79pmooney

36 spoke wheels have the advantage of riding better with a broken spoke. Means using spokes until they break is more feasible. (They probably also go longer before they do break.) So money AND labor saving. I rebuild my wheels with the same spokes and new rims, usually twice. I may shed a spoke or two that last build. (Rebuilds of identical rims taped together and the spokes simply swapped over are fast, easier and all the spoke seats are per-bedded.)

Now, I find trying to build wheels with more or less spokes than the rims and hubs are drilled for is living life the hard way, so in practice, I stick to what's readily available. For better, lighter road rims and hubs, that's usually 32 hole. I do seek out 36 hole for my lesser/heavier wheels for my city bikes (in part so I can keep riding the Campy Tipo hubs I am rather fond of).

79pmooney

I actually do set up a couple of bikes with prime numbers of spokes. 33 front and rear. (32 for each wheel plus a spare for the front and left rear plus a spare for the right rear.) The primes get taped under the left chainstay with scotch tape. Near invisible, forgettable and easily accessed.

70sSanO

When the OP asks about the power savings of 4 less spokes, I think the he needs to let us know what wheels he is using. Are the wheelsets sub 1500 gram or 2500+?

In addition to weight, there is also rim profile, that was already stated above. But honestly, if anyone is talking about 6 lbs of wheels, there is no power savings with a few less spokes.

John

msu2001la

Are sub 1500 gram 32 spoke wheels really a thing?

70sSanO

LOL! Good question. I really don’t know. But I’m willing to bet someone on Weight Weenies has a set. Might use Chinese carbon rims.

John

tomato coupe

You need to carry more spare spokes - 33 isn’t a prime number.

Germany_chris

I'll bet you could get close with the right part choices

WhyFi

Don't you make light of serious business.

Leinster

36 spokes must be close to the point at which each spoke is actually in the slipstream of the spoke in front of it. My Yuba Mundo Lux has a 48 spoke rear wheel, and it cuts through the air like a sledgehammer through jam.

79pmooney

Not thinking. I know my primes but my brain isn't always on.

Moe Zhoost

Since wind resistance is proportional to the cube of velocity (in this case, of the spokes) it seems to me that this resistance can be drastically reduced by increasing the diameter of the wheel. At any given bike speed, larger diameter wheels will turn slower. These guys get it:

tomato coupe

Wind resistance is proportional to the square of velocity, not cube, and a larger diameter wheel has more wind resistance because there is more surface area.

cjenrick

aero stuff is complex,

https://link.springer.com/article/10...83-021-00341-6

will not matter to most folks, racers? of course they would be interested in any advantage they could get,

cumulative effects, that is, savings over the course of a 100 mile ride might be of interest to some.

use to see 28 spoke down at the track, might make a difference at 45 mph if you win a match sprint by an inch,

testing would be difficult as you would need. say, a 30 mph wind while spinning the wheels.

seems the rear wheel does not see as much drag as the front as it rides in the slipstream,

so maybe 32 front, 36 rear,

rsbob 

But if you have 36 leg hairs per square inch versus 32, you should run 32 spoke rims. Or shave your legs like the pros.

79pmooney

No. The hub is still traveling at the bike speed as are the hub ends of the spokes. The spokes at the bottom are stopped. The spokes at the top are going twice the bike speed. Nowhere does the wheel diameter change any of this. You have however saved a lot in hub bearing drag. But 25% of almost nothing isn't worth writing home about.

cjenrick

130 page pdf on wheel drag>

https://ir.canterbury.ac.nz/bitstrea...=1&isAllowed=y

rsbob 

Ultimate 200 page pdf on leg hair drag>

https://cyclingleghairvsshavedanalysis

trainman999

cjenrick My question is, what are the power savings when using 32 over 36? is there a percentage figure out there? The answer to this question depends on how fast you can go. Lets say you are an avrage fit rider on a 25 mi time trial,you avrage 18 mph,you are going to be about 1hr 22+ min. 32 or 36 spokes are not going to make a difference you are not going fast enough. Lets say you are fit enough to make the same time trial in 1 hr on the 32 spoke, you will need another 15-20 seconds to get there on the 36 spoke. If you are a world class time trialest avraging closse to 30 mph you will prrobly need around a minute more on the 36 spoke

urbanknight

Absolutely! About 10 years ago, I built a set of wheels with American Classic hubs, Kinlin XR-200 rims, and DT Revolution spokes (I think Competition on the rear drive side). If I recall, they showed 1385g on my scale (no rim tape or skewers, just like everybody else does). Now that was 28 spokes front and rear, but 8 more spokes would still keep it way under 1500g. They weren't aero, but they climbed well... at least that's what I told myself.

I miss those wheels, but it was silly to brag about shaving 1lb off the bike after I added 50lb to the motor.

Germany_chris

I assume you got them custom built?

The standard anymore seems to be to just order machine built wheels which is weird because I can generally get a set of wheels built by my local wheel builder for less and he'll touch them up for free if they ever go out of true.

urbanknight

Yes, custom built by me :-D

Moe Zhoost

Yes, my mistake. I was thinking about power needed to overcome, which is proportional to cube. The OP's concern was limited to the aerodynamics of spokes moving around an axis, so it seemed that the other factors (like the bike and rider moving through the air) were irrelevant to the argument.

Moe Zhoost

The OP's only concern was the drag on spokes spinning about an axis. Here you go adding the reality of the additional factors like movement of the bike on the road to the argument. Geez, I hope this thread doesn't get too serious.

Troul 

Waxing is the only wtg for the real psycyclist.

msu2001la

I'd just like to point out that these are definitely not sub 1500g 32 spoke wheels.

I know that it's entirely possible to build a sub 1500g 32 spoke wheelset, particularly for a rim brake setup, I just don't understand why anyone would do this.
A lightweight 32 spoke wheel is compromised on both ends of the spectrum. If you are chasing grams, there's little sense in building with extra spokes. If you are worried about strength, there's little sense in building with ultra-light parts.

You can put snow tires on a Corvette.