After much searching and a lot of struggling with other methods, I stumbled upon your explaination. You did a far better job of it than even Park Tool's clumbsy attempt. Well done sir! Thank you!
I've been doing it wrong for years! I measure to the nipple seat and this explains why I sometimes struggle to get it spot on. You're never too old to learn!
Well, that might also work, if you round up the calculated spoke length. It is not so much critical to support the nipple head, unless it's an alu nipple, in which case you should always base off your ERD close to top of the nipple head. Hope this helps! Cheers.
Effective Rim Diameter is NOT a measurement of nipple slot to nipple slot. This gentleman's explanation is a perfect example of what Jobst Brandt lamented as taking a simple reference and turning it into a "religion". ERD is simply a reference to the ends of the spokes in an already built and functional wheel. For any given rim there can be multiple ERD's - simply because differing sizes of nipples, differing profiles for nipples AND differing threadings for the nipples and spoke threads can result in differing MAX and MIN thread insertion. Take any wheel. Pick it up. If it is tensioned, dished, trued - i.e. - it appears to be a functional wheel - the ERD is simply the end of one spoke to the end of the other spoke at 180 degrees measured in millimeters. This is why when wheel builders measure a rim, they commonly use a pair of spokes or spoke rods combined with a caliper. They test the nipple and threads to be used, set the rods - and try to EMULATE where the spoke ends will be in the future when the wheel is built. The measure they guestimate using that method is plugged into a spoke length calculator. A careful and consistent practitioner often gets it within a 1/2 millimeter. ERD is not an industry standard specification, nor is it a white paper subject. It's simply a reference to the ends of spokes in an already built and functional bicycle wheel. MrRabbit - Wheels By Fleming - 5000+ Wheels Built since 1984 =8-)
Robert, thank you for your response. The purpose of measuring ERD is to calculate the optimal spoke length for a wheel. You are correct that ERD is a function of several variables, so if a manufacturer publishes an ERD for a particular rim, an assumption is being made about the type of nipple that is being used and whether nipple washers are being used or not. That’s why I always measure it with the actual components I am going to use for a particular wheel. You say: “If a wheel is tensioned, dished, trued - i.e. - it appears to be a functional wheel - the ERD is simply the end of one spoke to the end of the other spoke at 180 degrees in millimeters.” That is not correct. The fact of a wheel being “functional” does not mean that the spoke length is optimal. Here is my email address: bill@billmouldwheels.com. I’d suggest we take this conversation “off-line” and maybe have a phone call. Maybe I am just misunderstanding the point you are trying to make. Bill Mould
Useful video Bill, this is appreciated However, Roger Musson showed in his book 'Professional guide to Wheel building' a (in my opionion) nice method to quickly determine the ERD without dealing with too many figures: prepare 2 sets of a piece of spoke with a glued 'normal' nipple at the end. Cut the spoke end in a way, that the distance from slot to spoke end is an even measure, e.g. 250mm stick both spokes in opposite holes and tie the ends with a rubber band together in order that the ends points to each other and the nipple sits nicely in the hole. Then simply measure the face to face distance of the spoke ends with a ruler or a caliper. E.g. a distance of 103mm will result in an ERD of 603 mm (103+2x250) Keep up your useful work! Cheers, Georg
Hi Bill. I know this a old video, but I have a question. I have a pair of Mavic Cosmic Carbone SSC wheels. I want to upgrade them with lighter hubs and new spokes to get rid of some of that stock weight. Besides that because they are old. The spoke keep breaking on me. Would you recommend me to do that?
Bill, many thanks for uploading this video. I have a pair of Mavic XM719 Disc 32h 26" rims, a Shimano XT rear hub and will have a front hub soon. I plan on using Sapim CX Ray spokes with 12mm brass nipples and to get correct lengths I'm making sure to find out what I need to measure, how and why before I order anything. This video shows exactly what I wanted to know.
Something doesn't seem right here to me. The ERD should be a separate variable independent of any dimensions of the nipple and only unique to the rim, not the wheel build. You can determine spoke length for a wheel build using a constant ERD unique to your rim, and plugging in different nipple dimensions. It just means the spoke length will change, not the ERD. Can you explain why I might be incorrect?
Thanks for the feedback. What you say seems reasonable because manufacturers list ERDs on websites and sometimes put the ERD on the rim. When they do that, they are making an assumption about the type of nipple that will be used. Some alloy nipples have a long hexagonal head which requires a longer spoke and a different ERD calculation. If you use nipples like that and don't change the ERD calculation, your spokes will be too short. Likewise, if you use a washer under the head of the nipple, you need a slightly longer spoke. What I have said is correct. I've done this thousands of times.
