JohnAdams

I just got a new bike, used.

The tires say inflate to 110psi MAX, 7.5bar, but when I pump to 60, it already feels really hard to pump, I'm afraid they will pop. It was the pump at the bike shop so I don't think that is broken.
Should I try to get up to 90?

700x23C tires.

Thanks

10 Wheels

What brand are the tires?

keisatsu

if they are rated 110 then they'll go to 110, as long as they are mounted correctly.

Generally you won't want to run the tires at full pressure though, what pressure you like them at though will involve some experimentation on your part. Personally I run 100 psi up front and 105 rear.

I wouldn't run them at 60 psi, you run the risk of pinch flatting, 90 psi however sounds acceptable.

hamish5178

The first few pumps do always seem to be the ones that feel like they're doing the most.

JohnAdams

Thanks,

The brand is "Swallow" I think, that's what the tires are labeled. It seems hard to go past 60, they only go up like 3-5psi per pump after, they ride pretty well at 60, some roads are slightly bumpy here and it feels pretty rackety on the bike. I will try going up to 70 or 80 first I guess.

Kimmo 

Maybe the pump's gauge is out?

SBinNYC

You did not state what kind of pump nor how you measured the pressure. I would not suspect a 700c x 23 tire would feel hard at 60 psi. Either your gauge or your thumb needs to be recalibrated. You want to look for tire deflection, while you are riding. Deflection should not be more than 15% from the tire being unloaded, according to Frank Berto. www.bikequarterly.com/images/TireDrop.pdf

JohnAdams

lol'd @ thumb.

It was a guage on the pump at the shop. I'll try a different one, thanks guys.

FBinNY 

If the tire says 110psi max, it'll hold that much, plus have a safety margin above that. So you don't need to worry as long as they're seated properly.

OTOH- just because you can, doesn't mean you should pump to max pressure. Here's an article about optimum tire pressure that you can use as a guide to find a starting place for the ideal pressure for best overall performance.

BTW- actually reaching ideal pressure, say 90psi with a hand pump can be difficult. If you're struggling, consider buying a pump with a narrower cylinder, which will lower the arm strength needed to do the job (though you'll need more strokes).

Andy_K 

Were they labeled in German by any chance? Usually they say "Schwalbe" here in the U.S.

Anthropy

I cheat and use my air compressor with the regulator set to 100 psi. I do not hit it all at once, but give it quick bursts, until it is at full pressure. I use a hand held gauge to double check the settings. If I am airing up for the first time, I simply set the regulator to about 20.


Tom

Al1943

For high pressure road bike tires the pump needs to have a small diameter high pressure cylinder. If you are using a big bore pump used for large volume low pressure tires that would explain why the pump gets "hard" at 60 psi.

fietsbob

23 wide means less than an inch of air between the pothole and the rim,
hard tires roll easy.

MilitantPotato

Correct tire pressure depends on three things: Tire size, rider weight, and road conditions.

A heavy rider on narrow tires needs high PSI, on rough roads you need a very high PSI.

23C at 60psi, you'd need to weigh ~100lbs to have about the right pressure.

That PDF is a good starting place. There's a formula floating around that seems to be a great starting place for most people.

Over inflation (up to Max PSI ratings for tires) is fine for really, really smooth surfaces, but if you're not getting proper deflection you end up hopping over small road imperfections. Sucks for you, the bike, and eats up energy. Traction also tends to suffer.

TimeTravel_0

there's no need (or any desirable reason) to pump up to the maximum inflation.

here's the formula that seems to be a good starting place to find your optimal psi:

Tire Width=20: Pressure(psi) = (0.33 * Rider Weight in lbs) + 63.33
Tire Width=23: Pressure(psi) = (0.33 * Rider Weight in lbs) + 53.33
Tire Width=25: Pressure(psi) = (0.33 * Rider Weight in lbs) + 43.33
Tire Width=28: Pressure(psi) = (0.33 * Rider Weight in lbs) + 33.33

Tire Width=32: Pressure(psi) = (0.17 * Rider Weight in lbs) + 41.67
Tire Width=37: Pressure(psi) = (0.17 * Rider Weight in lbs) + 26.67


Example: You are 150lbs running 28's

Pressure (psi) = (0.33*150) +33.33 = 82.83psi (rear)
Front Pressure = .9*Rear Pressure = .9*82.83psi = 74.55psi front

As far as I know, this is for 700c.

Mr Pink57

^^ Thanks for the simplified formula, it is hard to see the chart without the grid showing up.

My recommended pressure for 38c tires is 67 front 61 rear the rear is fine the front is about 2lbs over max recommended tire inflation but from reading that article I should be fine, the rim is a MTN rim anyways so it is kinda wide.

Suburban Grind

TimeTravel_0:

^ How does your formula take into effect the weight of the bike, since it is part of the load the tire carries? Is there an assumed bike weight?

And does one use the "stated" tire carcass width, or an actual measured width (which with most racy tires seems to be at least a couple mm less than rated)?

I've found the thin tread on some of the better high pressure tires can be much more compliant, and the amount of deflection I can achieve with the thumb press bluffs me into thinking they're as much as 15-20 psi less than they actually turn out to be. Seems to depend on the model of tire, to me at least.

vintagebicycle

If your pump is hard to pump at 60psi, then maybe you need a better pump. First, I'd go find a reliable gauge and make sure your only at 60psi, if you are, then maybe you need new pump. I'd not worry as much about the tires popping as I would having one slip off the rim or having a low end or single wall rim fail.

TimeTravel_0

it's not my formula and I have no idea how to factor in bicycle weight. like I said, it's a starting point...not some sort of hard or exact calculation of what your psi should be. start with the formula results and adjust for what feels good / avoids pinch flats.