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Thread: Rim Questions

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    Rim Questions

    I've been shopping around for rims for custom builds and have come across a couple questions I hope some of you wheel builders could answer:

    1. For one group of rims I've been looking at, and I've only found it for this manufacturer, there are ratings along the lines of "max spoke tension (>300kgs) maximal strength (>100kgs) and torsional strength (50kgs) [and I assume "kgs" is kilograms]. I can't seem to find any other rim manufacturers who advertise these ratings. Do these ratings indicate possible suitability for tandem use? The manufacturer lists similar ratings for their smallest dish wheel (24mm), but the smallest rim does have a 90kg max rider weight.

    Second, what is the structural difference between tubular and clincher rims? The rim weights seem to be significantly different (the tubulars often being over 100g lighter than similarly sized clinchers)?

    Thanks,
    LKW
    .

  2. #2
    What??? Only 2 wheels? jimmuller's Avatar
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    Quote Originally Posted by LastKraftWagen View Post
    1. For one group of rims I've been looking at, and I've only found it for this manufacturer, there are ratings along the lines of "max spoke tension (>300kgs) maximal strength (>100kgs) and torsional strength (50kgs) [and I assume "kgs" is kilograms]...

    Second, what is the structural difference between tubular and clincher rims? The rim weights seem to be significantly different (the tubulars often being over 100g lighter than similarly sized clinchers)?
    I'm not a professional wheel builder so I can't really answer you with authority. I've built a few wheels though, including the rear on our tandem. Since it has now survived at least 500 miles and one short tour with the bike loaded to a gross weight of > 100lbs without riders, I'll assume it worked out pretty well. kgs would certainly be kilograms. I have not generally seen specs like that on any rims. I'd think any rim described as for touring would do. For example, we have Mavic A319s, not the most expensive rim available but they've worked out well.

    Clincher vs. tubular? That describes what kind of tire it should have. A tubular tire, a.k.a. sew-up tire, is very different from the "regular" tire we all know. Sew-ups are the original high-performance racing tire (and if you go back to before Michelin invented the clincher a long time ago, they are the original tire at all). Sew-ups must be glued on to the rim, a moderately tedious task. You cannot use the incorrect tire for each type, though I've heard of people mounting a sew-up on a clincher rim as an emergency flat repair. Some may disagree here but IMHO you do not want to consider tubulars for a tandem without good reason such as racing. Yes, tubular rims may be lighter, and model for model a tubular tire is lighter too. (Look up the Vittoria Corsa SC vs. the Vittoria Open Corsa SC.) But they are not for the faint of heart, or the light of wallet.
    Real cyclists use toe clips.
    jimmuller

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    I knew there was a difference between clincher and tubular tires, and that the rims were designed differently, I am just curious about the rim weight differences. My thoughts are to always use clinchers for tours and everyday riding, the new rims being researched are "wishfull daydreaming" for sportier riding and racing (especially TTs). Emails to manufacturers have not yet resolved the "kgs" ratings are tandem suitable or how they (the ratings) compare to other rims.

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    Senior Member Team Fab's Avatar
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    Quote Originally Posted by LastKraftWagen View Post
    I knew there was a difference between clincher and tubular tires, and that the rims were designed differently, I am just curious about the rim weight differences. My thoughts are to always use clinchers for tours and everyday riding, the new rims being researched are "wishfull daydreaming" for sportier riding and racing (especially TTs). Emails to manufacturers have not yet resolved the "kgs" ratings are tandem suitable or how they (the ratings) compare to other rims.
    The rims are much lighter due to the lack of the bead hook area. There is much more metal needed to build the part that the tires lock into.
    if you look at a cross section of a tubular rim vs clincher you will see all the metal(or carbon ) that is needed.

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    Senior Member Team Fab's Avatar
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    just another gosling Carbonfiberboy's Avatar
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    Spoke tensions are usually given in "kgf," meaning kilogram-force as opposed to kilogram-weight. It's a technical difference only, but it does indicate someone who understands the nomenclature of wheel building. I build most of our tandem wheels. I use 100-110 kgf on the front and 110-120 kgf on our almost symmetrical rear, both depending on rim. Most rim manufacturers give a maximum spoke tension of ~130 kgf. These spoke tensions are plenty to stretch a 14-15 DB spoke enough so that it can never go close to slack, and are plenty for tandem use. I've found that the deeper the rim, the truer the wheel stays. This is probably because the spoke tensions vary less during use on a deep rim which spreads loads out among more spokes.

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    Senior Member waynesulak's Avatar
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    Quote Originally Posted by Carbonfiberboy View Post
    Spoke tensions are usually given in "kgf," meaning kilogram-force as opposed to kilogram-weight. It's a technical difference only, but it does indicate someone who understands the nomenclature of wheel building. I build most of our tandem wheels. I use 100-110 kgf on the front and 110-120 kgf on our almost symmetrical rear, both depending on rim. Most rim manufacturers give a maximum spoke tension of ~130 kgf. These spoke tensions are plenty to stretch a 14-15 DB spoke enough so that it can never go close to slack, and are plenty for tandem use. I've found that the deeper the rim, the truer the wheel stays. This is probably because the spoke tensions vary less during use on a deep rim which spreads loads out among more spokes.


