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  1. #1
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    Need help installing a new Sinz bottom bracket

    I've pulled the old bottom bracket from my son's Trek MT60 and am trying to replace it with a Sinz sealed bearing unit. There is a small protrusion or bump inside the bottom bracket shell on the frame that is keeping the new bottom bracket from easily going in. The old bottom bracket only had the spindle passing through the frame so it wasn't an issue, but the the new bb has a larger diameter shell that's getting caught on the inside of the frame. Admittedly I didn't have too much time to mess with it before work this morning so I might be able to push it through if I try messing with it but before I did I wanted to know if there was a trick to it or if I'm missing something.
    Thanks!
    Egg

  2. #2
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    I just fitted a Sinz BB to a Marin 20" I'm building up.

    Is it a protrusion on the threads? If so you probably need a tap running through it to cut it out. If it's not in the threads is it part of a fixing for a cable that runs underneath the frame to go to the rear derailleur? If you're stuck fire a picture up.

  3. #3
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    Quote Originally Posted by MIOM View Post
    If it's not in the threads is it part of a fixing for a cable that runs underneath the frame to go to the rear derailleur?
    That's exactly what it is, the fixing point that holds the cable guide to the bottom of the bottom bracket shell. I don't believe it's something that comes off. Almost looks like someone covered a rivet with metal. I might be able to file it down just enough to get the BB in.
    Egg

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    Quote Originally Posted by Locotiki View Post
    That's exactly what it is, the fixing point that holds the cable guide to the bottom of the bottom bracket shell. I don't believe it's something that comes off. Almost looks like someone covered a rivet with metal. I might be able to file it down just enough to get the BB in.
    Can you drill it out from underneath and then use a small self tapping screw for the cable guide?

  5. #5
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    Quote Originally Posted by MIOM View Post
    Can you drill it out from underneath and then use a small self tapping screw for the cable guide?
    I'm at work now so I can't look at it until I get home but I'm thinking I might be able to just file it down a bit. I don't think it needed much more room to sneak it through. It's just the outer edge of the bearing that hit. Once it clears the bb shell is much narrower in diameter so there will be plenty of clearance. Just have to get it to that point.
    Egg

  6. #6
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    Use a high-speed die grinder, dremel tool or even a electric hand drill with a small abrasive grinding wheel to get in and grind the protrusion so your new BB fits in.

  7. #7
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    That's the plan. We've got company coming over tonight but I'm going to try to sneak out for a bit to work on it if I can.
    Egg

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    Let us know. I had vowed not to put any more money into my sons hidden canyon, but I feel like the cranks and bb are such garbage that I can't help myself. Good luck!

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    I had to not only grind down the metal nub but also a small metal ridge that went around the center of the shell. It only stuck up about 2mm but it was enough to keep the new bb from going in. So, the good news is I got it ground down enough to get the new bb in but now I can't get the non drive bb cup to screw in all the way. I stopped trying this morning out of fear that I was going to strip the cup because my tool kept slipping. My fear is that the cups on the new bottom bracket are wider than the old stock ones. I'm afraid there isn't enough room in the shell to thread everything in. I'm hoping it's just really hard to screw it in but I'm fearing the worst right now.

    The new bb is 68 x 113. In theory it should thread right in. Anyone else replace an old cup and cone with a sealed unit on one of these small kids bikes?
    Egg

  10. #10
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    Possible that you got a 73mm bottom bracket instead of 68mm? BB looks like this?
    Sinz Expert BMX Bottom Bracket > Components > Drivetrain > Bottom Brackets | Jenson USA Online Bike Shop

    So long as the drive side cup is firmly torqed against the shell, does not matter if the NDS cup protrudes from the shell a bit, it just needs to provide tension against the center cartridge to hold it in place. If the protruding NDS threads bother you, you can put a lockring over them or else add a spacer between drive side cup and the frame shel to shift entire BB and chainline a couple mm toward right sidel.

  11. #11
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    That's the one I have, with the exception that mine is 113mm. I'll have to take it out and measure it to double check the size. No one marked the check boxes on the bottom bracket or box it came in as to the size. Only thing I'm going on is knowing the size I ordered and what it says on the packing slip.

    It's sticking out way too far for a spacer to accommodate it. If you look at that pic on the Jenson site, mine isn't even in past the red locking compound.

    I'm at work now so I can't look but I'm wondering if maybe it's not going over the bearing but instead butting up against it.
    Egg

  12. #12
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    My son and I just installed one of these last night. 68x113 was marked on the BB itself. The tolerance on the NDS cup was very tight. At first he couldn't even get the cup off the BB when we took it out of the box. Added a smear of grease but still very tight. It went into the frame with no problem but we just had the BB faced and threads chased.

