Help - Tire Pressure / Floor Pump Issue

[Dubz]

Thanks, Muirenn. That's very helpful.

How do I know how much pressure is in the tire to begin with? Can I know this from my Floor Pump?

Cheers.

[Dubz]

Cheers, Muirenn.

I actually have a pressure gauge on my pump. I got the same one that my LBS uses (Bontrager Recharger Track Pump). They recommended it. When I connect the pump, the current pressure doesn't show. The gauge says zero. It's only when I pump that the needle moves up. This is why I'm confused.

Also, noob question here: what are valve caps on the stem and washer nuts?! I'm seriously technically deficient when it comes to biking. I'm trying to learn though. I've learned so much in the past few months since I first decided to buy a bike.

I thought the stem was the bit the handlebars attach onto because when I got my bike my LBS said that they switched around the stem to give me a more comfortable reach. I'm 5' 3" but prefer the unisex model of the bike I got versus the WSD. With the WSD, my arms felt wrong - like they were too bent. With the unisex model, I felt like my reach was too far until the LBS switched around the stem. Then it felt fine.

On my wheel, I only have a black cap which I take off the Presta valve. There's no other cap. I had to unscrew the silver round thingy to loosen it. I pushed in the silver round thingy in slightly to make some air come out and then fixed on the floor pump to the narrower hole (my pump can do Schrader valves too so it has a wider hole as well) and locked it in place. Then I pumped.

[Dubz]

Oh ok. That makes sense now. Cheers.

Do you think it would be best for me to always pump the tyre up to max (assuming that this means it's at 120 PSI which is the manufacturer's maximum tyre pressure) and then let some air out and then pump up to what the correct tyre pressure should be (using the formula you linked to)? Otherwise, I could buy a separate type pressure gauge which would measure the pressure and then use my pump to get to the PSI I need.

[Dubz]

Thanks for all the help, Muirenn. I'm probably being a bit of a pain here. Are you Irish by the way? Muireann (with an 'a' usually) is an old Irish girl's name?

That last link was really useful. That girl is amazing. How she kept going with all those injuries is unbelievable. Fair play to her. Great info too.

Basically, my problem is that I can't guess how much air to pump into my tire when it's already inflated because my gauge doesn't say how much pressure it's at already. So if I was able to attach my floor pump and see that it was at 100 PSI already, then I'd know that I just had to add 10 PSI more from my pump (as an example) to make the pressure inside my tire become 110 PSI. At the moment, I can only attach the pump and add more pressure until the tire goes hard (so I start at 0 PSI on the pump gauge and go up to 60 PSI as an example). But this doesn't allow me to know what the total PSI in the tire is at that point because the pump gauge would read 60 PSI at this point, when the pressure inside the tire could be 110 PSI because I started with pressure already in my tire (or I'm guessing even 120 PSI if the pump isn't allowing me add more air and the tire feels completely rigid, since 120 PSI is what the manufacturer gives as the maximum tire pressure). I hope that makes sense.

[Blueberry]

So once your pump gauge starts reading, it is usually reading the pressure in the tire. You usually hear a little whoosh when the pressure in the tube of the pump exceeds the tire pressure. Reading the gauge when you hear that will tell you the approximate pressure in the tire. You can always remove the pump and depress the center portion of the valve to let air out of the tire if you are afraid you have overinflated it. So - if you want the tire to be at 110, you would pump until the gauge on the pump reads 110. Make sense?

[BikeDutchess]

As soon as you pump it once, the gauge should move to show the then-current pressure for the tire. The gauge doesn't just show what pressure you add (by pumping), it shows the total pressure in the tire (some show the total pressure as soon as you hook it up, and some may not show the total pressure until you actually start pumping). You would rarely start from zero (in the tire) unless you had a flat and/or just mounted a new tube in the tire.

ETA: Blueberry and I were writing at the same time.

