Bicycle Mechanics - what size rear axle?
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06-24-10, 02:40 AM
Hi so I am updating my 1984 nishiki cresta gt from a 5 cog freewheel to a 7 speed shimano megarange. The thing is it doesnt fit. So the extra length of the new freewheelcatches on the dropout or rear fork. So that means I need a new axle and some spacers to make it work. I am not sure which size is proper any advice would be appreciated thanks.
Its hard to understand the problem you're having from what you've typed here. Perhaps you need either take a picture of this problem to show people on the forum, or you could go to your local bicycle shop.
06-24-10, 05:16 AM
Just for the hub mod alone...
1. You need to change the axle at the very least to one that allows at least 126mm from outside of locknut to to outside of locknut. You might even end up having to go up to 130mm.
2. You need to provide spacers on the drive side such that the distance from the center of the drive flange to the outside the of the drive locknut is at the very least 43mm. However since most modern basic 7 speed freewheels are going on modern day 7sp freewheel hubs - it might be better to go 45mm or 47mm. Most 7spd 130mm/135mm freewheel hubs are set at 47mm nowadays.
3. Once that is done, you use the non-drive side to fill-in various spacers as needed until you have completed as closely as possible the total 126mm or 130mm locknut to locknut spacing.
- you have to re-dish the wheel....
- you have to do some cold setting of the rear triangle to ensure the newly modified hub will fit properly again.
- you have to re-dial the stop screws on the rear derailleur
- you have to red-dial the shifting
- you MIGHT have to consider a new chain...
In other words...you have a lot of work ahead of you.
06-24-10, 05:23 PM
You probably have a 120mm OLD (over locknut dimension) rear hub. A 7-speed freewheel will probably need a 126mm OLD hub to fit. So you will need an axle about 6mm longer. Actually, if it is a quick-release axle, you can probably get by with the current one. There won't be much axle sticking out past the locknuts, but you don't really need much more than couple mm with QR. I've spaced 126mm QR hubs out to 130mm using the same axle and had only a few mm sticking out on either side and it works fine. You will, however, still need a longer quick-release skewer.
06-28-10, 07:02 AM
i realized it will be easier to upgrade to a 6 speed freewheel for now. I wish i knew that earlier but oh well.
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