rgpg_99

I've always used shrader valves in all my bikes and never had an issue with slow leaks. A few months ago I replaced the wheels in both my bikes and I went with presta valves. I noticed that for all my wheels, and with different brand inner tubes, the tires do not stay completely inflated for more than a week, so that I have to constantly pump the tires. They don't go flat, they just lose pressure.

I've taken the wheels apart to see if there was any debris or metal shreds that could have damaged the tube, but the rims were clean. I immersed the tubes in water and pumped them fully, and I could not find any type of leak (not even from the valve). But the fact remains that I have to keep pumping the tubes every week, while my shrader valve tubes would stay fully inflated for months on end.

I would also like to mention that I don't use the plastic caps at the end of the presta valves as I understand they are there just to prevent damage to the tube while it's folded and stored away. Is that correct, or should I use the caps anyway?

cny-bikeman

You don't say how much pressure is lost or what pressure you pump them to, but if all four tires leak faster than before it's logical to assume the difference is the tubes. If you chose tubes that are rated for smaller tires than they are mounted in (ex: 19-28mm in a 28mm tire) then the tubes may be stretched further than the original tubes were, and would therefore allow more air to escape. The presta tubes often are thinner anyway. The caps have no influence on leakage. If some leak significantly faster you may have damaged the tubes in the process of replacing them.

HillRider

I assume you are shutting the little thumb nut on your valves snugly. The plastic caps aren't essential but closing the valve nut is. Also, do your new wheels use different size (smaller) tires and much higher pressure than your old ones?

For high pressure tubes and tires (say 60 psi or above), topping up the tire pressure every week is expected and for even higher pressure (100 psi and up) every two or three days is common. Your previous Schrader tubes were either used in very low pressure tires or you didn't realize the pressure had decreased. No bike tire holds full pressure for "months on end". Even car tires don't do that.

rgpg_99

Two of the wheels are 700x28c, and two are 26x1.95 ". Both sets have matching tubes according to tire width. For the 700c ones, the maxiumum pressure on the side of the tire is 120 PSI. I inflate those at 100/110 PSI, and a week later they are at 65/70 PSI. For the 26" ones, the maximum pressure is 85 PSI, and I inflate them at 70/75 PSI. A week later they are at 45/50 PSI.

As mentioned before, exhaustive inspection of tubes has not uncovered any damage to the tubes themselves.

rgpg_99

Maybe a combination of both. I did tend to use lower pressure on the tires, and I didn't check the actual pressure that often, going instead by feel (as in, "do the tires feel they need air?). When I said "fully inflated", I should have said the tires were still inflated enough to ride comfortably. I didn't check that the pressure had stayed at exactly what it was a couple of months before.

rgpg_99

Yes, that part is properly taken care of.

look566 rider

Bingo! What this person /\ said.

rm -rf

Most presta tubes are thin, to save weight and have less rolling resistance. So the air diffuses through the rubber faster than you are used to seeing.

The extra thick "touring" tubes that are presta will hold pressure for at least a month. My 18-23c road tire tubes will be low in a week, enough to tell by pressing on the tire. I pump the tires if it's been more than 2 or 3 days since the last ride. After 7-10 days, starting at 105 psi, it's probably dropped down to 80 psi.


Tire pressure depends on the size of the tire.

There's no advantage to putting in excess pressure. It won't make the bike ride any more efficiently, and the ride is very bumpy.

I weight about 170 lbs. Here's what I would use:
23c tires: 95 psi front, 105-110 psi rear.
25c tires: 85-90 psi front, 100-105 rear.
28c tires: I haven't tried these, but I would start with 80 psi front, 90-95 rear, maybe lower.
1.95 inch: perhaps 40-50 front, 50 rear?

