Lacing disc wheels when building.....

Discussion in 'The Workshop' started by bing!, Jun 30, 2014.

  1. bing!

    bing! Active Member

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    We built Donny a set of wheels last Saturday. I build vintage, road and regular mountain bike wheels. I havent built mtb disc wheels in a few months and for the likes of me, I couldn't lace the rear wheel to look like so, following Zinn's instructions. I knew that there were special instructions, but couldnt catch it the first couple of times.


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    I finally had to lace the right rear, turn the hub and insert spokes on the left to make sure it's laced per Shimano's recommendation. I've done this before, but when I'm working with someone else in the garage, my brain just doesnt work right :( .

    Did a little research, and I found a great little trick. Insert spokes on the left side heads in, and continue with Zinn's instructions. Doh! It took me and hour to figure this out myself :(
     
  2. mtnbikej

    mtnbikej Well-Known Member

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    I find that having another wheel to reference is a good way to double check that I am doing it properly.
     
  3. mfoga

    mfoga Intense Whore

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  4. bing!

    bing! Active Member

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    Yeah. I follow that on regular wheels (caliper/v brake). But correct me if I'm wrong, it does not specify corrections for disc wheels.

    On disc wheels, particularly the rear rotor side, the pulling spokes are installed in reverse to have the pulling spokes heads in, elbows out.
     
  5. scottay

    scottay New Member

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  6. mtnbikej

    mtnbikej Well-Known Member

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    I build my own, so I know the lacing is correct. I just don't do it often enough to always remember. So I always know that the one I am referencing is correct.
     
  7. bing!

    bing! Active Member

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    Hahahaha, same here but for a different reason. I build wheels for different kinds of bicycles. I can't remember which is correct just by looking at it. I have to reference lacing to a diagram :). But after wasting 1 hour on it this weekend, I finally found the "why" and won't be confused again. However, when I switch back to building road wheels, I might be confused again :(
     
  8. mfoga

    mfoga Intense Whore

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    Guess not but I have multiple sets of wheels and they are all built the same way, some by me, some by various manufacturers.
     
  9. bing!

    bing! Active Member

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    Ok. It's not a big deal, but since I do this for other people and they usually have at least $ 500 on a set of wheels, I'd rather not get cited for that. Below is Zinn's take on it. I have his book, and I've used it effectively, however, the blurb on correcting for disc wheels is like a five word sentence on 6 pages of instructions. Being familiar with the instructions I kept scanning through and kept missing the blurb :(

    Dear Rob,

    I use the method recommended by Shimano, and I can explain that argument. The idea is that you want the pulling spokes coming to the outside of the hub flange (head in, elbow out) so that you have the widest pull angle to the rim.

    Pulling spokes on a rear wheel that oppose the drive forces of the chain trail behind as the wheel rotates forward — a pulling spoke at the top of the hub flange would be pointed back, behind the bike.

    However, pulling spokes opposing braking forces on a rotor point the opposite direction. Grab the top of the rotor and pull back on it, thus rotating the wheel the opposite direction of travel. This is the braking force direction your pulling spokes need to be opposing. So, a pulling spoke at the top of the hub flange opposing a disc brake points forward, ahead of the bike.

    If you want to end up with the Shimano-recommended pattern, you can use the wheelbuilding chapter of Zinn and the Art of Mountain Bike Maintenance to build your wheel. It describes how to lace front and rear disc-brake wheels resulting in the heads of the pulling spokes on the inboard side of the hub flange. Front wheels have pulling spokes opposing the disc brake to the outside of the hub flange on both sides, while rear wheels have the pulling spokes opposing the disc brake to the outside on the left and the pulling spokes opposing the chain tension to the outside on the drive side.

    Lennard


    Read more at http://velonews.competitor.com/2009...g-patterns-and-more_89375#IKDzB3lczuhPuJ7x.99
     
  10. mfoga

    mfoga Intense Whore

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    Wait you mean the guy trying to sell his book who has written something special about this is saying it has an advantage? Shocking:lol:
     
  11. bing!

    bing! Active Member

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    It's Shimano's recommended lacing pattern, and it is industry standard. Knowing the why helps me remember how to lace disc wheels. I'm supposing its not just because its purty ;)

    Oh, and most wheels builders concur. I just used Zinn cause he is my go to guy. He will answer my emails because I bought his book :) :)

    Shimano recomends a specific lace rotation for each side of each wheel in their Hydraulic Disc Brake - BR-M765 Service Instructions. One issue most bicycle wheelbuilders will face when working with this pattern is that lacing the rear wheel it is done from one side to the other (like a motorcycle wheel), rather than from the inside to the outside as has been standard practic with bicycles for years. The goal of this pattern is to keep the outside spokes on each respective side in full tension while brakeing and only the drive side of the rear wheel being changed. - http://www.peterverdone.com/archive/bikewheels.htm
     
  12. Judge Shredd

    Judge Shredd Member

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    I tried lacing up a set this weekend, but coulndt get either front or back to dish properly. On the front, brake side(left) tensions were around 24-25, but on non brake side were low 20's and i still had to move the rim over the the left another 2mm.

