Author Topic: S-7 Tire on an S-2 Wheel  (Read 2238 times)

Offline mlorenger

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S-7 Tire on an S-2 Wheel
« on: July 09, 2014, 02:09:18 PM »
General question with possible answer...

I recently picked up a shed resting '59 Wasp.
The tires it has are aftermarket S-7's 1-3/4" and when I went to fill the tires up last night, I did so very slowly, the tires seemed too "loose" and the tube was almost slipping out so I coaxed the opposite side while adding more air, i.e. 10lbs, 15lbs, etc.

I figured it was because the tires were old and maybe stretched out from sitting, but then it dawned on me that these tires were too small for the actual wheel, if in fact it were a balloon-er Wasp.  Because the Wasp should be rolling on an s-2 tire, correct?

So that is my question:   Can an s-7 fit on an s-2 wheel and still work properly?  How can I check my rim to see if it is an s-2?

Thanks!
1959 Spitfire?
1963 Typhoon
1974 Varsity
1983 Traveler
2006 Ranger 2.6
2008 BMC Streetfire
2010 Gunnar Fastlane

Offline rickpaulos

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Re: S-7 Tire on an S-2 Wheel
« Reply #1 on: July 09, 2014, 04:25:08 PM »
The bead seat diameter (BSD) is the critical measurement. That's where the bead sits on the rim.

S-2 & S-7 refer to the width and shape of the rim, not any specific diameter. Both come in several diameters.

In general S-2 is balloon, S-7 is middle weight.

in 26" Schwinn 26 x 1 3/4 Middleweight, bsd=571mm
in 26" Schwinn 26 x 2.125 Balloon,        bsd=559mm
the difference is too much for any hope of swaping.  Even 2 mm can be a royal pain.

26" x 1.75" is not a Schwinn size but is the same bsd as balloon of 559.

Look at this reference chart.
http://www.schwinnbikeforum.com/index.php?topic=24638.0

You can also look at the Sheldon Brown page on rim sizes.
http://sheldonbrown.com/tire-sizing.html

neither of these references are 100% complete.

Wire bead tires don't stretch much. 

Walmart tires that come in a box, stretch like crazy. Those sure are not your racer kevlar beads in there, more like cheap nylon.

For identifying your rims, if they are stock, see the drawings on the first link above.  They came in chrome or painted.  Other brands of rims have rather different shapes and usually don't have the knurling.  It's plenty common to find the wheels have been changed out on older Schwinns.



"We shows girls love on Valentine's Day, and they let us blow things up on the Fourth of July. I just pray they never fall on the same day."  HS.

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Offline Nick

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Re: S-7 Tire on an S-2 Wheel
« Reply #2 on: July 09, 2014, 11:50:53 PM »
My Wasp also had the wrong tires on it when I found it, I
don't remember what they are but I'll look at it tomorrow
and let you know.



Offline mlorenger

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Re: S-7 Tire on an S-2 Wheel
« Reply #3 on: July 10, 2014, 06:34:50 AM »
Thanks guys.

I looked last night, the rims are indeed s-7 as well as the tires.  Odd, I was actually hoping for s-2 so I could have a better tire selection!
1959 Spitfire?
1963 Typhoon
1974 Varsity
1983 Traveler
2006 Ranger 2.6
2008 BMC Streetfire
2010 Gunnar Fastlane

Offline bartcycle

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Re: S-7 Tire on an S-2 Wheel
« Reply #4 on: July 10, 2014, 10:30:42 AM »
I figured you had S7 rims because the tires would not mount at all on S2 rims and would just fall off.  Mounting new tires on S7 rims can be somewhat tricky because sometime the tire doesn't want to seat and you have to pull the bead out in the low spots.

Offline rickpaulos

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Re: S-7 Tire on an S-2 Wheel
« Reply #5 on: July 10, 2014, 04:29:09 PM »
I suspect the mounting problems are due more to the old rims not being manufactured to tight tolerances.  Modern tires seem very consistent in all sizes.  I do remember having all kinds of battles in the 1970s and early 1980s trying to get 27" tires to fit. Some brands were just impossible to install alone.  Those old rims haven't  magically change to the correct size.  Even today many new 27" tires won't hold on steel rims, again because I think the old rims weren't and still aren't exactly the right size.  I think the manufacturers finally got the standards correct and figured out how to be consistent.

I don't think anyone has made 571 rims (Schwinn s7 middleweight) in the past 30 years or so no chance of verifying that size. But new 27" tires fit very well on all new 27" rims and all 559 tires fit fine.
"We shows girls love on Valentine's Day, and they let us blow things up on the Fourth of July. I just pray they never fall on the same day."  HS.

A:jan B:feb C:mar D:apr E:may F:jun G:jul H:aug J:sep K:oct L:nov M:dec
A65 B66 C67 D68 E69 F70 G71 H72 J73 K74 L75 M76 N77 P78 Q79 R80 S81 T82 U83 V84

Offline bartcycle

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Re: S-7 Tire on an S-2 Wheel
« Reply #6 on: July 10, 2014, 06:11:33 PM »
26x 1 1/4, 1 3/8  tires for S5 and S6 rims sometimes are stubborn to fit.   Actually 571mm rims are made today and are called 650c.  They are made for skinny tires. 

Offline Nick

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Re: S-7 Tire on an S-2 Wheel
« Reply #7 on: July 11, 2014, 10:30:50 PM »
I checked my Wasp today and it has 26 X 1.75 tires on it.
It looks like it has the original S-2 rims.
Still holding air.