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  1. #3026
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    Original request.

    Quote Originally Posted by Appendage View Post
    All very scientific, but in the case of tubeless MTB tires, one of the advantages is running a low pressure so that the tire will deflect and deform to absorb bumps. The supple, grippy ride is a product of the ready deformation of the tire.
    Well now you are changing the request. The original request was to prove that a wider rim is faster that a narrow rim. The link I provided proves that, also proves that a 29er is faster than a 26er tire.

  2. #3027
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    I don't buy that...

    Quote Originally Posted by red5jedi View Post
    Here is a cut and paste from here:

    Wider tyres roll faster than narrower ones: Many riders have argued for years that narrower tyres especially on the road are faster and more efficient than wider ones when in fact, the opposite is true. According to Wheel Energy, the key to reducing rolling resistance is minimising the energy lost to casing deformation, not minimising how much tread is in contact with the ground.

    All other factors being equal, wider casings exhibit less casing 'bulge' as a percentage of their cross-section and also have a shorter section of deflected sidewall. How big a difference are we talking about here? For an equivalent make and model of tyre, Wheel Energy claims the 25mm-wide size will measure five percent lower rolling resistance on average the supposed average limit of human detection than the more common 23mm-wide one.
    ... for all conditions. There is a reason why the Prius comes with 175mm or 195mm narrow tires with a 65 aspect ratio, and not 17" rims, 235mm wide, with 45 aspect tires. A wider contact patch makes a bigger front that has to flex when it comes in contact with the ground.

    Now, for dirt bicycle applications, a wider tire might have more rolling resistance, but you can also drop the pressure for better traction, and for better enveloping over rocks and roots and such. If the tire envelopes over something, it doesn't bounce the bike up in the air, or flex the suspension and lose energy that way. Lower pressure means more rolling resistance if the trail/road is perfectly smooth, but not if the trail is rough.

    Roadies all use 23c tires, when 25 and 28c tires are available. Skinny tires roll with less resistance on a long skinny contact patch. The part of the tire that hits the ground first has a more narrow wave to flex.

    For me, the wider rim was a no-brainer. 20g heavier than the skinny rims, but in my case the bigger tire, lower pressure, more stiffness, and extra durability will be more of an advantage to me than a measly 20 grams. Heck, I'm already dropping 70g per wheel with these things.

  3. #3028
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    I stand corrected.

    Quote Originally Posted by pimpbot View Post
    ... for all conditions. There is a reason why the Prius comes with 175mm or 195mm narrow tires with a 65 aspect ratio, and not 17" rims, 235mm wide, with 45 aspect tires. A wider contact patch makes a bigger front that has to flex when it comes in contact with the ground.

    Now, for dirt bicycle applications, a wider tire might have more rolling resistance, but you can also drop the pressure for better traction, and for better enveloping over rocks and roots and such. If the tire envelopes over something, it doesn't bounce the bike up in the air, or flex the suspension and lose energy that way. Lower pressure means more rolling resistance if the trail/road is perfectly smooth, but not if the trail is rough.

    Roadies all use 23c tires, when 25 and 28c tires are available. Skinny tires roll with less resistance on a long skinny contact patch. The part of the tire that hits the ground first has a more narrow wave to flex.

    .
    You sound sooooo much more scientific that that article. All that testing they have done must be wrong you should go tell them .

  4. #3029
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    Let's keep this thread about 29er chinese carbon rims.

  5. #3030
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    Quote Originally Posted by pimpbot View Post
    Roadies all use 23c tires, when 25 and 28c tires are available. Skinny tires roll with less resistance on a long skinny contact patch.
    No they don't.
    Roadies use narrow tires because they are lighter and more aerodynamic, which are also considerations (for them).
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
    29er Tire Weight Database

  6. #3031
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    I think I'm missing something here. I get that if you have a wider rim, you have a bigger number at the bottom of the area equation. And everyone's saying that with the wider rim, you spread the sides wider, too, which I get. But if you're spreading the base of the tire into the rim hook and, as Varaxis notes, a tire has very limited stretch, it would seem the height of the tire would have to decrease by a proportional amount and the volume of the tire would remain roughly the same.

