clockwork247

can i just get a 700X28c Presta valve tube and slap it on? will there be any problem? yes it's hella weird that a 700X28c wheel bike uses a schrader valve but i bought it like that lol.

fuzz2050

There should be tubes available; remember that a 27 inch inner tube is the exact same thing as a 700c inner tube. If you want to use presta valves, you can just stick them in, but you risk a puncture from the valve stem wiggling about. They make fancy, and not so fancy adapters that you should be able to find for next to nothing. Or you can put a few turns of duct tape around the valve stem, it's ugly but it works.

FBinNY 

Yes you can substitute a PV tube, but there may (or may not) be problems with the fit of the base of the valve against the larger valve hole. This was less of an issue in the past when the valves had decent base flanges within the tube, but those are rare today.

I use 1/4" stainless steel washers which I've filed down a bit narrower on 2 sides and curved slightly to protect the base of the valve. I've made a bunch of these so I can use my PV tubes to bail out others who have SV rims.

Retro Grouch 

That's the kind of part that internet sellers with lots of volume can stock and excel over local bike shops. I just googled 700c Schrader valve tube and got lots of hits.

clockwork247

yeah i found some on amazon, i think i might even stick with schrader valves, i heard they don't hold air in as well as presta but it's more convenient, just drop by a gas station and pump, so much easier if i'm on the road and get a flat... I've had both type, the pumps for schrader is also cheaper (found one at walmart, compact foot pump with PSI meter, i can slip it anywhere, only 10 bucks).

JanMM

Don't believe everything that you hear.
They both hold air.
Our RANS tandem came with schrader valves - I'm not rushing to change them out to Presta. Probably will do that when it comes time for new tubes, just for standardization - all my other bikes have presta.

FBinNY 

+1

Whatever their differences, if any, there may be in how they hold air it's so small as to be negligible. Presta valves do have some minor advantages for bike tires, they are:

They're narrower, so smaller hole is needed and better clearance between tire beads on narrow rims.
They're lighter, so if you're spending a fortune to shave grams, this is a cheap way to start.
They're springless, which is probably the most significant. the simple no-spring checkvalve design means they don't need a pin to keep them open during pumping, so there's no air loss when the pump is disconnected.

These are all minor benefits, and SV tubes are very available, so if you have SV rims, and an SV pump head, you might as well stick with SV tubes. About the only reason to change them is as JanMM says, to match the pumps and valves throughout the bike fleet.

well biked

GMC Denali and the "new" Schwinn Varsity, with both bikes sold at big box stores, so lots of them out there. These bikes use a semi-deep rim with Schrader drilling, with stock tires being 700 x 28. Because of the depth of the rim, a standard length Schrader valve won't work, so you have to find a longer Schrader valve tube that works with 700 x 28. We see enough of these bikes that our shop carries the long Schrader valve tubes that work with 700 x 28.