Bicycle Mechanics - Swapping Shimano Nexus 3 for Shimano Nexus 7.
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So I have a Breezer Freedom with a Shimano Nexus 3 speed hub. I have put a few thousand miles on it with no significant problems. Only issue is that I don't ride it more because my commute is kind of hilly and the gearing does not have a wide enough range. So I am considering swapping it for a Shimano 7 hub. I could get an 8 speed hub but really 7 gears would be plenty for my commute.
There is no way I am going to do this myself but I am just trying to get an idea for the cost and time to do this.
Other than obviously getting the hub and a grip shifter (together those appear to both cost around $175 to $200 on Amazon), what other significant parts does one need to do this? How long would it take a bike shop to do this and how much do you think they would charge?
I certainly don't want to have to get a new rear wheel as Breezer rebuit my rear wheel under warranty and it is doing great.
Any other tips for doing this project?
10-29-10, 12:11 PM
The Nexus-3 and -7 have significantly different dimensions (http://bike.shimano.com/publish/content/global_cycle/en/us/index/tech_support/tech_tips.download.-Par50lparsys-0015-downloadFile.html/08)%20Hub%20Dimensions.pdf) (pdf file) so you'd have to rebuild the rear wheel. With the cost of a new Nexus-7 plus whatever your LBS charges for 36 spokes and the rebuild itself it might just be cheaper to buy a prebuilt Nexus-7 wheel (there's one on eBay for $170.99 (http://cgi.ebay.com/WHEEL-26-INCH-7SP-ALEX-X101-NEXUS-7-COASTER-SILVER-/200521668162?pt=Cycling_Parts_Accessories&hash=item2eb005d642#ht_589wt_811).)
10-29-10, 12:23 PM
Another thing - the Nexus-7 comes with either a coaster brake or a roller brake. Since you already have a rear caliper brake you probably don't want the coaster brake. The roller brake is fine and has the additional advantage of being effective even in wet weather but if you don't want to use it you can probably just not hook it up. Otherwise you'd have to re-route your rear brake cable, which could be an additional complication.
10-29-10, 02:42 PM
Third consideration. Note the O.L.D. dimension on the hubs listed in the linked to PDF above. The 3 speed and 7 speed hubs may differ. With the wheel removed measure your rear dropout inside width and see if it is close to the listed dimmension for the 7 speed hub. The breezer Freedom is a aluminum frame so cannot be cold set to a different rear dropout spacing width.
The 7R46 Shimano hub is listed as 130mm width. The wider 3R40 is listed as 127mm width. The narrower version is 120mm. If you have the 120mm version of the 3R40 fitted then I doubt if you can fit the 7R46 as a replacement. If you have the 127mm version of the 3 speed then the 7R46 can be fitted with minor springing of the aluminum rear frame IMO or w/o the roller brake fitted it may be very close to the required width.
Again if tour original hub is 120mm OLD then an alternative is a Sturmey Archer 5 speed wide range hub. About the same 250% range as the Shimano 7 speed and it is available in close to 120mm width as is the SRAM P5 IGH hub.
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