I've just replaced my mountain bike tyres/tubes with new 26x1.50 city slicks. Max psi is 80 but my foot pump won't push more than 50 in. Is this because it's a schrader valve, or do you think my foot pump is past it. If it's the valve type is there any work around apart from bying presta tubes.
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1It's almost certainly your pump. I switch between two "floor pumps" -- the type where you stand on their "ears" and work the T handle up and down. One can easily get up to 100 psi (though getting to 80 seems to take forever) while the other very quickly works up to 60 or so and then runs out of steam. It has to do with the "compression ratio" of the pump cylinder. – Daniel R Hicks Sep 17 '16 at 17:24
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You say 'foot pump'. Could you upload a picture of the pump? I suspect that it is a pump meant for car tyres, the type with a single or twin short, large diameter cylinder. A bicycle floor pump typically has a thin long cylinder and is able to build up a much higher pressure than the other type. – Carel Sep 17 '16 at 20:11
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Do you have the same problem on the front AND the back wheel ? – Criggie Sep 17 '16 at 20:13
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its the same type as this. and yes its the same front and back.new tyres and tubes http://i63.tinypic.com/28ji92u.jpg – Martin Sep 17 '16 at 20:44
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@Martin: Those pumps are not meant to build up the pressure for bicycle tyres. Even if the manometer could indicate higher pressure the system will not build it up. Get a pump of this type: http://thesweethome.com/reviews/best-bike-pump/ – Carel Sep 18 '16 at 08:07
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@carel. Thank you. Borrowed my friends pump today, same type as you linked me to.pumped it up no problem. – Martin Sep 18 '16 at 18:49
6 Answers
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The valve isn't the limiting factor for the pressure -- you can go well above 80 psi with a Schrader valve.
If you're holding 50 PSI in the tire (the tire should feel a bit firm, but you can likely push it in a bit with your fingers), you shouldn't be leaking. I'd try depressing the core (pin in the center of the valve) a bit with a key/small screwdriver/finger nail to make sure its free and try pumping it up again.
If you're not holding the air in the tire, you either have a bad valve or a leak in the tube (in which case, get a new valve core/tube in the former case, and patch/get a new tube in the latter case and check the tire for damage).
Failing that, I'd try a different pump -- not all pumps are able to reach high enough pressures, but 50 psi is on the low end for the limit of a bicycle pump not specifically intended for low pressure situations like fat bikes (then again, a pump designed to do sports balls only needs to pump about 8-10 psi, so its possible). I'd try a floor pump like this one.
Batman
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Get a high quality pump is my advice. I've had a couple of £15 track pumps blow on me when getting up to 100psi, despite being well within the rating. I ended up buying a £50 Lezyne pump and have never looked back!
Adam B
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Batman has good suggestions.
I would add from my experience that when a pump seems to have a hard stopping point, like absolutely refusing more air or not letting me depress the handle, it's usually a problem somewhere between pump and tire valve, as a tire would probably keep going till it popped. Usually I haven't pushed the pump down far enough, or something similar which closes the valve.
Let us know what you discover.
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When you get up to a fairly high pressure, most of the pump stroke is spend simply getting the air in the pump cylinder up to the pressure of the air already in the tire. Until that happens, the one-way valve in the pump blocks any airflow (to keep the air from coming OUT of the tire). So it's not at all uncommon, with a standard "floor" pump, to have a situation where the only last inch or two of movement actually moves air. And sooner or later the pressure gets to the point where the piston in the pump simply can't go further, leaving an inch or so of "dead" air in the bottom of the pump. – Daniel R Hicks Sep 17 '16 at 17:28
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When it hits 50/54 I can put all my weight on the pump and it just springs back up refusing any more air. I'll borrow another pump to test. – Martin Sep 17 '16 at 18:24
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Two tricks for baulky pumps.
1) You can get a bit more air in by going hard on the pump at the end. Try for at least 3 full strokes per second, faster if you can. A minipump is easier than a long pump.
2) Go slower - Work on a steady stroke, but at the end do a quick hard ram to seat the plunger. This will force the pressurised air through the valve in the tyre.
