signalnc

2 part question--#1--will a new road rim with a new 8 speed cassete fit in between 126mm rear d/o spacing?

#2--is changing from schraeder valve to a presta valve as simple as changing the tube?

thanks

cmdr

#1 Sorry, no. Not without cold setting the frame.
#2 Again no. It would put strain on the area around the valve stem.

cascade168

This is easily accomplished with a Schrader>Presta conversion sleeve like this:

https://biketoolsetc.com/index.cgi?id...tem_id=WB-PSS1

Available at many bike shops. And, you do need the new tube, of course ;-)

signalnc

ok thanks-- is there any great benefit to having either presta or schreader?

Raiyn

Nope <dons flamesuit> They both hold air, but the OCP's will look down their noses at you if you run anything other than presta

z415

Not that I know of. From personal experience it seems that the Presta holds air better, presumably because it has a built in screw cap, but then cars have schreaders... so, I guess its not that much. One thing though, Prestas seem a little more fragile than schreaders. My roommate bent his.

Most road tubes have prestas and 26" mtb tubes have schreaders so I would venture to guess the prestas are lighter.

https://www.sheldonbrown.com/brandt/presta-schrader.html

Check that site^

signalnc

ok thanks

Raiyn

There are plenty going each way. Enough so that the "most" comment is moot.

DVC45

I'm glad there's a thread going with my question already in it. Talking about "timing is everything"!

Anyway, my LBS sold me a new rim for my roady this morning (my current one is beyond repair, so he said), I didn't realize that the new rim is cut for schraeder, I asked him if its okay to use presta on it. He said that its okay.
So, should I return the rim and look for another LBS?

signalnc

ok-I have another tire size question--650 compared to 700--will I notice a difference?

cny-bikeman

#1 Frame can be cold set to different spacing but needs to be done by someone who can make sure the frame is centered and dropouts parallel when finished.

#2 Don't know if they're still available, but there used to be grommets available that would decrease the size of the hole on a schraeder rim to presta size.

well biked

#1 It's usually not too difficult to spread a 126mm spaced frame apart by hand and squeeze a 130mm hub in there each time you install the wheel. It makes installing the wheel a little more of a pain, but particularly with a steel frame it's usually very do-able. As for cold setting, you can only permanently cold set (bend) the rear triangle if your frame is steel. If you decide to cold set the frame, here are the instructions:
https://sheldonbrown.com/frame-spacing.html

There's another cold setting method that will work (and I've used it), where you use a length of threaded rod, washers, and nuts in the dropouts to spread the frame, but Sheldon's method is better because you bend one side at a time, which assures that you'll have proper frame alignment when you're done. Instructions for the threaded rod method here, scroll down to the heading "spreading rear dropouts":
https://www.vintage-trek.com/refurbish.htm

In just going from 126mm to 130mm, from my experience there's no need to worry with dropout alignment. I've got thousands of miles on a frame that I cold set from 126 to 130 and I didn't re-align the dropouts. I've had absolutely no problems. Sheldon points out in his instructions that there's only about 1/3 of 1 degree difference in the dropout alignment as a result of spreading from 126 to 130, and he also points out that the likelihood of a broken axle would be increased if the dropouts were misaligned in the other direction.

#2 My favorite way to deal with that is to use the rubber grommet type adapters mentioned above, if you can find some, that stuff into the Schraeder hole and give a nice snug fit for a presta valve. That being said, I've run presta valves in Schraeder rims before with no problems, but for a high pressure road tire it would be best to use an adapter-

urbanknight

Yep. The presta tube will likely get a blowout right at the valve hole. Working at a bike shop, I've seen customers come in very frustrated that they were getting flats on a daily basis, only to find out they were using presta tubes on rims drilled for schraeder. You could get the sleeve mentioned above, but the LBS employee was talking out of his/her @$$

Just to be sure, 650 tires only work on 650 wheels which only work on 650 bikes, while 700 tires only work on 700 wheels which only work on 700 bikes (a few minor exceptions). If you already knew this and are trying to decide which kind of bike you want, 700 is the standard while 650 is favored for some triathlete type people and riders shorter than 5'. The gearing has to be different to make the final drive ratio the same, but I can only imagine the rest is a minor difference in handling and aerodynamics.

signalnc

thanks-I'll stick with what's on the bike