Ronno6

Even though inner tubes definitely hold air, they do not hold air indefinitely.
The lighter the tube, the thinner the thickness, the quicker they will lose pressure.
I will usually top mine off after a couple of days (120psi on 23c tires.)
If you ever use a CO2 inflator to pump your tire up after a road repair, you will find that
CO2 will bleed out more quickly due to its smaller molecule size.
What yo are experiencing is normal in my experience.

rydabent

All tube lose pressure. Smaller ones faster than larger ones because of the volume of air. I check my tire pressure before each ride and top off if necessary. I dont find this a big deal. Riding with low pressure increases the chance of a snake bite flat.

Wanderer

I have found that Schwalbe tubes, in the heaviest size that will fit your tires, hold air better than any I have ever used. And, I have been using tubes for a long time....... LOL

wphamilton

+1 Bigger, heavier tubes hold air better than thin lightweight ones. As a rule of thumb I go a size up on the 28's (28-32 size instead of up to 28), get cheaper tubes on the theory that they're heavier (thicker), and just put up with the slight extra rolling resistance.

Grand Bois

Once a week is not "constantly". I air my tires every time I ride, even if it has only been one day.

I don't want to offend anybody, but I think Schrader valves are dorky.

jsdavis

My car tires hold pressure really well. I inflate to about 35 PSI and they'll hold the pressure for months. I check the tires every month or so but I really only have to add air maybe once or twice a year and a lot of that is really due to the weather.

JanMM

The caps keep dirt and crud off/out of the valve. Just like with Schrader valves. They might prevent air leaking from a faulty valve, at least if an o-ring is part of the design. That said, lots of people don't use them and suffer no bad results. Not absolutely necessary.

David Bierbaum

I like Schrader valves, because I can use one pump and one air pressure gauge for my bicycle and my car.

Having said that, I'm currently using presta tubes on my bicycle... Cheap Walmart Bell presta tubes. They hold air, but pumping air INTO these things is a major chore!

pierce

except, a pressure gauge suitable for bicycle tires that reads up to 150psi or whatever has like 5 psi ticks in the 27-37psi range most cars run in... I use two seperate gauges, one 0-50 for cars, and one 20-150 for bicycles.

and a pump suitable for high volume low pressure car tires won't pump sufficient pressure for a bike tire, while the high pressure bicycle tire pump won't move enough air to inflate a big car tire in less than hours.

any good bicycle floor pump will fit on either shraeder or presta valves, for instance my trusty ol' Specialized Air Tool Comp...

rekmeyata

The caps are too weak to hold pressure there just for dirt, some don't even use them, I do, they weigh next to nothing so their not tiring me out when I'm riding!!

The thumb nut on the valve core of the presta tube should not be closed real tight, it should just stop, if you snug it too tight it will ruin the valve. Besides, even if you didn't close it it won't leak since it's the tubes air pressure that puts pressure on the valve which keeps it in the extended position which keeps air from coming out. However, that doesn't mean you should not close it, however if you put the cap on with the valve open the cap will strike the valve and depress it blowing the air out. Keep in mind when you do open unscrew the valve to put air in don't snug it too tight, just to the point where it stops.

Presta valves are a bit more delicate then Schrader, their subject to bending if you're not careful while pumping. There are also better quality and cheaper quality presta valves, I had a set Slime tubes once and the presta valves were junk. If your having trouble with destroying the valve then get a carry on pump with a hose instead of connecting the valve directly to the head of the pump. Topeak makes a really nice called the RaceRocket HPX which is a bit longer then the HP version but so much easier to pump to high pressures, and it's convertible to Schrader without taking the head apart to make the change.

Lot's of good floor pumps on the market today, but I don't see the need to spend $80 for one, I bought a Zefal from Walmart for $18 on sale and been using it for 3 years and it works great, it's no problem for it to get to 110psi.

Latex tubes lose about 25 to 33% of it's air in a 24 hour period, ultralight butyl tubes lose about 5 to 10%, and normal weight tubes lose about 1 to 5%, while heavy ones may lose only a pound a week. So normally you would have to put air in your tires before every ride. During the first 24 hours they lose the most amount of air due to the tube being under high pressure, as the pressure drops so does the percentage of air loss.

