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View Full Version : Bike tire inner tube sizing.


Tripler
10-18-2012, 11:19 PM
Last week, I rode my bike to work--had a blast! But, my awesome day was ruined when I found my rear tire's tube had ruptured near the stem. I'm fixin' to order a new tube from Amazon, but don't know diddly squat about the inner tube sizing.

I see "700x35/43C" embossed into the rubber in large letters, and "700x38C" in smaller letters somewhere else. I don't want to order the wrong thing and have to send it back--are these the sizes I should be looking for?

Tripler
. . . had to call the wife for a ride home. :mad:

tellyworth
10-18-2012, 11:22 PM
Is that size on the tyre or the old tube?

It's likely that a tube in either size will do fine. Order two, and carry a spare.

running coach
10-18-2012, 11:24 PM
The tubes stretch. If your tire is a 700x38C then the 35/43 tube will fit.
The numbers on the tube is the range it will fit.

Tripler
10-18-2012, 11:33 PM
That was the size of the tube on the tube itself, telly.

Seems the leak had sprung forth from the valve cutting into the side of the rim. The tube was deflated long enough to shift on the rim and I didn't catch it when I filled the tire.

The tubes stretch. If your tire is a 700x38C then the 35/43 tube will fit.
The numbers on the tube is the range it will fit.

Sweet! Thanks for the help! I had a Schrader valve on the original tube. Am I stuck with ordering a Schrader, or can I get a (seemingly more resilient) Presta valve?

Tripler
Lookin' forward to biking again.

running coach
10-18-2012, 11:37 PM
You can get Presta valves in that size but since the rim is drilled for a Schrader, you'll need a rim hole adapter. (http://amazon.com/Schrader-Presta-Rubber-Rim-Hole-Adaptor/dp/B000XNZU1S)

Rick
10-18-2012, 11:40 PM
Looking at Amazon, it appears that a 700X38 tube comes in both a schrader valve and a presta valve. They are not interchangeable. Presta vs Schrader (http://sheldonbrown.com/brandt/presta-schrader.html)

Tripler
10-18-2012, 11:59 PM
Got it. . . thank you both!

I'm ordering a 700 x 35-43 now. I just will have to keep the tire either inflated, or keep the tube from shifting again. Should be easy enough. . .

Tripler
Much obliged, guys!

Dag Otto
10-19-2012, 12:01 AM
If you think you will be riding often (and it's cool that you are commuting) you may want to order a spare tube or two. If you get a small saddle bag, you can carry a tube, tire levers, a patch kit, and whatever else you need to fix a flat on the road. You'll need a pump too, larger frame pumps are more useful, but a mini-pump work also. Swapping out a good tube for a flat one is much quicker than trying to patch one on the side of the road. Just remember to check the tire and remove whatever (glass, thorn, wire, etc.) caused the flat in the first place.

Presta valves are not necessarily more resilient than Schrader valves, but they are more common on bikes and have an advantage when you need to let air out of a tire quickly. Most bike pumps have a pump head than can adapt to either type of valve.

How long is your ride to work, one way?



Hint: if you carry a spare tube in your saddle pack, stick it into an old sock to protect it. If you just shove it in the pack, it will eventually wear a hole in it just from rubbing against some part of the pack. I learned about this the hard way.

Kevbo
10-19-2012, 11:24 AM
The OP is taken care of, just a couple of notes for folks who find this thread via a search:

Old Chicago Schwinn bicycles used proprietary sized rims and tires, which are not the same as others with similar or identical numbers. Beware! Tubes stretch enough you can get by, but you have to get tires made for a Schwinn. The one exception is the 26" Schwinn balloon tire size, which was adopted when Mountain Bikes became popular. Current mountain bike sized tires will likely fit an old Schwinn cantilevered frame cruiser.

700C road bike wheels and 29er MTB wheels are the same diameter. The only difference in the size of the tubes is the width range, with 29er tubes being wider. 29er MTB tubes tend to be specified in inches, and 700C in mm. 25.4mm/inch is the exact conversion factor, but 25 or .04 for the inverse is plenty close enough to get the right tube. 29er tubes are more likely to be Schreader valved, 700C more likely to be Presta, but there are exceptions, so pay attention.


700C tubes will stretch enough to work fine in old 27" road bike wheels. You may need a bushing/grommet for the valve hole as a lot of the old 27" rims were Schreader, and the narrower 700C tubes tend to be Presta valves. And of course you will need to convert between inches and mm.

If I have a choice between two sizes of inner tube who's range covers the tire size, I get the wider tube, and may even "fudge" to a very slightly too big tube. (no more than, say 5-7mm) It was probably manufacturing defects, but I have had brand new tubes split when first aired, so I prefer they stretch as little as possible. You do not want a tube that is way oversized though. If it does not have to stretch at least a little to fill the tire, then it will have wrinkles that can result in wearing through the tube over time.

scr4
10-19-2012, 12:07 PM
I had a Schrader valve on the original tube. Am I stuck with ordering a Schrader, or can I get a (seemingly more resilient) Presta valve?

I haven't seen any evidence to suggest Presta valves are more resilient or reliable. Schrader valves are used on bicycle air shocks which are usually designed to be pumped to 250 psi or higher. The main advantage of Presta valves is the narrow width, but if your rim is wide enough for (and already drilled for) Schrader, I'd stick with it.

For future reference, it's usually better to look at the size marking on the tire, not the old tube, because there's no guarantee the old tube was of optimal size for that tire. But you just ordered the same size tube as was in the bike, so it shouldn't be a problem.