    If the threads weren't perfect I could see it being a problem and the cup butting against the bearing instead of sliding inside. Probably could make do for a Shimano UN54 BB with the plactic NDS cup but not for the Sinz.

  13. #13
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    I brought it over to a friends house last night and using a much nicer BB tool than what I had and he was able to get it installed without an issue.

    The new issue (because this project can't just be easy) is figuring out the gearing and chainline. I new it would be a stretch but tried using a 9sp cassette with a med cage rear der. It seems that a proper chainline isn't possible without the chain just about hitting the rear tire when it's up on the largest ring on the cassette. I have to do some research to see what others have done. I'm running an 11-34 cassette and a 36t ring up front. There is also an issue with the chain tension. Even with the most possible tension on the largest cassette ring there isn't enough in the smallest to keep the chain from falling off. He likes to jump so I'm going to have to figure out a way to fix this. I'm not sure if I'll be able to find a bash guard that will work on the 110bcd crank or not. I don't think there is a way to mount a chain guide on the BB using a square taper. Back to the drawing board....
    Egg

  14. #14
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    I don't see what crankset you're using mentioned. 110bcd leads me to believe a Sinz. To gain tire clearance, are you running the chainring in the outermost position?

    There are bash guards by BBG for 110.

    Medium cage 9spd should have the capacity for 11-34 in a 1x9 application. Is the derailleur installed on the hanger correctly? Might need to be rotated a bit. Either way this issue is not a function of frame size.

  15. #15
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    Quote Originally Posted by bme107 View Post
    I don't see what crankset you're using mentioned. 110bcd leads me to believe a Sinz. To gain tire clearance, are you running the chainring in the outermost position?

    There are bash guards by BBG for 110.

    Medium cage 9spd should have the capacity for 11-34 in a 1x9 application. Is the derailleur installed on the hanger correctly? Might need to be rotated a bit. Either way this issue is not a function of frame size.

    Yes, running a Sinz 145mm. Mounting the ring on the outer position improved the clearance with the tire but it caused the chainline to be ridiculously off. (It maybe lined up with the 2nd smallest ring on the cassette) Moving it to the inner position improved the chainline a little (still way off) but at the same time moved the chain closer to the tire. I'm in the position now of needing to shim the chainring out closer to the frame to get the proper chainline but doing so will cause the chain to hit the tire. The rear der is installed correctly and adjusted but I'll double check it tonight.

    I didn't think this would be an issue but could it have to do with the fact that I'm using a standard 135mm mtb hub (Halo Spin DR) in a frame that is spaced for 130mm? I read online somewhere that it wasn't an issue to do this. The rear hub fits a little tightly in the dropout but it doesn't require force of any kind.
    Egg

  16. #16
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    Other ideas: smaller length BB, check the dish of the rear wheel - maybe dish it to the NDS a bit.

  17. #17
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    Quote Originally Posted by bme107 View Post
    Other ideas: smaller length BB, check the dish of the rear wheel - maybe dish it to the NDS a bit.
    My first thought was shorter BB but I was worried it would move the chain closer to the tire. Dishing the wheel over might allow me to do that. I was going to have the wheel dished because it wasn't totally centered in the frame but when I showed it to my friend/wheel builder he didn't think it was off enough to justify moving it. Maybe we should try that.
    Egg

  18. #18
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    I think your clearance problems are a combination of the short chainstays, 9-speed cluster, and MTB tires. I think probably best solution would be to drop the 11t cog from the casette and shim the entire casette toward right, further away from hub flange. This will get the chainline in biggest cog further away from the tire and will also help allow the RD to keep tension on the chain when in the tallest (13t) gear since it need not cover such a wide span of cogs.
    Other potential fixes; narrower rear tire, longer cage RD.

  19. #19
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    Keep the rim dished between the axel locknuts, moving the rim off centerline of the frame is not good idea.

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    Quote Originally Posted by GrayJay View Post
    I think your clearance problems are a combination of the short chainstays, 9-speed cluster, and MTB tires. I think probably best solution would be to drop the 11t cog from the casette and shim the entire casette toward right, further away from hub flange. This will get the chainline in biggest cog further away from the tire and will also help allow the RD to keep tension on the chain when in the tallest (13t) gear since it need not cover such a wide span of cogs.
    Other potential fixes; narrower rear tire, longer cage RD.
    Would going down to an 8sp cassette help at all?
    Also, how would a long cage RD help? I was thinking it was the opposite, that I should swap out the medium for a short.


    Quote Originally Posted by GrayJay View Post
    Keep the rim dished between the axel locknuts, moving the rim off centerline of the frame is not good idea.
    The wheel was built by an experienced builder but at the time of the build it was trued only in the stand as we didn't have the bike with us. When the wheel is on the bike the rim is maybe an 1/8" closer to the drive side chain stay than the non drive side. Do you think moving it over a bit would help?

