Measured ERD of Light Bicycle rims not matching?
02-02-24, 12:44 AM
#26
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Like Andy I measure everything myself. I prefer measuring the depth from the rim's outer edge, with the nipple I plan to use in place.
This tells me EXACTLY the diameter where I want the spoke to end. Generally I don't use online calculators and rely on the same method I used back in the Bronze Age.
However when I do use a calculator, I do a test calculation for one of my front wheels whose spoke length I know, and use any difference as a correction factor.
This tells me EXACTLY the diameter where I want the spoke to end. Generally I don't use online calculators and rely on the same method I used back in the Bronze Age.
However when I do use a calculator, I do a test calculation for one of my front wheels whose spoke length I know, and use any difference as a correction factor.
02-04-24, 08:38 AM
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The biggest problem with ERD isn't measuring, it is knowing what the calculator thinks you should have measured.
Regardless of the nipple design, a spoke that penetrates the base of the nipple by 2mm is going to prevent nipple failure just as well as any other nipple. So I can see the argument for just saying "ERD is the shortest distance across from spoke end to spoke end". But it isn't an argument, because different groups are defining it differently.
DT is not measuring to the rim diameter or the end of the spoke. They are measuring to the slot, which is about 1mm short of the spoke end. But then their calculator is going to reflect that type of measure.
Does anyone know how the old Wheelsmith yellow sticks measure out? Are they 350mm long? Or 348mm to reflect the 2mm of nipple head thickness? That's the closest to an industry standard, because nearly every shop wheelbuilder has used them to get ERD at some point.
Regardless of the nipple design, a spoke that penetrates the base of the nipple by 2mm is going to prevent nipple failure just as well as any other nipple. So I can see the argument for just saying "ERD is the shortest distance across from spoke end to spoke end". But it isn't an argument, because different groups are defining it differently.
DT is not measuring to the rim diameter or the end of the spoke. They are measuring to the slot, which is about 1mm short of the spoke end. But then their calculator is going to reflect that type of measure.
Does anyone know how the old Wheelsmith yellow sticks measure out? Are they 350mm long? Or 348mm to reflect the 2mm of nipple head thickness? That's the closest to an industry standard, because nearly every shop wheelbuilder has used them to get ERD at some point.
The measurements I get with the rim rods equal what I get measuring standard nipples to the bottom of the slot.
You subtract the overlap from 700 to get the ERD so I guess the rods must be 348 to the shoulder.
I am away from home for the next month so can’t actually measure them.
Last edited by Dan Burkhart; 02-04-24 at 09:37 AM.
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