Shimano Nexus 8-speed, gear slippage- Mtbr.com
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  1. #1
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    New question here. Shimano Nexus 8-speed, gear slippage

    Guys, 1.5 years ago I bought this Shimano Nexus hub, shortly after I bought new Lapierre City bicycle.

    I was very concerned regarding of what I read on Sheldon Brown's website about these internal gear hubs being improperly lubricated for use in wet climates. I live in Ireland, and it's very damp here, rains often. Another complication is that my bike is stored inside my house, in a heated space, so when I bring it outside every morning, the air inside the hub obviously contracts as the hub cools down and moisture together with sand and dirt can get inside. This risk is very real since Nexus hubs aren't sealed well, compared to Alfine hubs, in order to prevent that.

    Therefore I decided to follow Sheldon Brown's advice and properly lubricate my hub, in order to prevent water and dirt contamination in future. I did it in January 2015 right after the hub was built into my bike's rear wheel by LBS. First, removed manufacturer's grease using special spray and then dried hub's parts. Then I applied Phil Wood marine grease for outer bearings, white lithium grease for the gears and Phil Wood Tenacious Oil for the pawls and in the hub shell 'to slop around', just like you can see on this picture:


    (picture taken from here) (actually you can see marine grease applied too, where left side outer bearings will sit)

    During all 1.5 months of riding (3-7 times per week, making 2 * 6 km trips) I had and continue having two problems.

    First problem is the gears slip now and then. It can happen once during my 6-km trip, it can happen twice, or not at all. It's especially frustrating when it happens as I'm accelerating standing up on my pedals (and it's always followed by four letter words). I know that gear isn't there 100% and this is very discouraging. Like shwinboydescribed the same issue with Alfine 8-speed in parallel thread, this makes you in-confident and you don't commit to your full power efforts while riding.

    Is this normal? I read somewhere on Amazon, in comments, that a Shimano hub can 'skip' a gear now and then (suddenly go up or down one gear, as I understand), but this is supposedly normal "until the unit 'beds' in". Does this mean that 'slipping', which I have, will also go when the unit 'beds' in? Anyone had such experience?

    Second problem is the sound I hear on 4th and 6th gears. It's like grinding or something, not too strong as sound, more as vibration I feel with my feet. I am also wondering if this is normal and if it will go away too.

    Like I said, I've been riding my upgraded bike for 1.5 months, 5 times per week in average, making 12*5 = 60 km per week. So it's like 60*6.5 = 390 km (242 miles).
    Last edited by sciff; 02-28-2015 at 06:47 PM.

  2. #2
    Loud tyres save lives
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    I have the cheaper non-red band version of the Nexus 8 on my hybrid which is coming up for four years old. The original hub moved gears smoothly and didn't slip but I could feel vibration in the third and fourth gears (fifth is direct drive as I understand it) and over time the eighth gear as well. It went back to the Shimano servicing unit in the UK early on and came back exactly the same so I assumed that was just the way it was.

    As it neared the end of the warranty and the vibration felt worse I decided to have another go at sending it away and this time it came back much smoother than it had been before. The report said it hadn't been properly lubricated at the factory (in line with what you've said) and they'd replaced the internals with a new hub which was set up properly. Third and fourth were smoother than they'd ever been, three years on there's a slight vibration with them but it's barely noticeable.

    The gears very occasionally miss and will click into place shortly after but it's so rare that it doesn't affect my cycling, I know what you mean about not being confident about putting power down as I did have a problem with slipping but it turned out to be the belt tension not the hub that was the cause. I don't remember ever having slipping as much as you mention either time the hubs were new.

    I'll admit I let the bike shop do all the work on my hub as I'm concerned about getting it wrong with the belt and the bike shop have always made a good job of it and they're not that expensive.

    John
    2014 Trek Fuel Ex 8
    2015 Trek Farley 6
    2016 Trek Stache 7

  3. #3
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    Since it seems like you are mechanically inclined, try taking the whole thing apart, cleaning it, as before, but instead of greasing the actual mechanism, dip it up to the sprocket mount, sprocket side up into a jar of ATF for a couple of minutes, then let the excess drain. You'll see many posts about people doing the same for their Alfine 8s, and it isn't far off of the recommended service that Shimano suggests. Absolutely, continue to use waterproof grease on the outer bearings.

    Before doing that, though, check the cable tension adjustment, as frequent skipping is usually a good indicator that it's off. If that's okay, check that there is no play in the bearing preload (rock the wheel side to side, feeling for looseness) as that is also a potential cause of slipping.

    Once you've done those steps, you'll have reached the end of anything you can do without replacing stuff, and considering the hub is within its warranty period, you can try to contact Shimano. I wouldn't mention you slopped non-Shimano lubricants in it, though...

