when a 20 inch tire isnt a 20 inch tire

[dragnusa]

So I went to replace the tube on the front of the huffy rail. well heres what I found out a 20 inch tire isnt always a 20 inch tire. the rail tire says its a 20x1 3/8 so I figured I could just take a tube from another skinny tire 20 inch so I pulled out an old girls huffy 20 inch and snagged the tube out of the front tire. went to put it in the rail tire and it was to small. So I laid the tires out together and WOW what a difference in size.

 

[expjawa]

This is just like with 26" tires - the 20" only designates the (theoretical) outside diameter of the mounted, inflated tire. It says nothing about the wheel diameter it mounts on. Just as there are 5 or 6 different wheel sizes that are used with what can be called 26" tires, there are several also used with 20" and you have to know what you need so that you can buy appropriately. What I don't get is that the outside diameter is that much different, usually its just the bead diameter that's varies significantly. Are you sure that they're actually both called out as 20"? I'd sooner guess either the small one is 16" or the big one is 24", just from the look of it. I would think that there's got to be an ISO size call out on the tire to indicate the rim size. I'd be curious what that is.

 

[The Black Monark]

What are the #'s on each tire?

 

[yoothgeye]

It's been covered here a million times, but I don't mind telling people again. fraction and decimal tires ARE NOT interchangeable.

a 20x1.5 is NOT the same as a 20x 1 1/2

fractions replaced with fractions and decimals replaced by decimals.

 

[expjawa]

It's been covered here a million times, but I don't mind telling people again. fraction and decimal tires ARE NOT interchangeable.

a 20x1.5 is NOT the same as a 20x 1 1/2

fractions replaced with fractions and decimals replaced by decimals.

I'd originally written something to that effect as well, but if you look at the actual tires shown, it seems like there's more to the issue than a simple sizing misunderstanding. Different 20" sizes should still be around 20" in outer diameter. The tires shown, though, are significantly different.

 

[yoothgeye]

It's been covered here a million times, but I don't mind telling people again. fraction and decimal tires ARE NOT interchangeable.

a 20x1.5 is NOT the same as a 20x 1 1/2

fractions replaced with fractions and decimals replaced by decimals.

I'd originally written something to that effect as well, but if you look at the actual tires shown, it seems like there's more to the issue than a simple sizing misunderstanding. Different 20" sizes should still be around 20" in outer diameter. The tires shown, though, are significantly different.

Not true, hold up a 26x1.5 by a 26x1 3/8 WAYYY different.

 

[expjawa]

Fair enough, a 26x1.5 is closer to 25" in diameter. I run those on my LHT. OTOH, if you compare a 26x 2.1 to a 26x 1-3/8 (which is more to what my point was), the outside diameter is pretty close. But that's a case - like with 700c - where the naming convention has essentially broken down, since the rim diameter has become the standard rather than the tire OD. I'm not sure that this is the case with 20" tires at this point. He claimed that they were both narrow sized 20's, so my point is that their outer diameters should still be pretty close together. They're not, there appears to be several inches different.

 

[dragnusa]

I understand the whole decimal/ fraction thing and the whole s2 s7 schwinn thing .Ive just never seen two tires be that much different in size from a company like huffy. and where would you get a tube to fit a rail 20 inch rim

 

[The Black Monark]

What are the #'s on each tire?

 

[expjawa]

What are the #'s on each tire?

This. Start by telling us what the ISO number on the tire is, so we know which wheel size you're actually dealing with. All else comes from there.

 

[dragnusa]

the redline tire off the rail says 20x 1 3/8 ( only thing I can read on the side wall) and the other is 20x 1.75 both off huffys about 10 yrs apart. Ive just never seen that much variance in 2 20 inch tires.

 

[The Black Monark]

Here's a link that explains it:

http://sheldonbrown.com/tire-sizing.html

 

[Bicycle808]

There's a lot of difference between 406mm and 451mm. Close to 2". I don't know why anyone even bothers with anything other than etrto.

 

[LukeTheJoker]

I managed to find another size of 20 inch tires that don't match too...

:lol: :lol: :lol: :lol: :lol: :lol:


Seriously though, this knowledge is good to know, nearly made the mistake of ordering the wrong ones from the U.K. for a build a while back, before finding a post on here explaining the difference. Would have been a costly mistake!

Luke...

 

[Tinkerbull]

:mrgreen:
ISO 5775