# I've been biking around at 55 psi...



## z3phrn (Mar 19, 2011)

I've been using a mini frame pump for the past 3 years to inflate my tires (using the old "feel if it's full enough" method) and was quite shocked to realize that they were only around 55psi when I got my first full-sized floor pump yesterday. I guess I just haven't had many problems with flats since I started using conti gatorskins & 4000s', so I suppose it's time to inflate the tires to proper psi. Me + bike weighs around 170 lbs, so I think 90 psi should do it? Is there anything I should watch out for (besides a really, really bumpy couple of weeks of adjusting to the newfound rigidity)?


I feel like an idiot.


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## sometimerider (Sep 21, 2007)

What size tires? What model pump? (Gauges on consumer pumps aren't renowned for their accuracy.)

This page, assuming you weigh about 145, says you can use 90 psi if your tires are 25C or larger.


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## z3phrn (Mar 19, 2011)

I got this one, it seemed legit:
http://www.amazon.com/Serfas-TCPG-Bicycle-Floor-Pump/dp/B001MK3GFS/ref=zg_bs_16062031_1

As for tires, I'm running 700*23. I'm just afraid the tire is going to explode or something if I put in more. Too bad I don't have a spare tube to see what the max psi rating is. 

I'm mostly just wondering what correctly inflated tires affords me. I read up on Sheldon's: 
http://www.sheldonbrown.com/tires.html#pressure 
Having lowered rolling resistance obviously makes sense; is there some formula that describes this w.r.t. moving speed?
Also, I'm not sure how it affects cornering at high speeds... does it get better or worse (since it seems like the tire would have less traction)? 

Thanks.


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## sometimerider (Sep 21, 2007)

z3phrn said:


> I got this one, it seemed legit:
> http://www.amazon.com/Serfas-TCPG-Bicycle-Floor-Pump/dp/B001MK3GFS/ref=zg_bs_16062031_1
> 
> As for tires, I'm running 700*23. I'm just afraid the tire is going to explode or something if I put in more. Too bad I don't have a spare tube to see what the max psi rating is.
> ...


I don't know anything about Serfas pumps, but there's probably plenty of online reviews of it.

The tire isn't going to explode - assuming you don't greatly exceed the max. pressure speced on the sidewall. (And assuming you install tire and tube properly and don't leave any of the tube outside the confines of the tire.) BTW, if the tube explodes, usually the tire is also fatally damaged.

There's all kinds of discussion (and disagreement) of what "proper" tire pressure should be. On this site, it's mostly in the "Wheels and Tires" forum. It all relates to flat prevention, ride quality, efficiency, and handling.

I'm no expert, but think that cornering will be poor if under-inflated (could even roll the tire off the rim) or over-inflated (hard tires can chatter over rough surfaces - loss of traction). You need to find a nice moderate pressure.


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## wim (Feb 28, 2005)

z3phrn said:


> I feel like an idiot.


I wouldn't, it's not that big a deal. Myself + bike weigh about 165 lbs. and I ride around with 70 psi rear / 60 psi front in my 700x23 tires all the time. Granted, before I join a "competitive" group of riders, I up the pressure to the 90s to, so I think, keep from getting dropped. The harder tires make me feel faster, but I doubt if that's actually true to any meaningful degree.


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## PJ352 (Dec 5, 2007)

My advice is to reference the guide that sometimerider linked to as a starting point and experiment with pressures from there. Your optimal pressures will depend on a number of factors such as road conditions and style of riding, but don't over think this. As wim mentioned, I've done myself and you've experienced, riding at _somewhat_ lower PSI's isn't detrimental.

And get a few spare tubes, patch kits, etc. Flats DO happen.


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## Mr. Versatile (Nov 24, 2005)

The maximum recommended pressure for 700x23 tires is usually around 120#. Over that & you're taking your chances. If you have your tires at max pressure all the time you'll not only be uncomfortable from the very harsh ride, but your bike will actually have more roll resistance.
No road surface is perfectly smooth. When a very hard tire rolls over the imperfect surface the tire bounces up & down. This takes energy from forward movement. Slightly softer tires will absorb the imperfections in the road, giving a smoother ride and more traction. Tires absorbing imperfections also take energy away from forward motion. When the tires are rock hard It takes more energy for them to move vertically, taking the bike & you with them than it does for the tires to absorb the bumps.
There isn't any magic, optimum inflation number. In general small, light guys can use lower pressure. Heavier riders need higher pressures. If you ride with the pressure too low for you, snakebite flats can occur. A snake bite flat happens when you ride over a sharp edged bump like railroad tracks or a chuck hole. The tire will deform enough so the tire & tube is pushed sharply against the rim. When you get home & look at the tube there'll be 2 small holes in it directly across from each other.
You'll just have to experiment to find the optimum pressure for you. I tell these facts to club members & others with whom I ride, but they tend not to believe it. There are riders who weigh 150-160# that ride around with their tires at #140 psi. It's just really a shame when science contradicts tradition.