    I also don't get how the contact patch of a 26x1.9 tire is the same as a 29x2.4? It seems that the larger diameter tire will have a longer patch and the wider tire will have, well, a wider patch.
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  7. #3032
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    You are adding the extra width of the wider rim to the overall size of the circle that is the circumference around the tire laterally. Look at post 3023 Varaxis has shown that as you increase the length across the bottom (the rim width in this case) the top of the tire is almost exactly the same place until you get wider than the casing width of the tire and then it starts down. This is why if you have the same tire on a different width rim, you don't have to re calibrate your speedo because the overall height of the tire doesn't change.
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  8. #3033
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    The contact patch argument is based on the fact that the size of the contact patch is relative to the inflation pressure and the weight. I am not sure I totally agree that these 2 mentioned would be the exact same size because there are other factors, but the basic premise is that if you have 30 psi and are supporting 90 lbs the area will equal the pounds divided by the psi. In other words if you have 90 lbs and 30 psi the contact patch will equal 3 square inches because the tire will support 30 lbs of weight per square inch. There are other factors at play here including the fact that the stiffness of the sidewall will support some of the weight, etc.
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  9. #3034
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    I was able to get one of my 29 chinese carbon rims built up. They are LB rims and I decided to go the Bonty rim strip route because they seemed to work well on my RXL rims when I had them.

    I bought the Rhythm model and got the first one on my rim. It seated down well but I noticed one side of the rim the strip will sit under the bead and probably allow for a tire to seat properly but the other side sticks out, not enough to feel it but more it just doesn't look like it will allow the tire to seat on it.

    Is there a chance that I have it on backwards? Any ideas on how to get it to work or should I look at a different method? I have never tried Stans before but I did use gorilla tape on my ENVEs and they seemed to work.

    Any help would be greatly appreciated!

  10. #3035
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    Quote Originally Posted by skiahh View Post
    I think I'm missing something here. I get that if you have a wider rim, you have a bigger number at the bottom of the area equation. And everyone's saying that with the wider rim, you spread the sides wider, too, which I get. But if you're spreading the base of the tire into the rim hook and, as Varaxis notes, a tire has very limited stretch, it would seem the height of the tire would have to decrease by a proportional amount and the volume of the tire would remain roughly the same.

    I also don't get how the contact patch of a 26x1.9 tire is the same as a 29x2.4? It seems that the larger diameter tire will have a longer patch and the wider tire will have, well, a wider patch.
    Look at the graphs, equations & explanations in the thread I linked.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
    29er Tire Weight Database

  11. #3036
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    Quote Originally Posted by simpy16 View Post
    I was able to get one of my 29 chinese carbon rims built up. They are LB rims and I decided to go the Bonty rim strip route because they seemed to work well on my RXL rims when I had them.

    I bought the Rhythm model and got the first one on my rim. It seated down well but I noticed one side of the rim the strip will sit under the bead and probably allow for a tire to seat properly but the other side sticks out, not enough to feel it but more it just doesn't look like it will allow the tire to seat on it.

    Is there a chance that I have it on backwards? Any ideas on how to get it to work or should I look at a different method? I have never tried Stans before but I did use gorilla tape on my ENVEs and they seemed to work.

    Any help would be greatly appreciated!
    I saw a Stan's video,a while back when he mounted a rubber strip on a rim and then used the tire lever to push the strip over a little.
    So I do that as shown by the Stan's video, then I run the plastic lever just under the bead hook to make sure the rhythm strip is down below the bead hook

  12. #3037
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    Quote Originally Posted by pwu_1 View Post
    I saw a Stan's video,a while back when he mounted a rubber strip on a rim and then used the tire lever to push the strip over a little.
    So I do that as shown by the Stan's video, then I run the plastic lever just under the bead hook to make sure the rhythm strip is down below the bead hook
    Yup. G-Ted had a nice tip when the strips came out to help with the install. His tip was to insert a screwdriver in the valve stem hole of the strip and the rim to hold that portion of the strip in place while you work your way around the rim to get the strip snugly in place and centered all around the rim. Works like a charm.

