# New tires won't hold air.....



## cruzmisl (Dec 24, 2007)

Hi All,
I installed a set of new tires on my bike. I filled the tubes with air and away I went. All was good until I went to go for a ride and the tires had 15psi of air (down from 50). I pumped them up again and I lose about 10psi/day. Any ideas as to why? The tubes have presta valves if that matters. No nails or anything as they were losing air and I didn't even ride it yet.
Thanks,
J.


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## SteveUK (Apr 16, 2006)

I'll ask the obvious question: are you tightening the nut on the valve after you inflate the tyre?


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## eatdrinkride (Jun 15, 2005)

When I was just a little kid and my tubes would go flat I would remove them from the tire, pump them up with air and then submerge them under water. Do you have a sink or a bathtub at home? Just a thought. Just because they are new doesn't mean they don't have a hole in them. Maybe even a pinch flat (hole) from tire levers or whatever.

If you see bubbles coming from the tip of the valve stem then you most likely need to turn the the valve needle clockwise. Screw it all the way down. This prevents a Presta valve from leaking at the core.


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## markf (Jan 17, 2007)

the rubber the tubes are made of isn't 100% airtight. depending on the pressure 10 psi isn't *that* much. my roadie probably gets close to that. for mtb though, 5psi/day is more likely. do they ever go totally flat? or do they stabilize at say 20 psi? if they get all the way flat, you've got a slow leak, if not, it could just be the natural seepage of air out of the tubes.


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## comptiger5000 (Jun 11, 2007)

10psi/day is terrible. When I pump my MTB tires up to 65psi between rides (it sits on the tires, no wall hooks) It loses about 1-2 psi/day. It usually slows down after the first day or so, leaking about 5 psi/week on average. This is regular tubes and tires.


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## tduro (Jan 2, 2007)

At 5 psi/day, you can easily find the leak using the water bath method. Fix the leak before riding, as it's likely to worsen, or blow out, under stress. 5 psi/week is acceptable. 

As mentioned by someone else, make sure you close Presta valves after inflating. They're not spring loaded like Schrader's. Also, be gentle with the tube while replacing it. It's easy to damage it in the process. Before inflating fully, add a little air to stiffen the tube, then check for a pinched tube between the tire bead and the rim (all the way around - both sides). 

Let us know how you make out. There are probably others having the same issue.


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## cruzmisl (Dec 24, 2007)

I did screw the valves down tight after inflation. I'll try the water check this weekend and see what's up. Thanks for all the tips!


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## dan0 (Oct 12, 2005)

did you use tire irons ?


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## cruzmisl (Dec 24, 2007)

Yes, plastic ones....


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## dan0 (Oct 12, 2005)

cruzmisl said:


> Yes, plastic ones....


you probably pinched the tube, only use tire irons as a last resort with tubes.


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