    I want to thank everyone for the help. I'm very appreciative of everyone's suggestions.
    Egg

  21. #21
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    8sp cluster on same casette body would make no difference, it still locates the big cog in same place, you need to space it over.

    You need to determine if it is the wheel or the frame is at fault. To verify that the wheel is dished correctly, flip it reversed in the frame, see if the misalignment moves to other side or if it is still toward drive side when flipped. If the dishing is at fault, fix the wheel. If the frame is at fault and it is not centering the perfectly dished wheel between the chainstays, take a round file to the offending dropout and lengthen a bit to center the wheel. If the frame is misaligned and you just re-dish the wheel, it might get centered between the chainstay but entire wheel will still be skewed in the frame, makes for poor handeling, hard to ride no-hands when the wheel is trying to go sideways.

    Short cage RD will probably be unable to shift into a 34t. Have you adjusted the b-tension screw on the RD? You may need ot back it out some so that RD is further from the casette in order to shorten the chain enough that it is not slack in small cog.

  22. #22
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    Quote Originally Posted by GrayJay View Post
    Have you adjusted the b-tension screw on the RD? You may need ot back it out some so that RD is further from the casette in order to shorten the chain enough that it is not slack in small cog.
    Loco, This is what I was referring to above when I mentioned the RD needed to be rotated a bit. The "start" position of the RD needs to be clocked a bit so that when it reaches the 11T it still has some spring tension. This is totally separate from the 2 limit screws and their function. If the hanger or frame isn't in total alignment you may need to go back and adjust the limits after fiddling with the b-tension.

    A longer cage RD has the capability of taking up more slack in the chain. Long cages are usually spec'd with 3x systems for this purpose. Chain is usually sized for large ring large cassette combination, though such cross-chaining is never recommended and not needed. Cage will be near full extension in this case. At the opposite end, when you are in the small/small combo the RD cage will be fully curled. This is where you are having the issue.

    Short cages are for smaller ratio systems where chain growth isn't such an issue. You can get away with a Med cage in the 1x system you're attempting.

    Another possibility is that the chain is too long. Take a picture of the drivetrain in the highest and lowest gears for us.

  23. #23
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    Thanks again guys! I was away all weekend and didn't get a chance to mess around with it. I'm hesitant to put a longer cage der on just because the medium cage is so close to the ground already. I'm going to try taking the 11t cog off and spacing the cassette over as suggested. I'm also going to dish the wheel over a bit. One other thing I noticed looking at it this morning (sorry I didn't have time to take pictures) was that the drive side crank isn't pushed onto the bb spindle as far as the non-drive side. We used a Park Torque wrench putting it on and it took a ton of force just to get it to a little over 200 inch pounds. I think the spec was around 300 inch pounds. I'm wondering if we might be able to move it over a bit.

    I'm also starting to think it might make more sense to drop the 9sp set up and just go with a 7 or 8sp. I only went with 9 because I had a practically new drive train in my parts bin I could use but I've spend so much money on this build already picking up some 7 or 8sp stuff isn't a big deal.

    Biggest lesson learned so far is I should have never waited until now to do this. It should have been done over the winter. My son's been without a bike now for over a week and it's killing him. I'm really hoping to have it all figured out before the weekend but work and other life stuff is nutty this week. Anyway, I'll update as I make any progress and thanks again to everyone for the help!
    Egg

  24. #24
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    Spindles can be asymetric, might be that it protrudes further toward the right than left. Doubt that the chainline will move much with extra torque.

    8 speed casette is same width as 9 speed, cogs are just thinner and spaced closer together (see sheldon brown cribsheet). Doubt there would be any reason to use a 8-speed cogset if you already have 9-speed cassette and shifters. The real chainline benefit would come from using a 7-speed casette body which is 5mm shorter than 8/9/10 speed body. Trouble is I doubt that replacement 7-speed bodies exist for your non-shimano hub. You will get much the same benefity from dropping the 11 from your 9-speed cogset, spacing it over. Only downside is that the hub flange does not also move over but wheels are probably kid bomb-proof already as-is. Give it a try since you already have the parts. Casette still seems to stay on fine without the smallest knurled cog helping engage with the casette lockring.

  25. #25
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    After I typed that last post I remembered you mentioning there being no advantage to going down to a 7 or 8sp. I'm going to try shifting the cassette out by removing the 11t like you suggested. What is the concern with the hub flange not moving? Does it have to do with having all that extra real estate for the chain to possibly drop into? The wheels I had built up are super burly.
    Egg

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