27 X 1-1/8, 1-1//4 same as 700c?

[GTs58]

Here's the 1961 owners manual. But take into consideration that the tires & tubes were better. I installed some new tires and tubes on my 61 Conti a few years ago and replaced the Schwinn tubes, the front tire's stem was starting to rip from the tube. The difference between the two tubes blew my pants off! I inflated the new tubes with just enough air to give it some shape and to get the folds out. That new tube had an ID that would fit a 36' rim. I blew up the good Schwinn tube and it was a perfect fit for the rim. Also, the 61 Continental didn't use Schwinn Tubular S-6 straight wall rims. I live in AZ and if I pump up a lightweight tire and then set the bike in the summer sun the pressure increased considerably. And if your pressure gauge is off and the pressure is actually more than 90# when you inflate it, what happens then?

 

[Fritz Katzenjammer]

Here's the 1961 owners manual. But take into consideration that the tires & tubes were better. I installed some new tires and tubes on my 61 Conti a few years ago and replaced the Schwinn tubes, the front tire's stem was starting to rip from the tube. The difference between the two tubes blew my pants off! I inflated the new tubes with just enough air to give it some shape and to get the folds out. That new tube had an ID that would fit a 36' rim. I blew up the good Schwinn tube and it was a perfect fit for the rim. Also, the 61 Continental didn't use Schwinn Tubular S-6 straight wall rims. I live in AZ and if I pump up a lightweight tire and then set the bike in the summer sun the pressure increased considerably. And if your pressure gauge is off and the pressure is actually more than 90# when you inflate it, what happens then?


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I would assume the issue of pressures increasing when the tire is warm will be the same as on automobiles and motorcycles. Heavier vehicles instructions always include the warning to check pressure when the tire is “cold”, so the manufacturers are obviously aware of this and must be accomidating this in the tire’s design and their pressure recommendations.

Early in my automotive life my Dad suggested I check my pressures on correctly inflated tires after a good run on the highway on a warm day. The pressures had gone up into the 30s from the 26ish psi they were set at when cold, it was quite a surprise for the automotive green horn. I always made sure my checks were done on cold tires after that.

I’ve never repeated this experiment with my motorcycles but I have often amused myself by checking my tire temperature with my hand after an rowdy rip up a back road on the sportbike, its impressive how hot the tires can get so I would assume the pressures get pretty high as well.

gas law: PV = nrT... roughly: pressure x volume = temperature x (nr = fixed constants). So if the volume is fixed, the pressure increase is directly related to the increase in temperature. This gets really exciting if glass vessels are used, having experienced this by blowing some of my lab equipment through a false ceiling... never to be seen again. I suppose its still up there.

 

[Schwinny]

I'll put a plug in for community bike shops and bike salvage.
If you want an old true 27" tube that will be good to use, go to the bike salvage and go through their bins. I doubt you'll find anything but 700c marked and sized new tubes anymore, no matter what the box or tube is marked. With over-all size difference between the two, 8mm is very little and inconsequential in an inner tube.
It is common to hear of people using a size down in tubes width-wise, it's not the tube that is pressure sensitive, they will expand to fill the void. It is the sidewall coming apart or pulling the bead from the rim that is what the psi rating is about.
High pressure tires are to decrease rolling resistance. So the sidewalls and bead surface must be able to take it. The tube is being confined, thus building pressure. Unconfined, a small bike tube will get quite big before it bursts from being stretched so big (and at a much lower pressure). Confined in a tire casing you'd be hard pressed to blow out nearly any tube of any bike tire size at even 200 psi. It would be the valve stem that would fail, not the tube itself.
Most of us don't need ultra high pressure tires (over 100psi) I like to balance rolling resistance with compliance. The tire sidewall is also the first, and on older bikes, the only part of the suspension. A little kush never hurt. The weight the tire is suspending plays a big part. All else being equal, It will take a higher psi to balance out the rolling resistance differences between a 150lb. Rider and a 200lb rider.

 

[GTs58]

Has anyone ever compared a new China lightweight tube to an old Schwinn tube or other American brand? Pump up a China tube and see how it expands way out of shape and diameter size. A good old American tube will keep its circumference and shape and just enlarges in the tube's diameter. Here is what you can do with an inflated China tube.

 

[Jesper]

I have never used the "Slime" tubes (never see them in 700c narrow sizes), but like previous commenters, I do not think there would be any issue with it causing any deterioration of the tube itself (at least not for a long time; tubes sitting on store shelves would be useless when purchased if it did).
I have had to, in an emergency, use an improper size tube which essentially needed to be stuffed into the tire to mount completely deflated (I usually give them a couple pumps to give the tube a liittle shape and prevent pinching during installation). That tube was folded into the tire, but still worked okay. It was not under very high pressure (70psi) and was on a Raleigh Sports so slow speed (<15mph). My main concern was that I would feel a bump when moving, or feel the wheel being out of balance due to the excess tube in one area. I experienced no issues during its short use before being swapped for the proper size.
I use the 700c/27" tubes all the time without any issue and I still ride at very high pressure (100-140 psi) depending solely on the tire manufacturer's min/max specs.
A problem that I have experienced is from running high pressure with cloth rim tape (especially that which has been on the rim for a fair amount of miles) where the tube got near microscopic holes on the inner side of the tube where it pushed against the tape. I guess with the pressure it caused the tape to "dimple" into the holes and eventually caused leaks at those same spots. The tape was still in place and no edges of the holes were exposed, but leaks still occurred.
Using high pressure tape solved that problem. Never had that issue riding at lower pressures even with cloth tape that was probably 10 years old or more.
I never keep the tires at full pressure when transporting wheels/bike in the car due to excessive heat. I have seen (heard!) tires blow from that scenario.
I do not have bike shops pump up my tires because I had one blow from being over pressurized due to a faulty gauge; I only rode 2 miles before the tire exploded after leaving the shop. I always recommend that you have them pump your tires about 5-10 psi below the max pressure just to provide a little buffer in case their gauge is inaccurate. You should also get your gauge calibrated (bike shops should only use calinrated gauges!!) if possible, or do a "field" calibration by comparing pressure readings between your gauge and a properly calibrated one to detetmine it accuracy at the pressure(s) that you would normally ride at; and use a gauge (applies to analog only) which incorporates using the middle range of the gauge for best accuracy regardless of pressure. Gauges are less accurate at their minimum and maximum limits. Professional experince has proven this to be true; and I had to keep my pressure gauges calibrated every 6 months to perform certified work and povide proof or all my reports were declined.
Just ask a bike shop to show you proof of calibration (NIST cert.) on the face of the gauge. A true professional shop will have it, beware if they don't. It is not that expensive for a professional business to have this done regularly. New gauges are not necessarily accurate from the factory (be it on a bike pump or on engineering test equipment). Always verify accuracy or just take your chances!

