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Wheel building

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Hi,

I got a new set of stainless steel rims and spokes for my -37 16H from CW and I'm starting to assemble the wheels but I'm some what confused about the correct value for spoke tension.

I tried to google it for a while but the values were all over the place and CW doesn't seem to want to reply to my emails so I was wondering if anyone here knows a good value for the spoke tension?

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I do not work to a set tension but work to getting an even ping from the spokes. Beware the online figures given, the Harley ones are double that for a British wheel and will crack a hub flange.

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I believe you will find.. nobody knows.  If the spokes are "butted", the more slender part will reach its elastic limit and then go no tighter, without overloading the thicker part at the end until it's been stretched a long way.  They need to be tight enough so that the bottom spokes do not go slack when the wheel is loaded.  In practice, if they make a nice "ping" when plucked, they should be fine.  It's a bit like tightening a bolt in the Good Old Days before torque wrenches (and before the era when high strength alloy steel bolts became commonplace)...the spoke key (like a normal spanner) is roughly the correct size so that the torque the average bloke is likely to be able to apply is more or less correct.

(Edit...interesting about Harley specifying torque.. in the USA they seem to expect torque values everywhere and modern Quality Assurance no doubt requires them...but they tend to be very much heavier than a Norton...)

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Plus even if you get a British wheel spec then you have to account for the lower tensile strength of stainless vs steel. I account for that by going up a gauge size on the spokes.

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Don't go overboard on tension.  Stainless can be brittle, On Sunday I was shown a new rim where the nipple had pulled a lump out of the rim. Not seen that on a steel rim.

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Back in the 70's, first with a succession of Tiger Cubs and then my first few Nortons, our local MoT tester was known to pass almost anything- but you needed to give him the opportunity to say, "Your bike's passed lad- but you've got a couple of loose spokes there you should tighten!"

I still remember turning my headlight on, for him to make a comment along the lines of a dead glow-worm....

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I agree about the ping of a well tensioned spoke but, as I am sure you know, you need to check the run out of the rim (and perhaps the hub offset) before the final tensioning. That is, making sure the wheel rim runs true against a fixed pointer or run out gauge with the wheel on a truing stand. 

Some spokes may actually need to be slackened to allow tightening of the opposing spokes to pull the rim true. When the rim runs true all the spokes can be nipped up to ping before checking the rim still runs true.

Dennis

 


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