I absolutely trust your experience. I always use DT Swiss' online calculator and it accounts for nipple types and dimension given the same ERD. And DT Swiss will specify if their own rim is designed to be used with a washer and the ERD will account for it. The calculator will output a different spoke length if you change the nipple even if the ERD value remains the same. So changing the ERD seems a bit confusing and an unnesesary extra step of the process. I guess I need some more time to wrap my head around the process. I did build wheels for my bike and have put about 1,500 miles on them with no issues and they've stayed true. No broken spokes or nipples and its a disc bike and I often load 100 pounds or more on the rack. With the stock wheels built by a machine, I broke yo to two spokes a week. I plan to swap to alu nipples soon and was going to make a video of the re-build. But I want to share only accurate and useful info. Your channel is by far the best I've found on this stuff. Thanks for your videos.
You're correct Peeling Pedaler. The ERD is a property unique to each rim and doesn't depend on the nipples. However to actually select the correct spoke length, you need to derive a second value from the ERD, which does take into account things as the type of nipple, any additional washers, etc. It's the "effective effective rim diameter" if you will. ;) Also, don't blindly trust the ERD values given by the rim manufacturers. There are two or three distinctive ways to measure the ERD (e.g. with or without the assumed nipple head length, as shown here), and most times they don't explain how they've taken the measurement.
@@sp00n it is not unique or constant. Depends on which nipples you use, but what's more important is where you want your spoke to end. Some measure ERD with spoke ending at the bottom of the nipple slot, some like to base it off the head top or even the bottom of head, when using thinner 1.8 spokes, which tend to stretch after final tensioning. So, it really depends on few factors and might change from time to time even for the same rim.
Alternatively, to get the internal rim diameter, one might first measure the outside diameter, then substract the rim section depth twice. That will give you the internal rim diameter.
This is good but he should have stated that the reason you measure to the spoke screw driver slot, and not the top of the spoke is because you are trying to really measure to the end of the spoke. And the spokes should optimally come to the top of the spoke but below the screw driver slot so you can screw the spoke in.
@@BillMouldWheels what I'm saying that if the rim is a 29 and it was built at the factory with whatever the length the spokes,it should be the same, except the colors of the spokes would change. I used a online spoke calculator and it gave me different results,one said close to 270mm spokes and another said 263mm. So I decided to stick with the 263mm spokes lengths which was the original. The weaving patterns I'm using is three cross and I'm still learning how to lace a rear wheel. I don't know it's up to you in your measurements.
After much searching and a lot of struggling with other methods, I stumbled upon your explaination. You did a far better job of it than even Park Tool's clumbsy attempt. Well done sir! Thank you!
I've been doing it wrong for years! I measure to the nipple seat and this explains why I sometimes struggle to get it spot on. You're never too old to learn!
Well, that might also work, if you round up the calculated spoke length. It is not so much critical to support the nipple head, unless it's an alu nipple, in which case you should always base off your ERD close to top of the nipple head. Hope this helps! Cheers.
Effective Rim Diameter is NOT a measurement of nipple slot to nipple slot. This gentleman's explanation is a perfect example of what Jobst Brandt lamented as taking a simple reference and turning it into a "religion". ERD is simply a reference to the ends of the spokes in an already built and functional wheel. For any given rim there can be multiple ERD's - simply because differing sizes of nipples, differing profiles for nipples AND differing threadings for the nipples and spoke threads can result in differing MAX and MIN thread insertion. Take any wheel. Pick it up. If it is tensioned, dished, trued - i.e. - it appears to be a functional wheel - the ERD is simply the end of one spoke to the end of the other spoke at 180 degrees measured in millimeters.
This is why when wheel builders measure a rim, they commonly use a pair of spokes or spoke rods combined with a caliper. They test the nipple and threads to be used, set the rods - and try to EMULATE where the spoke ends will be in the future when the wheel is built. The measure they guestimate using that method is plugged into a spoke length calculator. A careful and consistent practitioner often gets it within a 1/2 millimeter.
ERD is not an industry standard specification, nor is it a white paper subject. It's simply a reference to the ends of spokes in an already built and functional bicycle wheel.
MrRabbit - Wheels By Fleming - 5000+ Wheels Built since 1984 =8-)
Robert, thank you for your response. The purpose of measuring ERD is to calculate the optimal spoke length for a wheel. You are correct that ERD is a function of several variables, so if a manufacturer publishes an ERD for a particular rim, an assumption is being made about the type of nipple that is being used and whether nipple washers are being used or not. That’s why I always measure it with the actual components I am going to use for a particular wheel. You say: “If a wheel is tensioned, dished, trued - i.e. - it appears to be a functional wheel - the ERD is simply the end of one spoke to the end of the other spoke at 180 degrees in millimeters.” That is not correct. The fact of a wheel being “functional” does not mean that the spoke length is optimal. Here is my email address: bill@billmouldwheels.com. I’d suggest we take this conversation “off-line” and maybe have a phone call. Maybe I am just misunderstanding the point you are trying to make. Bill Mould
Useful video Bill, this is appreciated
However, Roger Musson showed in his book 'Professional guide to Wheel building' a (in my opionion) nice method to quickly determine the ERD without dealing with too many figures:
prepare 2 sets of a piece of spoke with a glued 'normal' nipple at the end. Cut the spoke end in a way, that the distance from slot to spoke end is an even measure, e.g. 250mm
stick both spokes in opposite holes and tie the ends with a rubber band together in order that the ends points to each other and the nipple sits nicely in the hole. Then simply measure the face to face distance of the spoke ends with a ruler or a caliper. E.g. a distance of 103mm will result in an ERD of 603 mm (103+2x250)
Keep up your useful work! Cheers, Georg
how to measure with sapim double square?
