I ordered some 7 speed Sora shifters for the 1987 Schwinn Tempo. I will need to get a new 7 speed Freewheel and want to maximize my gearing as best I can with as little changes as possible.

This is my RD

Name: Shimano RD-1050, 105
Brand: Shimano
Primary Group: 105
Model: RD-1050
Years: 1987 - 1988
Country: Japan
Weight: 257 grams (avg)

From Velo base I have that as a 28 tooth max rear cog and 26 tooth max chainwrap. I would like to go up to a 14-28 Freewheel, which puts me one over on the wrap with my 52/39 chainrings.

Will the RD take that +1 tooth chainwrap from its spec? If not, would this be a good replacement? It would give me the option of going up to a mega range if I chose.

Tourney TX51 Rear Der.

Second question, will the FD work with the Sora shifters?

Thanks

From Sheldon Brown:

"A note about capacity:
Manufacturers have to assume that their customers are clueless, and will expect the chain to have some tension on it even in the bad gears where the chain is using small chainrings with small rear sprockets. Thus, the rated chain-wrap capacity is very conservative. A competent cyclist who uses the gears properly can generally exceed this by several teeth with no problem.

Most derailers also specify a maximum size rear sprocket. This is often a pessimistic value, based on the largest sprocket that is normally provided as part of that group."

I think you will be fine in terms of the rear derailer taking up slack as long as you avoid the small-small gear combination. I am running 50-45-24 chainrings with a 14-28 freewheel (40T total) and a derailer rated for 33T capacity. This is no problem, I just have to avoid the 2 small cogs when I am in the 24 up front (chain starts rubbing on the middle chainring then anyways). The 105 will definitely be a nicer derailer than the alternative you present.

+1 The RD you have is much nicer than the one you are thinking of buying. It will probably work, and it is bought and paid for.

Thanks! Im thinking a 32 rear would be pushing my luck though?

32 would be pushing it. Take the inch, not the mile.

The 105 will handle it. Just watch your clearance from the rear spokes.

Most likely you could get away with a 30t, though. I've run 13-30 freewheels with that RD with good results.
Top

The 1050 105 you have is better than the Tourney. If you are planning on running larger cogs (like a 32), I would highly recommend a Deore XT/LX or even an Exage 500LX (M500) c. early 90s as a replacement. They can handle the larger cogs (long cage) and you would have no issues with chain wrap. And they are 7sp index and the quality is equal or better than your 105.