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  1. #1
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    29er Wheelbuild Lefty / Delgado Disc questions

    Hi,
    I have some wheel build questions. Longish intro...

    I have built the following wheels for a new ride using a Park TM-1 Tension Meter:

    Front wheel:
    Cannondale Competition 32H Lefty Hub
    Spokes 2mm non-butted DT Swiss
    Nipples: Brass
    Rim: Delgado Disc
    Dish: Centered between flanges

    Rear Wheel:
    Surly New Disc 32H Single Speed Hub, QR
    Spokes: 2mm Non-butted DT Swiss
    Nipples: AL
    Rim: Delgado Disc
    Dish: Centered between flanges


    I attempted to build both wheels to a tension of 107 KgF. I chose 107 KgF because it equals the 24 reading on the TM-1's scale.
    23 = 95 KgF
    24 = 107 KgF
    25 = 121 KgF



    I built the front wheel for a Lefty and it was pretty smooth going, relieve stress after every truing iteration and slowly bringing the tension up to about 24 (107 KgF).

    The rear build was a bit more problematic, it seemed that when the wheel was true in the stand that the tension was not as even as on the front wheel, there were greater variations. I tried to build the wheel by bringing the tension up evenly and relieving stress after every iteration. When the wheel was trued it seemed to cause a greater tension deviation as seen on the tension diagram.

    My first question:
    Do I need to worry about the tension variation on the rear wheel which graphically seems to be all over the place?

    My second question is based on the perceived difference in flexiness of the wheels.
    The rear wheel with the Surly Single Speed hub does not flex when I try to bend it by placing it on my lap, grabbing the wheel at the twelve o-clock position and squeezing with my elbows down on the 3 and 6 o-clock.
    The front wheel however flexes about 1 cm and then sproings back into position. This does not affect the trueness, however it is weird when compared to the rear wheel which is rock solid.

    Why does the front wheel feel so much more flexy? Is it the C-Dale Competion hub with different flange diameters? Other than the nipples, the hubs are the only difference.

    Cheers,
    Marty
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  2. #2
    The Top Cap Guy
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    Marty

    Could the 'springingness' of the front wheel be due to the fact its not an equal dish? Where as the rear wheel is using same sized spokes on both sides and with equal tension (theorectically) they pull and flex the same side to side? You know what I'm saying? Just guessing here.

    As far as the rear wheel tension.... Most the time on new builds its not a problem but fixing things and re-using rims - sometimes I come accross what your explaining. Typically I get the tension up around where I want it - then true the wheel, trying to keep the drive side tension as close to right as possible (thats the one that gets pedaling force acted upon it).

    Hope this helps some - I'm not an expert in wheel building - still a novice (only been doing it a couple years). I sometimes have to take a problem to a local master to get his opinion (which he eats up). But I'd wait and see what MC says - he would have a great opinion I'm sure.

    FF
    "If I'm leading, I'm bleeding."

  3. #3
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    i noticed you didnt write your spoke length.


    the other day when i had my delgado rim built up, the builder passed me a worksheet where he wrote the precise spoke length. there was 2 different lengths, one was shorter than the other by 1mm. it was laced to a XT hub with centrelock.

    he used DT competition butted spokes.

    he told me to come back again after i had abused, ride offroad, the wheel, for him to recheck the wheel.
    Si Vis Pacem, Para Bellum

  4. #4
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    so, what sort of application did you use to make that graph? that's not simply a MS Word or Excel graph, is it?

  5. #5
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    Quote Originally Posted by WarPigs
    i noticed you didnt write your spoke length.
    The rear wheel with the Surly singlespeed hub had a spoke length of 293mm for both sides.

    The front wheel with a Cannondale Competition Lefty Hub had 295mm spokes on the drive side and 293mm spokes on the left side.

    The dish was not really difficult on the C-Dale hub, I dropped a plumb line down the center of the steerer tube and it pretty much was exactly between the flanges, in between the "S" and "T" of the SYSTEM INTEGRATION etching on the hub. So I centered the rim between the flanges.

    The idea that the spokes are different lengths makes some sense to me but it seems that the spoinginess is equal on both sides of the wheel.

  6. #6
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    Quote Originally Posted by the Inbred
    so, what sort of application did you use to make that graph? that's not simply a MS Word or Excel graph, is it?
    I used openoffice which is free, almost exactly the same as MS Excel.

