Cycling UK Forum

Where do I measure a spoke to find its gauge?
Across the thread or just below on the butt?
Also, is this correct?

13 gauge is 2.3 mm
14 gauge is 2.0 mm
15 gauge is 1.8 mm
16 gauge is 1.6 mm
17 gauge is 1.5 mm

If it is a plain gauge spoke -- same diameter along its length -- then it doesn't matter where you measure it. But some spokes are double butted. eg they are 2mm at each end and 1.8mm (or even 1.7mm) for most of the length. Some are single butted which means they are thicker at one end (I'm not sure which because I've never built a wheel with single butted). So you need to measure at both ends and in the middle to determine the diameter and type of spoke.

Got that but where do you measure ? SB DB and SG spokes to be used.
Can't re thread without knowing which cutter to use thus need to now gauge.
Eg I have some which may be 17/15 Db but can't be sure as I am not familiar enough to do it by feel.

Where do you measure, thread or plain shaft? As threads are rolled, not cut, it may increase or decrease the diameter.

the spoke is measured on the plain part before it is threaded, i.e. the wire diameter from which the spoke is made.

The diameter of the threads themselves is indeed fractionally greater because the threads are rolled.

cheers

Excellent. For once I had assumed correctly.
Just measured just below the thread to get 2mm so 14G
Thanks

Ah, yes. Just took a micrometer to a spoke and it is about .3mm wider at the thread. I'd forgotten they were rolled not cut.

BTW the list of dimensions is (in round numbers) accurate enough but

a) in reality the official sizes in SWG are (of course) defined in thousands of an inch and

b) many spokes are made to nominal metric dimensions these days, that are theoretically a fraction smaller diameter than SWG sizes.

The latter point is something of a nonsense; the spoke threads are still rolled at 56tpi.

There appears to be no problem in using old 14G nipples on new 2.0mm (nominal) spokes or new nipples on old spokes. Sapim and DT 15G spokes are described by the manufacturers as '1.8mm' spokes these days.

I think the thread tolerances were always generous, because most spokes were either painted or galvanised for many years. Unlike other screw threads, this almost certainly means that the connection is not at full strength until rather more threads than normal are engaged (vs a standard nut and bolt). All this means that even though the spokes are often (intentionally or otherwise) made to slightly different dimensions, you can usually mix and match bits pretty well.

[edit; BTW the sizes in SWG are very simply in fixed intervals of several thousandths of an inch; however to make it work over the full range the intervals vary in size, and one of the breaks is within the range of interest for bicycle spokes.

So 14SWG is exactly 0.080" and the smaller gauges 15, 16, 17 etc are successively 0.008" smaller. However 13SWG and 12SWG are successively 0.012" larger.]

cheers

mattsccm wrote:Where do I measure a spoke to find its gauge?
Across the thread or just below on the butt?
Also, is this correct?

13 gauge is 2.3 mm
14 gauge is 2.0 mm
15 gauge is 1.8 mm
16 gauge is 1.6 mm
17 gauge is 1.5 mm

Keep in mind that spokes like DT Swiss almost always have a smooth transition between the two (or three) gauges of the spokes, Sapim and Wheelsmith have a more noticeable taper that can be seen or felt easily by sliding the fingers on.

Usually I'm not too worried about the itsy-bitsy-teeny-weeny fraction of mm in gauge, as tolerances in the rims and hubs, plus the way the wheel is built would play a much bigger role in the wheel's lifespan.

A spoke ruler is a nice present for Xmas