Originally Posted by
noglider
Luis, you have the terms reversed. The old clusters were called freewheels, and the new ones are called cassettes. Anyway, you can't put the 6-speed freewheel on the 10-speed freehub, but you might be able to use the freehub as it is. The way to find out is to try it. Do you have tires and tubes?
Given that you have these wheels on hand already, they're the best thing to try next. They cost no extra money. They might work!
Commenting or enlarging on Tom"s post, to Luis:
No argument with trying the 10-speed wheel set. I generally have the frame cold-set and the dropouts re-aligned to establish spacing that fully matches the wheel (130 or 135?) when I make this sort of enhancement, because I greatly value the lifetime of my hub bearings. But there is bound to be argument about this point. However, it is one of the choices you face, Luis, in considering this swap. In my experience it costs about $40, even at Ann Arbor's best shops.
I'll also ask, is there an additional 4 mm of brake shoe adjustment slot on both the front and rear brake calipers? That's how far "down" the brake shoes need to move to be able to properly interface to the brake track of the 700c rim, if they were properly adjusted for the 27 inch rims.
You'll probably need to be vigilant about potholes and significant road debris with these wheels. If you've already used them on a road frame you probably already know how to do that.
The wheels with the 10-speed cassette have a much narrower spacing sprocket-to-sprocket than the old 6-speed. The old chain, which might have the same width as the old 5-speed chains, should be replaced with a low-cost or best-value 10-speed chain. I don't know what chain to recommend - my indexing bikes are mainly Campagnolo so I use Campy chains on them. I would probably try the basic model of SRAM or Shimano chain. It does not need it because of indexing, it needs it because the wider chain will catch on the next larger sprocket and shift itself to lower and lower gears with no input from you. This can result in noise and chain jamming - not pleasant to stop on the public road to clear chain jams, getting your hands really dirty on the way to work.
If this cost (chain plus frame adjustment plus possible calipers) comes close to the cost of lacing and tuning some good rims like Mavic Open Pro on there, I would just replace your old rims with new Open Pros and carefully tension, true, and dish the resulting wheels. When made well with stainless spokes they have made very strong long-lasting wheels. If you will be looking over your shoulder (looking for tragedy to come and get you, so to speak) with either the original wheels sans spoke, the 700c's with reduced spoke count, or with low-priced factory wheels that may not have been finished correctly (tensioned, stress-relieved, trued), it might be better just to build good rims onto the existing hubs. Done right they should be better than when the bike was new. And if you sell the bike, you can always keep the good wheels and sell the bike with a set of $25 replacements.