  13. #3038
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    Guys, how would you calculate ERD for this rim? I know someone most probably did it in this thread already, but I'm not sure if it was for this exact rim (chinese carbon, 2012).

    The thing that confuses me is I want to use use the DT Swiss Standard Alu Nipples, but I can't find the height of the nipple head specified anywhere. Which is weird, because that's how ERD is supposed to be calculated, as far as I've seen (2nd attached pic).

    So I'm guessing 2mm for the nipple head height, but it's just a guess, and I'm not sure if it's better to guess less or more.

    So the ERD I calculated according to the schema pic is:
    20.50 - 3.60 - 2.0 = 14.9 * 2 = 29.8
    632 - 29.8 = 602.2

    Then the last pic is output from the DT Swiss calc (the hub data are taken from the correct DT Swiss hubs, but the calc later insisted on generic type, but the numbers stayed in).
    Attached Thumbnails Attached Thumbnails (Cheap) Chinese Carbon Rims?-29er-rim.jpg  

    (Cheap) Chinese Carbon Rims?-spokes-erd.jpg  

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  14. #3039
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    [QUOTE=ypocat;10059105]Guys, how would you calculate ERD for this rim? I know someone most probably did it in this thread already, but I'm not sure if it was for this exact rim (chinese carbon, 2012).
    /QUOTE]

    I measured the ERD. Form the bottom of the slot in the nipple I came up with 606mm. Measured in several spots, both rims. No variance.

    I asked Brian at light bicycle if the "stronger" wider rims with extra carbon added to the ERD, essentially I was asking him where is that extra carbon in the stronger rims. He didn't really answer but did say that the published spec was now 604 (at the time the web page was still saying 603).

    I'm using 292mm cx-rays 32/3 cross on CK hubs. I've got them laced but not brought up to tension yet. I'll post up when done with feedback.
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  15. #3040
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    [QUOTE=reamer41;10059430]
    Quote Originally Posted by ypocat View Post
    Guys, how would you calculate ERD for this rim? I know someone most probably did it in this thread already, but I'm not sure if it was for this exact rim (chinese carbon, 2012).
    /QUOTE]

    I measured the ERD. Form the bottom of the slot in the nipple I came up with 606mm. Measured in several spots, both rims. No variance.

    I asked Brian at light bicycle if the "stronger" wider rims with extra carbon added to the ERD, essentially I was asking him where is that extra carbon in the stronger rims. He didn't really answer but did say that the published spec was now 604 (at the time the web page was still saying 603).

    I'm using 292mm cx-rays 32/3 cross on CK hubs. I've got them laced but not brought up to tension yet. I'll post up when done with feedback.
    I'd sure like to know what the ERD of the stronger ones are too. I just order 293 and 294mm DT Swiss Super Comps to go with Hope Pro 2 EVO hubs based on 603 ERD rim, but I tried to round up to the longer side so hopefully will be OK even with 604.

  16. #3041
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    Quote Originally Posted by ypocat View Post
    Guys, how would you calculate ERD for this rim? I know someone most probably did it in this thread already, but I'm not sure if it was for this exact rim (chinese carbon, 2012).
    ERD is not calculated, it's measured. My rims were 603mm.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
    29er Tire Weight Database

  17. #3042
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    ypocat, I agree with your calcs. However, I agree with meltingfeather that ERD should be measured. Lots of instructions online. I believe that ERD will vary based upon the weight of the build, as I believe that the extra weight comes from thickness in that bottom section (primarily).
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  18. #3043
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    My rims were 603 but they were at the light end of the weight range.
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  19. #3044
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    I just got a reply from Nancy regarding spoke tension, as I could not remember what was posted on this forum. I will paraphrase:

    Nancy:
    Tension for "transportation riders" (Comfortability) 80-90kgf or exercise on a regular basis.
    Tension for "enthusiast riders" (Balance) 100-110 kgf are good for people with enjoyful and training purposes.
    Tension for "professional rider" (Performance) 120-130 kgf are charged for riders who are experienced in riding or competition.

