Comment about Bicycle wheels – how many spokes?

Doug

New member
Re: https://bike.bikegremlin.com/380/how-many-spokes/#3.1

The above post is what brought me to BikeGremlin Forum, but at the bottom of that post it reads "Comments are closed." Yet although comments are now closed, and while I do support and have wheels with 36 spokes as recommended in that post, by the laws of physics there would be a reason to make a comment. Basically, 36 spokes would be the best choice for 700c and old fashioned 27 inch bike wheels but 32 spokes would work about as well for 26 inch bike wheels too.

There are a number of different hub designs and rim designs having different dimensional specifications and perhaps a book could be written about the different wheel strengths various combinations of those hub and rim designs could produce, yet there would be a way to make a reasonable approximation of the strengths of various combinations of rim diameters and number of spokes, and hubs can practically be excluded in making such approximations with only rims and number of spokes needing consideration.

A rim dimension which does not change from one rim design to another is bead seat diameter, BSD, with 630mm BSD for 27 inch wheels, 622mm BSD for 700c wheels, and 559mm BSD for 26 inch wheels. Then BSD rim circumference = πD = ~3.1416 x BSD. Then division of BSD rim circumference by the number of spokes being used produces the circumferential distance between equally spaced spokes, and the closer the spokes are, the stronger the wheel would be, within limits.

3.1416 x 630 mm ÷ 36 spokes = 54.99 mm circumferential distance between spokes for 27 inch wheels
3.1416 x 622 mm ÷ 36 spokes = 54.28 mm circumferential distance between spokes for 700c wheels
3.1416 x 559 mm ÷ 32 spokes = 54.87 mm circumferential distance between spokes for 26 inch wheels

A 26 inch wheel with 32 spokes is slightly stronger than a 27 inch wheel with 36 spokes and slightly weaker than a 700c wheel with 36 spokes, and using the same type of hubs and rims for all three wheels would slightly increase the relative strength and durability of a 26 inch wheel, so it appears satisfactory to build 26 inch wheels having 32 spokes.
 
Re: https://bike.bikegremlin.com/380/how-many-spokes/#3.1

The above post is what brought me to BikeGremlin Forum, but at the bottom of that post it reads "Comments are closed." Yet although comments are now closed, and while I do support and have wheels with 36 spokes as recommended in that post, by the laws of physics there would be a reason to make a comment. Basically, 36 spokes would be the best choice for 700c and old fashioned 27 inch bike wheels but 32 spokes would work about as well for 26 inch bike wheels too.

There are a number of different hub designs and rim designs having different dimensional specifications and perhaps a book could be written about the different wheel strengths various combinations of those hub and rim designs could produce, yet there would be a way to make a reasonable approximation of the strengths of various combinations of rim diameters and number of spokes, and hubs can practically be excluded in making such approximations with only rims and number of spokes needing consideration.

A rim dimension which does not change from one rim design to another is bead seat diameter, BSD, with 630mm BSD for 27 inch wheels, 622mm BSD for 700c wheels, and 559mm BSD for 26 inch wheels. Then BSD rim circumference = πD = ~3.1416 x BSD. Then division of BSD rim circumference by the number of spokes being used produces the circumferential distance between equally spaced spokes, and the closer the spokes are, the stronger the wheel would be, within limits.

3.1416 x 630 mm ÷ 36 spokes = 54.99 mm circumferential distance between spokes for 27 inch wheels
3.1416 x 622 mm ÷ 36 spokes = 54.28 mm circumferential distance between spokes for 700c wheels
3.1416 x 559 mm ÷ 32 spokes = 54.87 mm circumferential distance between spokes for 26 inch wheels

A 26 inch wheel with 32 spokes is slightly stronger than a 27 inch wheel with 36 spokes and slightly weaker than a 700c wheel with 36 spokes, and using the same type of hubs and rims for all three wheels would slightly increase the relative strength and durability of a 26 inch wheel, so it appears satisfactory to build 26 inch wheels having 32 spokes.

Hey Doug,

That's a good point (I'll see to include a link to this discussion in the article). Thank you for taking the time to write this. :)

My thoughts out loud (interested to hear your thoughts on this):

There is a limit of how in-detail I dare to go in an article. The linked article is what I consider to be basic, general. Most wheels today use 622 mm BSD.

My wheelbuilding article list

In addition to your calculation:
For 559 mm rims ("26 inch"), 32 spokes laced 3 accross give better angles for spoke entry into the rim (sometimes even better compared to using 4 across lacing even with a larger 622 mm rim, depending on the flange diameter and the exact rim's ERD), while also providing a better angle of spokes exiting the hub's flanges compared to a 3 across laced 36 spoked wheel (not every 36-spoke hub can be laced 4 across without much spoke head overlap).

Having said all that, all else being equal, 36 spokes give more strength and rigidity compared to using fewer spokes. For larger rims, like the 622 mm ones, even 40 spokes is not an overkill for the rear, for loaded touring, tandems etc. But such hubs and rims are not easily sourced. So, for ultimate strength, 559 rims with 36 spokes are often a good compromise (still widely available in remote locations accross the globe, often more than the 622 rims).

Similar goes in case of a spoke breaking (I often must work with cheap, low quality spokes). With 36 spokes, even with rim brakes, if one spoke breaks, the wheel often stays true enough to get home without breaks rubbing. With 32 spokes, that is less often the case (on 26" rims it's less of a problem, and it's definitely less of a problem than with 28 or fewer spokes, but I think that 36 spokes are a good idea nonetheless).

Edit/PS:

Why I created the forum (and auto-close comments for articles 45 days after the first-published date).

Relja
 
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