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  1. #1
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    Shimano XT FH-M788 12x142 rear hub - broken freehub body

    I have ridden about 300ish miles on the hub. The freehub body cracked.

    In 20+ years, I have never broken a freehub body before. I do not ever recall seeing a broken one.

    Shimano is sending a warrantee freehub body through my LBS. That is going to take a couple weeks.

    I was not willing to miss riding for a month. So, I bought another XT hub and swapped the freehub body from it. According to Shimano technical documents (here) the XTR freehub body is interchangeable. The XTR may hold up - it is titanium. However, the XT and XTR freehub bodies cost nearly as much as the entire hub. I was not willing to risk the money. I would rather spend XTR hub money to build a new wheel with a non-Shimano hub. I happened to find an XT hub on amazon for $51.50. You have to use the FH-M788 (or the FH-M988 for XTR). The older versions are not interchageable with the M788 12x142.

    If you need to do the switch here are the tools required:
    Two 17 mm cone wrenches;
    Shimano cassette tool;
    a 15mm hex wrench;
    I also used a 30 inch cheater bar.

    Finding the allen wrench is the most difficult part. I ended up with a 15 mm hex bit 1/2 inch drive socket from Napa autoparts (they had to get it from their warehouse).
    • Sears: no
    • Home Depot: no
    • Lowes: no
    • Ace hardware: no
    • Advance Auto parts: no
    • McMaster Carr: Yes - time to ship
    • Fastenal: No
    • Amazon: sort of - Amazon as seller only found a full impact wrench hex socket bit set for $47.50. Or 3rd party sellers with 3-5 days to 4 week shipping lead times.
    • Old crank bolts: No, they are 14 mm. I think mid 80s campy crank bolts may have been 15mm, but I am not sure.
    • Old pedals with hex: considered, but do not have any pedals with more than 2 bolt flats. Would require destroying pedal too.



    There is a Shimano 15mm allen wrench - TL-FH15. I did not find it for sale online.

    Ah, you say, "I am far smarter and craftier than this crit_boy fellow. I will simply buy a bolt with a 15mm head and make my own tool".
    Nope. I thought of that too.
    -M8 is too small. M10 is too big. I am not sure whether M9 exists (or would have worked). None of my sources had any M9 anything.
    -I guess you could try to grind down a larger bolt head. But, you have to put big torque to loosen the FH body on both your old wheel and a new hub. Be careful - an inaccurately ground down tool may strip out the FH body.

    For my old wheel, I had a 30 inch cheater bar on the end of a 1/2 drive socket wrench and had to pull hard. Creaking spokes, etc.

    For the new hub, I ended up destroying the hub body. Once again 30 inch cheater bar, (broke strap wrench), channel locks on rotor mount (which chewed the rotor mount teeth up and bent the hub), and pull hard. I felt a bit bad about destroying the new hub, but there is zero chance of me building a wheel with it. So, no real loss. I am sure you could do this without damaging a new hub. I was in a hurry and did not take sufficient time or planning to avoid destroying the new hub.

    I did the whole swap in about 15 minutes. Not difficult to do. Also, not my first time working on hubs.

  2. #2
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    Shimano XT FH-M788 12x142 rear hub - broken freehub body

    Did you try combining hex wrenches (10 and a 5, 3, 4, and an 8, etc.)?

  3. #3
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    Quote Originally Posted by Bcparker21 View Post
    Did you try combining hex wrenches (10 and a 5, 3, 4, and an 8, etc.)?
    I considered it. I even mocked it up. But, I did not try to break the FH loose with my pile of allen wrenches in the hub. These are gorilla tight. The FH body tightens with pedaling.

    I have been around the block enough times to appreciate using the right tool for the job. Bucking up allen wrenches may work, but I did not want to risk shagging out my old FH body (that would require new wheel build) or the new XT hub (that would destroy my hope at riding for a couple weeks).

  4. #4
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    I have ridden about 300ish miles on the hub. The freehub body cracked.
    Like this ?



    I got a warranty FH-body from Shimano.

    (I thought it was a 14mm allenkey)
    Belgian beer and Scotch whisky.

  5. #5
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    Yep. Like that.

    It is very definitely a 15 mm hex. The tools listed in the first post are correct for the job. I was posting them to help out someone with the same problem. Different hubs may require different tools.

    The hub in the photo is not a FH-M788 with a 12x142 axle.

  6. #6
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    Cool, interesting about getting the freehub off the new hub.
    I bought a couple of cheap Shimano hubs from one of the ChainReaction sales for much less than the freehub was worth. Figured I was getting a freehub plus axles, cones and bearings. But, I've been wondering of I'll be able to get the freehub off. I was thinking of holding the hub with a pipe wrench.