    Did I do something wrong, or maybe didnt get the proper spoke length.

    Hope pro2 hubs (32h)
    Sun mtx 33 rims (32h)
    L spoke length was 1mm longer than the right
     
  13. mtnbikej

    mtnbikej Well-Known Member

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    Prowheelbuilder.com Calculator shows:

    Front 20mm: 259/L 261/R
    Front 15mm: 259/L 261/R

    Rear 135mm: 260/L 259/R
    Rear 142mm: 260/L 260/R


    Also, make sure your tensions are correct.

    Rear Disc side should be 61% of the Drive side.......ie: 100 KgF vs. 61 KgF
    Same applies to the front...non disc side should be 61% of the Disc side.

    So whatever your final tension on the DS(rear) and disc side(front) are, the opposite sides should be 61% of that.
     
  14. b3rnard

    b3rnard Member

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    so, what would happen to disc wheels that's built in complete opposite of the recommended lacing pattern, will it fall apart?
     
  15. bing!

    bing! Active Member

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    Nope. This is all just an effort to make the strongest wheel possible. The worse case scenario is that the elbow will get stressed more than it should and may fail sooner than its supposed to. But that isnt even likely. That's according to the gurus. I just try to follow what others have done before.
     
  16. bing!

    bing! Active Member

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    Considering everything else is correct, its perfectly normal to have the non-brake side/non-drive side to be lower in tension. I think it's the offset that makes it so.

    Again, if everything else is correct, if the drive side is already at or close to max, you can move the dish to one side by loosening the spokes on one side and tightening the other. This will keep the tensions the same and move the dish in the direction you want.

    2mm aint no biggie. You'll be able to make that correction.
     
  17. Judge Shredd

    Judge Shredd Member

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    Ok thanks for the info. I was going crazy thinking both sides needed to be at the same tension. So what would be a good tension for the front brake side and rear drive side. I had them around 23-25
     
  18. mtnbikej

    mtnbikej Well-Known Member

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    That is a big difference in tension. 23-25. Try evening those out first.

    Then after they are set, go 61% on the non-sides.
     
  19. bing!

    bing! Active Member

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    The non-drive side will be whatever is needed to hold the drive/brake side to its optimum tension, dish and true.

    Your primary concern is that the drive side to be at or close to max target Kgf, and that the wheel is built with the spoke tensions to be as close to equal to others on the same side.

    So, if drive side target 24, it should between 23 to 24., and the non-drive side, if the median is 20, 19 to 20.

    What I gave you there is a pretty lofty target for a first time wheel builder. For starters, get within 3 notches on the Park meter. A target Kgf of 24 will vary from 21 to 24. Stretch dem spokes, get it dished, get it true and check for hops. Then after its built, you can fine tune it from there.

    I think I got Krillers wheels to within 0.5 on the Park meter (about 5 kgf) any hop or dip or wobble to less than 1.0 mm :)

    ADVANCED:

    Heres a little trick. When you get it built and the tensions are off, you can balance it by checking the tension of all the spokes on the drive side and loosening or tensioning each spoke that's off to get to the target Kgf.

    Then true again, trying to keep corrections on the non-drive side. Chasing the true this way will have the effect of balancing the tension. Always recheck for dish, radial and axial true. Before you correct on the non drive side, take a reading of the surrounding non-drive spokes. If the spoke you planned to turn is on the median tension, then the spoke that actually needs to be turned is likely next to it or within 2-3 spokes away :). That is, if you have the drive spokes at close to equal as possible.

    This is gonna take time as you need to recheck the drive side a few times as each correction will affect the rest of the wheel.

    note: am a self taught wheel maker and dees is how I door eet.
     
  20. Judge Shredd

    Judge Shredd Member

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    Thanks this helped a million. I was ready to throw these wheels in the trash haha.
     

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