    I just got my new rims, 399g and 379g. I am lacing to CK hubs. Plan to use Sapim CX Ray spokes with alloy nips. Considering 3x on high tension sides, and 2x on low tensions side. CK states max of 120 kgf, and wants all hubs laced 3x. I read somewhere that CX Ray spokes benefit from a higher tension. What tension do you guys think I should shoot for? My weight is 160 lbs, mostly cross country type riding, minor jumping, age 62. Wheels will go on a Tallboy.
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  20. #3045
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    You should go 2x on HIGH tension and 3x on low tension. This is recommended by the best builders I know.

  21. #3046
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    Quote Originally Posted by hssp View Post
    You should go 2x on HIGH tension and 3x on low tension. This is recommended by the best builders I know.
    Interesting. Any reason given for this set up?

    I've always just done 3x both sides. Lazy, I guess. But curious!
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  22. #3047
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    Quote Originally Posted by kindacreeky View Post
    I just got a reply from Nancy regarding spoke tension, as I could not remember what was posted on this forum. I will paraphrase:

    Nancy:
    Tension for "transportation riders" (Comfortability) 80-90kgf or exercise on a regular basis.
    Tension for "enthusiast riders" (Balance) 100-110 kgf are good for people with enjoyful and training purposes.
    Tension for "professional rider" (Performance) 120-130 kgf are charged for riders who are experienced in riding or competition.
    Different tensions for different uses is whack.
    110kgf is plenty.

    Quote Originally Posted by kindacreeky View Post
    I just got my new rims, 399g and 379g. I am lacing to CK hubs. Plan to use Sapim CX Ray spokes with alloy nips. Considering 3x on high tension sides, and 2x on low tensions side.
    Any pattern mixing is jut going to be for fun/interest. You're not going to realize any benefit from it.
    Quote Originally Posted by kindacreeky View Post
    CK states max of 120 kgf, and wants all hubs laced 3x. I read somewhere that CX Ray spokes benefit from a higher tension. What tension do you guys think I should shoot for? My weight is 160 lbs, mostly cross country type riding, minor jumping, age 62. Wheels will go on a Tallboy.
    Spokes don't benefit from different tension levels. You build wheels to what the rim mfr says unless what they say is ridiculous (see above). In that case you build 32-spoke wheels to 110kgf.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
    29er Tire Weight Database

  23. #3048
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    meltinghfeather is right. I would build them up 3X and shoot for 110 kgf on the high tension side front and rear. 3X is stronger than 2X and I don't think you can do 4X with 32 holes and since the drilling is straight on these rims even if you could do 4X it would put the nipples at the wrong angle since they are on the edge at 3X.
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  24. #3049
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    Quote Originally Posted by hssp View Post
    You should go 2x on HIGH tension and 3x on low tension. This is recommended by the best builders I know.
    Appreciate the advice. This is my first wheel build, and I am just learning about this science. I am an engineer, and am trying to understand the physics of this. With a 2X pattern, the spoke pulls more outward on the hub flange. With the 3X, the pull is more tangential. I can see why CK would specify the 3X only pattern, as that would stress the hub flange less (more meat in hub when pulling tangential than more straight out). Can anyone explain why it would be preferable to put the 2x on the Drive side of the rear?

    Also, I have read in this forum that 2x gives a more rigid build. Is this true? On my Tallboy, with FS, I am mainly interested in improved lateral rigidity and more accurate tracking out of this wheel, but of course want to keep weight down too.

    Last night, I checked some wheels built for me by Dave's Wheels at Speedreams.com. He built a 26er wheel for my Blur and he put 2x on the low tension sides front and rear; and 3x on the high tension side. So I was going by that example.
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  25. #3050
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    Quote Originally Posted by meltingfeather View Post
    Different tensions for different uses is whack.
    110kgf is plenty.


    Any pattern mixing is jut going to be for fun/interest. You're not going to realize any benefit from it.

    Spokes don't benefit from different tension levels. You build wheels to what the rim mfr says unless what they say is ridiculous (see above). In that case you build 32-spoke wheels to 110kgf.
    Appreciate the comments.
    Kindacreeky,
    Tennessee Singletrac Sculpter

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