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Oring/O-ring Boring. What governs stretch?

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Oring/O-ring Boring. What governs stretch?

Old 06-26-20, 03:00 PM
  #1  
bikebikebike
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Oring/O-ring Boring. What governs stretch?

I have several sensors mounting with Orings and they break over time. When going to a Hardware store I am seeing a lot of variability in oring elasticity/stretch, which is a big deal in sensor mounting.
Does anyone have a resource for targeting stretchy orings , rather than the thicker Buna rubber ones more directed towards sealing?
I really need robust rubber bands, not seals. more a bike mount band kit
Either a discussion of this or a source . Onesies and twosies are more expensive and hard to reproduce results.

Most of mine came with sensors from China and OEM is not a good source.

Sources state:
"To provide an effective seal, the O-ring's inside diameter (I.D.) must be smaller than the piston groove diameter, so that the O-ring is slightly stretched, fitting snugly in the groove.
This stretch should be between 1%-5% with 2% as the ideal in most applications. A stretch greater than 5% is not recommended."
"With the O-ring calculator, engineers can specify the groove dimensions for a specific O-ring or a specific groove.
The O-ring calculator calculates the most relevant size O-ring for any given groove and includes O-ring inner diameter stretch and the desired Polymer Group or Seal Hardness. ."
Examples: Garmin Bike mount band kit (replacement) 6 for $15.77,CatEye CA5447010 Rapid X Spare Bands- 2 for 8.95,Ascher Bike Silicone Mount Band, Cycling Bicycle Rubber Straps, Pack of 4 $6.99
All seeming less than ideal

Last edited by bikebikebike; 06-26-20 at 03:25 PM.
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Old 06-26-20, 04:23 PM
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Do you have any inner tubes that you had a blow out that you can't patch? If you do, there is your rubber source.

If you do not have any tubes that you want to use a scissors on, next time you are in a bike shop, ask a mechanic if you can have a blown out tube out of their garbage bin. If they look at you with an odd look, just tell them size does not matter, you want to use it to make some rubber bands, and tell them the thicker the better.

Most of my sensors are attached with zip ties, not with a stretchy band.
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Old 06-26-20, 07:32 PM
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Originally Posted by Tourist in MSN View Post
Most of my sensors are attached with zip ties, not with a stretchy band.
+1, would read again.
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Old 06-27-20, 09:01 AM
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Are you confusing the specs for o-rings used to seal things from fluid and/or gas leakage with specs for using as rubber bands? Even so, there are many different specs for O-rings that operate in different environments. IE, space shuttle booster vs air chuck on floor pump.

Didn't see anything about UV resistance in your specs. Maybe that's an issue for those companies using O-rings that were only intended to seal.

As suggested, cut up an old inner tube o use nylon wire ties (tie wraps).
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Old 06-27-20, 11:27 AM
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Originally Posted by Iride01 View Post
Are you confusing the specs for o-rings used to seal things from fluid and/or gas leakage with specs for using as rubber bands?
Yes.

As Iride01 pointed out, these are two very different purposes with different engineering.

​(​​​​​I wouldn't use rubber bands either.)
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Old 06-27-20, 05:31 PM
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You guys aren't using ceramic o-rings?

Seriously, I haven't had issues with any garmin or cateye bands.
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Old 06-27-20, 05:37 PM
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Originally Posted by znomit View Post
You guys aren't using ceramic o-rings?

Seriously, I haven't had issues with any garmin or cateye bands.
Just the OP apparently is having issues. I still have my garmin quarter turn mount for my edge 500 using the same two o-rings I put on it 10 years ago. And Garmin gave me a a lot of extras too that I still am waiting to use. Most sensors and crank magnets I have nylon wire ties holding them on.
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Old 06-29-20, 07:02 PM
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Originally Posted by Iride01 View Post
Just the OP apparently is having issues. I still have my garmin quarter turn mount for my edge 500 using the same two o-rings I put on it 10 years ago. And Garmin gave me a a lot of extras too that I still am waiting to use. Most sensors and crank magnets I have nylon wire ties holding them on.

+1. I bought spares probably 10 years ago when Garmin came out with the quarter mount and have never broken one
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Old 06-30-20, 09:23 AM
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The O-rings I've got from Garmin and Cateye do look an awful lot like the polynitrile (?) O-rings I buy at my Local Hardware Store (LHS) to fix plumbing problems. (Great, now we can debate LHS vs. Home Depot web orders...)

My biggest worry is that when one of the Garmin O-rings break, I'll have forgotten where I put the extras.
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