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  1. #1
    Senior Member conbon's Avatar
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    Master Mehcanics: replacing rim, whats biggest ERD difference tolerable?

    Have an old wheelset, Mavic Gel 280 tubular rear (ERD 615), Matrix ISO tubular front (ERD 606). I'm looking to swap out to a set of clinchers, and I want both front and rear rims to match. I don't want to have to replace spokes, they're all tied and soldered together, and I really don't want to have to undo/redo all that if I don't have to. So my logic is, run a set of rims that are right in between the 2 original rims as far as ERD goes, maybe even a little on bigger side (smaller ERD) so that front spokes are just a touch short, and have the rear spokes poke through a little and just dremel them down. I know, when lacing a wheel or replacing a spoke, usually one size bigger or one size smaller (ie +/-2mm) is tolerable, so is a difference of 9mm ERD split in half, so a difference of +/-4.5mm ERD on each wheel, going to be able to be made up by having the spokes just a couple mm too long on one wheel and a couple mm to short on the other wheel? Is my logic making any sense to anybody?

    -Connor

  2. #2
    Senior Member mrrabbit's Avatar
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    If the current rim has the following state:

    1. True
    2. Dished
    3. Properly Tensioned
    4. (Assume 12mm standard profile brass nipple)
    5. The spokes are boxed spokes - not recut and rolled...
    6. AND the spokes currently terminate at the screwdriver flat of the nipple

    Then you can go with and ERD that is +2mm or -2mm in difference.

    With a 10mm brass nipple (DT) is it closer to +2mm and -4mm difference. (Don't want those threads showing...)

    =8-)
    4000+ wheels built since 1984...

    Disclaimer:

    1. I do not claim to be an expert in bicycle mechanics despite my experience.
    2. I like anyone will comment in other areas.
    3. I do not own the preexisting concepts of DISH and ERD.
    4. I will provide information as I always have to others that I believe will help them protect themselves from unscrupulous mechanics.
    5. My all time favorite book is:

    Kahane, Howard. Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life

  3. #3
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    I just transferred the hubs and spokes to new rims on my 1989 MTB, and I did it without knowing the ERD on either the old or new rims. I found some new, old stock rims on ebay that seemed right (different maker but pretty much the same) and did the transfer. I used the tip I got on my 'Re-use Old Spokes?' thread about taping the two rims together and transferring the spokes. That was the coolest thing - when you pull the tape off, the old empty wheel falls away and you're holding a fully-laced new wheel. If you do this, be careful to line up the valve holes and make sure the left and right spoke holes agree. Of course it still has to be tensioned and trued, etc., and you probably will have to at least rough it in before a shop will true it. Mine turned out great. I got them tensioned, dished and basically trued, then took them to the LBS for final truing. The guy picked one up and spun it, saying "I don't think this one needs anything". I made them do it anyway because they both had some radial eccentricity. Pretty minor, but an experienced wheel man should be able to get it a little better than me.
    On the old spokes; I had several reasons to re-use them. The bike has very low miles on it even though it's a 1989. The spokes are 14 ga Wheelsmith stainless steel with a bright polish. And, doing the transfer meant I didn't have to re-lace.
    By the time I got the wheels to the shop, they looked for all the world like brand new wheels. I don't take dirty stuff to the shop, and I really want this bike to look good when I take it out for the first time in 15 years.
    Inquiring minds want to know.

  4. #4
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    I'm a fanatic about minimum 2mm engagement of the spoke into the head of the nipple. Your goal is that the new build ends with the spoke ending between the bottom of the screwdriver slot and the top of the nipple, with 1mm shy of the slot as the absolute minumum.

    Look at your existing nipples (while tight) and note where the spoke ends up. Then see how far the nipple can thread onto a spoke beyond the top. That'll tell you how much room you have either way.
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  5. #5
    Senior Member conbon's Avatar
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    Quote Originally Posted by mrrabbit View Post
    If the current rim has the following state:

    1. True
    2. Dished
    3. Properly Tensioned
    4. (Assume 12mm standard profile brass nipple)
    5. The spokes are boxed spokes - not recut and rolled...
    6. AND the spokes currently terminate at the screwdriver flat of the nipple

    Then you can go with and ERD that is +2mm or -2mm in difference.

    With a 10mm brass nipple (DT) is it closer to +2mm and -4mm difference. (Don't want those threads showing...)

    =8-)
    I'm going off ERD's I found (multiple sources) online for the rims, didn't actually measure them myself.

    I'm thinking of using Mavic open pros, they have an ERD of 608, so the front will be just a little short, then I might cut/thread the rear spokes.

    The more I think about it, the more I'm considering just buying a box of spokes, seams that that would be easiest. If you coulf go like +/-5 ERD without any problem I would wing it, but I'll probably just end up replacing spokes in one of the wheels.

    Thanks for all the suggestions everybody, I appreciate it.

    -Connor

  6. #6
    Senior Member mrrabbit's Avatar
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    Mavic Open Pro ERD is:

    602 when aiming for the screwdriver flat of the nipple.
    605 when aiming for the top of the nipple.

    =8-)
    4000+ wheels built since 1984...

    Disclaimer:

    1. I do not claim to be an expert in bicycle mechanics despite my experience.
    2. I like anyone will comment in other areas.
    3. I do not own the preexisting concepts of DISH and ERD.
    4. I will provide information as I always have to others that I believe will help them protect themselves from unscrupulous mechanics.
    5. My all time favorite book is:

    Kahane, Howard. Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life

  7. #7
    Senior Member conbon's Avatar
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    Looks like I found my new front wheel, back wheel will be getting new spokes...off to QBP!

    -Connor

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