Classic & Vintage - 6 speed to 7 speed freewheel conversion

Newbie here, don't know much about vintage, I'm a 9 speed/10 speed guy. Anyway picked up a sweet Trek 410 with 6 speed freewheel. Could I replace it with a 7 speed one without width problems? If so is there a chain compatibility issue to deal with? Also thinking about putting on some aero brake levers. Maybe that would detract from it's originality.......... Thanks guys!

I recently put a seven speed on my sons road bike and it is the same width as the six I took off. He has friction shifters so I didn't even need to adjust them. Chain worked well also.

You may get lucky, but many 7 speed freewheels are wider than 6 speeds. You will need a wider axle, need to add a spacer, re-dish the wheel and adjust the stops on the rear derailleur if this is the case. You may also have to wrestle the wheel into the dropouts due to the slightly increased width of the rear spacing.

Make sure your 6 spd. is a normal spaced 6 spd, not an ultra spaced 6. I ran into this on my Puch. Even though the drop-outs were spaced at 126mm, it came with an ultra spaced freewheel. I think this is because the bike used a separate derailler hanger, instead of one formed as part of the drop-out. When I went to a 7 spd freewheel, I couldn't get the derailler to go over far enough to engage the large cog. It is really close, if the hanger was in line with the drop-out it would work fine. If you have a standard 6 spd, it should work fine.

A 6-speed standard to 7-speed conversion worked fine with two of my hubs, but my circa 1981 Campagnolo Gran Sport and Ofmega hubs would each require changes in the axle spacers and a corresponding bit of rim redishing, neither of which I have "gotten around to" yet. :)

A 6-speed standard to 7-speed conversion worked fine with two of my hubs, but my circa 1981 Campagnolo Gran Sport and Ofmega hubs would each require changes in the axle spacers and a corresponding bit of rim redishing, neither of which I have "gotten around to" yet. :)