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## z3phrn (Mar 19, 2011)

Mr. Versatile said:


> The maximum recommended pressure for 700x23 tires is usually around 120#. Over that & you're taking your chances. If you have your tires at max pressure all the time you'll not only be uncomfortable from the very harsh ride, but your bike will actually have more roll resistance.
> No road surface is perfectly smooth. When a very hard tire rolls over the imperfect surface the tire bounces up & down. This takes energy from forward movement. Slightly softer tires will absorb the imperfections in the road, giving a smoother ride and more traction. Tires absorbing imperfections also take energy away from forward motion. When the tires are rock hard It takes more energy for them to move vertically, taking the bike & you with them than it does for the tires to absorb the bumps.
> There isn't any magic, optimum inflation number. In general small, light guys can use lower pressure. Heavier riders need higher pressures. If you ride with the pressure too low for you, snakebite flats can occur. A snake bite flat happens when you ride over a sharp edged bump like railroad tracks or a chuck hole. The tire will deform enough so the tire & tube is pushed sharply against the rim. When you get home & look at the tube there'll be 2 small holes in it directly across from each other.
> You'll just have to experiment to find the optimum pressure for you. I tell these facts to club members & others with whom I ride, but they tend not to believe it. There are riders who weigh 150-160# that ride around with their tires at #140 psi. It's just really a shame when science contradicts tradition.


Thanks for the tips! I set my tires to 90 and took it out for a good 70 miles. I could definitely feel the difference (compared to 55psi) in tire rigidity and rolling resistance. It feels like I went at least 5-10% faster on flats. Couldn't tell for sure since the gps died halfway thru, bummer. I've still got to get used to the bumpiness though, it ripped off all my weight bench callouses on my hands... it's going to be a painful day tomorrow when I try to do a deadlift lol.


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## Slow Ride (Jul 10, 2008)

So far this season been riding 60 psi front and back, velocity aerohead rims, 25c Continental tires. A Gatorskin in back flexes less than a GP4000, so capable of lower pressure. Ditto for GP 4 Season up front. 185 pounds body weight. My disclaimer is So Far. Don't know if it will be that way all season, but working for now. Point is it is possible to run low pressure and be OK, but certainly need to be more diligent of potholes.


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## tihsepa (Nov 27, 2008)

tires are not meant to work as suspension. You are going to have a problem someday. I hope its not bad like rolling a front in a corner. 
The bottom line. Your doing it wrong. 55-60 is way too low for a 23 or 25 tire.


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## AndrwSwitch (May 28, 2009)

I like my 23mm tires at 80 and 95 front and back. I'm about 155 lb right now, so dressed and with the bike, that's probably about 185.

I think 90 is higher than you need. The faster feeling can be deceptive - lower speeds will feel harsher too.

The other thing that can be deceptive is the pressure reading on your pump. That's the pressure in the pump, which also has volume. If you've been using it to inflate a tire, the pump and tire pressures should be equal, but if you've just hooked it up, depending on the pump, sometimes air from the tire has escaped into the pump, so both have a lower pressure than the tire did before, even if it's higher than atmospheric pressure.

Anyway, a floor pump with a gauge is nice because it makes it a lot easier to repeat experiments with pressure, and then consistently use "your" pressure once you figure out what it is.


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## Mr. Versatile (Nov 24, 2005)

z3phrn said:


> Thanks for the tips! I set my tires to 90 and took it out for a good 70 miles. I could definitely feel the difference (compared to 55psi) in tire rigidity and rolling resistance. It feels like I went at least 5-10% faster on flats. Couldn't tell for sure since the gps died halfway thru, bummer. I've still got to get used to the bumpiness though, it ripped off all my weight bench callouses on my hands... it's going to be a painful day tomorrow when I try to do a deadlift lol.


Are you riding with gloves? I always use these:http://shop.spencocycling.com/p-18-rip-it.aspx
They have gel padding & are very easy to take off/put on. The last me about 3 years riding between 5-6,000 mi. per year. Find them on Ebay.


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