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1.5-1.75" tube in a 1.25" tire

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1.5-1.75" tube in a 1.25" tire

Old 06-12-15, 07:41 AM
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1.5-1.75" tube in a 1.25" tire

I am doing a complete teardown and refurbing an early 90s Specialized Hard Rock for a coworker’s wife to use on a 50mi charity ride in a few weeks and the 1.5” slicks that were on the bike when I got it arent exactly new. I had some 1.25” new tires that I impulsively bought off nashbar a handful of months ago, so I put those on.
The tubes are 1.5 – 1.75” though. The tires mounted fine, it just took a bit more stuffing of the tube than usual. I figured I would inflate them and let them sit for a few days as I finished the bike, then take it out for 10mi of difficult riding(I am 6’5, the bike is for a 5’4 woman) to fine tune it.

Is there any downside to using tubes that are made for wider tires than what you are mounting? It’s a hooked rim, so I wouldn’t figure the tire would just blow off. Does the tube not inflate enough to create stability, or something like that, if its made for a tire larger than the one used?
If there is no downside in terms of safety and performance, then why not use tubes that are larger than needed? It’s a slight weight gain, but is also a thicker tube…so less chance of pinch flats, correct?
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Old 06-12-15, 08:12 AM
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the tube, rubber thickness, like a balloon , is thicker the less space it is expanded into ..

but the installation is more challenging and perhaps will crease on folds, if too big.

Thorn Resistant tubes start out with more rubber, & is thicker on the outside, than the rim side.
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Old 06-12-15, 08:24 AM
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I just did this on my wife's bike - had to really stuff the tubes in there, and really work them carefully so they didnt get caught between the tire and the rim. I dont think you'll need to ride the bike around afterward to make sure it's ok, but do spin the wheels and watch both from the side of the wheel and over the wheel to see that the tire is seated properly and is spinning true. I had to re-position my wife's several times to get it right. In any case I installed them several weeks ago and everything is fine, she's been on several rides with no issues.

On a side note, thin shrader tubes seem almost impossible to find for some reason. I'm about to install some super thin slicks on one of my mtbs and am already dreading it, lol.

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Old 06-12-15, 08:25 AM
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It's basically the Cinderalla story. If the tube fits, it's OK. By fit, I mean that the unstretched inflated tube's width is smaller than the tire. Odds are it was, or you would have a hard time stuffing it in there.
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Old 06-12-15, 09:12 AM
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Yes, both tires are seated properly and spin fine(except for some wobble that ill have to struggle to true). Thanks for the confirmation.

Me riding the bike for a handful of miles is to make sure its shifting well, brakes well, and everything that should be tight is tight. I may be paranoid, but I always ride anything I have completely torn down and refurbed to make sure its all how it should be. In the past Ive found a front hub that has a little too much play or a brake lever that has to be pulled a little too much.

Good to know the tube sizing isn't some hard line yes or no. Oddly, I googled this before asking and found a bunch of posts asking if a smaller tube could go in a larger tire, but not the reverse.
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Old 06-12-15, 09:24 AM
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It's always good to work your way around the rim on both sides to make sure the tube isn't pinched between the tire bead and rim before bringing it up to full pressure. If it passed that test, you're probably good to go.

My preference is always to use tubes right around the size of my tires -- not because I'm worried about pinching them or over-stretching them, but just because it makes the whole process a little easier.
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Old 06-12-15, 10:42 AM
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I use Sunlite 26 x 1.5 - 1.95 TR tubes in Nashbar City Slicks (32-559). Half a stoke on the pump and fit the tube in to the tire - getting rid of any creases, them mount on the wheel. Works well and easy on 18mm (inside width) Velocity Aeroheat rims, much more difficult on 14mm (inside width) Arraya rims. Rim width is a major factor in how easy this is to do.
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