Slot?
Hi Bill. I know this a old video, but I have a question. I have a pair of Mavic Cosmic Carbone SSC wheels. I want to upgrade them with lighter hubs and new spokes to get rid of some of that stock weight. Besides that because they are old. The spoke keep breaking on me. Would you recommend me to do that?
Aldrin, if you can shoot me a phone number to bill@billmouldwheels.com, I will try to call you tomorrow and offer you some help.
Bill, many thanks for uploading this video. I have a pair of Mavic XM719 Disc 32h 26" rims, a Shimano XT rear hub and will have a front hub soon. I plan on using Sapim CX Ray spokes with 12mm brass nipples and to get correct lengths I'm making sure to find out what I need to measure, how and why before I order anything. This video shows exactly what I wanted to know.
Thank you for the nice comment.
Something doesn't seem right here to me. The ERD should be a separate variable independent of any dimensions of the nipple and only unique to the rim, not the wheel build. You can determine spoke length for a wheel build using a constant ERD unique to your rim, and plugging in different nipple dimensions. It just means the spoke length will change, not the ERD. Can you explain why I might be incorrect?
Thanks for the feedback. What you say seems reasonable because manufacturers list ERDs on websites and sometimes put the ERD on the rim. When they do that, they are making an assumption about the type of nipple that will be used. Some alloy nipples have a long hexagonal head which requires a longer spoke and a different ERD calculation. If you use nipples like that and don't change the ERD calculation, your spokes will be too short. Likewise, if you use a washer under the head of the nipple, you need a slightly longer spoke. What I have said is correct. I've done this thousands of times.
I absolutely trust your experience. I always use DT Swiss' online calculator and it accounts for nipple types and dimension given the same ERD. And DT Swiss will specify if their own rim is designed to be used with a washer and the ERD will account for it. The calculator will output a different spoke length if you change the nipple even if the ERD value remains the same. So changing the ERD seems a bit confusing and an unnesesary extra step of the process. I guess I need some more time to wrap my head around the process.
I did build wheels for my bike and have put about 1,500 miles on them with no issues and they've stayed true. No broken spokes or nipples and its a disc bike and I often load 100 pounds or more on the rack. With the stock wheels built by a machine, I broke yo to two spokes a week. I plan to swap to alu nipples soon and was going to make a video of the re-build. But I want to share only accurate and useful info. Your channel is by far the best I've found on this stuff. Thanks for your videos.
Thanks for the kind comments.
You're correct Peeling Pedaler. The ERD is a property unique to each rim and doesn't depend on the nipples. However to actually select the correct spoke length, you need to derive a second value from the ERD, which does take into account things as the type of nipple, any additional washers, etc. It's the "effective effective rim diameter" if you will. ;)
Also, don't blindly trust the ERD values given by the rim manufacturers. There are two or three distinctive ways to measure the ERD (e.g. with or without the assumed nipple head length, as shown here), and most times they don't explain how they've taken the measurement.
@@sp00n it is not unique or constant. Depends on which nipples you use, but what's more important is where you want your spoke to end. Some measure ERD with spoke ending at the bottom of the nipple slot, some like to base it off the head top or even the bottom of head, when using thinner 1.8 spokes, which tend to stretch after final tensioning. So, it really depends on few factors and might change from time to time even for the same rim.
Amazing. This is just crystal clear.
Thank you. I appreciate the feedback and encouragement.
Alternatively, to get the internal rim diameter, one might first measure the outside diameter, then substract the rim section depth twice. That will give you the internal rim diameter.
Great stuff! Thank you.
This is good but he should have stated that the reason you measure to the spoke screw driver slot, and not the top of the spoke is because you are trying to really measure to the end of the spoke. And the spokes should optimally come to the top of the spoke but below the screw driver slot so you can screw the spoke in.
so helpful!! thank you
The bigger the e.r.d.,the spokes will remain the same as the original,that was built at the factory.
I don't understand that comment.
@@BillMouldWheels what I'm saying that if the rim is a 29 and it was built at the factory with whatever the length the spokes,it should be the same, except the colors of the spokes would change. I used a online spoke calculator and it gave me different results,one said close to 270mm spokes and another said 263mm. So I decided to stick with the 263mm spokes lengths which was the original. The weaving patterns I'm using is three cross and I'm still learning how to lace a rear wheel. I don't know it's up to you in your measurements.