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I purchased a new bicycle and I'm confused about the tire pressure. The guy at the bicycle shop told me to inflate to at least 100psi.

However the bicycle itself has the words 'Maximum inflation - 65 PSI'

The bicycle is a Giant Escape. I can't remember if they called it a commuter bicycle or a road cruiser (it doesn't have the drop style handlebars). The tire itself is a 'Giant S-X3, 700x32' and it says '32-622'

I rode the bicycle at 65 psi and, while I'm new, it felt kind of low to me. I wasn't hitting the rim or anything extreme like that; I just prefer a stiffer ride - but I'm afraid to go past what the tire has printed on it.

Can anyone tell me what I should be inflating my tire to? I'm ~175 pounds if that matters, most of the sites I've found on the topic give recommendations based on weight. Still, I'm worried about damaging the tire or rim.

I will be doing 100% street riding.

Thank you

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I would say you should be running about 80-90 PSI. A good quality 700x32 should be able to handle that with no problem. I don't know why road tires often have such low sidewall pressures listed -- either they're poor quality or they're pretending to be off-road tires. –  Daniel R Hicks Jul 29 '12 at 2:15
    
@DanielRHicks, or the tire manufacturer's counsel decided that they're more likely to be sued for a single blowout during a heat wave than for umpteen pinch flats. –  Mike Samuel Jul 31 '12 at 18:32
    
What kind of tire is this?? –  joelmdev Aug 4 '12 at 22:53
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See Related Question. Possible duplicate. bicycles.stackexchange.com/questions/2744/… –  Benzo Aug 6 '12 at 14:23
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4 Answers

up vote 4 down vote accepted

2 major things to consider when deciding what PSI to run your tires are the rims and the tire itself. Most tires can handle higher tire pressure than what is printed on them but are "guaranteed" to handle the PSI printed on the sidewall. If you are buying quality tires, you have a better chance of pumping them higher with out blowing them out. Coming back to the rims, just because the tire can handle the PSI doesn't mean the rim can. I am going to assume you have aluminum rims, and unless they are POS, they should be able to handle higher pressure. I found that the tire's printed PSI is sometimes higher than the rim's capabilities when I used to ride nylon mag wheels back in the old days. I bought a 100psi rated tire and it kept blowing off the rim. That was when I decided to switch to spoked rims.

There is a good chance you will be able to ride at higher PSI, just be aware that there is no guarantee past the printed PSI.

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"when I used to ride nylon mag wheels". Non metal rims don't shed heat well. Did they blow out on long windy descents where you were braking round turns? If your rims can't shed heat, then they heat up the air inside the tire which raises the pressure and can lead to blowouts. A buddy of mine who used rim breaks solely on his touring tandem put heat sensitive dots on his rims so he could tell when they were heating up. On long descents, he got in the habit of stopping periodically to let the rims cool. I do the same on my touring single since I'm heavy and a slow descender. –  Mike Samuel Jul 31 '12 at 18:39
    
No, they would just blow out soon after pumping them. Even after pumping them up to 20psi, spinning them to check the seat, pump to 40, check, pump to 60, check. I'd ride a few blocks and BANG!! The mags were heavy and too flexible, after going with spokes I never looked back. Tires stay on, breaks work better... –  BillyNair Jul 31 '12 at 22:25
    
Odd. I suppose parts that fail close to home are better in some ways than ones that don't fail until you're riding aggressively. –  Mike Samuel Aug 1 '12 at 1:00
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I don't know what kind of tires you're running, but 65PSI is a really low maximum pressure for a 700x32 tire. I wouldn't exceed it if I were you. I'd probably throw them out and get a pair of tires that are a little more confidence inspiring.

Tire pressure is more of an art than a science (even moreso with mountain bike tires), and much of it is going to come down to preference. The skinnier the tire, the higher the pressure. The bigger the rider, the higher the pressure. To a lesser extent, the higher the TPI (threads per inch), the higher the pressure. There is a sweet spot between the min and max pressures, and it depends on the mentioned factors and more, and each rider just has to feel it out for themselves. That said, Michelin has a chart that can provide a decent starting point for road tires and you can go up or down from there as you please. Keep in mind they've designed this around their own tires, and ultimately other reputable sources probably have other opinions on the matter. enter image description here
In Michelin's words:

Just as with your car tires, proper inflation pressure is very important to how your bicycle tires perform and last. And as with car tires, the most important variable that affects what the proper pressure should be is the load your tires are asked to carry.Thanks to more than a century of tire technology research, Michelin engineers have found that there's a certain amount of deflection in the tire profile that's optimal for balancing grip, efficiency, comfort and durability. That deflection is based on the tire's construction and the weight of the rider. Obviously, your style of riding can have an effect too, but the chart below should give you a reasonable guide of where to start when experimenting to find the proper tire pressure for you.


There are a few related interesting tidbits at Michelin's site.

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Ride the tire at anything under the 65psi listed by the manufacturer unless the loaded bike (with you on it) deforms the tire more than 15% of the tire height or you experience bottoming-out on the rim that causes a flat. There's no need for a rock-hard tire unless you like to be rattled to pieces. Higher-pressures will not make a bike tire roll faster. (Likewise, narrower tires will not make you go faster.)

Detailed info:

Ideal tire pressure has a great deal to do with tire width and the bike rider's weight which might also include anything sizeable that might be carried on the bike (backpack, panniers, luggage, heavy items on a bike rack or basket).

Narrow tires require quite high pressures and have a smaller adjustment range for various rider weights. Wide tires, conversely, do not need high pressures for an ideal balance of speed and comfort. "Inflating tires to the maximum pressure recommended by the manufacturer tends to underinflate narrow tires and to overinflate wide tires."*

Folks often overinflate their tires thinking that they'll go much faster and somehow have less drag, when all it really does is provide a harsher ride. Pick a pressure that allows some deformity to the tire (about 15% horizontal drop in the height of the tire if you want to be really fussy) when you are in loaded/riding position. Enough pressure to prevent the tire from bottoming out or causing pinch flats. (Generally, old tires that are worn thin or improper/lack of rimstrip is often a more common cause of those types of flats.)

Some very thorough independent testing resulted in saying "with great certainy that increasing your tire pressure (beyond a certain point) does not make your bike faster on road surfaces that range from very rough to very smooth. In fact, on very rough road surfaces, higher pressures are a lot slower than lower pressures, because the suspension losses are so great. On most surfaces, tire pressure (beyond a certain point) simply doesn’t make a difference in speed." https://janheine.wordpress.com/2010/10/18/science-and-bicycles-1-tires-and-pressure/

*This and other technical details provided by a Bicycle Quarterly Article: http://www.bikequarterly.com/images/TireDrop.pdf

Don't ride around on rock-hard tires - unless you absolutely must because your tires are too skinny and/or your load is too large. Many people would be better off riding much larger, better quality tires with supple casings.

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I would go with what is printed on the tires. Perhaps a bit more if you think the tires feel too squishy. If you use too much pressure, it's not good for the tires. It depends on the type of bike you are used to riding, but if you are used to riding a road bike, the 700x32 tires will feel squishier than what you're used to. But that's, ok. It's a commuter bike, and this will make the ride a bit more comfortable in exchange for a little lost speed. It sounds like the guy at the bike store doesn't know what he's talking about, as I've never seen a 700x32 tire that requires 100 psi. Also a good rule of thumb is to try and look at the tires as you are riding. If they don't deform much when riding on smooth pavement, they probably have enough pressure.

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I run my 700x35s at 100 psi. –  Daniel R Hicks Jul 29 '12 at 2:13
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