Commuting - Nexus 7 speed hub

Hi, every one, today I found out a clearence commuting bike with a Shimano Nexus 7 speed internal gear hub, price is 265$, my question is if the real gear can be changed, ie, later the rear gear will wear out, or if you want change the gear ratio, Can the rear gear be changed without give out the whole Nexus hub. Thanks for help.

Lei Lin

If it is anything like a 3 speed hub it should be no problem the rear cog is held on by a retaining ring which can really cause posterior pain(I.E really annoying) if you take it off yourself without the proper tool but it will not ruin the hub.

I'd advise getitng a specialty sprocket puller if your'e going to be doing gymnastics like that.

There's a "proper" tool for removing the retaining ring for three splined cogs???

Other than a small screwdriver?

My understanding is the sprokets and chain will never need replacing from wear and, if you want to change the gear ratios' (like you want harder or easier gears), you would change the front chainwheel.

Anyone know if this is wrong?

I'd say this would be wrong.

While the sprockets and chain would probably last longer, they won't last forever. The amount of wear that would indicate the need for replacement on a derailer bike, would usually be unnoticed on a hub gear or single speed.

AFAIK, Shimano, SRAM, and Sturmey Archer all share the same three-spline cog design. The newer Nexus 8 speed may be a exception, I don't know. BTW, these are the same cogs used on every Shimano-type coaster brake these days. Different sizes are easily swapped, being held on by a circular spring retaining clip. These clips are easily removed using a small flathead screwdriver. 16 and 18 tooth cogs are very common. I just bought a 20 tooth, and I have 12-15 tooth cogs in my parts box.

16, 18, and 20 tooth cogs easily found and cost $2 to $4 each. Usually cheaper than changing a chainring.

where do you buy these 2-4$ sprocket? thanks

LeiLin

I just got a 20t three splined cog from bikepartsusa.com. It was $3.

Sometimes, you can find them in a LBS junkbox for less.

Or you get them for free with a whole kid's bike included, usually dumped in the alley. They're typically all crudded up stuck on a coaster brake hub. But they're easily cleaned up.

This page shows how to remove them.
http://www.parktool.com/repair_help/coaster.shtml

How many teeth are on the bike already? Sprockets larger than 20 teeth and smaller than 16 are kinda hard to find. But they do exist. Sheldon Brown carries these sizes, for more $.
http://sheldonbrown.com/harris/sturmey.html

Thank you very much, the info is much appreciated

Lei Lin

Hub grear bikes do wear out chains and sprockets..... but very s-l-o-w-l-y compared to to derailer bikes. It's a really good thing about them. Also as shecky has brought up, hub gear cogs are dirt cheap compared to 8,9 or 10 gear casettes.

Hub grear bikes do wear out chains and sprockets..... but very s-l-o-w-l-y compared to to derailer bikes. It's a really good thing about them.

This was what was described to me.

The wear on derailer bikes mostly comes from the chain moving accross cogs. Since a single cog drive has no shifting between cogs, there is wear, but it is so slow and so removed from any performance that it doesn't nessatate cog and chain replacement except in unusual circumstances.

Replacement of the rear cog as a gear ratio change, though more involved, has to be less expensive than a chainwheel change.