PapaGanoosh

I have an old silca pista pump and it seems to be stuck at 10 psi. I was wondering if there is any way to zero the gauge and adjust so it is more accurate? There seems to be two screws at the back, but when I tried twisting them it doesn't do anything to the needle, does anyone know what these screws are supposed to do?

Here are pictures of my gauge:

Mark Kelly 

Prise the face off the dial. Pull the needle off the spindle, pulling straight up. Move the needle to zero. Press the needle back onto the spindle. Bourdon tube gauges are fairly linear, so don't bother about re-calibrating.

Caveat: I've never had to do this to a Silca, but I've done it to many many pressure gauges in breweries and wineries.

PS the two scews hold the outer bits onto the working parts of the dial.

PPS If you don't like such cowboy methods, air pressure gauges are made in their thousands by companies such as SMC and Festo for industrial pneumatics.

Zef

I recently pulled the gauge off my 25ish year old silca pista pump because I got tired of viewing the gauge backwards as it aligns backwards to where the hose comes out. I could not fix my problem unless I put a washer/spacer on the threaded part that connects the gauge to the pump and it did not seem like that would leave much thread to engage so I left as is...if I could live with it for 25years I could live with it somemore. I noted the screws you mentioned and they seem to just secure the guage to the outer housing...keeps it from rattling around inside.

Unfortunately I don't think there is a way to fix this except installing a replacement gauge or cracking the housing open to inspect for a way to zero or move/bend the needle.

Other than it bothering you, it should be of little consequence if the gauge is reading accurately when you inflate something. Not very many things in our life that require inflating are inflated to less than 10psi and even less around that pressure need any sort of accuracy...and those that do would probably require a pump with a gauge that had smaller increments of measure.

If you have another gauge or can borrow one, inflate to various bike tire operating pressures and compare the readings. If they check out then try to get past the zero error...if not then replace.

-j

PapaGanoosh

Thanks for the reply Mark. Sorry if this is a dumb question, but when you say pull the needle off the spindle, do you mean pull up on the white needle along with the attached rod in the middle like in this picture (I'm only assuming it is going to look like this):



or am I trying to pull up on the white needle only leaving the rod in place and realigning the needle without pulling the rod out?

fietsbob

You got it loose from the pump, put a new gage on. Silca sells parts. thru usual distribution

dsbrantjr

That gauge looks like it has a standard pipe thread. If you don't want to get replacement parts from Silca, you can get dozens of types of gauges from EBay, cheaply. If you need a different pressure range, units or bigger dial you can get it as well.

As for your current gauge, you probably want to try and remove the pointer from the axle and relocate it to re-zero it. I'd suggest pulling up the pointer with needle-nose pliers while pushing the axle down with a nail or similar item, so as to not put strain on the internal works of the gauge.

Looigi

Yep. I've done this too, but I confirmed against another gauge/pump to be sure. It's always worked. Of course if it's just reading high by 10 psi it's easy enough to pump to an indication 10 psi higher than you want. Put a sticker on the gauge to remind yourself if need be.

FBinNY 

This is how it's done. At the gauge factory the gauge is placed on a line pressurized to the 12 o'clock value, and the needle pressed on. Some needles are pressed on pretty securely and the professional way to remove them is to use a hand jack which is like a miniature gear puller, and pushes the pin through without damaging the needle.

If you cannot remove the needle, you can simply bend it to a calibrated mark, It won't look great, but will read OK.

Depending on the construction of your gauge, there's alternate method which is OK if the gauge suddenly didn't zero after being dropped. The needle is driven by a rack and pinion arrangement. When dropped sometimes it slips one gear tooth. Flex the needle up above the post, and wind it back slowly. When you get to the end of the rack you'll hear or feel it slip one tooth (be careful, you only move one tooth), then when you relax it should stop just below the zero post. Lift it above and return it to the right side of the post, and you should be OK, but may want to check the calibration with another gauge or two.