changing a 5sp hub to 7sp
 

What is the procedure for changing a 5sp hub (120mm) to 6/7 speed(126)? are there cons to this? Thanks!

Search is your friend, this is a common topic. Sort by relevance, and you should find a lot of useful info.

Sheldon Brown is also a good resource on this subject: http://sheldonbrown.com/frame-spacing.html

You need a longer axle and wider spacing to the rear dropout. That Sheldon Brown link above should tell you what you to achieve those.

Neal

Sheldon says you don't need a longer axle.

Well, not all 5-speed axles I've seen have been the same length!

Neal

The minimum overlock width for a 5-speed hub is 120mm, but by the late 1970s Schwinn had gone to a 126mm OLD, to make room for the pie plate spoke protector and the useless high gear overshift guard. You can easily drop a 7-speed freewheel onto a later Varsinental, but you may have to grind down the shift lever stops to give the right side TwinStick lever a bit more travel. (Been there ... done that.)

One con is that the wheel will have more dish and be more prone to bending the axle.

On 130mm 8 sp freewheels that was a real problem. On 126mm it wasn't nearly as common. It did happen but not often. Personally, I can't think of any reason to go from 5 to 7 sp. Unless you wanted an indexed shifter. You really don't gain anything. Good luck on whatever you choose.

PS, did you ever think about a SS/fixie. You're already at 120mm. Maybe you could sell the frame on ebay to a hipster and list it as a fixie ready ready vintage bike. :D

Cold setting...
 

You will likely have to cold set the stays. This means that you will have to bend the stays to allow the wider hub to fit. You will also have to ensure that the stays are centered to the centerline of the bicycle. The wheel will have to be redished and you just might have trouble with bent or even broken axles.

The bent or broken axle is a pretty common thing in my experience. A great many bikes show up at The Old Shed with bent rear axles and even the odd broken ones. I might also add that a lot of vintage road bikes also arrive with bent stays that need to be recentered at the very least.

My question is, why bother? You can get the same range with a five speed but you will have slightly larger jumps between gears.

ah, i'm not respacing the frame, it is already at 126mm. I'm thinking about picking up a 5sp wheelset and respacing it to work with the frame. I'm not into respacing frames, thats for sure.

Thanks for all the replies, but I was really just looking for someone to tell me what the downsides were to adding some spacers and redishing the wheel were.

Well, you'd need a longer axle, by 6mm. The 7-sp freewheel, if you got one that simply threaded on, would put you right at the inside dimension you'd need, just off-center. The re-dish would only be a couple millimeters, so I'd do it if that particular wheelset is one you want. It's more labor than anything, but not complicated.

The only trick is to find a freewheel that threads right on. I'm clueless as to that. The other stuff, no problem. I doubt the torque is a problem. I lengthened a 126 to 130 and added an 8-sp freehub where there was a 7-sp freewheel, and it's been one of the best set of wheels I've had.

Both rear axles I have broken -- one solid, one hollow/QR -- were 120mm with 5-speed freewheels.

Huh? In the bad old days when I had only 10 (actually, often 8 or 9 because of crosschain issues) ratios to juggle, I had to accept either too narrow an overall range of gears or excessively large ratiometric gaps in the progression. I finally compromised on commuting with 52-42/16-18-21-24-26, which came up short at the top end. For recreational cycling, I used 50-42/14-16-18-20-23, which made the steeper climbs a struggle, particularly towards the end of a long ride. Having at least 6 cogs in back makes a huge difference by giving me just barely enough ammunition to obtain a low/mid 40s to mid 90s range with 6 or 7% steps through the middle. I have augmented my old 50-42/14-23 10-speed standby with a most welcome 26 tooth cog.

You're a BEAST man. I've got a couple of Stumpjumpers at home that were raced and they still have original axles. One's a 1982 and the other a 1986. Both have solid axles. Anyone who can brake a solid axle is either riding a Chinese POS bike or is a BEAST. Personally, I'd rather be a beast.

You know, that's true for me, too, John. The most recent one that broke was a Campy axle as well. I hadn't the wheelset very long, so I can't take all of the blame. But I still generally avoid 7-speed freewheels from the theoretical idea of more-dished and weaker wheels.

Neal

That's why God invented the cassette hub. That way your axle is supported by 3 bearings instead of 2.