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  1. #1
    Senior Member Tunnelrat81's Avatar
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    Shimano Deore Fr. hub axle too short from factory?

    Found something interesting yesterday while doing some pre-race tuning on a friend's mountain bike. It has a front Shimano Deore (6 bolt) disc hub. He bought the bike new from the local shop maybe 6 months ago and has put fairly regular miles on it since it was new.

    Pulling the front wheel off, I noticed that there was a washer loose on the skewer. "Stange" I thought, and I then noticed that there was more. It appears that the newer shimano axles are only threaded as far as they need to be, allowing the "nubs" to be smooth where they rest in the fork's dropouts. First of all, the locknuts were loose to my hand, not locked at all to the cones, on BOTH SIDES. This likely lead to the cone tightening with use and causing the bearing friction from too much bearing preload.

    On the left hand side, the locknut was directly next to the cone. This differed from the right side (non disc side) where there was a *familiar washer sandwiched between the cone and the locknut. The same type of washer that was on the opposite end, floating on the skewer. So the washer that had begun it's life between the cone and locknut had been removed and placed 'outside' of the locknut for some reason. The spacing ended up the same, but instead of the textured locknut being in contact with the dropout face when installed, it was against a smooth washer, that was then against the dropout face...not exactly the most secure looking configuration.

    In trying to replace it, I quickly realized the reason that it had been removed. With that washer installed, there wasn't enough threading on the axle to thread the locknut in place. And with the washer on the outside, the spacing (and wheel dishing) were in their appropriate positions, but the "nub" of axle was significantly shorter than the opposing side of the axle. It looked like the axle was just simply too short, by 2-3 mm, leaving the threaded section of the axle too short by the same distance too.

    Trying to leave that washer out completely resulted in lock nut spacing narrower than the fork, and when I tried to adjust the brake caliper to accommodate the new spacing, the needed adjustment was outside the range of the caliper...so it wasn't happening. The spacing required the washer's added thickness, but the only way to add it was to have it the way I'd found it, on the outside of the locknut, and diminishing the available dropout contact on that end of the axle.


    SO TO MY QUESTION...

    Am I missing something here? Could I be overlooking something that's going to allow this to all go together as designed, with the washer sandwiched between cone and locknut where it belongs? Or is it possible that they built the hub with a short axle, and during assembly of the bike simply moved the washer to the outside to 'make it work?' One thing that I neglected to do before sending it off with him was to measure the fork's dropout distance to make sure that it was 100mm. If for some reason it's wider than 100mm, and the actual locknut spacing on the hub is correct WITHOUT the washer, than it may not be a hub problem, just a strange design involving asymmetrical washer spacing on the ends of the hub. But I don't think that's the case. Everything indicated that everything was in line except the axle length. Spacing, Dish and caliper alignment were all perfect with the washer where I'd found it.

    Of course I adjusted and tightened both locknuts down (remember they had both been completely loose), but this final issue seems very wrong to me, and I like to follow up on stuff that I don't understand, especially when it's someone else's bike I'm working on. Any input would be appreciated. Thanks.

    -Jeremy

  2. #2
    AEO
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    Senior Member AEO's Avatar
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    too many ball bearings in the hub?

    if they are the standard 8~10mm axle, then the axle should be slightly longer than O.L.D.

    which is approximately 108mm to 112mm
    Food for thought: if you aren't dead by 2050, you and your entire family will be within a few years from starvation. Now that is a cruel gift to leave for your offspring. ;)
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  3. #3
    Senior Member Tunnelrat81's Avatar
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    I'll take a measurement if I get the chance. I don't actually think that would cause the issue I have because, although that would allow the washer to be installed, it would decrease the OLD to less than it should be. I'm pretty sure the OLD with the washer completely removed is less than 100mm. The OLD including the washer between the cone/locknut seems to be perfect, but the threading on the axle doesn't allow for that configuration since the locknut wouldn't have enough threading to mount to.

    If the axle is between 108 or 112, then it's probably within the acceptable range, but I may still have to replace it with a fully threaded axle simply so I can adjust it toward the opposite side and split the overhang distance. The threaded portion of this axle simply doesn't seem to extend far enough for me to do that.

