Air in tires

I asked a similar question a month or 2 ago. I have a road bike with 100psi and I lose 20-30psi per week, regardless of how much I ride...

Everyone said this was quite normal...

Never happened to my old MTB, but that never ran at those pressures...

Jyag said:

I've been riding my bike frequently, and have been noticing I have to fill up my tires a lot. I know this is probly from me riding alot, but I'm not sure. Well my road bike is from the 80's, but thats all I can afford since I'm only 15 yrs old. I'm getting a trek for christmas, and I doubt I will have to keep filling them up. Can anyone help?

Rubber tubes are porous so expect them to leak air over time. Expect to lose around 20% air pressure of a week period.

FWIW, bell has a rubber inner tube for which leak a lot less under the 'airtight' brand.

It's something that you'll just have to deal with. The majority of tires out there will leak slowly on you. One of the reasons for this is the pressure. A road bike requires a lot of pressure...around 100psi or so.

Mountain bikes require quite a bit less, and the air isn't being forced to leak as much.

I reccomend getting a pump, with a psi meter, so that you can properly keep your tires inflated. Just check 'em in a couple seconds before you set off for the day.

fauxpas said:

Never happened to my old MTB, but that never ran at those pressures...

Sure it did you just didn't notice. A MTB tire is a high volume, low pressure deal. A 700c road tire is high pressure and much lower volume. So if the same amount of air was to be lost out of each the pressure drop in the low volume tire is always going to be far more visible.

I ride 700c tires at 130psi. I expect if I fill front and back to that pressure today, 24 hours later tires will be 110psi (ish). I ride MTB at 50psi and if I fill today, they'll probably be around 45psi in a weeks time.

--brett

Jyag said:

I've been riding my bike frequently, and have been noticing I have to fill up my tires a lot. I know this is probly from me riding alot, but I'm not sure. Well my road bike is from the 80's, but thats all I can afford since I'm only 15 yrs old. I'm getting a trek for christmas, and I doubt I will have to keep filling them up. Can anyone help?

I don't get this on my road bike unless I have a defective tube or valve. If the tubes are latex, then they will lose air like this but if they are butyl, then they shouldn't. I would replace the tubes with new ones, and keep the old ones as spares.

I ride every day and check pressures every 2-4 days... If I am training (not commuting) I check them before every ride...

A mate at work has an MTB and was wondering why he kept getting flats. He had so little pressure in the tubes, the tyres sagged like a sharpei dog. He thought that's what they were supposed to look like...

I have to top off my tires every time I ride. I keep 100 front, 105 rear. After a 30 mile ride and then two days later I'm down 15-20 lbs. That's normal for bicycle tires.