By the way, this would also be a good opportunity to inspect the rim tape and make sure it's in decent condition. If it's worn through (or just worn down) in some places and metal is poking through, order a new tape as well.

scr4
10-19-2012, 12:14 PM
If I have a choice between two sizes of inner tube who's range covers the tire size, I get the wider tube, and may even "fudge" to a very slightly too big tube. (no more than, say 5-7mm) It was probably manufacturing defects, but I have had brand new tubes split when first aired, so I prefer they stretch as little as possible.
Hmm. I've always taken the opposite approach myself, reasoning that a fold or crease in the tube is worse than stretched rubber.

By the way, if a new tube bursts when first pumped up, the most common cause is incorrect installation - namely, the tube was pinched between the rim and tire. I've had tubes burst immediately, or a few hours later in the middle of the night. Eventually, I started inspecting the tire thoroughly after replacing a tube: I inflate the tube slightly, then run my finger between the rim and the tire all along the circumference, on both sides, to make sure the tube isn't pinched there. Ever since I started doing it, I haven't had a new tube burst.

Another thing that helps is to NOT use a tire lever for installing a tire. The tire lever should only be necessary for removing the tire.

snowthx
10-19-2012, 12:20 PM
Seems the leak had sprung forth from the valve cutting into the side of the rim. The tube was deflated long enough to shift on the rim and I didn't catch it when I filled the tire.

Make sure you address this before you install a new tube. If there is a rough spot on the valve hole, you will incur another flat for the same reason. If you are not comfortable smoothing it out on your own, a local bike shop can help you repair it. Always identify and fix the source of a flat before installing a new tube.

And, what Dag Otto said about having some basic supplies to handle a flat in the field. Practice changing the tube out while you are at home using only stuff that is on your bike.

running coach
10-19-2012, 12:35 PM
I've found that with narrow road tires/rims, a lever might be needed to get the tire back on. I had one combo, even the shop couldn't get the tire on.

Use a Quik-Stik (http://rei.com/product/546083/quik-stik-tire-changer), not a lever.

I personally prefer Presta, I've had trouble with the Schraders sticking in the pump head(multiple pumps, floor and frame).

Tripler
10-19-2012, 10:23 PM
If you think you will be riding often (and it's cool that you are commuting) you may want to order a spare tube or two. If you get a small saddle bag, you can carry a tube, tire levers, a patch kit, and whatever else you need to fix a flat on the road.

I did better. I mounted ammo cans (http://i43.photobucket.com/albums/e396/TriplerSDMB/P5130050.jpg)! ::cough::NERD!::coughcough::



How long is your ride to work, one way?


It's about 5.7 miles, according to Google maps.


Hint: if you carry a spare tube in your saddle pack, stick it into an old sock to protect it. If you just shove it in the pack, it will eventually wear a hole in it just from rubbing against some part of the pack. I learned about this the hard way.

With the hard-cased side of the ammo can, is there any reason I can't leave it in the original packing box? Should I take it out and flex the rubber from time to time, or maybe even repack it to make sure no cracks develop?

snowthx, this is the first 'adult' bike I've had in almost a decade, and I happily learned quickly that it came with an awesome invention--that tension lever bolt that fastens the axle to the frame. I don't know the actual nomenclature, but that little flip handle made getting the tire off sooooo much easier.

But all y'all, I will be inspecting the tape and re-installing the tube correctly. I'm going to examine the hole in the rim too. I don't think the rim is burred; I think it's just that I let the tube slip along the rim so the hole could have a friction point on the valve neck. :smack:

Thanks for the advice, guys!

Tripler
"On the road again. . . just can't wait t'git on the road again. . ."

chacoguy
10-19-2012, 11:17 PM
You can't blow up a bike tire? :dubious:








:D

snowthx
10-22-2012, 05:35 PM
snowthx, this is the first 'adult' bike I've had in almost a decade, and I happily learned quickly that it came with an awesome invention--that tension lever bolt that fastens the axle to the frame. I don't know the actual nomenclature, but that little flip handle made getting the tire off sooooo much easier.

AKA: Quick-release. Happy riding!!

Kevbo
10-23-2012, 12:09 PM
If this is your first experience with the quick release lever, then you are due a warning:

The lever has a cam action, so you put the lever in the loose position, tighten the screw side to the correct point, and then turn the lever 180 degrees and it cams tight. The lever should start to offer resistance at about straight out, and be pretty snug when fully thrown. The QR skewer compresses the axle enough to effect the bearing adjustment, and this is taken into account by good bike wrenches, so it is important not over tighten the QR...if you need a tool to open it, then that is way too tight unless you are a kid or a very petite flower of a thing.

The wrong way is to use the lever as a wrench to just screw the thing tight. Yes, people really do this. This leaves the wheel tight enough to stay on for a while, and then come off when the worst possible circumstance happens.

As a result, ridges have been added to the fork openings that prevent a wheel from coming off unless the threaded part is backed off. These are known as "lawyer lips", and are an object of scorn among the cycling community. Basically, they make the front QR about 60% as useful as it would otherwise be. Instead of leaving it alone, you have to back off the adjustment each time, then futz around to get it right again.

scr4
10-23-2012, 01:02 PM
As a result, ridges have been added to the fork openings that prevent a wheel from coming off unless the threaded part is backed off. These are known as "lawyer lips", and are an object of scorn among the cycling community.

It's only scorned by roadies; it's an essential safety feature for a bike equipped with disc brakes.

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