ganchan

I have a cruiser with 2.125-inch balloon tires which are rated for around 45 to 65 psi, as I recall. I tend to run them in the upper 40s; I check the pressure once a week and they've usually dropped to 40, so a couple of pumps from my floor pump and they're OK again. The problem is with my front tire. It reads 40, I give it the usual amount of air, and the gauge pressure reads...40. I'm afraid to keep pumping, because who knows how much I might end up over-inflating the thing if it's just the reading that's off. The rear tire pumps up to 48 or so as usual, so I'm thinking that the problem isn't with the pump. On the other hand, the front tire never seems to go unnaturally low; it still feels firm, for whatever that's worth, so it can't be dropping significantly below 40 during the week....

Thoughts, theories or recommendations? Something going on in the stem, maybe?

Wilfred Laurier

The guages built into floor pumps are usually not considered very accurate. If you know that you were getting air into the tire, and the pressure didn't change, then I would say almost certainly that your's doesn't work for spit.

Go to a hardware store, bike shop, or auto parts store and get a separate pressure guage. Just make sure it reads into the pressure range you want to achieve (up to ~65 psi).

ganchan

Do you have a particular preference among gauge types (pencil-style, round, digital readout, etc)?

Wilfred Laurier

I prefer the round ones. I think most of the pencil style ones have too low a pressure range for bicycle use. The only ones I have had bad luck with are digital ones. Bike shops usually have nifty ones that read up to high pressures and work with both presta and schrader valves, although that feature might not be too useful for you.

cny-bikeman

Give it a few more strokes - the tire is not going to blow off, after all. If air is not going in it will quickly become very hard to pump. If air is going in and the needle stays at 40 then there has to be something wrong with the valve or the way you have the inflator chuck mounted on it.

fietsbob

You can buy new floor pumps, now they out the dial gage on top if the pump shaft rather than at the base.

gyozadude

My theory? Valve stem insertion. Most likely, cruiser tires are using schrader valves. The insertion of the pump head onto the valve is important for proper tire pressure readings. Probably the rear tire has a center valve tip that is a hair more proud than the front, so the pump head center pin will depress it properly and give you good pressure readings. Most likely, the front is more depressed and you don't get good depression. If the pumping gets very hard and hits like 80 to 100 psi with little air going in, then the center pin on the valve isn't depressed at all. If it's slightly depressed, then air goes in slowly, but the valve shuts on backstrokes slightly even if there is a check valve in your pump. Situations vary.

Simply solution: put the chuck on deeply and securely over a schrader valve. Also, write the manufacturers and demand a metal center pin for schrader pump heads. The plastic ones supplied by most manufacturers pretty much guarantees that after a few uses, 80% of the newbies will put it on wrong because it wears in the pump head and now you really gotta mount the head over the valve good. And the secondary problem is if you mount it deeply enough, you now risk scraping knuckles on the spokes when detaching, and/or wiggling the valve stem too much and causing a flat due to tube damage at the valve stem base. I get better performance from an old Kmart metal barrel pump with old-school pump head for most schrader applications (my Dad bought it in the day - has leather washers in it and still works - go figure). Newer pumps are all disappointing. But that's more reason to ride presta valves, I guess. Still, something so simple as $0.15 could solve many problems (for newbies). But again, if you don't care about newbies pumping tires, well, not a problem. :-)