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I've been looking at tourers recently and they tend to have 36 spoke wheels (as does my hybrid on the back after I broke my original rim). What I don't understand is why high spoke counts aren't used on more bikes. Race-style road bikes with low spoke counts and smooth roads I understand. Maybe 26" wheels are tougher than 700C (I don't know). But CX bikes run (sometimes much) rougher surfaces on 700C and similar tyre widths to tourers -- without luggage but surely it's shock load that breaks spokes. Or 29er hardtails -- rougher conditions still, and it's not like you can expect good technique from all riders all the time.

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    Related but don't answer my Q: Why should I choose 36 or 32 spokes (or another number)?; Other than spoke count, is there a strength ratings for wheels?. I have some guesses (tradition, distance from repair) but think that it's better to keep them out of the Q. – Chris H May 18 '17 at 8:28
  • My first (27") tourer had a 40-spoke rear, and 48s were not unheard of. More spokes == stronger wheel. And quite often you'd see a touring bike with a built-in holder for spare spokes. But the newer tubular aluminum rims are a bit tougher than the older steel rims. – Daniel R Hicks May 18 '17 at 12:09
  • @DanielRHicks yes, I've seen references to such high spoke counts on Sheldon's site, but never come across them (when thinking about a custom wheel recentlymore than 36 didn't appear to be an easy option). My question might amount to "why do tourers have more need for strong wheels than bikes that take more impact on the wheels?" but I'm not sure. – Chris H May 18 '17 at 12:59
  • Adding more spokes means adding more holes to hub flanges, which weakens them, I guess the same holds true for rims, albeit to a lesser extent. Using fewer spokes requires stronger materials (meaning heavier or more expensive). So an equilibrium must have been reached and 36 is surely a number that stuck around for compatibility, availability or market reasons (maybe). – Jahaziel May 19 '17 at 17:00
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    FWIW, 40 spoke wheels are commonly found on tandems. So parts aren't hard to come by. – whatsisname May 21 '17 at 21:06
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Summing up comments into an answer, including a few points of my own:

  • More spokes are stronger; more holes in the rim weaken it. So a sweet spot must be found.
  • Standard numbers are good, for hole count and spoke gauge

  • Tourers have to keep going a long way from support, so durability counts (see also brakes); a little extra weight on a laden bike makes little difference unlike in a race.

  • One broken or loose spoke in 36 doesn't make the wheel go as far out of true as one in 32 (I've experienced this on my hybrid)
  • Although materials have improved, touring is a conservative discipline in which there's no imperative to change what works.
  • Touring can mean sitting and spinning over rough roads for hours on end with a lot of weight on the frame. In CX most of the weight is above the suspension formed by the rider's legs and the rider can stand as required.
  • CW for a reason -- please add anything I've missed, or sort out my wording – Chris H May 26 '17 at 15:55
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Touring bikes are often heavily loaded with paniers in addition to the rider. The spokes transfer the load from bike frame to the rim and road. Higher spoke count wheels means that the overall load is shared through more spokes resulting in a lower loading per spoke and thereby lowering the chance of spoke failure. This is more important for a touring bike than reducing weight for performance purposes as the rider may be a very long distance from support or repair facilities.

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    I think the question is, why for example downhill mountain bikes that have even heavier loads and where weight does matter use thicker spokes and stronger rims instead of more spokes. – ojs May 18 '17 at 16:27
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    @ojs: Standard spokes more readily available - more specialized spokes (& wheel/spoke tools) in the low spoke count wheels may be harder to find when touring (potentially anywhere in the world). I think there is a different loading characteristic in Cx and DH bikes (impluse vs time distributed load) as the rider and suspension spreads the load over a longer period than the cargo load on a touring bike. I do believe marketing also plays a part. Touring bikes are more utilitarian and considered not as "sexy" as the other bikes mentioned so there is less effort to "one-up" the competition. – PaulD May 18 '17 at 16:47
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    Think also about the difference in consequences of breaking a spoke on a CX circuit race where you've probably got at least a spare wheelset in the pit, vs breaking a spoke 40 miles from a bike shop in either direction. – Jamie A May 18 '17 at 17:09
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    Also, think about the dynamics of racing. If your equipment lets you ride 1% faster than someone else with the same power/skill as you, being 1% faster is all you need to win. So even if there's a 2% chance of equipment failure, you'd win 98% of the time. If your rival has equiptment that never fails, but is 1% slower than you, they'll only win 2% of the time. Obviously simplified, but a win/lose binary is very different from touring, where getting to where you're going a minute or two quicker is of little consequence. – Jamie A May 18 '17 at 18:51
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    I agree with PaulD and @JamieA: touring bikes are more about reliability. So, if you are 40 miles away from nowhere, loosing out of 36 is less drastic than loosing one out of 32 or 1/16. This also means a 36 spoke wheel gets "less out of true" if a spoke breaks (Useful for rim brakes) and also, the increased load for the remaining spokes is less, so the entire wheel is less prone to break another spoke. – Jahaziel May 19 '17 at 16:55

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