Nipple washers
01-23-20, 08:17 AM
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Nipple washers
I would like to increase the spoke tension but concerned that nipples may over time pull through rim. I have dt prohead nipples on 2mm dt spokes with 1-2mm of thread exposed through nipple (at tire side) on heavily ladened tandem. I see dt makes Pro Head Reinforcement washers. I'm considering release/retension of spokes one at a time while adding these washers. Bad idea? Would such a process distort wheel if not done from fully un-tensioned wheel?
01-23-20, 08:53 AM
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Be interesting to note where your starting point is. Have you measured spoke tension? Also (I request your patience in satisfying my curiosity) have you broken spokes? Have you pulled a spoke through a rim? Do the wheels go out of true frequently? I'm trying to understand why you're focused on spoke tension. If, for example, you already have the spokes at pretty high tension but are using a 24 spoke wheel would it be useful to consider going to a 36 spoke setup? Or are you already at 36 all set to 165kgf (at which point I'd wonder if increasing spoke tension would be advisable).
As you probably have found, the DT washers are set up for the Squorx nipples with spherical seating surfaces. They are expressly made to strengthen the setup when installed with their thinwall rim profile. I think for maximum effect you want the matching washer/spoke setup (other nipples might benefit from the washer, but a nipple that seats properly all the way round the washer will spread the force better). One other thing would be that a washer makes spoke alignment more difficult if the hole is not big enough. An analogy would be looking at a construction site through a hole in the fence. If you can get up close to the hole, you can see the whole site. If you have to stand a bit away from the hole you can see less. If you add a washer to a rim with small holes the nipple can't swivel to align with the spoke. This might have the paradoxical effect of INCREASING the stress on the edge of the hole. I think Jobst Brandt (a wheel guru of renown and some controversy, now passed) suggested bending the spoke just before the threads so that the nipple would come out of the hole more or less straight, and there would not be a long bend in the spoke induced by the nipple sticking straight out of the rim.
As you probably have found, the DT washers are set up for the Squorx nipples with spherical seating surfaces. They are expressly made to strengthen the setup when installed with their thinwall rim profile. I think for maximum effect you want the matching washer/spoke setup (other nipples might benefit from the washer, but a nipple that seats properly all the way round the washer will spread the force better). One other thing would be that a washer makes spoke alignment more difficult if the hole is not big enough. An analogy would be looking at a construction site through a hole in the fence. If you can get up close to the hole, you can see the whole site. If you have to stand a bit away from the hole you can see less. If you add a washer to a rim with small holes the nipple can't swivel to align with the spoke. This might have the paradoxical effect of INCREASING the stress on the edge of the hole. I think Jobst Brandt (a wheel guru of renown and some controversy, now passed) suggested bending the spoke just before the threads so that the nipple would come out of the hole more or less straight, and there would not be a long bend in the spoke induced by the nipple sticking straight out of the rim.
Last edited by WizardOfBoz; 01-23-20 at 09:07 AM.
01-23-20, 08:56 AM
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I would not release the spoke tension one at a time and then retension it (after adding a washer) out of choice Sure this is what happens when a spoke breaks and a replacement is installed but why give the rim a chance to distort if you don't have to. If you're not comfy working with all the spokes at the same time I would offer you're not ready yet to do this job.
Have you actually measured the current average spoke tensions? Rim type and spoke counts? Tandems are about the worst case for a rear wheel living a care free life. Why do you want/need more tension? Nipple washers are generally thought of as a reinforcing device for rims that are otherwise rather light weight, light weight rims and loaded tandems generally don't belong in the same sentence. Andy
Have you actually measured the current average spoke tensions? Rim type and spoke counts? Tandems are about the worst case for a rear wheel living a care free life. Why do you want/need more tension? Nipple washers are generally thought of as a reinforcing device for rims that are otherwise rather light weight, light weight rims and loaded tandems generally don't belong in the same sentence. Andy
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01-23-20, 02:24 PM
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01-23-20, 05:26 PM
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Be interesting to note where your starting point is. Have you measured spoke tension? Also (I request your patience in satisfying my curiosity) have you broken spokes? Have you pulled a spoke through a rim? Do the wheels go out of true frequently? I'm trying to understand why you're focused on spoke tension. If, for example, you already have the spokes at pretty high tension but are using a 24 spoke wheel would it be useful to consider going to a 36 spoke setup? Or are you already at 36 all set to 165kgf (at which point I'd wonder if increasing spoke tension would be advisable).
