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#1
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spoke length problem
Warning: Actual bike tech content below.
I'm building up an antique bike for a kid. After a false start with the original rims (very light, but in a very obscure size) I ended up replacing the wheels with 20" Sun rims on hubs that I had lying around: a Campy front hub, and a Shimano 3CC 3 speed rear hub with coaster brake. I measured both hubs and used Sun's online ERD value of 396mm for the rim. I plugged dimensions into three different online spoke calculators. It looked like I could use the same spoke length front and rear if I went 2x front and 3x rear. Here were the calculator results: Sapim said front 189mm, rear 188mm. DT said 186 front, 186 rear. United Bicycle Institute said 185.6 front, 185.1 rear. So I ordered 14 gauge Sapim spokes, 186 front and rear. The front wheel built up perfectly, as usual. But the rear wheel won't tension up. The spoke threads are bottoming. I just double checked my hub dimensions. They seem to be spot on. And again, everything was perfect in front. The spokes measure 186 with 10mm of thread. The nipples are 16mm long with an unthreaded 5mm deep hole at the end that slides over the spoke. I can think of several possible solutions: 1) buy shorter spokes. 2) sacrifice a few nipple threads by drilling into the end of the nipple to counterbore another 2mm or so. It's for a little kid, and I doubt he'll be stressing the wheel very much. 3) acquire a die and extend the spoke threads. The cut threads won't have a full thread form, but there should be plenty of strength in the existing threads. 4) put washers under the spoke heads. It's a double wall rim so there's room in there. 5) and next time, maybe go 2mm shorter than the calculators say? But why? These spokes aren't stretching. I can't get any tension at all. I'm curious if anyone's had a similar problem. If so, did you determine what caused the error? I'm prepared to smack my forehead if necessary. -- - Frank Krygowski |
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#2
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spoke length problem
Real time. ERD is estimate
Use a wheel beam...search here in RBT Beam rim with hub hole n shim rim up Then quadrant rim with 3-4 experimental spokes in 4 groups pre measured real time with tape or steel yardstick - Wal sewing Then arrive at 'exact' length |
#3
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spoke length problem
On Wednesday, November 29, 2017 at 7:58:57 PM UTC-8, Frank Krygowski wrote:
Warning: Actual bike tech content below. I'm building up an antique bike for a kid. After a false start with the original rims (very light, but in a very obscure size) I ended up replacing the wheels with 20" Sun rims on hubs that I had lying around: a Campy front hub, and a Shimano 3CC 3 speed rear hub with coaster brake. I measured both hubs and used Sun's online ERD value of 396mm for the rim. I plugged dimensions into three different online spoke calculators. It looked like I could use the same spoke length front and rear if I went 2x front and 3x rear. Here were the calculator results: Sapim said front 189mm, rear 188mm. DT said 186 front, 186 rear. United Bicycle Institute said 185.6 front, 185.1 rear. So I ordered 14 gauge Sapim spokes, 186 front and rear. The front wheel built up perfectly, as usual. But the rear wheel won't tension up. The spoke threads are bottoming. I just double checked my hub dimensions. They seem to be spot on. And again, everything was perfect in front. The spokes measure 186 with 10mm of thread. The nipples are 16mm long with an unthreaded 5mm deep hole at the end that slides over the spoke. I can think of several possible solutions: 1) buy shorter spokes. 2) sacrifice a few nipple threads by drilling into the end of the nipple to counterbore another 2mm or so. It's for a little kid, and I doubt he'll be stressing the wheel very much. 3) acquire a die and extend the spoke threads. The cut threads won't have a full thread form, but there should be plenty of strength in the existing threads. 4) put washers under the spoke heads. It's a double wall rim so there's room in there. 5) and next time, maybe go 2mm shorter than the calculators say? But why? These spokes aren't stretching. I can't get any tension at all. I'm curious if anyone's had a similar problem. If so, did you determine what caused the error? I'm prepared to smack my forehead if necessary. They're too long, obviously. Is lacing 4X a possibility? Otherwise, you buy new spokes. You could also find a shop with a Phil or other spoke cutter. -- Jay Beattie. |