Slussman

What? I've been running 120psi on my fixed gear for a few years and I only pump them up once a month - and even then they're usually still at >100psi. Maybe I'm just lucky.

pierce

heh, yeah, latex. I remember my old tubular clementi setas (ok, we called them sew-ups).... had to pump those up at LEAST daily, and sometimes mid day on a century+ ride.

in the mid 80s, I got a set of ultra-light inner tubes in my now-700c-equipped roadie that were some kind of kevlar or something, thin hard almost clear plastic, held air for WEEKS and were very puncture proof. those inner tubes lasted like 10 years, then turned brittle and failed. couldn't find them again, its a shame, as those in 23c tires rode almost like tubulars.

dddd

I've noticed this with other premium tubes, too, and the bigger tube width means that when you do puncture, the air may leak out so slowly that the repair can be done at home.

I miss the 1980's when there were so many very high quality tubes sold by Specialized, Panaracer and others. These were sold at barely any premium in price, but were wider (yet thinner-walled) than any standard tubes sold today.
Believe it or not, one of the part-out items I keep for myself (and prefer to new parts) when I dismantle are the 1970's and 1980's Specialized tubes made in Japan (and from Cheng Shin in Taiwan). They also hold air better, suffer nary a tear at the valve stem junction, and take patches better than today's tubes. They actually seem to last forever.

Valve stems can vary quite a lot these days, in terms of whether the nut needs much tightening to fully retain air, and in terms of how much pressure is needed from the pump, above what is in the tire, to break the valve open. I've had a few slow leaks that were from a Presta valve that was not heavily tightened, yet most Presta valves seal on their own from the pressure itself. And I've had Presta valves that would not release air quickly, almost not at all, yet could be pumped up with no increase in resistance noticed.
It's almost like today's tubes are designed for today's riders, who so often will not bother to repair a punctured tube. So, these tubes are more like certain other disposable items, i.e. lower in quality.
A WalMart bike is good for what it is, it is disposable and designed to allow the buyer to more-easily shrug off the occasional bike lost to theft when left parked outside some train or subway station, supermarket of place of employment.

There are premium tubes available from premium tire brands (mostly European), even if these tubes are made in Thailand, China or wherever.

GeorgeBMac

+1 -- for my 700x28s running at 110psi (Mfg recommended 100 - 120psi)

For my 700x34s running at 65-70 (Mfg recommended 60-80psi) and get away with every second or (if I'm lazy) third day... But I usually try to check it every ride just to be sure I didn't get the days screwed up..

Also: I keep them at about half between the min & max recommended by the manufacturer partly to avoid pinch flats and partly to make the bike easier to peddle.

I like free

Bottom line is rubber is porous. The tighter the stretch the tube the bigger the pores get. Granted they are microscopic but they are there none the less. What you describe is normal and a function of the rubber and the pressure not the valve. So the pressure loss is exponential. At 100 psi you will lose pressure faster and it is closing the pores as it does so the loss ratio becomes less with every lb of pressure until it reaches at point that the pores are more or less closed (maybe around 40 lbs which is standard for a scrader valved tube).

Sixty Fiver

I once pulled my Raleigh Superbe 3 speed out of winter storage and checked the tyres which had been filled to 50 psi in the fall and 6 months later they were still at 50 psi... ancient tubes with automotive / multi use tyre sealant made them virtually leakproof and after I sold the bike to a friend he told me he almost never has to top up the tyres.

I only do this on lower pressure tyres and internal gear hub equipped bikes as changing tyres can be a pain and a higher degree of flat protection was always a good thing.

High pressure low volume tyres need to be checked before every ride while ymmv with other set ups... Schwalbe tubes are some of the very best I have ever used and exhibit very low pressure losses over lengthy periods of time.

zacster

I pump my tires up before almost every ride, with the few times that I don't when I'd been out the evening before. It's just a routine. You'll get fewer flats that way since pinch flats are usually caused by under inflated tires. I also keep my tires at the maximum recommended pressure. I've never found the ride too harsh, and it feels like a lot less drag that way.

I also prefer presta valves, but my son keeps breaking them as he isn't careful with the pump.