Spokes - how do I calculate length and which pattern?
 

I am in the process of getting a new rear wheel. The rim and hub have been ordered but I am a bit stuck at spokes - I am not sure how to calculate the required length. I am also unsure of the differences between different lacing patterns.

First of all, here are the hub and rim I have ordered (48-hole models):
http://www.wiggle.co.uk/p/cycle/7/Ha...ub/5360042432/
http://www.bike-mailorder.de/shop/Si...ch::20270.html

I plan on ordering DT Alpine III spokes to match these parts but what length do I need? Does it depend on the lacing pattern?

I am not sure what lacing pattern to use. Are there any objective differences between them? I once read a study on the internet with lots of numbers and graphs but I did not understand any of it :o

In any case, please recommend me a spoke lacing pattern and tell me how to determine what length spokes I need. Can the length be determined based on the info available on the web about these components? Or do I need to measure them when they arrive?

I stuck some numbers into the DT Swiss spoke calculator on the web but it wanted some figures which I did not have (I believe it wanted rim inner diameter - can this be determined somehow? I did not see any such number on the shop website where I got the rim; there is an "Aero profile length", though - is this useful?).

I have recently discovered that spokes are far more expensive than I figured for small pieces of metal, so I would rather not buy the wrong size ;) Unfortunately, local shops only have straight-gauge spokes available, so I need to order online and can't leave it to the shop that will actually build up the wheel.

Hub

d=58mm
cleft = 35mm
cright = 19mm

Rim

Guessing that D=590mm You really need to look up the ERD...measuring yourself is better.

3 Cross Lacing


http://www.mrrabbit.net/wheelsbyflemingapplications.php

Grab the spreadsheet.

Find the closet matching rear hub - try Chosen A4082 in 58mm

Plug in at the top 24 holes, 3 cross and plug in the ERD below for diameter.


...or try using SpokeCalc.

But you really need to get the ERD for the actual rim - else you are going off a cliff.

=8-)

Many thanks!

This website seems to say ERD is 590mm: http://www.halorims.com/halo/product...hp?id=RMHA7W2B
The spoke counts seen there are lower but the wheel is still the same size, right? Or is there some possibility that number is not applicable in my case?

I believe that with a 48 spoke build that a 4x pattern becomes a good option along with the 3x. If this is for a heavy duty tandem wheel then at least at the rear you want the crossing pattern that gives the spokes an angle that is the closest to tangental to the hub's spoke circle as you can get.

On the spoke length calculators watch what it asks for. Some ask for spoke count for one side only (so 24 in this case) while others ask for total spoke count and do the single side math for you in the program. In other words READ THE INSTRUCTIONS :D

Yep....that's it. 590mm

3 cross...or 4 cross as BCRider suggested...I'm more partial to 4X for 48 hole wheels. In my spreadsheet that would mean plugging in 24, 4 and 590.

Round down drive side to nearest mm before ordering.

=8-)

Thanks! However, I am running into a strange difference between two spoke calculators.

Using the table you provided, I enter the data (24, 4, 590) and go to the closest matching hubs (d=58 and offsets 35 and 19,5). I get results 282.79 and 281.30.

However, putting the same data into the DT Swiss calculator, I get 270.8 and 268.3. This is a rather large difference. Am I using this calculator wrong or what is going on? Here is what I enter into the DT Swiss calculator:
ERD=590mm
Pitch circle diameter = 58 mm
Flange distance = 35mm/19mm
Diameter of spoke hole = 2,8 (I have no idea but the preset rims all seemed to have values like that)
Spokes: Alpine III
No of spokes = 48
Intersections = 4
Nipple = messing 2.0, 12mm

The result is a difference of about 12-14mm. Rather big. Is there really that much inaccuracy in calculators or did I do something wrong?

Edit: spocalc.xls seems to agree with your spreadsheet 282.4 and 280.9.
Just in case, please confirm that I am not doing something wrong here :)

Why would the DT Swiss site be so much off? Did I just mess up the numbers or is that site inaccurate/"special"?

Edit 2: it seems that the closest length of Alpine III spokes that are available to me are 284 mm - is the 3-4 mm extra length too much or is this amount generally insignificant?

Probably need to read DT's instructions again...or maybe it is broken. Lot's of folks were using until a little while ago - something about hub and rim selections getting removed or something.

=8-)

284 mm will be too long...282mm and 281mm are the max you want to use...282mm and 280mm should work as well. Use 12mm nipples...

=8-)

Alright, thanks for the clarification.

Hmm... I'll ask DT Swiss why the 280-282 mm range is not available in any online shop I can see. Maybe they do not even manufacture them in this size? Let's hope they do. Assuming they do not, what other type of spoke would you recommend? Does anyone else make triple-butted spokes?

By the way, do you have a link to a diagram which cleanly shows how the 4X lacing pattern should be done? I figure I should try to lay out the spokes the right way and just leave tensioning & truing to the LBS when I get the components. I do not have much faith in the local LBSes - nobody here has even seen a 48-spoke wheel, so I fear they might have no idea what this 4X thing is...

Thanks again for all your help! The parts arrived in August and fit perfectly. I laced it up myself. The third set of spokes took three tries to get right but it still went better than I expected. The LBS tensioned it and I now have a proper rear wheel :)

:thumb: