Tube / tyre of different sizes ?

Questions about purchasing bicycles and parts

Tube / tyre of different sizes ?

Postby Smurk » Mon Feb 18, 2013 8:38 pm

Hello

So I have got that old road bike which I just bought (tubes and tires to change). I have checked on the existing tyre and it was written "27 * 1 1/4". Fine, I went to the bike store, asked for "27 * 1 1/4" tires and tubes, the guy asked me if I was really sure, I said yes, went home and tried to fit everything on the bike. Except that when I removed the old tyre, I noticed that the inner tube was size "700/something" (maybe 30, I can't remember now). How comes? Did the previous owner make a mistake? Was I supposed to buy that last size for the inner tube?
Anyway, I don't like spending money for nothing, I still put everything on my bike. The tyre size looks good, maybe a bit large (I remember that it's lots of sport to put a tyre on my mountain bike, these new tires are Schwalbe brand, maybe they usually are on the large size?), but well tight enough, not too bad. The tube looked way too big before I inflated it. After it's been inflated, I don't know because there's the tyre on it, but it's probably not even touching the inside rim of the wheel. Will it be a problem if I was supposed to use a smaller size for the inner tube?
And what's that psi recommendation on the tires? Do people really have a machine to measure the pressure? I just wanted to ride a bike, not to get an engineering diploma... :/
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by BNA » Mon Feb 18, 2013 9:17 pm

BNA
 

Re: Tube / tyre of different sizes ?

Postby KenGS » Mon Feb 18, 2013 9:17 pm

Smurk wrote:I have checked on the existing tyre and it was written "27 * 1 1/4". Fine, I went to the bike store, asked for "27 * 1 1/4" tires and tubes, the guy asked me if I was really sure, I said yes, went home and tried to fit everything on the bike. Except that when I removed the old tyre, I noticed that the inner tube was size "700/something" (maybe 30, I can't remember now). How comes? Did the previous owner make a mistake? Was I supposed to buy that last size for the inner tube?

Previous owner made a mistake. 700s are are made for a slightly smaller rim diameter than 27inch tyres (8mm if you want to know) . Use the tubes that match the tyres.
Smurk wrote:The tube looked way too big before I inflated it. After it's been inflated, I don't know because there's the tyre on it, but it's probably not even touching the inside rim of the wheel. Will it be a problem if I was supposed to use a smaller size for the inner tube?

If that was the case then the tyre would be to big and then you have a problem. If in doubt, take the wheel to the bike store.
Smurk wrote:And what's that psi recommendation on the tires? Do people really have a machine to measure the pressure? I just wanted to ride a bike, not to get an engineering diploma... :/

The psi recommendation is how hard you need to pump up the tyres. When I was young I just used the thumb test . Now I use a track pump (one that stands up) which has a pressure gauge on it.

Everything you need to know is on Sheldon Brown's site: http://sheldonbrown.com/tires.html
--Ken
Helmets! Bells! Rego!
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Re: Tube / tyre of different sizes ?

Postby Smurk » Tue Feb 19, 2013 9:35 am

Thanks. Yes, it doesn't feel too bad the way it is now... I will try the bike on a small ride first, in case something blows up. I certainly don't want to be stuck in the middle of nowhere while pulling my son to day care (the reason why I bought that bike). I feel smarter every day, now I know how to change the rear wheel. Super Me!
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Re: Tube / tyre of different sizes ?

Postby il padrone » Tue Feb 19, 2013 9:57 am

27" tubes are no longer available generally (or if they are I never see them). 700C tubes are so close in size that they will happily fit into a 27" tyre fine. When it is inflated the tube will just stretch to fit. Don't stress too much over it.

Your main problem with this bike will be the availability of quality 27" tyres. There are Taiwanese cheapies in K-mart sometimes.
Riding bikes in traffic - what seems dangerous is usually safe; what seems safe is often more dangerous.
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Re: Tube / tyre of different sizes ?

Postby Smurk » Tue Feb 19, 2013 2:50 pm

OK, thanks a lot for your, err, completely different opinion! :)
Since I found both tubes and tires of the same size, I guess I won't have to check if another tube size would fit as well for the moment.
The tires I found are Schwalbe brand, and it doesn't look too bad if I trust internet reviews.
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Re: Tube / tyre of different sizes ?

Postby il padrone » Tue Feb 19, 2013 3:14 pm

So hang on...... you bought tyres and tubes that were 27"? Well done if that is the case :) . Like I said, 27" gear is getting harder and harder to find.
Riding bikes in traffic - what seems dangerous is usually safe; what seems safe is often more dangerous.
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Re: Tube / tyre of different sizes ?

Postby Smurk » Tue Feb 19, 2013 7:08 pm

Yes, I found them in actually the first bike store I tried (but it had been adviced by a friend of mine who knew I was looking for 27 per 1 1/4). The bike store is called Ride 365 in Belconnen (Canberra). Very nice people. But indeed it took them two staff members to find the last 27'' tires at the back of the store. :D

Maybe I should go back and buy a few more, in case there is no more in a few years. :D
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