You might want to look at servicing your pump, which means lubricating the plunger seal, or replacing the o ring if its worn or torn.
Criggie
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The pressure inside the tyre can never exceed the maximum pressure the pump can build up which is limited by the pump's piston minus the losses. Water doesn't run uphill even if you give it a long run-up. – Carel Sep 18 '16 at 10:45
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@Carel Try it and see. You're overlooking the timing factor, that it takes time for air to move about. – Criggie Sep 18 '16 at 20:03
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I have a cheap (6£ from Lidl) foot pump and pump my tires to 5 bar front and 6 bar rear without any problems. You can also test on the petrol station. They have those large compressors for car tires, but they can easily go over 50psi. When I'm away from home, or just feel very lazy I use them to pump my tires. Just choose the compressor without any electronics, those more "Intelligent" tend to have sometimes problems with pumping bike tires.
JTO
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@carel. Borrowed me friends pump today, same type your linked me to http://m.thesweethome.com/reviews/best-bike-pump/ pumped it up no problem. Many thanks for all advice and help guys. – Martin Sep 18 '16 at 19:03
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Luckily for you, it doesn't matter, because you do not need more than 50 psi in 1.75" tires; it's around perfect. For most of the summer, I rode my 1.75's 45 psi rear, 40 front. Currently running 50/45.
Refer to this table. The 1.75" thickness lands between 1.7 and 1.9; around 51 psi is the baseline recommended from both.
You probably want a little more in the rear and less in the front. You're close enough there.
The 80 psi stamped on the is the maximum, not the best pressure for optimal performance.
That said, it should be easy to get to 50 psi with your pump. If you're struggling to get there, there is some issue there.
One common source of frustrations is that the pin inside the pump's chuck (the part that you clamp on to the inner tube's valve) is not pressing down on the valve stem to open the valve. This is a problem with Schrader valves somewhat more than with Presta valves, because in addition to both types of valves being held in place by pressure, the Schrader valve stem is spring-loaded.
Many cheap pumps have a plastic valve pin inside the chuck. These plastic pins tend to get marred and deformed and stop pressing down on the pin properly. Before buying a bicycle pump, look inside the chuck and make sure it has a metal pin (such as brass).
When attaching the chuck to the valve, you must press firmly. The dial on the pressure gauge should jump to indicate the tire pressure (except when the tire is completely flat). You then know that the valve is open. At that point, flip the lever to clamp the chuck. If you clamp the chuck before the needle has moved, you're clamping it on with the valve still closed; it will be impossible to pump.
It's possible to half-assedly clamp the chuck onto a Schrader valve in such a way that the valve is somewhere between the fully open and closed situations. The chuck's pin is exerting some force on the valve stem, but not enough to keep it open; however, if enough effort is put into pumping air, then the valve opens due to the pump pressure, and air is forced into the tire. Effectively, the valve is then acting as an ad hoc pressure regulator! If you exceed the regulator's pressure (say 100 psi or whatever it happens to be, by dumb luck), then the valve opens slightly and lets air into the tire (where the pressure might be only, say, 40 psi at the moment). Then the valve closes unless you keep working hard to maintain that 100 psi). The result is that you're making a 100-psi-grade effort to get a tire from 40 to 50 psi. If your pump has a pressure gauge, you will see exactly how much pressure you're generating, from the swings of the needle. When the valve isn't opening, the gauge shows you the pump-side pressure, not the tire pressure. If you see the needle swinging well past 50 psi, you know that your pump is well capable of that; just the air is not getting through the chuck and valve, or not very easily.
Kaz
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The ideal pressures depend on riding conditions and load. You can use a lot lower tire pressure for a 120 lb rider on a 15 pound bike vs a 240 pound rider on a 30 pound bike (who would be running well over 50 psi on a 1.75 inch tire). The tables need a big asterisk to them for experimentation. – Batman Sep 21 '16 at 19:55
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@Batman I'm 170 pounds; I two days ago I got home just nicely on what turned out to be barely over 30 psi in the rear tire (fixed a flat at work, filled tube by finger feel without using any gauge, rode home). – Kaz Sep 21 '16 at 20:28