They do not follow ISO spec at all. I have concerns about the extra stress being applied to the tire bead in a manner it is not designed for.meltingfeather said:The "build up" of the rim being key to success with rim strips and tape-only set-ups is what gave me the idea that increasing the BSD might be what they were up to. I wasn't going to pull the tires and tape off of a 355 wheelset to check, and this isn't apparent from the schematic profiles (below), but the Crest's "shelf" also seems to be more sloped toward the center channel than that of the 355 (which I don't think is sloped at all), meaning the tire/rim fit at the bead gets tighter as the tire seats.
I don't know how this bodes for ISO standard compliance, or if there is anyone who actually cares. The rims are designed to work with ISO 622x? tires, so that may be enough.
How so? I'm not that familiar with the spec itself, but I don't see anything that conflicts in the ISO 5775 wiki, according to which, "[r]ims are designated by their nominal rim diameter and their nominal width, separated by a cross (×)."shiggy said:They do not follow ISO spec at all.
Fair enough, and I agree, but if it works reliably (which needs to be defined, I guess), that's the true test, IMO.shiggy said:I have concerns about the extra stress being applied to the tire bead in a manner it is not designed for.
The full ISO design spec includes actual BSD, rim sidewall height, hook dimensions and shape.meltingfeather said:How so? I'm not that familiar with the spec itself, but I don't see anything that conflicts in the ISO 5775 wiki, according to which, "[r]ims are designated by their nominal rim diameter and their nominal width, separated by a cross (×)."
Interestingly, the wiki also describes ERD as "nipple-seat to nipple-seat," so we now have three different definitions: Roger's, Sheldon's, and this wiki's. Of the three, Roger's is the only one that ties ERD to the ends of the spokes, which is, like I said, exactly what the ERD is in the spoke length calculation. Anything else is either a simplifying approximation or just plain wrong.
*edit* I deleted the ERD section from the wiki, since it clearly has nothing to do with ISO 5775.
Fair enough, and I agree, but if it works reliably (which needs to be defined, I guess), that's the true test, IMO.
Gotcha... makes sense, thanks for the info.shiggy said:The full ISO design spec includes actual BSD, rim sidewall height, hook dimensions and shape.
The ISO designation is simply that. Only gives you the basic size info, not anything about the design spec.
You're not alone, though I don't understand this way of doing it.shiggy said:Nipple seat to nipple seat is what I consider ERD and have always used with the DT Spoke Calc.
I see this:meltingfeather said:You're not alone, though I don't understand this way of doing it.
DT instructs measurement according to Sheldon's definition on the "Help" page linkable in the calculator.
No reference to adding the nipple head thickness.DT MyCalculations Help said:Instructions references
* The rim diameter is measured at the nipple seat and corresponds to the rim diameter of the DT Swiss spoke length calculation table.
Second set of bullets, second bullet:shiggy said:I see this:
No reference to adding the nipple head thickness.
I've heard that too. It's just bad info they're putting in. The math is simple and DT's calculator does nothing tricky. I have duplicated its results repeatedly with my own calculator.shiggy said:I also see people say they need to make adjustments to the DT results. I make none.
Those instructions are pretty sketchy with no reference to using the "1 meter beam" to measure the spokes or how to measure the spokes other than accounting for overlap or gap between the two.meltingfeather said:Second set of bullets, second bullet:
If you don't have a DT spoke length calculation table, you may as well carry out the calculation of the rim diameter: all you need are 2 long spokes (if possible > 300 mm), 2 spoke nipples, Loctite, 1 nipper pliers and 1 meter beam. To start with screw the spoke nipple by use of Loctite onto the spoke until the nipple and the spoke thread end precisely. Afterwards you cut off the bend (both spokes should have the same length). These 2 spokes can be used as measurement spokes. The spokes are inserted opposite one another in the rim. The excess end of the spokes has to be deducted of the total length of both spokes as to obtain the inner diameter of the rim.
The only interpretation I make is that the "nipple and spoke thread end precisely" means flush. I see no other possibility.
They also link Rinard's spokecalc (though they have the old, non-working link), now hosted on Sheldon's page, on which ERD is clearly defined, with diagram, in accordance with the above instructions (to the end of the nipple). The only thing I can think of is that the bullet you cited is in reference to using the table, which may account for this discrepancy.
In any case, the spokes should engage as many threads as possible, and ERD in the spoke length calculation is what it is (described above in previous post), whatever your interpretation for measurement.
