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I have a Giant hybrid (with 700x32c 65 PSI tires), stock tires, that I mainly ride on nice roads to and from work ~3.5 km/2.2 miles each way. I weigh 230 lbs/104 kg up from 200 lbs when I bought the bike sadly two years ago.

I check my tire pressure before I start riding again (If it's been more than 2 weeks) or every week. And I've put about 640 miles on the tires, but in that time I've had 3 blowouts.

That seems like a lot.

After doing a bit of reading it feels like my tires might be under inflated (I have a decent floor pump I use and I try to keep it right at 65 PSI) for the weight load (270 lbs/122 kg including bike), but I can't tell. I haven't measured displacement under load (I'll do that when I get a new inner tube) to see if it's above 15% or not, but I don't thing there's any tire or rim damage that would be poking the tube either.

How do I tell what's causing the frequent blow outs? Low tire pressure or too close to the limit? Or are my expectations wrong on how often they occur?

edit: Okay, I removed my back tire and inspected the tube and there's a small hole bigger than a pin prick around the size of a pin head. There also seems to be pitting/cracking on the inner tube (Forte 200x28-32C made in Taiwan 2012 37 03).
Leak point

This appears to be the puncture.

Tire puncture

Do I just have low quality inner tubes? I've just been having the bike shop I bought the bike at replace my tubes.

General guide for optimum tire pressure on a road/mountain bike

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  • 2
    Are you getting blow outs or punctures. Blow outs are sudden and catastrophic tire failure. Punctures are just a hole that that lets air out slowly.
    – mattnz
    Commented Feb 19, 2015 at 3:37
  • 2
    I weigh about 230 and run 700x35c Kevlar-belted tires. I typically inflate them to 100psi. Flats are incredibly rare. I'm guessing you have a problem such as a spoke end poking through. You need to determine where the holes are and look for whatever is making the holes.
    – Daniel R Hicks
    Commented Feb 19, 2015 at 3:48
  • They seemed halfway between. My tire was fine at work, but right as I left I felt like I slipped on a rock then a block later I felt it running flat.
    – Joshua Olson
    Commented Feb 19, 2015 at 4:07
  • Could just be cheap tires. Tires is one of the things most often skimped on, even when purchasing a high end bike. Most people buying a hybrid would not even stop to think about asking what kind of tires were on the bike. That isn't to insinuate anything negative about people who buy hybrids, I've bought one before myself. However, I think that many people who put any serious mileage on a bike will come to the conclusion that a road/touring/cyclocross bike is a much better option as the drop handle bars allow the ride to be a lot more comfortable due to enabling more hand positions.
    – Kibbee
    Commented Feb 19, 2015 at 14:04
  • @Kibbee, that's right, I've just changed from Schwalbe road cruiser to marathon plus and the max pressure is higher for the marathon plus. In my case I dropped a size as well, but the difference at 700x35c is 85 psi for the marathon plus vs. 65 for the road cruiser. I'm probably putting a similar amount of weight on the bike, maybe even slightly more, but back-heavy because some of that is baby+seat, right over the back wheel. On another note I've put about 5000 miles of city riding on my hybrid - I like to be able to look over cars and in stop-start traffic road drops aren't much use.
    – Chris H
    Commented Feb 19, 2015 at 15:25

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What do you mean halfway between? A blowout is bang and an instant flat. A blowout is not caused by under inflation.

Pinch flats is an indication of under inflation. You will see a slit on the side of the tube where it was pinched against the rim.

At your weight you should be at the tire maximum pressure. Get a quality pressure gauge. Pumps can be off.

If you can put larger tires on that bike the go that route. Large tires are less susceptible to pinch flats.

When you get a flat inspect the type of hole and it match up to the wheel and tire. When you take the tube off leave it same side up so you can lay it back on the tire / wheel and see what caused the flat. If you have debris in the tire you must remove it. If it is a spoke need to fix that.

OP posted a picture of the tube and it appears to be a puncture. I assume that is the bottom/outside of the tube (you are not twisting it). You need to get the debris out of the tire or you are going to keep getting puncture flats. If it is just small debris then it can take a few days to wear through before it flattens the new tube.

Also inspect the outside of your tire on a regular basis for debris. A piece of glass will eventually works it's way through (even a puncture resistant tire).

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  • It sounds like a fast puncture - not a blowout. But a bit odd. Switching to fatter tyres is certainly one option but they'd need to be good ones as you don't want the max pressure to drop (too much).
    – Chris H
    Commented Feb 19, 2015 at 15:20
  • I've posted a picture of my tube.
    – Joshua Olson
    Commented Feb 19, 2015 at 18:45
  • That looks like a puncture. I will update my answer.
    – paparazzo
    Commented Feb 19, 2015 at 18:55
  • Added a pic of the tire too.
    – Joshua Olson
    Commented Feb 19, 2015 at 20:09
  • But double sure that tiny hole does not have some tiny debris.
    – paparazzo
    Commented Feb 19, 2015 at 20:22
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Depending on your attentiveness while riding, the hazards in the area you ride in and a few other factors, that may be a reasonable amount of flats. I know a few commuters in my area that expect roughly a flat a week in their roughly 100 mile weekly commute. I've ridden with this particular pair of guys, however and found they have a tendency to shortcut through glass filled abandoned parking lots and the like, and they don't pick careful lines through that mess.

I will say this about flats, when you change a flat, you should always figure out why/how you got the flat. If you don't, you'll just get the same flat again. Pull the tube, keep it oriented, re-inflate it and figure out where the hole(s) are. There are articles out there telling you where to look based on the placement of your tube holes and their configuration. If you are getting repeated puncture flats from objects, you may consider switching to more puncture resistant tires. Keep in mind more expensive does not mean more durable. I've bought ultralight and expensive race tires before that didn't make it 13 miles around a loop before picking up 3 punctures from gravel that wasn't even that sharp. I ended up switching to a much heavier but more puncture resistant tire that was 30% cheaper and hasn't had any punctures since. I don't race, so that works fine for me.

If your awareness doesn't keep you out of glass patches and the like (or they are just unavoidable in your area, I am pointing at you Honolulu) and you get repeated puncture flats, you may also consider switching to a tubeless setup with juice in your tires to minimize the impact of these.

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  • I'm a pretty tame rider (at least since I've had this bike since I only use it for commuting) and it's all well paved areas, I pop down over curbs and the like, but that's about it.
    – Joshua Olson
    Commented Feb 19, 2015 at 18:44
  • So, based on the picture you just posted (which appears to be the outside|tire facing surface of the tube), did you find the hole in the tire or remove an object from it?
    – Deleted User
    Commented Feb 19, 2015 at 18:46
  • I had to inflate it to find the hole.
    – Joshua Olson
    Commented Feb 19, 2015 at 19:34
  • @solarmist Correct. You found the hole in the tube. Did you find the corresponding hole in the tire?
    – Deleted User
    Commented Feb 19, 2015 at 19:40
  • Okay, I think I found it. Just off the tread there's a slit that on the inside is just a tiny hole.
    – Joshua Olson
    Commented Feb 19, 2015 at 20:00

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