20" tires

[Girlsbike]

So I feel really stupid but I've tried multiple tires and I just can't seem to figure it out. I'm ratstoring a Huffy lil gypsy for my daughter and I can't find a front tire that fits. They are all to large of diameter when I fill it with air it just falls off. I have a slick in the rear and it fit perfect. I'm just at odds with this thing. I have try multiple tires and try widths Any help would be great.

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[Starnger]

Check what is ISO size of it. ISO for normal 20x2.125 tire is 57-406, that means 57mm wide and 406mm diameter. Yours can be for example 400mm (reffered to as 18") diameter, then it would be 6mm too small.
Basic rule - only trust ISO, and never what inch size states. There are four different 24" sizes, at least three different 26" and so on. I don't know why the former designers and engineers messed the system up so much, but now it is just not reliable.

 

[RustyGold]

The general rule of thumb is that fractional sized tires aren't interchangeable with decimal sized tires. So, a 20" x 1 3/4" tire isn't the same as 20" x 1.75". The 20 x 1 3/4 is a Schwinn size and has an ISO diameter (as mentioned by stranger) is 419mm, standard 20 x 1.75 is 406mm. Then, to make everything a little more confusing, there is another 20" size that is primarily for mini-bmx race bikes and recumbents and has a 451mm ISO diameter.

 

[clamdigger]

That said, it is time to measure your rim. It is important to note that it is the " bead seat diameter " that you want : https://sheldonbrown.com/rim-sizing.html

 

[Girlsbike]

That's the thing I measured the seat diameter and it's 16" or 406mm which according to Sheldon brown it should be a 20" tire.

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[RustyGold]

...and what size is the tire you are trying to put on?

 

[Girlsbike]

I guess I didn't measure that. It has to be like 16 1/4 ID.

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[RustyGold]

The size printed on the sidewall

 

[Girlsbike]

I've tried a 20 x 1 3/4 is the last one I tried.

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[hamqqea]

I've tried a 20 x 1 3/4 is the last one I tried.

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20 x 1 3/4? That's a Schwinn S-7 size. For a larger wheel diameter.

 

[Girlsbike]

20 x 1 3/4? That's a Schwinn S-7 size. For a larger wheel diameter.

So if I go with a 1.75 it should be smaller diameter?

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[RustyGold]

This is one case where your math teacher was wrong...1 3/4 does not equal 1.75.

 

[Wildcat]

All the tires you tried must be the Schwinn tires.
Usually someone tries to put a standard 20" tire on a Schwinn rim and it almost fits but won't go the last little bit. The Schwinn size is just large enough that you had to buy their tires. My father would cuss everytime one of those would show up in the parts pile.
There is much more selection using the standard size, for 20" tires and the larger ones also. You'll probably be the same as original for that bike with a 20 x 1.75 tire. ISO 406 as noted above should be easier to find than the other sizes.