  7. #7
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    Quote Originally Posted by Slash5 View Post
    But, I've been wondering of I'll be able to get the freehub off. I was thinking of holding the hub with a pipe wrench.
    Pipe wrench would probably destroy the hub - at least aestheticly. I think the safest way would be to lace the hub into a rim. You do not have to tension the spokes. Just lacing it up is enough. I have removed a freehub that way before. It worked and no hub damage.

  8. #8
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    Quote Originally Posted by crit_boy View Post
    Pipe wrench would probably destroy the hub - at least aestheticly. I think the safest way would be to lace the hub into a rim. You do not have to tension the spokes. Just lacing it up is enough. I have removed a freehub that way before. It worked and no hub damage.
    I've had success wrapping the unlaced shimano hub in an old tube and then placing it in a vise while I undid the freehub bolt. This worked well and left no marks on the hub. They weren't m788s that are mentioned here.

    But if you don't want to use the hub later then a pipe wrench would be fine. I've bought them donor parts as it's often cheaper than even buying new cones and balls, let alone the axle or freehub.

    Tim

  9. #9
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    Broke mine almost the exact same way, discovered it today. Thought I had a loose cassette but much worst. 1 week before my first race since I started riding in April.

  10. #10
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    Well, second freehub body broke. That one lasted about three weeks. Hopefully, LBS will warranty second one.

    I was climbing a hill, not super steep, no shifting. It made a loud pop. No more freewheeling. I would be surprised if I was making 200 watts when it popped.

    I have no disassembled the wheel yet. But, this failure is worse than the first one. I had to walk out.

    I am thinking this is a design defect - not manufacturing defect.

  11. #11
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    I called Shimano yesterday to see if they upgrade the XT to the XTR since there is a problem with the free hub cracking/breaking. NO!! Very quick and sternly said, I even offered to pay the difference and still a NO. Customer service solution was to buy the XTR and sell the warrantied XT replacement. So I went to my LBS and suggested the same "solution" and he called his dealer and he said no problem. Part ships from California today and should have it by next week. For now I'll use the replacement XT for now and swap out to the XTR. So see what your LBS can do for you.

  12. #12
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    Quote Originally Posted by m5161968 View Post
    I called Shimano yesterday to see if they upgrade the XT to the XTR since there is a problem with the free hub cracking/breaking. NO!! Very quick and sternly said, I even offered to pay the difference and still a NO. Customer service solution was to buy the XTR and sell the warrantied XT replacement. So I went to my LBS and suggested the same "solution" and he called his dealer and he said no problem. Part ships from California today and should have it by next week. For now I'll use the replacement XT for now and swap out to the XTR. So see what your LBS can do for you.
    Did you buy the XTR freehub body or get it as a warranty through dealer?

    I was quoted $309 for an XTR freehub body. No way am I going to drop $300 on a shimano freehub. I would think the XTR Ti may hold up better. But, with the disappointment of the XT, I would not throw more good money at the problem. $309 is pretty close to a hadley hub or dinner out, beer, and a pizza from chris king.

    I asked my shop the same thing - see if Shimano would upgrade the warranty to XTR. I didn't hear back. But, I expect a "no". Shimano is too big to care that XT freehub bodies are failing. I would guess they will keep sending warranty parts every couple weeks.

    Problem is the shop is going to get sick of dealing with it. They are losing money in these exchanges. I remove the body from the wheel and drop it off. They have to spend the time/money to call shimano, receive the new part, and contact me to pick it up.

    The other problem is that I have no faith in the hub. On my ride yesterday, I kept thinking that I needed to back off - I didn't want to damage the hub.

  13. #13
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    Still no hub yet, maybe today. Now there's a hicup, apparently now just the freehub body is being sent instead of the upgrade. Story is that the new hub bodies supposed to be stronger now. Can't believe that since you've broken the replacement hub...so go figure. Looking to purchase some I9's or something, just have to convince myself to shell out that kinda money. Will be money well spent...I guess

  14. #14
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    Or a Hope Evo hub ?

  15. #15
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    Hub Replaced.....

    Got hub replaced with stock replacement, will ride with until middle of next month. Will order I9's end of next month though. Rode this past Sun at Mt. Creek, raced my 1st race ever and man what an experience. Hubs held up to pressures they were put through. So far so good.

  16. #16
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    Quote Originally Posted by m5161968 View Post
    raced my 1st race ever and man what an experience. Hubs held up to pressures they were put through. So far so good.
    Congratulations on your first race. It gets to be addictive. And you are right about being hard on your stuff in a race. You have to do what you have to do.


