Schwinn tire woes

I just put the Hwa Fong "brick" tire back on and pumped it to 50psi and
took it around the block. It seems to work just fine. Now I remember
that the seating problems were with the original tire, which had picked
up a kink in the metal bead at some point.

The blowouts I have gotten with the IRC Metro are probably due to too
wide a tire (2.00"😉 for my 1.0" rim. If you're in the SF Bay Area and
would like to buy a nearly un-used IRC Metro 24x2.00 tire really cheap,
drop me a note.

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Orthonormal said:

The IRC Metro is marked "to fit 24x1.50-1.75" rim. I measured my rim,
and it is 1" on the inside. Is that my problem? Are there any high
pressure slick tires for a 24x1.00" rim?

Not all 24" rims are alike. One problem is with older tire sizing the
diameter number wasn't the rim diameter or bead seat diameter, I think
it it was outside tire diameter of some nominal tire. It doesn't make
much sense now, but that's how they did it back then.

The tire on my Schwinn says "24x1 3/4 to fit S7" rim. This doesn't
quite match the chart in the link below which says S7 is a 26" size.
Nor is that size found on the chart. But that link might be interesting
anyway.

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

In tire sizing a 24 x 1-3/4" tire is not the same as a 24 x 1.75" tire.
They are two different sizes to fit two different size (diameter) rims.
It makes no sense, but that's the way tire sizing happened.

Schwinn used the odd-ball 1-3/4" size which fit an odd-ball S7 size
rim. It's not a true 24" rim in the way we think of standard 24" rims.
So you need a special tire for it. The tire needs to use fractional
sizes rather than decimal sizes. Your bike shop will be able to order
such a tire. Tire choice, however, is going to be very limited.

Schwinn did the same with their 20" unicycles using a similar odd-ball
size tire. It didn't fit the standard 20" tires that BMX bikes use.

One option is to rebuild the wheel with a standard 24" rim so you'll be
able to use regular 24" tires. The problem there is that a wheel
rebuild with a new rim and new spokes and wheel build labor will be
spendy (figure $70 - $80 or so give or take $20). The advantage there
is that you'll get to use standard tires from now on and you'll get to
select a good strong rim that is better than the stock rim. That was
the option I went with when I upgraded the wheel on my Schwinn giraffe.
The giraffe now uses a standard 20" tire.

David's link to Sheldon Brown describes the oddities in tire sizing.

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I'm aware of the distinction between 1-3/4" and 1.75" widths. As you
can see, I listed the original tire as a 24x1.75, which is exactly how
it's marked. I don't have one of the older cycles which use 24x1-3/4"
tires.

I've measured the bead seat diameter, and 507mm is the closest size on
Sheldon Brown's chart. The "traditional designation" for that ISO
diameter is 24x1.50 - 24x2.125.

I honestly think that the problem is that I have a 1.00" wide rim and
the tire is designed for a rim that's 1.50" to 1.75" wide.

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Orthonormal said:

I honestly think that the problem is that I have a 1.00" wide rim and
the tire is designed for a rim that's 1.50" to 1.75" wide.

Since the rim is 507mm, and there doesn't seem to be a slightly smaller
rim size, I guess it points to that. Surprising if true though--on MTBs
it's common to run wider than 2.0 tires with narrower than 1" wide
rims. They're made to be compatible though.

I thought the "fits 24x1.50-1.75" on the tire was all about replacing
those tire sizes and not at all about rim width, but maybe I'm wrong.

Could the issue non-hook-bead rims?

David said:

Could the issue non-hook-bead rims?

Meant to type:
Could the issue BE non-hook-bead rims?

Welcome Orthonormal! There is a large community of Bay area riders, who
have a mailing list for rides they do, sometimes more than one a
weekend. This weekend is the California Mountian Unicycle Weekend at
Lake Tahoe, and next weekend (Setp. 29-Oct. 1) is the Berkeley
Juggling/Unicycling Festival.

Your Schwinn is from the "modern" era, the most advanced unicycles
Schwinn made. They were made from 1986-93. Then there were none for two
years, and in '95 they came out with a "retro" version that lost some
of the improvements they'd made in the 80s.

All of those Schwinns (everything from 1986 onward) use 1.75 rims, not
the older 1 3/4 dinosaurs. Sounds like your IRC Metro tire was just too
wide. Here are some 24" tire choices at Unicycle.com:
http://tinyurl.com/5cta9
The last one should definitely fit your rim.

Or maybe not perfectly, as the rim you described may not be the
original rim. I thought those blue Schwinns used Araya rims? But maybe
not...

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Thanks John,

I am pretty sure that it's the original rim, since the unicycle arrived
brand new in a Schwinn box with that rim. I do have the last tire on
that list (the 24" Schwinn white wall tire), it's the 2nd tire I
described, and what's on the uni now.

Unfortunately, I think the one I have is defective. There is one spot
on the bead that always rides up. Now I remember why I went looking
for a new tire. Maybe I will just order another one of the same
model.

David, that's what I originally thought, but it actually says "to fit
24x1.50-1.75" rim". If it were meant to be a replacement for a
24x1.75" tire, then I can imagine repeating the process with a 24x2.25"
tire that's meant to be a replacement for a 24x2.00" tire, and so on.
I am a little bit surprised that it doesn't work anyway, since such a
wide range of tire sizes fit on my MTB wheels.

--John S.

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PS - How do I get on the bay area list?

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Update: I contacted tech support at Schwalbe tires because they had a
few tires that looked like they might fit. I described my problem, and
got a helpful and detailed response back from Tim Unger. Tim suggested
that older rims with the folded over lip don't grip the tire's bead as
well as modern extruded rims. That, and maybe the tire really was too
wide for the rim.

So what the heck, I've ordered a 24x1.75" (507mm) rim and some spokes,
and I am going to attempt to build the wheel myself. The IRC Metro
tire should fit perfectly, and the path is open for even fatter tires
if I ever wear this one out.

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