    What number of spokes do you prefer with a stiff rim like a Velocity Deep V and what with a somewhat less stiff rim similar to a Velocity Dyad?

    For Reference what is you team weight?

  8. #8
    just another gosling Carbonfiberboy's Avatar
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    Quote Originally Posted by waynesulak View Post
    What number of spokes do you prefer with a stiff rim like a Velocity Deep V and what with a somewhat less stiff rim similar to a Velocity Dyad?

    For Reference what is you team weight?
    I prefer to lace rims on the hubs I have, which happen to be CK 36H. Others who've tried various spoke counts would know more. Even 36H wasn't enough with a light rim like a Open Pro or Velocity Aerohead - they didn't stay true on our rough roads. ~300 lb. team weight, 145 rear spacing.

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    Sorry, blind as a bat in a snow storm, but I understand and will take your word for it.
    Quote Originally Posted by Team Fab View Post
    The rims are much lighter due to the lack of the bead hook area. There is much more metal needed to build the part that the tires lock into.
    if you look at a cross section of a tubular rim vs clincher you will see all the metal(or carbon ) that is needed.

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    Assuming these are images of clinchers vs. tubular...Again, "In the greater scheme of life I have no vision." Thanks though, I get the reason now.
    Quote Originally Posted by Team Fab View Post



  11. #11
    Nigel nfmisso's Avatar
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    Quote Originally Posted by waynesulak View Post
    What number of spokes do you prefer with a stiff rim like a Velocity Deep V and what with a somewhat less stiff rim similar to a Velocity Dyad?

    For Reference what is you team weight?
    I use 40 spokes with Dyad rims on our tandem; team weight is around 500 lbs.
    Nigel
    Mechanical Design Engineer

  12. #12
    WillFam-Clovis,CA
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    Wheel building

    Quote Originally Posted by waynesulak View Post
    What number of spokes do you prefer with a stiff rim like a Velocity Deep V and what with a somewhat less stiff rim similar to a Velocity Dyad?

    For Reference what (is you) does your team weigh?
    My belief, after building about 9 wheels, 4 for tandems, is that the rim is important, but less so than than the quality of the build process and the load that you anticipate. I am glad I went strong when I built my triplet with Dyad Deep V 48 hole - tensioned around 110 kgf. Tensioning evenly is very important to a strong wheel that stays true. At one point we were a combined weight of about 590 pounds not including the trail-a-bike and the trailer. That's a lot of weight, but the rims are still very true after close to two thousand miles. We no longer pull the trailer, and are one rider less, so recently are closer to 450 lbs, not including the trail-a-bike. The additional weight of the wheel I'm sure affects handling, but I like the confidence that they are staying strong and true over losing a pound or two.
    If you are going to build your own, make sure to get or barrow a spoke tension measuring tool, even if it's a cheap one. It is well worth the additional safety of the precious cargo and will help the wheel stay true.
    IMHO - Spoke tensions stay even in the long term, more on a basis of how well the wheel is built, less on the what the rim is made of. Even steel rims can be torqued in or out of alignment pretty easily. I recently trued a steel rim for a friend, telling him that I did not think the rim could ever be straight. I did not take the time to untension the spokes and start from scratch because the wheel wasn't worth the extra time, but I was amazed that the wheel ended up pretty decent. It would be smart to re-check every once in awhile, but it did get a Dad riding with his boy again!
    Last edited by WillFam-Reno; 03-07-14 at 05:42 PM. Reason: Spelling

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    Do you tension the spokes with a tire mounted and inflated to ride pressure or without the tire installed? I have read about and can feel a noticeable difference in spoke tension on my wheels between inflated and deflated tires.

  14. #14
    The Rabbi seely's Avatar
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    Quote Originally Posted by LastKraftWagen View Post
    Do you tension the spokes with a tire mounted and inflated to ride pressure or without the tire installed? I have read about and can feel a noticeable difference in spoke tension on my wheels between inflated and deflated tires.
    Tension is measured during the build process without a tire on the rim. Your tension will drop when a tire is installed and brought up to pressure, which is fine provided the wheel was tensioned enough during the build. We build all of our rims to 120kgf.
    commuter turned bike mechanic turned commuter (also a Velocity USA employee, but this is my personal account)

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    The Rabbi seely's Avatar
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    Quote Originally Posted by WillFam-Reno View Post
    My belief, after building about 9 wheels, 4 for tandems, is that the rim is important, but less so than than the quality of the build process and the load that you anticipate. I am glad I went strong when I built my triplet with Dyad Deep V 48 hole - tensioned around 110 kgf. Tensioning evenly is very important to a strong wheel that stays true.
    I totally agree with this... a good rim is important to achieving even spoke tension, but the longevity of the wheel is largely the build. Even tension is critical, no matter the rim.
    commuter turned bike mechanic turned commuter (also a Velocity USA employee, but this is my personal account)

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