That's very interesting. My weight maxes out around 140 lbs, so by that formula I should run about 100 psi in a 23mm tire and 65 psi in a 32mm tire, whereas I actually run 100 psi and 80 psi respectively. I'm going to drop the pressure in the 32mm to about 70 psi (manufacturer's rated minimum is 65 psi), and see how it feels.

That math-amajjiger says I should inflate to just under 110. I typically go up to 120, both front and rear, and figure that after a day or two they are around 110. I start to feel really slow once they get down into the 90-95 range, but that could be do to a myriad of other factors.

I'm not a troll; I'm real! Okay, so since I posted this, I've not gotten another front flat, but did hit a pothole going real fast and blew out the back. I've changed it; so far so good. I do have rim tape on. I've inspected my rims and there are no areas where the tape has slipped or is missing. No debris whatsoever inside the tire or rims. I am using Giant tubes I got from JensonUSA.com. I have had flats though with other brands, including the $11 one I got at Performance Bikes (not my fav, but it's close.) These are not pinch flats nor do I think they are being caused by overinflation, based on the info given by you guys in this thread. I've found the little teeny-tiny holes in each used tube. No slash marks etc. I'm going to take it to the LBS asap, but it probably won't be til the end of the week. Thanks for your help.

PS it is now hard for me to tell how high I've inflated my tubes, because the tenpack of tubes I got from Jenson are 32mm valves (I need 60s). I've put on valve extenders, but my pump is a Schrader and the extenders are not threaded on the ends (bad news), so I have to jam a Schrader adapter on the ends of these things and pump for dear life, until they seem more or less full. The gauge on my pump is unresponsive with the extenders on. So I don't know if the streets in my city of Dayton, Ohio are just so crappy and potholed to hell / covered in glass that I'm experiencing a freakish number of flats or what. I might just go get some Cyclocross tires or something, but I love mine and want to keep them!

How old are your tires? When they get near the end of their life the rubber gets soft and thin and then it's easier to get a flat.

it's just a recommended range. That's how I use it.
some tires just don't have the same amount of flex or puncture/pinch resistance as others.

spend a little money on a good floor pump(not a walmart pump), inflate to 118, ride bike, be happy

this exact thing problem( front wheel as well) happend to my friend, it turns out there was a tiny nub of metal poking thru his rim tape that was puncturing all the tubes. we lined the rim with cloth tape (some random sports tape i had lying around) and its been fine ever since

+1 Most 700 x 23 or 25 tires you can take to 110-120 psi no sweat. If you are a big guy, inflate to 90-100. Gauges on most floor pumps aren't that accurate, use a good tire pressure gauge instead; at least to "calibrate" your floor pump.

More likely to get pinch flats from underinflated tires. Also, debris like tiny glass shards or pieces of wire are more likely to stick into an underinflated tire.

OP, take the tire off the rim, flip it inside out and CAREFULLY go over it to see if you've got a piece of glass or metal embedded in the tire. Easiest way is to note where the hole in the tube is and that'll tell you where to look on the tire.

Sometimes, a tiny burr in the rim tape will cause a flat even though to look at it you'd swear it couldn't happen. Replacing the rim tape in a case like yours will more than likely solve the problem.

Valve hole in the rim of the wheel sometimes has a burr in it that'll cut the stem and cause a flat. Or getting too rough with the stem when airing up the tire will cause a leak where the stem is glued to the tube.

It has been my experience that carrying a spare tube, patch kit and tire levers will persuade the flat tires to go bother someone else less prepared.

New signature.

Ok I just want to chime in here because I've been having mystery flats on my front wheel -- v. slow leak -- held the tube under water, ran a cue-tip along the inside of the rim, checked the rim tape, all that, and nothing. Then, one day, voila, no slow leak for about a week and a half. Then the other day I was messing around doing a lot of skidding and whips and then... slow leak is back. Thoughts?

Also, I've got an awesome the Topeak Road Morph Pump. It fits easily in my bag, has a flexible tube attached to the nozzle so you don't mess up the stem, a gauge, a fold-out thingy on the base to step on, and, with a bit of muscle, it gets me up to 110-120 without fail. Pretty effin sweet.

Honestly, probably just replace the tube and forget about it. It's possible that something shifted and plugged up the leak for a while, but now that you know there's an issue you might as well replace it.

Those pumps are some of the best on the market also.



There, that's all the positivity you'll see out of me for a year or so.

Yay!

Thing is (forgot to mention this) I've already replaced the tube twice. And patched places that look even slightly sketchy. Whatevs -- done all the regular checks and tests, and at this point it's impossible for anyone to know what's going on without checking it out. Probably the only thing left to do is suck it up, take it down to the LBS, ask them to fix it -- and to show me what they fixed. Then I'll be maybe a little smarter. That'd be nice.

this was what I did when I had a mystery slow leak. I pulled the tire and tube off of the wheel, but kept them oriented the same way (so each part of the tube would correspond to one part of the tire, and one part of the wheel.) Then after finding the leak, i matched up the puncture to the corresponding part of the wheel and tire, and scrutinized that.
Turns out I had a tiny little sliver of metal that was embedded inside the tire, but not long enough to see and feel. I guess when I pumped up the tube, after riding a bit, the sliver would rear its ugly head and prick the tube ever so slightly before working its way back into the tire.

+1

I weigh just about 200lbs and it surprises to sometimes see people inflating to the same pressures I do but they weigh a lot less than me. I use the recommended pressure from that chart and I don't get pinch flats. The last time I had a pinch flat was when I hit a bad pot hole at 35+ mph

I'm curious how the ride feels when one inflates to the same pressures as someone, perhaps, 50 lbs heavier compared to what the chart would have them at.

Faster.

Elaborate.

It would feel faster.

JK I dunno. You've got 2465 posts so I'm thinking you know the answer.

Less rolling resistance. As long as you avoid sliding out or blowing out a tire, aside from having a slightly harsher ride you're only going to benefit from having less tire touching the ground.

It's the reason people use high-pressure, thin tires on road bikes in the first place, as opposed to a hybrid tire for instance.

So then what's the point of that crazy formula then? Seems like we're back to inflate-to-max.

And around we go...

I know it feels faster because it may have less rolling resistance, I once pumped to 145 just because. I think it will just make the ride feel rough because the tire won't conform to the shape of the road and grit as well as it would at lower pressure (I have an image in my head of the wheel just bouncing over every pebble). A tire that does not deform to the shape of the road surface loses traction. How much until things get a little risky, I don't know.

Oh yeah. Hmmm... does that mean that with enough pressure the bike will start to float? ;)

The "crazy formula" is for comfort and traction as well as avoiding pinch flats, not for overall rolling resistance.

Here's another thought: do you have thorns? They're all over the place in Denver, and are responsible for a ton of nasty flats. I learned pretty quickly that it's important to rub down the tires before installing new tubes, since if the thorns are still stuck in the tires, the next tube will be a goner.