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I've got a fifteen year old Giant road bike and would like to get new wheels. I've got 700x25tires on the original wheels now and a 7sp. cassette, but since it's so old I'm not sure what size wheels I need with all the sizes available these days. I would like to get some that are lighter (everything now is probably lighter) that are also strong. I'm not hard on wheels, but I'm on the heavy side (6'4", 210lbs.). I don't want to spend a lot considering the age of the bike, but will I need to buy and new cassette and rd as well? Will any 700x25 wheel work? Any help would be much appreciated. Thanks!
 

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Getting into a whole lot of problems

And most will say, if the cassette and rim are not damaged, have the hub rebuilt or overhauled and ride the wheel you have. What you will run into is finding a 700 wheelset that is light because the newer technology of today's wheelsets (lighter) left the 7 speed hubs and technology behind. Not only is your hub heavy so is the cassette, spokes and rim, most of what you will find is used or NOS (new old stock) and it is spaced at 126mm where todays bikes use 130mm spread. Derailleur is not a problem, so from what I can see, overhaul what you have and save for a newer bike if you want light weight. One other option is to have the hub rebuilt, buy a lighter weight rim that is probably a 32 hole rim and have the new lighter rim laced to the old rebuilt hub. This route will still be cheaper than buying a uber light wheelset. Perhaps a Velocity rim or Mavic open pro. Rock solid wheelset/marginal hub, cheaper than a new bike or wheelset build price probably $150-$200?
 

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Do you have an indexed or friction rear shifter? I ask because you can get an 8-speed cassette for around $20, but an indexed shifter for a 7-speed won't work on an 8-speed. I have a 13-year-old Giant hybrid with a 7-speed cassette, but have been happy with my wheels for my purposes and not researched new ones except to discover that an 8+ speed cassette won't work on my wheels.

Guess our Giants are around for the long haul! :)
 

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700x25 is the tire size. You have what are known as "700c" wheels. You can put tires from 20 to 28 (or even 32 if your frame has clearance) mm wide on the 700c rims. Modern road bike wheels are mostly 700c wheels. However the width of the axle is 126mm instead of the current 130mm. 130mm became the standard when they went to 8 speeds, since they needed more room for the extra cog.

If your bike is steel, you can have the rear triangle spread by a shop so it'll accomodate a 130mm axle. Then you can run a modern wheel. Your rear derallieur will probably work with 10 speed shifters, should you care to upgrade to a 10 speed drivetrain. You'll probably also need to change the chainrings so the narrower 10sp chain doesn't fall between them, and of course you'll need the chain.

If you can't or don't want to spread the rear triangle, you can run an "8 of 9 on 7" drivetrain, which uses 9sp parts to fit 8 narrower cogs on the narrower 126mm hub's freehub body. I do this on my Vitus, which is a glued together aluminum frame from the 80s that can't safely be spread to 130mm. Sheldon Brown has a good web page explaining 8 of 9 on 7, google for it.

I have a stock of my old gear from the 80s including a bunch of wheels. They're not significantly heavier than modern wheels. The hubs are a bit heavier but that's because I couldn't afford the expensive hubs back then. The rims are the same or lighter... one set uses some 370g clincher rims, which is as light as you can get these days for clinchers. They are less aerodynamic than modern rims however... plain box-section rims.
 
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