Originally Posted by

**desconhecido**
Spokecalc will give you the computed value based on the numbers you insert -- it's not aiming for anything. The "effective rim diameter" that you insert into the program is the diameter of the circle of the ends of the fully tensioned spokes. I've compared Spokecalc calculations to the values computed by the DT spoke length calculator and to values calculated discretely from the equations in Brandt's book. They are the same in all three cases. According to Brandt, spokes can stretch about 1mm when tensioned and the rim diameter can shrink by as much as 2 mm (1 mm in radius). So, a gross estimate is that the length of the spoke needs to be about 1mm to 2mm shorter than the length calculated if you determine ERD by measuring a real untensioned rim. The DT spoke length calculator, as I recall, suggests a spoke length which seems to be the calculated value rounded down to the next integer.

You can see that an important question is where the ERD value that you are using comes from. If you are careful, you can measure the diameter of the rim pretty accurately with a couple of steel rulers. Or, you can position a couple spokes in opposite spoke holes, thread them up to nipples the way you want them to be when tensioned, and carefully mark the spoke overlap at the center. Then, disassemble the spokes, position the marks, and measure. Check several sets of spoke holes in case the untensioned rim is not perfectly round. I've checked a bunch of rims in the last several months and compared the values that I come up with to the values in the spokecalc database and they seem to be relatively close. Note that the values in the database for various rims have different sources and sometimes I have found different values in the database compared to internet sales site listings and even manufacturers sites, when available. Anyway, the best thing to do is to measure as accurately as you can the diameter of the spoke end circle that you want and then estimate the combined effect of spoke stretch and rim shrinkage and compare that to the spokecalc database or to values published elsewhere. They should be close to the same. If they're not, measure it again and then go with the value that you measure. And then, measure it again.

Now, whether or not the spokes that you have will work is another question. Figure out where you want the spoke ends and measure and calculate based on your measurement/estimation. If the spokes are longer than that, take a spoke and a nipple and see how much you can overthread the nipple before bottoming out. I would think that you would want to have 2 - 4 mm of excess nipple threadability, but that's your judgement.

Just for reference, the Sheldon Brown site says that Sheldon would calculate a spoke length and then round up to the nearest available length which could be more than 1mm for spokes that only come in 2mm increments. So, it's likely typical to be able to handle spoke lengths a little off from the ideal.

I've ordered all my custom length spokes from Colorado Cyclist and have checked the length on every order and they have always been 100% on the money. They charge $0.50 for 14 gauge DT and $0.90 for 14/15/14 gauge DT. Includes standard nipples -- 12mm brass, I think. Perhaps your supplier will exchange just the nipples for 10mm nipples, if possible? As Mr. Rabbit suggests.

But to address your concerns directly -- my wag is that your spokes will be fine, but I think you should verify it. Once the wheels are built, you shouldn't have to significantly retension the spokes. Maybe a little when you gas up your tires to full pressure which can compress the rim a little and maybe a little tweaking after a while, but not much.