As you probably have found, the DT washers are set up for the Squorx nipples with spherical seating surfaces. They are expressly made to strengthen the setup when installed with their thinwall rim profile. I think for maximum effect you want the matching washer/spoke setup (other nipples might benefit from the washer, but a nipple that seats properly all the way round the washer will spread the force better). One other thing would be that a washer makes spoke alignment more difficult if the hole is not big enough. An analogy would be looking at a construction site through a hole in the fence. If you can get up close to the hole, you can see the whole site. If you have to stand a bit away from the hole you can see less. If you add a washer to a rim with small holes the nipple can't swivel to align with the spoke. This might have the paradoxical effect of INCREASING the stress on the edge of the hole. I think Jobst Brandt (a wheel guru of renown and some controversy, now passed) suggested bending the spoke just before the threads so that the nipple would come out of the hole more or less straight, and there would not be a long bend in the spoke induced by the nipple sticking straight out of the rim.
As you probably have found, the DT washers are set up for the Squorx nipples with spherical seating surfaces. They are expressly made to strengthen the setup when installed with their thinwall rim profile. I think for maximum effect you want the matching washer/spoke setup (other nipples might benefit from the washer, but a nipple that seats properly all the way round the washer will spread the force better). One other thing would be that a washer makes spoke alignment more difficult if the hole is not big enough. An analogy would be looking at a construction site through a hole in the fence. If you can get up close to the hole, you can see the whole site. If you have to stand a bit away from the hole you can see less. If you add a washer to a rim with small holes the nipple can't swivel to align with the spoke. This might have the paradoxical effect of INCREASING the stress on the edge of the hole. I think Jobst Brandt (a wheel guru of renown and some controversy, now passed) suggested bending the spoke just before the threads so that the nipple would come out of the hole more or less straight, and there would not be a long bend in the spoke induced by the nipple sticking straight out of the rim.
"Acts like a ball and socket interface allowing the spoke to pivot and follow the perfect trajectory from hub to rim."
I thought adding washers would allow higher tension for this rim, but from comments here, adding washers without full rebuild is bad idea. Perhaps spokes won't pull through. Just thinking of how I might guard against.
01-23-20, 07:24 PM
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Can't say I've seen a Zac 19 rim with spoke hole cracks. It's not a super light weight rim so no surprise there. Can you give specifics beyond " After breaking down twice"? Meaning spoke breakage? Something else the wheel builder did? BTW how many miles on this wheel, loaded and otherwise? Andy
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01-23-20, 09:07 PM
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I thought about what DT was saying a bit. They may be (probably are) right. Perhaps this makes sense (?): The washer has a saddle shape, which should allow it to slide back and forth in the rim well. Assuming the washer itself imparts no limit to twist (having the cool hemispherical seat), and allowing for the fact that the washer causes the nipple to not insert as deeply into the hole (by the thickness of the washer) you'd get a thinner part of the nipple in the hole which gives you more clearance. Ok, I buy that. Cool.
01-23-20, 09:31 PM
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100kgf(+/-10%) on all 36 spokes 559 Zac19 rim, no dish. I don't let wheels go significantly out of true. After breaking down twice in the middle of nowhere, I have lost confidence in the wheel builder. If another failure, I will build my own wheel with different rim. Regarding alignment comment, DT appears to say the opposite, adding washers helps the spoke alignment angle ...
"Acts like a ball and socket interface allowing the spoke to pivot and follow the perfect trajectory from hub to rim."
I thought adding washers would allow higher tension for this rim, but from comments here, adding washers without full rebuild is bad idea. Perhaps spokes won't pull through. Just thinking of how I might guard against.
"Acts like a ball and socket interface allowing the spoke to pivot and follow the perfect trajectory from hub to rim."
I thought adding washers would allow higher tension for this rim, but from comments here, adding washers without full rebuild is bad idea. Perhaps spokes won't pull through. Just thinking of how I might guard against.
