Spokes for 20" with Nexus internal 7 hub.
 

What size spokes should I order - both sides are different - 36 holes - I broke a factory spoke and would love the best strongest spokes and any help with ordering the right sizes. I think the one that broke was 170mm long. I had a bike shop fix it - but what to try my hand lacing this one up - I have built wheels before in my younger days.

What is the ERD of the rim?

What are the hub spoke hole dimensions (flange to center both DS & NDS, spoke hole BCD)?

How many cross are you planning?

Read Sheldon Brown's article on wheel building for an explanation of what you need to know or measure.

You have not provided sufficient information, and thus we can't even guess.

Regarding spoke choice; what load will the wheel see? I am a BIG guy, and for my ETRTO 559 wheels, I used Wheelsmith DB14 spokes on the DS and DB15 spokes on the NDS, with 40h hubs and rims.

What is the ERD of the rim?
What are the hub spoke hole dimensions (flange to center both DS & NDS, spoke hole BCD)?

A: Wow - Not sure - it is the stock rim from a Dahon Vitesse i7
https://usa.dahon.com/bikes/vitesse-i7/

How many cross are you planning?
Whatever is best for strength - since I broke a spoke after about 4,500 miles

I'm a big guy over 200 lbs

The dimensions you need aren't stated specs. You'll have to either physically measure the current spokes and/or the rim ERD and the hub dimensions or email Dahon and see if they can provide you with specs.

Spoke durability is most prominently a feature of build quality--high, even tension and appropriate stress relieving during building, but generally butted spokes will be more durable because they are more flexible in their centers where they are least likely to develop fatigue failures and thus keep the elbows and threads of the spokes from flexing and developing fatigue. The most durable are probably triple butted spokes with a 2.3/1.8/2.0 profile like DT Alpine III or Sapim Force (2.18/1.8/2.0). At lower cost you can also just build with common double butted spokes (2.0/1.8/2.0) or single butted spokes (2.3/2.0).

If you've had a single spoke failure I wouldn't stress out too much about it. 200lbs on a 20", 36 spoke wheel sounds perfectly reasonable (smaller wheels are stronger). Factory wheel builds are typically not very even in tension and it'd be premature to assume many other spokes in the wheel have undergone significant fatigue. A good intermediate step would be to have a good wheelbuilder not just true the wheel, but bring it up to maximum balanced tension and stress relieve the wheel.

Measure from center of the spoke head in the hub to the face of the rim.

Spoke head center O ..... This distance ..... l - Rim face.

The difference in sides accomodates the offset(dish) of the wheel.

Buy what you need and follow the pattern.
Any good quality spoke - DT, Wheelsmith, etc.
New, Stainless steel and straight gauge.
Make sure to replace the nippel as well, unless the brands match.

BTW you mentioned you are a big guy.
I would strongly suggest that you have a professional wheel person do this.
This is really not the wheel to learn on.

Have them drop tension, replace the needed spokes and re-tension, re-dish and true the wheel.
Small wheels for folding bikes tend to carry a higher tension than one would expect.
The re tensioning allows the wheel to be in a balance -replacing a single spoke or
two ends up with old spokes tighter than new, but
each new spoke at slightly different tension than its neighbor. do to offsetting close old spokes tension ...

You get the idea.

Wheels for real use need to be built to survive. A tight spoke , hitting a hole or rock can pretzel the wheel pretty easily.
Good luck

.02, the likelihood of finding triple butted 2.3/1.8/2.0, or 2.18/1.8/2.0,
in a short length
for building a 406 20" wheel is pretty unlikely
*(unless ordering thousands)

Rear of Bromptons use a 2.5mm thick straight gauge spoke ,
28 in a 349 wheel-rim.

Front they use lighter gauge spokes, same count.



*I bought a (new XS) Schmidt Dynohub,
it uses a custom ordered straight pull DB spoke ,
made just for their wheel building section.
they would get that quantity..




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