    OP here - My third freehub body is on its way out. So, we are down to about a week and a half on them. I have babied this one. I have not shifted into the two biggest cassette cogs on this one - but still has not lasted.

    The second warranty is not back yet.

    I am trying to decide between new wheel builds either with a CK hub and SS freehub; or a hadley. Unfortunately, September is a bad month budget wise (car tax, professional dues, etc. - all due in the end of sept or beginning of oct). So, I will hopefully be able to have a LBS warranty a couple more freehubs.

  17. #17
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    When you can build up a strong wheel set, It is nice to know you have an almost bullet prof wheel set under you.

    I have had a good run out of my I9's & hope Pro 2's, But there are other good options.

    I tell people to only go for hubs that can run the XD free hub for XX1 & X01 just so they have that option with out another wheel build.
    Quote Originally Posted by crit_boy View Post
    Congratulations on your first race. It gets to be addictive. And you are right about being hard on your stuff in a race. You have to do what you have to do.


    OP here - My third freehub body is on its way out. So, we are down to about a week and a half on them. I have babied this one. I have not shifted into the two biggest cassette cogs on this one - but still has not lasted.

    The second warranty is not back yet.

    I am trying to decide between new wheel builds either with a CK hub and SS freehub; or a hadley. Unfortunately, September is a bad month budget wise (car tax, professional dues, etc. - all due in the end of sept or beginning of oct). So, I will hopefully be able to have a LBS warranty a couple more freehubs.

  18. #18
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    Quote Originally Posted by muzzanic View Post
    I have had a good run out of my I9's & hope Pro 2's, But there are other good options.

    I tell people to only go for hubs that can run the XD free hub for XX1 & X01 just so they have that option with out another wheel build.
    The I9s do look like nice hubs. I ride with a few people who use hope pro 2s. They like them. However, there are reports of hope failures in the clyde forum. I don't want to have to replace the replacement.

    Good point about the ability to go to 11. I think 11 speed is going to be common in the next couple years.

  19. #19
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    DT 350. XX1 compatible. Cheap. As indestructible as anything out there.

  20. #20
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    Wow, that sucks. I have an M775 XT hub, (10mm axle, regular QR style) and recently broke my freehub. It was on a bike I hardly ever ride, so it probably has about 200 miles tops on it. I was cranking up a steep hill in a low gear when CRICK! instant geared fixie bike! Mine didn't break like yours did. It seems that the internal pawls broke and got wedged between the outer shell and the inner body. Good thing I was only like 3 miles from my front door. I just rode back fixie style. ABC.. always be cranking!

    I did the same thing.... I bought a cheap M775 hub off Amazon for like $55 and robbed it for the freehub body (and QR, since I had a crappy QR on that bike). If it happens again, I'll just replace the whole hub. Problem is, this hub is on my bikepacking bike. I hope to God it doesn't pop when I'm 30 miles out in the boonies with 15 pounds of camping gear strapped to my 28 pound hardtail bike. Now, I'm wondering the wisdom of going out of bounds with a hub that might not be up to the task. Maybe I'll swap on my DT Swiss 240s wheelset for serious stuff.

    It was pretty easy to change out. Just remove the axle/cup and cone bearings, and there is a big hollow allen bolt in there. It comes right out as long as the wheel is built. I forgot what size, but I had the correct one in my tool cabinet. Also. you only really need one cone wrench. You can use a regular wrench on the outer locknut. I always take apart shimano hubs from the non-drive side. The cups and cones are easier to adjust from that end rather than the freehub side.




  21. #21
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    Shimano is losing it!

    I can see how though since axle sizes are getting bigger but free hubs aren't. I'm sure 29" wheels combined with 36t cassettes aren't helping either.

  22. #22
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    For all the great components Shimano makes, and has made over the years, it is amazing to me that their freehubs have been very fragile since, well, forever.

    Just a blight on their reputation, especially when compared to items like their XT and XTR brakes, which the shop guys at my LBS refer to as "Avid Rebuild Kits - Complete".
    The drive towards achievement and success is the motive power of civilization.

  23. #23
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    I didn't see this thread and was commenting on cause and prevention of this failure here...

    What is the future of gear counts?

  24. #24
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    add another cracked freehub to the pile. just figured out that I've got the same issue m7888 12x142. hoping to find a replacement for this weekend. wish me luck.

  25. #25
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    after searching hi and low for a 15MM. I tried a 9/16 hex and was able to remove the freewheel body with that. hopefully shimano has figured it out and updated the body on the replacement I swapped out. my last one lasted only about 200 miles

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