#4
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spoke length problem
On Wed, 29 Nov 2017 22:58:52 -0500, Frank Krygowski
wrote: Warning: Actual bike tech content below. I'm building up an antique bike for a kid. After a false start with the original rims (very light, but in a very obscure size) I ended up replacing the wheels with 20" Sun rims on hubs that I had lying around: a Campy front hub, and a Shimano 3CC 3 speed rear hub with coaster brake. I measured both hubs and used Sun's online ERD value of 396mm for the rim. I plugged dimensions into three different online spoke calculators. It looked like I could use the same spoke length front and rear if I went 2x front and 3x rear. Here were the calculator results: Sapim said front 189mm, rear 188mm. DT said 186 front, 186 rear. United Bicycle Institute said 185.6 front, 185.1 rear. So I ordered 14 gauge Sapim spokes, 186 front and rear. The front wheel built up perfectly, as usual. But the rear wheel won't tension up. The spoke threads are bottoming. I just double checked my hub dimensions. They seem to be spot on. And again, everything was perfect in front. The spokes measure 186 with 10mm of thread. The nipples are 16mm long with an unthreaded 5mm deep hole at the end that slides over the spoke. I can think of several possible solutions: 1) buy shorter spokes. 2) sacrifice a few nipple threads by drilling into the end of the nipple to counterbore another 2mm or so. It's for a little kid, and I doubt he'll be stressing the wheel very much. 3) acquire a die and extend the spoke threads. The cut threads won't have a full thread form, but there should be plenty of strength in the existing threads. 4) put washers under the spoke heads. It's a double wall rim so there's room in there. 5) and next time, maybe go 2mm shorter than the calculators say? But why? These spokes aren't stretching. I can't get any tension at all. I'm curious if anyone's had a similar problem. If so, did you determine what caused the error? I'm prepared to smack my forehead if necessary. Quite a lot of shops over here no longer stock threaded spokes but cut to length and thread (would one call them) blank spokes so assuming sufficient full diameter size it should be no problem in threading the spokes a little further. Assuming, of course that you can get the proper die. I include that comment as I once threaded some spokes a bit too far and a number of them stripped the threads out of the nipples as there wasn't sufficient thread contact :-( I believe that might be a better scheme then counter boring the nipples although the usual standard for thread length is one diameter for full strength so I would assume that something like 1-1/2 to 2 thread diameter would be sufficient even in brass nipples. Or alternatively use washers under the nipple head. I believe that someone else mentioned it but can you go X4 on the rear wheel? Re calculators. The old chap that runs (I think) the oldest bike shop in Phuket, Thailand doesn't use any sort of calculator. He has, what I think is, some sort of special steel ruler and he measures the rim to flange distance with the wheel and hub laying on the floor. After he measures things he pauses and looks wise for a moment and says something like, "Yup, 265.4, that'll do her" and gets down the 265.5 spoke box :-) -- Cheers, John B. |
#5
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spoke length problem
On Wednesday, November 29, 2017 at 8:58:57 PM UTC-7, Frank Krygowski wrote:
Warning: Actual bike tech content below. I'm building up an antique bike for a kid. After a false start with the original rims (very light, but in a very obscure size) I ended up replacing the wheels with 20" Sun rims on hubs that I had lying around: a Campy front hub, and a Shimano 3CC 3 speed rear hub with coaster brake. I measured both hubs and used Sun's online ERD value of 396mm for the rim. I plugged dimensions into three different online spoke calculators. It looked like I could use the same spoke length front and rear if I went 2x front and 3x rear. Here were the calculator results: Sapim said front 189mm, rear 188mm. DT said 186 front, 186 rear. United Bicycle Institute said 185.6 front, 185.1 rear. So I ordered 14 gauge Sapim spokes, 186 front and rear. The front wheel built up perfectly, as usual. But the rear wheel won't tension up. The spoke threads are bottoming. I just double checked my hub dimensions. They seem to be spot on. And again, everything was perfect in front. The spokes measure 186 with 10mm of thread. The nipples are 16mm long with an unthreaded 5mm deep hole at the end that slides over the spoke. I can think of several possible solutions: 1) buy shorter spokes. 2) sacrifice a few nipple threads by drilling into the end of the nipple to counterbore another 2mm or so. It's for a little kid, and I doubt he'll be stressing the wheel very much. 3) acquire a die and extend the spoke threads. The cut threads won't have a full thread form, but there should be plenty of strength in the existing threads. 4) put washers under the spoke heads. It's a double wall rim so there's room in there. 5) and next time, maybe go 2mm shorter than the calculators say? But why? These spokes aren't stretching. I can't get any tension at all. I'm curious if anyone's had a similar problem. If so, did you determine what caused the error? I'm prepared to smack my forehead if necessary. -- - Frank Krygowski https://photos.google.com/photo/AF1Q...McTvE1X9SAuRq5 https://photos.google.com/photo/AF1Q...NeMvV_TztSOdm5 https://photos.google.com/photo/AF1Q...v3rSfHjbj_XC8r https://photos.google.com/photo/AF1Q...rkasfHxXt1MZgI |
#6
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spoke length problem
All my experience is with buying too short spokes. I use the calculators to figure the right length. Then always buy a spoke 2-3-4 mm shorter figuring the calculators are over generous and the spokes will stretch when tightened. Went a bit overboard on this on one set of wheel and ended up with lots of threads showing below the nipple. In your situation the other suggestions of new spokes or cutting longer threads on the existing spokes is the best method. But just using washers under the nipples inside the rim would be the easiest fix and still be fine and dandy.
On Wednesday, November 29, 2017 at 9:58:57 PM UTC-6, Frank Krygowski wrote: Warning: Actual bike tech content below. I'm building up an antique bike for a kid. After a false start with the original rims (very light, but in a very obscure size) I ended up replacing the wheels with 20" Sun rims on hubs that I had lying around: a Campy front hub, and a Shimano 3CC 3 speed rear hub with coaster brake. I measured both hubs and used Sun's online ERD value of 396mm for the rim. I plugged dimensions into three different online spoke calculators. It looked like I could use the same spoke length front and rear if I went 2x front and 3x rear. Here were the calculator results: Sapim said front 189mm, rear 188mm. DT said 186 front, 186 rear. United Bicycle Institute said 185.6 front, 185.1 rear. So I ordered 14 gauge Sapim spokes, 186 front and rear. The front wheel built up perfectly, as usual. But the rear wheel won't tension up. The spoke threads are bottoming. I just double checked my hub dimensions. They seem to be spot on. And again, everything was perfect in front. The spokes measure 186 with 10mm of thread. The nipples are 16mm long with an unthreaded 5mm deep hole at the end that slides over the spoke. I can think of several possible solutions: 1) buy shorter spokes. 2) sacrifice a few nipple threads by drilling into the end of the nipple to counterbore another 2mm or so. It's for a little kid, and I doubt he'll be stressing the wheel very much. 3) acquire a die and extend the spoke threads. The cut threads won't have a full thread form, but there should be plenty of strength in the existing threads. 4) put washers under the spoke heads. It's a double wall rim so there's room in there. 5) and next time, maybe go 2mm shorter than the calculators say? But why? These spokes aren't stretching. I can't get any tension at all. I'm curious if anyone's had a similar problem. If so, did you determine what caused the error? I'm prepared to smack my forehead if necessary. -- - Frank Krygowski |
#8
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spoke length problem
On 11/29/2017 11:22 PM, jbeattie wrote:
On Wednesday, November 29, 2017 at 7:58:57 PM UTC-8, Frank Krygowski wrote: Warning: Actual bike tech content below. I'm building up an antique bike for a kid. After a false start with the original rims (very light, but in a very obscure size) I ended up replacing the wheels with 20" Sun rims on hubs that I had lying around: a Campy front hub, and a Shimano 3CC 3 speed rear hub with coaster brake. I measured both hubs and used Sun's online ERD value of 396mm for the rim. I plugged dimensions into three different online spoke calculators. It looked like I could use the same spoke length front and rear if I went 2x front and 3x rear. Here were the calculator results: Sapim said front 189mm, rear 188mm. DT said 186 front, 186 rear. United Bicycle Institute said 185.6 front, 185.1 rear. So I ordered 14 gauge Sapim spokes, 186 front and rear. The front wheel built up perfectly, as usual. But the rear wheel won't tension up. The spoke threads are bottoming. I just double checked my hub dimensions. They seem to be spot on. And again, everything was perfect in front. The spokes measure 186 with 10mm of thread. The nipples are 16mm long with an unthreaded 5mm deep hole at the end that slides over the spoke. I can think of several possible solutions: 1) buy shorter spokes. 2) sacrifice a few nipple threads by drilling into the end of the nipple to counterbore another 2mm or so. It's for a little kid, and I doubt he'll be stressing the wheel very much. 3) acquire a die and extend the spoke threads. The cut threads won't have a full thread form, but there should be plenty of strength in the existing threads. 4) put washers under the spoke heads. It's a double wall rim so there's room in there. 5) and next time, maybe go 2mm shorter than the calculators say? But why? These spokes aren't stretching. I can't get any tension at all. I'm curious if anyone's had a similar problem. If so, did you determine what caused the error? I'm prepared to smack my forehead if necessary. They're too long, obviously. Is lacing 4X a possibility? Otherwise, you buy new spokes. You could also find a shop with a Phil or other spoke cutter. 4x won't work. That would require roughly 195mm spokes. I happen to have a set of 170mm spokes (intended for the original odd rims) and the calculators tell me x2 would need 177mm. So I'm assuming 170 is too short. I'll see if some shorter nipples might work. If not, I'll probably go with washers under the spoke nipple heads. I'm more interested in knowing what might have gone wrong. I've never had this problem occur before. I just tried measuring the ERD myself, using a tape measure to get circumference of the rim tape's surface (1260mm) and a metric vernier caliper to get the "drop" from that surface to the face of the hollow rivets on which the spoke head rests (3.8mm). Circumference divided by pi minus (drop x 2) gives me 393.5mm. From https://www.sheldonbrown.com/spoke-length.html I get the advice to add a couple millimeter for the thickness of each nipple head, which gives me ERD = 397.5mm. That compares well with the online catalog value of 396, so I'm still baffled. -- - Frank Krygowski |
#9
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spoke length problem
Why yawl refuse real time measurement with a simply made device is intolerably STUPID
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#10
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spoke length problem
On Thursday, November 30, 2017 at 11:37:28 AM UTC-8, wrote:
All my experience is with buying too short spokes. I use the calculators to figure the right length. Then always buy a spoke 2-3-4 mm shorter figuring the calculators are over generous and the spokes will stretch when tightened. Went a bit overboard on this on one set of wheel and ended up with lots of threads showing below the nipple. In your situation the other suggestions of new spokes or cutting longer threads on the existing spokes is the best method. But just using washers under the nipples inside the rim would be the easiest fix and still be fine and dandy. Washers are so trailer. It is odd that the length was fine for the front but not the rear. The obvious explanation would be a mistaken flange height/spoke hole measurement. The ERD was correct for the front so it should be correct for the rear, assuming the as-manufactured rim is not out of spec. I assume Frank put the right number of spoke holes into the calculator. The only variable in the equation is the hub. No? -- Jay Beattie. |
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