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Life Expectancy of a Shimano Nexus 8-speed hub
 Redsfan member online
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Specialized Crossroads Elite
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posted 3/11/2012
at 2:51:38 PM
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I have a Specialized Globe City 6 bicycle with a little over four years of service (in-service early December 2007).

The rear wheel has a Shimano Nexus 8-speed hub. I was giving the bike a good spring cleaning when I noticed the rear wheel has a crack. The crack is right where the vertical side break friction area curves over to form the inside of the wheel. Obviously I need a new rim. However, I recently noticed skipping similar to what one would experience with a worn chain but only in gear 4 (remember this is an internal geared hub). I didn't test gears 1,2 or 3. I normally ride only in 5, 6, or 7. I am worried that my hub may be wearing out too. The bike (and hence the complete rear wheel) has just under 12,500 miles.

Any advice as to whether I should have a new wheel built with the existing hub or a complete new wheel would be appreciated. Also, if anyone has recommendations for a source for wheels built with internal geared hub, I would appreciate that too.

 Redsfan member online
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Spin Doctor Cyclewerks Cycling Club
posted 3/11/2012
at 3:08:38 PM
post #1 viewed 5147 times
Any thoughts on this machine-built wheel available from Harris Cyclery (the WE507 model):

www.sheldonbrown.com/harris/wheelsint.html ?

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posted 3/11/2012
at 3:13:20 PM
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Redsfan, I have a Nexus 8 that has a bit over 9000 miles, laced to a Sun CR18 rim. It is installed on my bad weather commute bike and local errand bike.

First thing to do if you have any shifting issues is verify that the yellow lines line up in the little viewing window on the top of the rear hub when you are in gear #4 (which is the direct drive gear). If the shifting is not quite right, this fixes the problem most of the time. 90 per cent of my riding is in gears 3 to 7, and I suspect that is the case for many users of this product. While you are at it, replace the shifter cable, because if it is the original from 2007 you are probably on borrowed time. If the shifter cable breaks, you will not be able to pedal the bike in any gear.

If you have verified the yellow shifter lines are lines up OK on gear 4, next question is weather the chain is over-worn or the front chain ring is wearing out. IGH hubs don't wear out chains as fast as derailleur bikes, but if that drive system has 12K miles you might have a worn chain and chainring.

Has the hub ever been re-lubricated? A few weeks ago I took the hub gear assembly out of the hub shell and re-lubed the two outer ball bearings. I also dipped the hub gear assembly into a bath of automatic transmission fluid to re-lube the internal gears. Too much detail to explain here but it was not too difficult. See website called hubstrippers.com for lots and lots of details.

I suspect Nexus 8 hubs will last decades if given a little bit of maintenance every couple of years. It is important to keep the shifter aligned on those little yellow lines on the rear hub, because if you ride it unaligned, the gears will not wear evenly in the middle of the gears, they will wear on the edges and the gears could then skip or not stay engaged. Most bike shops will never tell you how important that is because 99 percent of them don't know anything about internal geared nubs.

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Spin Doctor Cyclewerks Cycling Club
posted 3/11/2012
at 3:24:58 PM
post #3 viewed 5142 times
First off, I haven't re-lubed or serviced the hub in any way. Second, I am on the third chain on this bike. It is possible this one is near the end of its life, I will do a chain wear measurement when I reassemble; the bike is taken apart right now since I am not done with the cleaning. Third, at the bike shop I go to there is one part-time mechanic who knows the internal hubs really well but other than that I know more than the rest of them. However, I am well aware of the alignment and check that whenever I have to fix a flat or otherwise remove or reposition the rear wheel so it is normally pretty well aligned but I am concerned that the alignment might be affected when the wheel slips forward in the mounts as it is prone to doing. Finally, since I need to replace the rim, I think it might be economical to upgrade to the Shimano Alfine 8-speed rather than have a new wheel built on the existing hub. It probably won't cost me all that much more to get one with the Sun CR18 rims from Harris Cyclery than to have my local wheel builder rebuild with a new rim and new spokes.

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posted 3/11/2012
at 9:31:04 PM
post #4 viewed 5112 times
Well with 12K miles with no added lube or cleaning I would say it's a pretty good bet the hub is on life support, so if you can get a good buy on a hub that's compatible with your installed shifter, or that comes with a new shifter to match the hub I would go for it. You might also consider going for a hub brake and a manual on how to clean and lube the hub to go with it as the will result in a hub that should last about 100K miles and the rim the same.

Opus

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posted 3/12/2012
at 10:11:32 AM
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RF - I have an 8-speed Nexus on my Breezer Uptown. Similar age with a few less miles. I took it in last year to my LBS for re-lube that was only about $35. If nothing else, 5 year old grease can start getting pretty thick. I would recommend having it cleaned and re-greased before replacing anything as the maintenance might do the trick.

Steve

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posted 3/12/2012
at 11:29:26 AM
post #6 viewed 5076 times
I suspect that the skipping issue had to do with the shifter being out of adjustment. I had to move the anchor nut on the cable to get it lined up when I adjusted it yesterday.

I would like to re-lube the hub or have someone do the job for me. Unfortunately, the bike shop I do business with the most the owner and chief mechanic don't know very much about internal geared hubs (I may be his only customer with one) and would have to learn how to do the job unless the one part-time mechanic knows how to do it. I have been poking around on the Sheldon Brown portions of the Harris Cyclery website where I can buy the recommended grease but haven't found instructions on servicing the hub yet.

Anyway, I think the hub will be fine if I can get it serviced although I am a bit nervous about it.

My choices seem to be:

A: Find a way to get the hub cleaned and re-lubed and purchasing a new rim and spokes and having the wheel re-built (remember, this all started with me discovering a crack in the current rim so that is definitely soon to be in the scrap yard).

B: Purchasing a machine built wheel with the upgrade to the 8-speed Alfine hub which would have the advantage of letting me add disc brakes if I can verify the frame will accomodate them. Harris Cyclery sells a machine built wheel without the disc brake using Sun CR-18 rims (same as the one Raymondj uses) which I have been told by my wheel builder are good but not his first choice. The Harris Cyclery price on their website is $350 which is likely not current.

C: Having a new custom made wheel built possibly even upgrading to the newly available Alfine 11-speed hub or using a hub with hub brakes. That option would likely cost me over $750 just based on the price of the hub and shifter alone being close to $700.

Of course if I don't use the existing hub to build a new wheel, I will have one to experiment with without taking my bike out of service while I play with it.

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posted 3/12/2012
at 11:59:15 AM
post #7 viewed 5073 times
Here is the Volume 2 disassembly / reassembly instructuions / spare parts lists. The assembly instruction include several grease application points.

www.shimano.com/publish/content/global_cycle/en/us/index/tech_support/tech_tips.download.-Par50lparsys-0024-downloadFile.html/17)%20Inter%208%20ohaul.pdf

Here is the Volume 1 (install and adjust) / Volume 2 manuals from Sheldon. Assembly instructions include several grease application points.
sheldonbrown.com/nexus8/

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