Wheel Building 101 - Spoke Calculations
These tools for spoke calculations are also available:
Damon Rinard's Spocalc on Harris Cyclery's website.
...and Damon Rinard's 36-24 Spoking on Harris Cyclery's website (Mismatched Spoke Hole Counts) for when the rim you have doesn't match the hub you need, etc.
My current configuration in spoke calculations -
Pencil drawings, dimensions, and wheel calculations:
Please note that I am not liable or responsible, mechanically or financially, for any wheel repair or wheel build you may attempt as a result of the recommendations of this article. You will be relying on your skills and expertise for your various projects. Please use caution, wear safety glasses when tensioning your wheel, and take necessary precautions to ensure all of your mechanical connections are sound.
Views: 1324
Replies to This Discussion
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Permalink Reply by Matt M. 18.5KM on
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I did many of my dimensions with a General Vernier Caliper I purchased from Home Depot. I know Imperial to Metric conversions are an unnecessary additional step. However I get really annoyed when people tell me wheel calculations can’t be done in Imperial units.
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Permalink Reply by Velo Celt on
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Why not just use the calculator on Prowheelbuilder, or something like FreeSpoke. I've used them both, entering my own hub dimensions (with caliper in millimeters), or using stored data for specific hubs and rims. In every case I've been able to build wheels without issue. Everyone thinks wheel building is some arcane velo-nibelungen thing and it isn't - it's actually pretty easy.
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I don't really care for over-reliance on spoke calculators. I become anxious and very upset when mechanics look for the dimensions of a hub or a rim in a chart or from a website rather than making the dimensions themselves. I laud your decision to make your own dimensions.
I also become unnerved when spoke calculators don't fully report the decimal point, instead rounding up rather than saying what the calculation truly is. It's a little silly, maybe, but to me it makes a difference.
I don't think wheel building is some arcane practice. But we all need a resource which tells us how to get it done. Bear in mind that Damon Rinard is thorough in his instructions on different cross combinations and mix matching hubs to rims with less or more spoke holes.
In short, I like to know that I can do the math without a computer. I like to know all I need is the tools to measure with and a handheld scientific calculator for the trigonometric calculations. I don't like the idea that someone's software is deciding, perhaps incorrectly, what I will need to build a wheel.
There are people who don't have computers when they would like to build a wheel. I believe this discussion, if we were to print it out and hand it to them (and provided they know their high school math), would empower them to build their own wheels in any configuration they wish. This discussion puts all the necessary information for basic spoke calculations on one page.
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This is VERY handy - torque specifications from the United Bicycle Institute! I dabble with freehub bodies sometimes so I'm really glad to have this on hand! Shimano freehub binders are 305 - 434 in-lb ; or 34.5 - 49.0 Nm ; or 25.4 ft-lb - 36.2 ft-lb
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Permalink Reply by Elwood Gruschow on
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Interesting chart. So when I used to torque my Campy cranks to my Shimano cartridge I was over torque at 40 foot-pounds?
see you on the road
Elwood
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You don't want to over-torque cranks....especially the early aluminum ones. I get really nervous around square taper cranks if I don't have a torque wrench handy. Some think it doesn't matter. Whatever.....I'm a worry wart.
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7/19/2020 - Yes. I miscalculated the ERD for the Sun Rims CR18. But they are working well enough. I haven't taken the wheel for more than a 10 mile ride so my mistake only cost me $11 in spokes.
So my folding bike had alloy spoke nipples which were cracking in half. The original deep V rim's spoke holes were also widening up. I don't think the double butted spokes and the radial lacing on the left side were helping at all. I located a Sun Rims CR 18 in 20 inch (April 2020 the ERD is 394.55mm) and here are some useful dimensions if you also have an old SRAM Dual Drive hub:
Spoke holes, center to center, (flange diameter on both sides) is 67.5mm
Hub flanges are 51.4mm apart center to center
My hub is 135 OLD on my bike
Left side outside lug to center of hub flange is 34.2mm
Right side outside lug to center of hub flange is 50.1mm
The hub flanges are 3.4mm thick
The spoke holes are 2.4mm diameter
My hub has 28 holes
The OSB (offset spoke bed) is 1mm. W is the with of the rim at the edge. L is the center of the spoke hole nearest to an edge (rim surface or side face). W/2-L = OSB. On bike rims I haven't noticed much of a difference when entering the OSB but it's good to enter the OSB in SpokeCalc.
For an 135 OLD hub the WL is 33.3mm and the WR is 50.1mm (if you use SpokeCalc as listed above). DT Swiss calls WL and WR the Flange Distance.
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So I have a Sturmey Archer Dynohub manufactured in 1970 in perfect working order. Here are my dimensions.
36 hole
92mm OLD
Large Flange hole circle diameter 102mm
Small Flange hole circle diameter 42mm
Spoke hole about 2.4mm
WL large flange side = 24.5mm
WR small flange side = 34mm
Additionally I have an original double walled steel Sturmey Archer rim, markings say "6020X2":
ERD 396mm
Spoke Offset = 2mm
Because of the large flange on the Dynohub I used 2 cross spokes on the dynamo side and 3 cross spokes on the right side. So the spokes are 163.2mm and 189.9 respectively. I went through the dimensions to make sure but this is a perfect match for the original factory spokes from Raleigh Nottingham.
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