 

[DrRumack80]

Pasela Panaracer on the World Sport says keep inflated to 95 psi on the sidewall. CST Super HT on the Raleigh Record states 90 psi on the sidewall. Maybe they don't know what they are talking about. I've always ran high pressure on 27 X 1-1'4 bike tires.

Why would I run a lower pressure?

The Record supposedly had been in storage for a very long time - dry rot?

I would not pump up any tire/tube combo beyond 75psi on a 27" straight side rim. The S-6 rims on the Varsties/Contis/Suburbans were all straight side, as were the alloy rims on the fillet-brazed Super Sport and Sports Tourer. In my experience, the tire will begin to lift off the rim at any higher pressure. The only exception to the rule that I have found so far was the '73 World Voyageur I recently sold. The Kenda 27" tires were an extremely tight fit on those rims. Metal Park tire levers were required to finally get the last portion of the bead seated.

Perhaps your World Sport is new enough that it has hook-edge rims. By the late 70's/early 80's, I believe they were being offered on many bikes.

 

[ozzie]

I had 2 new Schwalbe tubes split at the seams within minutes of fitting. Put in a old Chinese made CST tube and it is still holding air. Printed on the box of the the Schwalbe tube was made in Vietnam. I now only fit Taiwanese made Kenda or BBB tubes. The rubber feels heavier and more like rubber! I was amazed the rubber grips on the two 1977 Suburbans I picked up last week still felt soft. They're real rubber not some hybrid modern rubber mixed with other synthetics like you find on many new tires, grips and tubes.

 

[borgward]

I'll put a plug in for community bike shops and bike salvage.
If you want an old true 27" tube that will be good to use, go to the bike salvage and go through their bins. I doubt you'll find anything but 700c marked and sized new tubes anymore, no matter what the box or tube is marked. With over-all size difference between the two, 8mm is very little and inconsequential in an inner tube.
It is common to hear of people using a size down in tubes width-wise, it's not the tube that is pressure sensitive, they will expand to fill the void. It is the sidewall coming apart or pulling the bead from the rim that is what the psi rating is about.
High pressure tires are to decrease rolling resistance. So the sidewalls and bead surface must be able to take it. The tube is being confined, thus building pressure. Unconfined, a small bike tube will get quite big before it bursts from being stretched so big (and at a much lower pressure). Confined in a tire casing you'd be hard pressed to blow out nearly any tube of any bike tire size at even 200 psi. It would be the valve stem that would fail, not the tube itself.
Most of us don't need ultra high pressure tires (over 100psi) I like to balance rolling resistance with compliance. The tire sidewall is also the first, and on older bikes, the only part of the suspension. A little kush never hurt. The weight the tire is suspending plays a big part. All else being equal, It will take a higher psi to balance out the rolling resistance differences between a 150lb. Rider and a 200lb rider.

Last summer I found a true 1-1/4 X 27 innertube at the peddler bike shop in Austin TX. New tube in nice bio degradable package. Made in Taiwan, as I remember. I will stock up on several now that I know they are not easy to find.

The Peddler Bike Shop | Austin

Serving all types of cyclists, including new and veteran riders, road and mountain aficionados, and recreation and transportation cyclists.

www.peddlerbike.com

Forget who made it. Will post the brand name once I buy some more tubes.

 

[DesmoDog]

<snip>
gas law: PV = nrT... roughly: pressure x volume = temperature x (nr = fixed constants). So if the volume is fixed, the pressure increase is directly related to the increase in temperature. This gets really exciting if glass vessels are used, having experienced this by blowing some of my lab equipment through a false ceiling... never to be seen again. I suppose its still up there.

PV = nrT is certainly applicable as you mention, but the thing that trips people up is the change in temperature since Fahrenheit (and Celsius for that matter) is not an absolute scale. A change from 70F to 105F is not a 50% change. It's more like a 6% change so the pressure would only go up the same 6% on a 105 degree day vs a 70 degree day.

Point being, IMHO if your tire explodes because you left it in your car on a sunny day, there was something wrong with it to begin with.

 

[razinhellcustomz]

A problem that I have seen with some multiple-size-fit tubes is during installation.
Sometimes a partially inflated tube seems too-long peripherally to fit inside of the tire, and one has to be careful to not let the tube fold over itself.

The best one I've seen lately was a 26x11/4 tube in a balloon 26" on a 41 Dx I bought last month.. the front tube held air, but the back was shot.. So I bought a 24" Slime tube and made it work for the rear tire.. The bike don't know the difference.. Stranger things have happened...