    *edit* Something's fishy about this hub anyway. I don't think shimano would intentionally let a hub roll off the production line and onto a bike with BOTH locknuts completely loose, and cones floating/threading in and out at will.

    -Jeremy

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    Senior Member mechBgon's Avatar
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    Quote Originally Posted by Tunnelrat81 View Post
    *edit* Something's fishy about this hub anyway. I don't think shimano would intentionally let a hub roll off the production line and onto a bike with BOTH locknuts completely loose, and cones floating/threading in and out at will.

    -Jeremy
    They don't send them out finger-tight, but I've noticed that many of Shimano's mid-level disc hubs end up that way after normal usage. It's predictable enough that I make a point of preemptively re-locking them whenever I see one. And not just the front hubs, either!

    Pulling the front wheel off, I noticed that there was a washer loose on the skewer.
    My guess is that the owner did that after the hub fell apart on him. Confirm there are eleven 3/16" ball bearings in each side of the hub (and all seated in the race, not riding up on the edge of it), and that the disc-side locknut isn't threaded on any further than necessary, and you should now have enough threading on the axle for the non-disc side to be assembled correctly (washer between cone and locknut).

    The reason for the smooth ends on the axle tips is so that they always seat the same in the dropout. Slight differences in seating with fully-threaded axles can result in rotor drag.

  5. #5
    Senior Member mrrabbit's Avatar
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    Perhaps its a Deore HB-M525 that's suffered from stripped axle threads? These are very easy to strip and someone who is desperate would remove a washer to grab another thread in...

    =8-)
    4000+ wheels built since 1984...

    Disclaimer:

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    2. I like anyone will comment in other areas.
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    Senior Member Tunnelrat81's Avatar
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    I'll find out the model number, as that would explain a bit. Although I don't remember seeing any stripped threads, I could have overlooked it. As I said, even with the washer on the outside of the locknut, the unthreaded end was only half exposed, as if it was simply too short. This week sometime I'll try and get a ruler on the fork dropouts or some calipers on the locknuts to confirm this. He's going to race the bike tomorrow as is, and I'll get a chance to follow it up after that.

    -Jeremy

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    iirc, the m590 front hub on my Surly had no washers between locknuts and cones. Have you looked at the Exploded View parts diagram on techdocs.shimano.com?

  8. #8
    Senior Member mrrabbit's Avatar
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    Quote Originally Posted by Tunnelrat81 View Post
    I'll find out the model number, as that would explain a bit. Although I don't remember seeing any stripped threads, I could have overlooked it. As I said, even with the washer on the outside of the locknut, the unthreaded end was only half exposed, as if it was simply too short. This week sometime I'll try and get a ruler on the fork dropouts or some calipers on the locknuts to confirm this. He's going to race the bike tomorrow as is, and I'll get a chance to follow it up after that.

    -Jeremy
    Shimano's basic disc front hubs have minimal axle protusion on their axles - 4mm. The first thread for the locknut start at 4.5mm. When I went to lock down the locknuts after an overhaul one day - I stripped the axle.

    You can barely tighten down those very thin locknuts without stripping the axle....

    In my opinion, they should have forgone the 1mm washers in favor of adding another millimeter to the locknuts on each side PLUS starting the first thread at 4mm.

    I had to make my own by cutting down and M10 axles and then using a drill as a lathe to shave off the first 4mm on each end.

    This is just one reason I'm trying to locate a used mini-metal-lathe...so I can do this kinds of stuff as well as shave spacers...

    =8-P
    4000+ wheels built since 1984...

    Disclaimer:

    1. I do not claim to be an expert in bicycle mechanics despite my experience.
    2. I like anyone will comment in other areas.
    3. I do not own the preexisting concepts of DISH and ERD.
    4. I will provide information as I always have to others that I believe will help them protect themselves from unscrupulous mechanics.
    5. My all time favorite book is:

    Kahane, Howard. Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life

  9. #9
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    I'm not familiar with that particular hub, and I don't work on enough different bikes these days to stay up on all the stuff as it comes out. But as far as I know, the only reason the ends of the axle would be turned down is because the axle was oversize compared to class 9mm front axles, and needed to be turned to fit the dropouts. (if they turned down a standard front axle it would be too small and not fit the dropout correctly).