[Dubz]

Thanks a lot, girls. Now I see why I'm confused. I thought I was being a bit thick. My pump isn't showing the current pressure on start up. It starts at 0 all the time. I think I need to bring it back to my LBS to see if it's working properly because it looks like it isn't. I don't think I've done anything wrong because I've looked at loads of vids online and have followed exactly what they say to do with attaching a floor pump to a Presto valve.

/ Warning - Rant Beginning: It's a bit frustrating tbh because the amount of simple things I've had to ask about or try to figure out myself is unreal. I don't mind learning or researching stuff, but some information either isn't out there or is hard to find. I wish there was a website for people starting out, who are non techies, with loads of vids to explain the basics. For example, I was having problems with my speed / cadence sensor not reading. It was only when I went back to my LBS that they showed me that there was a magnet on my pedal which was slightly out of line with my sensor and that my training wheel also needed a magnet. I had spent ages looking online to try and figure out the issue myself as I'm the type of person who likes to solve things on my own. I had no idea that sensors needed magnets or that I had one on my pedal and one on my normal rear wheel. It just didn't occur to me and it wasn't mentioned anywhere online or on the manufacturer's website.

Some of the guys in my LBS are really helpful and understanding, but some of them look at me like I've 2 heads when I ask these kind of questions. That's why I'm glad to have found TE. I wish there were more women working in bike shops. It would make life easier because I think they would be more understanding and you can ask embarrassing questioning without feeling like a total eejit. / Rant over!

So basically, I really appreciate your help.

@Muirenn - Yes, I'm Irish. From Dublin. But I live in London now. Dublin's my home, so I'll always love it. But London's great. Any time I go back to Dublin, I start getting homesick for London after a few days. I love it.

Ireland has very beautiful parts. You should visit. They've recently opened the 'Wild Atlantic Way' which is apparently the world’s longest defined coastal touring route. It's in the West of Ireland. Since you enjoy cycling, that might be something to consider checking out one day. Some of it is really spectacular. Especially if you like scenery that's a bit savage and untamed.

Here's the website for it and a vid as well, so you can have a look.

http://www.ireland.com/en-gb/wild-atlantic-way/#

https://www.youtube.com/watch?v=TNjsFzyKJOI

My bike is a 15" Starry Night Black / Volt Green Trek 7.2 FX 2015 btw. It's your average bike, I know. But I love it more every day.

[Dubz]

My pleasure, Muirenn!

[OakLeaf]

I'm wondering if you have the pump head set straight. It's possible - actually kind of easy - to get the pump head just slightly crosswise on a Presta (a not o) valve, so what happens when you press the plunger is that pressure just builds up inside the hose but doesn't go into the tube because the valve stem isn't depressed.

Without having watched all the videos and I'm not sure what's already been explained here - a Presta valve has no spring. The valve is held closed simply by the air pressure inside the tube, and the lock nut on the valve stem is just for extra security when going over bumps. So the corollary to that is that it needs air pressure from the outside to open the valve and fill the tube. But if the valve stem is jammed up against the gasket, which can happen if it isn't exactly straight, then the valve will never open. That's why it can be so very hard to pump a completely empty tube - without any air in the tube, the valve stem just wobbles around and is very hard to keep aligned.

I personally find it easiest to get the pump head on and straight at 12:00. Some do better at 6:00 - to me, I get too much pull from the hose in that position and I have to be bending down too far to steady the head effectively, but it's all what works for you. You'll want to hold the pump head straight - heel of your hand on the tire, fingers on the pump head - while you use your other hand on the plunger until you can feel air going into the tube.

Difficulty in getting the pump head on exactly straight can be a sign of wear in the gasket, too. Again, I didn't watch your videos - it sounds like your pump head has separate attachments for Schraeder and Presta? Most pumps use a single head, and in that case if it's been used much on Schraeder valves, it can wear pretty quickly to the point where it's no use on Presta valves. But even if it's only ever been used on Presta valves, it will wear. Every couple of years is a typical replacement interval. Rebuild kits are cheap and your LBS should have them.

As far as tire pressure - recommendations based on road conditions and rider weight are for the road. On the trainer, I would definitely inflate the tires to max recommended pressure to minimize tread wear and heat buildup.