tubeless tables + max-pressure warning)
- Michelin USA — Bicycle Tire Pressure Guide (road + gravel/cx tables)
- ENVE — Hookless Rim Technology 101 (ETRTO pressure discussion)
- CADEX — Hookless Compatibility (72.5 psi / 5 bar max reference)
- BikeRadar — Gravel bike tyre pressure (front/rear examples by system weight)
- René Herse — Tire Pressure and Performance (hysteresis vs suspension losses)
- René Herse — Why we call it a Revolution (comfort/speed and vibration discussion)
- Sheldon Brown — On-Road Bicycle Wheel Repairs (pinch flat / snakebite mention)
- LiveAbout — What Is a Pinch Flat and How to Avoid One (definition and causes)
- Schwalbe — Aerothan (mentions snake bite testing and pinch-flat resistance)