  7. #7
    The Top Cap Guy
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    [quote=marty_hd]The rear wheel with the Surly singlespeed hub had a spoke length of 293mm for both sides.....The front wheel with a Cannondale Competition Lefty Hub had 295mm spokes on the drive side and 293mm spokes on the left side.[quote]

    I just built up my New Surly Disc hub rear wheel with a Salsa Delgado Disc rim 32 hole 3 cross and used 292 spokes. And digging through my old specs - my Cannondale Competition Si Lefty hub used 295 and 292 spokes and that was based upon (Left Flange=58mm, Right Flange=45mm and center to flange Left=16mm, and Right=35mm)

    But none the less is still doesn't explain the flex differences.

    FF
    "If I'm leading, I'm bleeding."

  8. #8
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    Now I may or may not be 100% on this, but it would seem to me that since the C'dale hub specs a 2mm difference in spoke length that there is going to be a dish to the wheel and centering the rim between the hub flanges will not acheive this (I also believe this is why C'dale has a false axle to be used on a truing stand, so you can acheive the correct dish)

    Your rim should always be on the axle center, not the halfway point between the flanges.

  9. #9
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    Quote Originally Posted by MIlford_B.
    Your rim should always be on the axle center, not the halfway point between the flanges.
    I am pretty sure the Lefty axle is an exception, the Lefty is offset to the left and the axle only goes to the right side of the hub so centering on the axle would pull the wheel too far to the left. Not sure if that explains in clearly. Hear is a pic:


    I think the different flange sizes are partly based on the fact that the bearings are two different sizes, the left bearing is much larger than the righter bearing and the axle is tapered.

    I selected the center of the flanges as a center point based on looking down through the steerer tube at the hub, but I think it may be off a bit to the right. No big deal I can adjust that.

    That still doesn't really explain to me the flex of the front wheel over the rear wheel.
    Last edited by marty_hd; 01-07-2007 at 12:33 PM.

  10. #10
    meh....
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    Quote Originally Posted by marty_hd
    I am pretty sure the Lefty axle is an exception, the Lefty is offset to the left and the axle only goes to the right side of the hub so centering on the axle would pull the wheel too far to the left. Not sure if that explains in clearly. Hear is a pic:


    I think the different flange sizes are partly based on the fact that the bearings are two different sizes, the left bearing is much larger than the righter bearing and the axle is tapered.

    I selected the center of the flanges as a center point based on looking down through the steerer tube at the hub, but I think it may be off a bit to the right. No big deal I can adjust that.

    That still doesn't really explain to me the flex of the front wheel over the rear wheel.
    Part of the flex is probably because the flanges are fairly close together. Are they closer together than on the rear hub? Imagine if the flanges were touching, the wheel wouldn't "stand up".

    Monte

  11. #11
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    Just a question as I do not know, but is a wheel built for a lefty really dishless? If that's the case it's cool 'cuz I think that builds a stronger wheel. But I thought when I briefly looked at lefty wheels that they had dish, just like other front disc wheels.
    I'd like to hear from the experts what the right answer is.
    Cool graphs, BTW.

  12. #12
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    is it possible you laced the spokes to the wrong flanges? the spoke hole behind the valve when the valve is at the top and looked at from above should go to the right flange. probably not but worth checking.

    check the tension of pairs of spokes that cross each other. if one is high and the other is low, loosen one and tighten the other to bring them closer. because they cross each other you can do this without effecting the true of the wheel.

    you should be able to get a wheel made of quality parts to fairly even tension all the way around. say plus or minus a point on the park meter.

  13. #13
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    I'm pretty sure that the culprit is the fact that the Surly Disc hub has a substantially larger distance between the two flanges, which gives the spoke tension force a much larger lateral component. The Surly hub has 72.5mm between the flanges while the Cannondale hub has only 51mm. The only thing that I can think of to rectify your issue is more spoke tension.

  14. #14
    All Lefty's, all the time Moderator
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    Quote Originally Posted by marty_hd
    Why does the front wheel feel so much more flexy? Is it the C-Dale Competion hub with different flange diameters? Other than the nipples, the hubs are the only difference.

    Flange width. Narrower hubs (front vs. rear) will always create a loss in lateral stiffness. But the lefty is so much stiffer than most other forks, it will be a better overall front end in terms of stiffness. I also wouldn't sweat small variences in tension, it's just goping to happen. As long as it's dished, round and true, and the lions share of spokes are doing their job properly, you'll be fine. Cheers!
    This is a Pugs not some carbon wannabee pretzel wagon!!

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