  4. #4
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    I wish I could understand this issue better. I recently installed a Redline hub on my 1983 Trek 720 and I use a Jtek bar-end shifter with a cable adjuster at the hub end. After 600 miles of use, it should be broken by now but it still slips in various gears at the mid range and no amount of tweaking the cable around the yellow line alignment seems to matter. It only happens about once every 20 miles and I've been through all the trouble shooting suggestions except soaking the internals in a bath of ATF or Alfine oil. I like the silent and convenient operation of the IGH but it's an annoying issue that seems more like a design bug with Shimano's take on dog-clutched planetary gear systems?

  5. #5
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    Did some more riding and troubleshooting and it appears "slippage" could be the one-way roller clutch not properly engaging. There is silent operation in the first four gear positions, both in overrun and positive torque conditions, but things change when shifting into 5th gear. There is a momentary but distinct noise, similar to loose gravel, when the one-way roller clutch releases. The "noise" can also be exaggerated by pedaling in reverse but when applying drive torque to the pedals, there is usually a silent, instantaneous and positive response as the roller clutch does its job holding pedal torque. However, if I fiddle enough with releasing and applying pedal torque, I can induce a condition where I can feel a "gritty" click-like noise for approximately 1/4 pedal revolution before the one-way clutch fully engages. After many attempts, I was able to re-create the "slip" condition during this transition period if I applied enough torque - a scary experience and possible nut-cruncher if caught off guard. I dug up an earlier thread about this same condition so I'm thinking there is a design or manufacturing problem Shimano has to know about if it takes the precision of a switch watch for these hubs to function properly. I haven't torn into one of these hubs to fully understand how the sun gear dog clutches and other sliding elements relate to the suspect roller clutch issues but this could explain the problem. I lost confidence in the reliability of Shimano's IGH and if I can't figure out a way to correct the occasional but totally unacceptable "slip" condition, it will be an expensive "lesson learned" to revert back to a conventional rear sprocket and derailleur.

  6. #6
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    John, were you able to fix that? Mine is slipping in the 7th speed. It has ~1000km and mostly using gears from 1 to 5. Now that I changed the crankset and cassette I start using from 5 to 8. Since I saw the problem it made me think it was the clutch. The problem never appears in 1-4.. I will check cabling but it is using Shimano original, original grease, never had water or rain in it. No durty either. Thanks.

  7. #7
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    I'm convinced it's a design/manufacturing problem with the one-way roller clutch that Shimano knows about but won't spend the money to properly address on such a mediocre product. I've given up trying to resolve the issue on my example and I live with the 1/2 pedal rotation skip about once every five miles. I'm using my 1983 Trek 720 touring bike as an occasional commuter and I never risk standing on the pedals. Some day, I'll probably convert to something more reliable or even purchase a new bike. I still like the idea of an IGH but never another Shimano system.

  8. #8
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    I don't know if other brands are better, but this hub comes (as alfine) with really expensive commuting bikes .. When my hub skips/does not engage, it goes more than 1/2 pedal rotation and I fix changing gears again, continue pedalling and turning the shifter back and forth until it engages ... It takes sometimes ~3-5secs to stop slipping...


    I am using the hub with a fixed frame with heavy 700x37 tires. Previously I had 44x19 and used most 1-4 gears without slipping, now I have 38x23 and use 5-8 since the city I live is a hilly city. With this config. I have gears to go up hill, almost like a MTB, but I have to stop pedalling when going down hill. When riding in the flat I usually use 7 (slips a lot) or 8 with tail wind.

  9. #9
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    If your hub slips, it is nearly always because someone has maladjusted the gear cable.

    You can twiddle a derailleur adjustment until it sounds ok, but a hubgear is a precision piece of machinery and needs to be set up properly.

    If the yellow marks on an Alfine hub don't line up in 4th, don't ride the bike until they do, or it is highly likely you will damage it.

    It takes seconds to get it right, don't be a twiddler twit.
    As little bike as possible, as silent as possible.
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  10. #10
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    I've taken my hub almost completely apart a few times and thoroughly cleaned it and I'll admit it is an impressively engineered piece of hardware, especially for its pricepoint, but I still question Shimano's execution and reliability. I've tinkered with adjustments on either side of the alignment marks and insured my shift cable has no friction or drag and I still get the occasional slip condition. Sun gear mesh and tab engagements are fine so it still boils down to roller clutch engagement glitches. I don't know how the 11-speed compares but Shimano could have used a higher element count roller clutch design, not for torque capacity, but to improve engagement reliability or used a different type of one-way-clutch design - I'll bet the cheap Nexus (non-redline) 8-speed with the ratcheting one-way-clutch never has slip issues.

  11. #11
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    My experiences with Shimano IGH is that it lasts only a couple of years when used regularly even when properly maintained . My longest lasting Shimano was 5 years.
    You Experience may vary.

    I think you nailed it : price point

    I wouldn't touch the 11 speed with a 10 feet pole after reading the thread about it.
    "There is a big difference between kneeling down and bending over" -FZ

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