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2 questions; rear derailer adjustment, and checking pressure with Presta valves

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2 questions; rear derailer adjustment, and checking pressure with Presta valves

Old 06-17-16, 08:02 PM
  #1  
Erich_E
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2 questions; rear derailer adjustment, and checking pressure with Presta valves

2 question for a newbie.

1. I have a issue with some of the higher (smaller rear gears, did I get that right?). I have a Shimano 105 RD-5700GS 10 speed rear that seems to click around the 3 smallest gear. Whenever I'm in all the other gears they stay put, but somewhere around that 3rd smallest gear, it will click, click, click until I go up or down a gear. Once I'm in a lower or higher gear it stays put and appears to be perfect. What would be causing an issue with only of the gears?

2. Whenever I check the tire pressure with my floor pump it sounds like I'm bleeding out 5-12 psig. Is this normal, or am I attaching the pump wrong? The Presta valve doesn't seem to have a good way to seal around a pressure gauge like a Schrader valve does.

Thanks in advance for any help.
Feel free to forgo any snarky answers that point out how much of an idiot I am. I already know that.
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Old 06-17-16, 08:22 PM
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zeeway
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Re your Presta question, when I attach my floor pump to the valve, it does not leak air. I do lose some air when burping the valve before attaching the pump.
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Old 06-17-16, 08:38 PM
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Thanks for the reply, that's the same thing I was referring to, but it seems like I'm losing a bit more. I'll have to work on my technique.
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Old 06-17-16, 09:14 PM
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What I do when I'm ready to remove the chuck from the valve, I open the handle thrn press the chuck straight off with two thumbs or two fingers. That way the chuck comes off instantly with no loss of air from the tire. If the tube valve isn't super long, you can reach over the tire with your thumb on one side and your forefinger on the other to pop the chuck off. It may take a little practice.

Your tires lose a little pressure just sitting normally every day.
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Old 06-18-16, 07:13 AM
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A floor pump is a poor pressure gage. The internal volume of the pump's hose and plumbing has to be pressured up by the tire's air. Unless you stroke the pump a time or two this air won't get back inside the tire. Hence the air loss. A hand held gage has FAR less interior volume to fill yet even so a couple of PSI loss with a small hand gage is common. After a while one begins to learn how much air loss happens and can over inflate to compensate. Or get a hand held gage. Or just pump up to a gaged reading and remove the chuck and be done obsessing and go ride.

Ideally a frictionless system will have no loss of positioning movement between the shift control and the der's locations under each cog. In this world an adjustment that is perfect under the low gear will also be so under the high cog. But in the real world there's other factors like slight tolerances and cable friction. The Shimano upper pulley has some side play to help compensate for these but keeping the cable clean and freely moving is critical for maintaining the pulley's location directly under each cog as you shift across the cog set. Of course we assume that all is otherwise correct. Like matched components and correct cable clamping. Andy.
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Old 06-18-16, 08:01 AM
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Andrew is way more experienced and trained than I am. That said I'd clean and lubricate everything to make sure it is moving freely. I'm just restating what he said from my point of view thinking it might help shed light :-).
The cable tension is the most relaxed in your highest gear (smallest cog)....and the der is up against the limit screw. Also if your chain is quite worn and you do not use the small cogs much they may expose the wear on your chain.

if you have a work stand and look at how the chain is actually centered on the cogs you may see something....adj the Derrailor so the chain is centered on the cog while pedaling in my somewhat limited experience gets you within a few clicks usually. But if you see the chain is off center on the small cogs maybe your derallior hanger is bent ?

Bike shops have a gauge they attach to the hanger to check its squareness to the rear wheel...

as to tire pressure I came to realize I may never actually know what pressure is IN the tire.....but I do know where it is when I pull the chuck off. IMHO pulling it off may lose a little , and with mine anyway putting it back on seems to lower pressure some. But if I pump to XXX pressure I do not get pinch flats and that is my goal :-).
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Old 06-18-16, 02:48 PM
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Originally Posted by Erich_E View Post
.............

2. Whenever I check the tire pressure with my floor pump it sounds like I'm bleeding out 5-12 psig. Is this normal, or am I attaching the pump wrong? The Presta valve doesn't seem to have a good way to seal around a pressure gauge like a Schrader valve does.

Thanks in advance for any help.
Feel free to forgo any snarky answers that point out how much of an idiot I am. I already know that.
Are you saying that you are using the same "chuck" for both presta and schrader valves? You can't use 1 chuck for the other, you know. Some pumps have dual-chuck heads, and some have an insert that you have to pull out and flip over to switch between the 2 valve types. Then some are just made for 1 type and not the other.
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Old 06-18-16, 03:51 PM
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My pump has a valve with one hole for presta and one for a schrader
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Old 06-18-16, 03:55 PM
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Since a presta valve comprises a one-way check valve, a pump's gauge will only represent the tire's pressure while inflating the tire. That is, while slowly pushing air into the tire so that the pressure in the gauge, hose and tire is the same. When the chuck is remove from the the valve stem, pressure in the hose is released and is responsible for the hiss that is heard.
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Old 06-18-16, 04:52 PM
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Originally Posted by AlexCyclistRoch View Post
Are you saying that you are using the same "chuck" for both presta and schrader valves? You can't use 1 chuck for the other, you know. Some pumps have dual-chuck heads, and some have an insert that you have to pull out and flip over to switch between the 2 valve types. Then some are just made for 1 type and not the other.
My Topeak Smart Head does. I'll admit that I have to concentrate a little harder when using it with Schrader valve tubes.
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Old 06-18-16, 05:02 PM
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10 speed derailleur systems have the rear cogs so closely spaced that they can be pretty sensitive to relatively minor tuning tweaks.

The first thing that I do is to check the derailleur hanger alignment. It doesn't have to be off by very much to screw up the shifting somewhere along the cassette. Then I reinstall the derailleur as if for the very first time. I recently spent over an hour on Mrs. Grouch's brand new Catrike trying to solve a similar issue. It turned out the high limit screw was about 1/8 turn too far in. The problem didn't show up until about the 6th cog in.
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Old 06-19-16, 06:40 PM
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Erich_E
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Thanks for all the info guys!
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Old 06-21-16, 09:23 PM
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For the pressure checking problem I use one of these:




Don't cost much. Comes in a variety of bicycle appropriate ranges and for Presta or Schraeder. Hardly loses the tiniest spit of air. Lifetime warranty. Love mine.
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