GX 1x11 - chain gap changed after installing new wheel- Mtbr.com
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  1. #1
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    GX 1x11 - chain gap changed after installing new wheel

    Hi everyone,
    So the stock wheel on my Specialized Chisel comes with the pg-1130, 11-42 cassette and GX derailleur.

    I got a new rear wheel and put a 10x42 xg 1175 on. When I installed the wheel, it would not shift into the 42 cog and when I checked, there was virtually no chain gap. It seems the gap between the large pulley wheel and the 42 cog had pretty much disappeared even though it was close to optimal on the old wheel.

    Is it normal to to have the chain gap change like this even the largest cog is the same on both wheels?

  2. #2
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    Did you have to adjust the shifting at all or did you just drop the wheel in and it shifted perfect except for this issue? The only difference between these two setups is that your old one used the old standard slotted freehub that Shimano still uses and the new wheel uses the SRAM SD driver freehub which screws on. So if you had to adjust cable tension to adjust shifting, maybe the cassettes are in a different place, i.e. the new one is further inboard, which could theoretically effect B-tension adjustment.

    Another thought, what is the new wheel you got? Back when 142x12 came out SpecialED made some tweaks to the stock design and actually had a freehub that was 3mm further outboard than others, they called it 142+. so don't know if maybe they've done similar here with 148x12.
    Quote Originally Posted by Harold
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  3. #3
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    Hi LyNx
    After I dropped the wheel in, it shifted pretty well in all the other cogs except for the largest 42.

    Basically, it seems to work pretty well except that somehow the high pulley wheel is really close to the 42. There wasn't even any brake rub which is what I expected to see.

  4. #4
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    Well, not something you'd experience a lot, but maybe the RD was installed without the stop being right on the tab and when you installed the new wheel, the RD moved down/forward till they touched. I've had this happen when not paying attention installing newer RDs and if putting tension on the RD to start the bolt to thread in and then keeping it instead of letting go. Try loosening the bolt that attaches the RD to the hanger and move it back slightly so that the stop tab doesn't contact the hanger, see if you get your clearance back, if you do, then the RD wasn't installed properly and once it is, you need to tighten the B-tension screw in to gain the proper clearance. Other than that, no clue.
    Quote Originally Posted by Harold
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  5. #5
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    If the large cog is the same size the gap from it to the jockey wheel should remain the same.

    Did you also change the chain? If you've left it any longer the gap will be smaller.
    Did you also change the chainring? If it's smaller the gap will be smaller (effectively longer chain)
    Otherwise something has happened with the b-tension bolt. It's been screwed out. The bolt is not contacting the hanger correctly (less likely), or the hanger has rotated and isn't in the right position (really unlikely as you'd have to not have the thru-axle going through it to install the wheel).

    If chain length is correct, and hanger/derailleur are installed correctly, then just adjust the b-tension to get the correct (12mm) gap. Then put your old wheel back in and see if it stays correct with the swaps.

    Note that it may also not be shifting to the 42 if the 'L' limit screw is too far in. The cassette on the new wheel might be slightly more inboard than the old one.

  6. #6
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    Thanks for the great suggestions. This place always delivers.

    aussie_yeti, I did not change the chain or the chainring. Only the wheel.
    Last edited by hesitationpoint; 10-23-2017 at 06:34 PM.

  7. #7
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    I took some measurements and it looks like the new cassette is about 1/32 of an inch (0.8mm) more inboard than the old cassette. I think this might be the issue since the old cassette didn't have much chain gap - just enough for the chain to get into the largest cog.
    Do you think it is a good idea to put cassette shims/spacers in to try to even out the distance? I was hoping to just be able to swap the wheels out in a plug and play way since I have different tires on the wheels for difference purposes and would be swapping frequently.

    I've also attached a photo of my hanger b-tension bolt. Does it look okay to you guys?GX 1x11 - chain gap changed after installing new wheel-img_20171030_202030.jpg

  8. #8
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    If you have the room on the freehub to do that, that would probably be the easiest solution. What are the 2 hubs you have? Other than that, you have lots of B-Tension adjustment open to you, so just set up the new wheel and count the amount of turns you need to add to the B-Tension screw and to the barrel adjuster to get shifting right.
    Quote Originally Posted by Harold
    You're doing mtbr wrong, you're supposed to get increasingly offended by the implications that you're doing ANYTHING wrong.

  9. #9
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    Thanks, that makes sense. The new hub is a DT Swiss 350. The old hub is just the stocked Specialized one that came with the Chisel 1x model.

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