    That might explain why they turned down the axle's ends. As far as to why they work loose, that's probably related to abandoning the wisdom accumulated over the last century, deciding that keyed washers are unnecessary and saving a few cents by doing without. IME hubs, pedals and headsets using keyed washers generally keep their adjustments, those without don't.
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  10. #10
    Senior Member Tunnelrat81's Avatar
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    Just got a text from him a few minutes ago and confirmed that the hub is a HB-M525.

    Tech docs show that the axle ends are machined down, and washers are located on both sides between the cone/locknuts, as I suspected.

    @ FBinNY I agree about the keyed washers. I encountered my first hub with them a couple of weeks ago while adjusting a co-worker's front wheel on an older Centurion. The keyed washer made it amazingly simple to adjust; didn't even need cone wrenches.

    Oh, and here's a link to the tech docs for the M525.

    http://techdocs.shimano.com/media/te...9830647981.pdf

    There's another doc for a slightly different M525 hub, but this one looks accurate. The washers were larger in diameter than the locknuts, which matches this schematic.

    So far I'm thinking that the 'stripping' story may be to blame...but I'll have to look more closely since I didn't notice any stripping before. It's still possible that the axle needs to shift over a bit allowing the second locknut to thread on, but I didn't see any exposed threads available to back up into on the opposing side. That's the first thing I would have done to address this issue, but couldn't because the threading seemed too short. It appears that if I shifted it some more, I would *maybe* only get a 'half bite' of threading on both sides, and wouldn't be able to put much torque on the locknuts without the stripping problem. Boo. Seems like a poorly designed axle if you can't get full thread engagement across a locknut that's only ~3mm thick.

    *edit* Just noticed on the shimano website, their photo for the HB-M525 hub shows threads going all the way to the ends. Hmm.

    -Jeremy
    Last edited by Tunnelrat81; 06-17-12 at 12:00 AM.

  11. #11
    Senior Member Tunnelrat81's Avatar
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    Well the wheel didn't come loose during his 50mi. race yesterday, so that's good. =) I think I'll have him bring it over this evening after work to tear it down and take a closer look at it. If I can't get that washer moved to where it should be, we'll be off to the shop to ask them for a replacement axle. The shimano components are well within their warranty, so if there aren't enough threads to get proper torque, we'll ask for the shop to supply the part, either a couple of mm longer or simply threaded to the ends.

    I'll post up what I find. Thanks so much to those who shared your experience with this hub. It really helps to have first hand accounts from experience mechanics.

    -Jeremy

  12. #12
    Senior Member mrrabbit's Avatar
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    Quote Originally Posted by Tunnelrat81 View Post
    Well the wheel didn't come loose during his 50mi. race yesterday, so that's good. =) I think I'll have him bring it over this evening after work to tear it down and take a closer look at it. If I can't get that washer moved to where it should be, we'll be off to the shop to ask them for a replacement axle. The shimano components are well within their warranty, so if there aren't enough threads to get proper torque, we'll ask for the shop to supply the part, either a couple of mm longer or simply threaded to the ends.

    I'll post up what I find. Thanks so much to those who shared your experience with this hub. It really helps to have first hand accounts from experience mechanics.

    -Jeremy
    If your shop runs into the "distributor doesn't know what the hell they are being asked for even when given a part number by Shimano", give me a holler. I can always make an axle for you.

    =8-)
    4000+ wheels built since 1984...

    Disclaimer:

    1. I do not claim to be an expert in bicycle mechanics despite my experience.
    2. I like anyone will comment in other areas.
    3. I do not own the preexisting concepts of DISH and ERD.
    4. I will provide information as I always have to others that I believe will help them protect themselves from unscrupulous mechanics.
    5. My all time favorite book is:

    Kahane, Howard. Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life

  13. #13
    Senior Member Tunnelrat81's Avatar
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    I appreciate that. He didn't have a chance to bring it by yesterday, so maybe tonight I'll get a chance to work on it. I'll definitely be in touch with you if we need a solution the LBS can't help with.

    -Jeremy

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