One thing that's interesting is that Mavic's "Spoke Support Diameter," at least by literal interpretation, seems to agree more with your definition of ERD, and Mavic SSD needs to be corrected by 4-5mm to work in the DT Swiss Calculator (per Help page and personal experience building with Mavic rims).
I've heard that too. It's just bad info they're putting in. The math is simple and DT's calculator does nothing tricky. I have duplicated its results repeatedly with my own calculator.
I think it's pretty clear, as is Rinard's diagram, which they link.shiggy said:Those instructions are pretty sketchy with no reference to using the "1 meter beam" to measure the spokes or how to measure the spokes other than accounting for overlap or gap between the two.
Specifically for use with the table, which you don't do. For use with the calculator the measuring instructions apply, and while the translation isn't great, I don't think it's unclear.shiggy said:Since DT defines ERD as nipple seat to nipple seat it makes no sense to measure to the end of the nipples.
If it works for you, great, but something is amiss if you're using a dimension likely at least 4mm shorter than what I use and still end up with spoke ends between the bottom of the slots and the ends of the nipples. I'm assuming that your spokes always end up there, is that right? I'd say the calculator accounts for the discrepancy, but my calculator (an excel spreadsheet into which I entered every formula) duplicates DT's precise length to the 1/100th of a millimeter, so I know we're doing the same math.shiggy said:The above is how I measure ERD and I use the working length of the "gauge" spokes as from the cut end to the base of the nipple head--the nipple seat. If I used your method I would bottom out the nipples before I reached adequate tension.
I still do not think it is totally clear. And the link is dead. I had to do a search to find the info archived on SB's site.meltingfeather said:I think it's pretty clear, as is Rinard's diagram, which they link.
Specifically for use with the table, which you don't do. For use with the calculator the measuring instructions apply, and while the translation isn't great, I don't think it's unclear.
What doesn't make sense to me is measuring to an arbitrary point that has nothing to do with the geometry in the calculation.
If it works for you, great, but something is amiss if you're using a dimension likely at least 4mm shorter than what I use and still end up with spoke ends between the bottom of the slots and the ends of the nipples. I'm assuming that your spokes always end up there, is that right? I'd say the calculator accounts for the discrepancy, but my calculator (an excel spreadsheet into which I entered every formula) duplicates DT's precise length to the 1/100th of a millimeter, so I know we're doing the same math.
I ain't telling you to change what you're doing, or even that it's wrong, but something doesn't make sense to me.
It doesn't always have to, though. Thanks for the info re: ISO spec. :thumbsup:
Fair enough. I linked it. In any case, it's the same exact page that used to be hosted on Rinard's site.shiggy said:I still do not think it is totally clear. And the link is dead. I had to do a search to find the info archived on SB's site.
Then who knows what's going on? :crazy: Your policy is probably a good one, but I've had good results sharing information and don't just sling it around. I may be a little more careful moving forward.shiggy said:Yes, my spokes end up above the nipple slot. This is why I refuse to tell people what their spoke lengths should be. I have found the spoke calculator and measuring methods that work for my builds.
I bet that sucked. I've had somewhat the opposite experience, though only once (that was enough). A customer bought hubs, spokes, nipples, and rims (Mavic) on his own from a large, online retailer with a good reputation, storefront, and who according to the manager, "builds over 300 wheelsets a year." He had them figure the length and supply the spokes for the build. 2-3 threads showing all around. :madman:shiggy said:I have even received rims and spokes from very good builders and had the spokes be 2-3mm too long. Bottomed out the threads before I reached my desired tensions. Would not stay true and I could not retrue the wheels. Did my own calc and rebuilt with shorter spokes. Perfect since then.
Bottom line is, whoever is building the wheel should be the one that specifies (and takes responsibility for) the spoke lengths.meltingfeather said:Fair enough. I linked it. In any case, it's the same exact page that used to be hosted on Rinard's site.
Then who knows what's going on? :crazy: Your policy is probably a good one, but I've had good results sharing information and don't just sling it around. I may be a little more careful moving forward.
I bet that sucked. I've had somewhat the opposite experience, though only once (that was enough). A customer bought hubs, spokes, nipples, and rims (Mavic) on his own from a large, online retailer with a good reputation, storefront, and who according to the manager, "builds over 300 wheelsets a year." He had them figure the length and supply the spokes for the build. 2-3 threads showing all around. :madman:
I now supply the spokes based on my own measurements and my own spoke calculator.
:thumbsup:
I do have one question for you: how do your measurements compare to Mavic SSD specs? Since you measure rims, I assume you don't use Mavic's specs and the DT-recommended correction.
