Calla lily

I put some Continental grand prix 4000s ii 28mm on my bike and I can not pump them any higher than 70psi. I have a cheap high volume floor pump that says up to 100psi. I have also tried my Nashbar mini pump, and with either, they won't go above 70psi. Neither of these pumps have a gauge so I'm checking with a Nashbar Dial Tire gauge. I checked the gauge in case it's off on my car tires and at least the schrader is accurate. I don't think I need that much more pressure in the tires, I was thinking 80/85, so getting to 70 with the mini pump I think would be fine if out on the road, but is it the floor pump that just sucks? Or what?

Fyi, I had my husband try and he also couldn't pump them any higher, and considering I put those tires on myself (which was very, very frustrating), I don't think it's a question of strength.

SkyDog75

Your pump probably doesn't suck, but it's the wrong pump for the job. It's difficult to achieve high pressure with a high volume pump.

High volume pumps have a wider diameter plunger and bigger chamber so they can move more air into a high volume tire like a mountain bike tire. They're great for pumping up big tires in fewer strokes, but those tires are typically run at low pressures. When pumping up a tire to a higher pressure, it can takes a lot of 'oomph' to push that bigger plunger hard enough to overcome the pressure in the tire.

The bigger the plunger in the pump, the more surface area it presents. And pressure being measured in pounds per square inch, the more square inches the plunger presents, the more pounds it's gonna take to push it.

As for the pressure rating of the pump... It might technically be capable of pushing 100 psi with a high volume pump ...if Hercules is doing the pumping.

Mini pumps are also difficult to get to high pressure, but for a different reason. With a floor pump, you can use your body and arms to press against the ground. You can get a lot of leverage that way. With most mini pumps, though, you're using one arm against the other. Some mini pumps like the Topeak Morph series have a small hose and foot pedal so you're basically using them like a small floor pump and it's a lot easier to achieve high pressure with these.

So to get to the point... I hate telling anyone to spend any money, but you should really spring for a decent high pressure floor pump. Decent ones start in the $20-40 range: Nashbar White/Orange/Earl Grey, Topeak Joe Blow, Blackburn Airtower 3, Giant Control Tower 3, Park Tool PFP-8, Lezyne Sport Drive...

italktocats

ride to a gas station?

Shimagnolo

https://www.amazon.com/Decker-ASI300.../dp/B000IE0YIQ

Set dial to air pressure desired; Turn it on; It shuts off when pressure is reached.
Note you will need to use an adapter if you have presta valves.

speedy25

If you want a pump that easily handles higher pressures get a Joe Blow Sport. I bought one and liked it so much I got another. Works very well with presta and shrader and I have had no problems at all with the chuck. I cant say that for other higher priced pumps I have come across over the years.

-SP

1nterceptor

Maximum PSI for that size and model is 115; I think 70 PSI might be a tad too low:
continental bicycle Grand Prix 4000 S II

I agree with the suggestion that a new high pressure pump(home & carry) should
be added to your collection.

cyccommute 

I suspect that it's a question of technique and strength. I often see people pumping tires with a floor pump wrong. They often push down on the piston until than feel resistance and then pull up. You really have to bottom the pump piston out to get the air into the tire. Otherwise you are just compressing the air but not getting it into the tube.

You may also be underestimating just how much force is needed to put 100 psi into a tire. The piston on the pump is about a square inch which means you have to put 100 lb of force on it to get the air into the tire. For a woman, that may be a significant percentage of your body weight and, as your body weight distribution isn't the same as a man's, that could be difficult. Even for guys, 100 psi requires quite a bit of effort.

There is also the problem of checking the air with a gauge. If you don't make the seal between the valve and the gauge properly, you can lose a lot of air during the check. Road bike tires don't have much volume to begin with and even losing a little bit of air can have a big impact on the pressure.

Cheap (or bad) pumps don't make the job any easier. A good floor pump with a gauge doesn't cost that much. A Leznye Steel is a pretty good pump for about $60 at REI. They also have the Topeak Joe Blow Sport for $50. I own both and find them to be good pumps. You might be able to find a better price on-line.

dabac

What is it that's keeping you from reaching higher pressures?
A pump connected to a tube/tire isn't an overly complicated system.
When you depress the plunger, the pressure has to go somewhere.

Either the operator is unable to depress the plunger fully.
Or the pump is burping/leaking pressure once you reach some threshold value.
Both should be noticeable by the operator.

Calla lily

Thanks. I went and bought a high pressure pump (from Walmart because I need it by tomorrow) and was easily able to get them to 90/100 (which may be higher than I want/need). I know 70 is low but should work to get me home I would think. Although based on how hard it was to get these tires on, if I get a flat on the road, I would rather walk or call for a ride.

SkyDog75

I agree in concept, but she's got a high volume floor pump, whose bigger barrel changes the math. A high pressure pump might have a one square inch plunger. For comparison, Zefal's high volume pump has a 1.75" barrel, which means the face of the plunger is about 2.4 square inches. Using a pump with a one square inch plunger, it would take 100 pounds of force on the pump handle to put air in the tire at 100 psi. With a 2.4 square inch plunger, it would take 240 pounds.

fietsbob

Try a pump at the Bike Shop, If it works better, Buy it..

You have a small volume tire needing higher pressure. you need to put in more work to get the compression high enough to be greater

than the pressure already in the tire-tube ... a Long stroke smaller diameter pump may get you up to pressure sooner..

berner

I weigh 157 pounds and for a 28mm Conti Gatorskin on the front I pump it up to 60 PSI and sometimes a bit more. The rear tire is 29.5mm and is Pumped to 70 PSI. I generally use the lowest pressure I can get away with. If I use higher PSI I don't go any faster.

jdw777

and I thought I was done with accessories for awhile... I like it, makes a daily pressure check/adjust easy.

I'm assuming you have one, how long have you had it?

Peace o/

Canker

70psi would be low on 23mm but not 28s. The whole point of running wider tires is you can run lower pressure and get a smoother ride. Running 28mms at 100psi defeats the whole purpose of riding 28s well unless you are rather heavy.

Shimagnolo

I've had it for years; I don't remember when I bought it.
Never had any trouble with it.
One nice thing about not having a tank (unlike most compressors) is that it is usable immediately;
No need to wait for a tank to come up to pressure.

Only gripes are: The air hose and AC cords are rather short.
I wish they would have used detachable connectors for both, so I could put longer ones on it.

Calla lily

Thanks. I actually replaced a wider tire (the stock 40mm on my Salsa Vaya) with these to train for a century on. I have no experience with tires narrower than 40mm. I was thinking 70 is too low and after a short ride today, 100 is probably too high. I'm going to lower them some. Do you take into account the weight of the bike. The Vaya isn't exactly light.

WizardOfBoz

I agree with the point about technique and body weight. If you can see the gauge as you are pumping, you should see the needle go up above 100 as you pump, and you should "bottom out", or be close to it. That is, you don't stop the stroke until you physically can't push the thing down anymore. The mechanics of the pump should stop your stroke, not air pressure. If you are stopping before that, you are getting less than the highest pressure possible from your pump. If you are "bottoming out" and the needle on the gauge only is going to 70 psi, that's an issue with the pump (likely the piston seals or the check valve).

FWIW, I weight 240 and was a defensive end in college, and I really have to graunch down on the pump handle to get 116psi (which is the limit for my 26mm wide tires). I use a Park PFP-8. For me, a great pump. But it's pretty high volume. Depending upon your size/strength/weight and fitness level, you may want a smaller diameter floor pump to make higher pressures easier.