79pmooney

Yes, you are right. I stand corrected. i was thinking TT and road speed. This thread is about racing the wheels on a bike stand. (Where are we going to find a stand for Didi's bike?)

Bill in VA

Or why mine has 3 blades...

cbrstar

So here is a question is 36 spoke but done with titanium spokes lighter and better then 32 with steel spokes? I've heard 24 spoke wheels are more Aero but I also can't help but think it might be the shape of the rim.

In the early 90's I remember the 32 spoke craze hitting the BMX scene but people quickly realized that they could build a 36 spoke wheel lighter and stronger. But that's also when double walled rims started showing up but by then 32 spoke was already passé. The 32 spoke wasn't really transferred over to BMX but more so MTB.

old school HUTCH BMX articles 1986-87 (jjrbmx.com) I can't find the original article but..

Diamond Back Turbo Lite Rim (It was full of diamonds cut out of it) 27 oz, (I happen to know that the regular version was about 445 grams or 15.7oz and this one had Diamonds cut out) 13.5 oz =382.72 grams per rim
Spoke SRP titanium = 7 oz. I think it's safe to divide these by 2 = 99.22grams
Hub = Hutch aluminum with titanium axles 14oz (Pair) I think they listed these as a pair because the rear is obviously going to be heavier then the other. It's cheating but I'm going to divide it by two. 198.5 grams

= 680.44 grams per wheel or 1360.88 grams for the wheel set.

When I check the vintage Araya catalog BMXmuseum.com Reference / 1980-1995 Araya Catalogs Some of the road bike rims show a 10 gram difference between 24 and 36 spoke but the BMX ones seem to be rated the same.

I couldn't find 32h hubs with the weights listed. I used this site to calculate spoke weight. Spoke Weight Calculator | SpokeService | Canada's Bicycle Spoke Supplier

Rim = 455 grams
Spoke = 222.4grams (Saipan Race)
Hubs = 198.5 grams (I decided to use the same Hub they did though titanium axels were hard to get bitd.

= 875.9 gram which is 195.46 grams heavier.

One interesting thing about the spoke site is you can easily see the difference in weight between 32 and 36. And depending on the thickness of the spoke you can save up to approx. 30 grams.

urbanknight

There can be reasons. Lightweight touring might be one. Wanting lightweight wheels you can run every day is another. The reason being, a broken spoke on a 32 or 36 spoke wheel will frequently allow you to continue riding on that wheel while a 16 or 20 spoke wheel will likely get horrible out of true and possibly even be a danger of the rim collapsing. I built my 28 spoke wheels for two reasons: 1) with daily riding, I wanted enough spokes to be able to ride home should something happen, and 2) that's the number of holes the hubs were that I got a killer deal on (I really wanted 24 on the front, but whatever). But yes, I understand your point.

Reynolds 

Or Raleigh's 32/40.

blue192

As someone with a bike that has 36 spokes and another with 32, my main concern is that the wheel is of sufficient quality to get me from point A to point B via route C. I suspect riders looking at wheels based on the aerodynamics are not using them to commute or a utilitarian purpose and instead racers and amateur time trial type of rider.

Troul 

I couldn't find a 36H front & rear CF wheel set for a fair price that I was able to find the 24Hs

cjenrick

lots of interesting info out there, this site covers a ton of new wheels>

https://www.hambini.com/testing-to-f...icycle-wheels/

highlights of above link>

• Wheels that performed well were noticeably resistant to generating areas of turbulence
• Wheels that performed well mitigated generated turbulence quite well
• Wheels that performed well had a lower rotational drag compared to their competition
• Wheels with a deeper rim section are generally more aerodynamic than shallow sections
• The difference between wheels of a similar depth is very small and it would be difficult for a human to be able to detect this during riding
• The difference between a low profile wheel and a deep wheel would be picked up by a human riding.
• The FLO cycling and Hunt wheels performed badly, they appear to have been designed by individuals with a limited understanding of aerodynamics of rotating objects. As such they generated unnecessary separation and could not deal with the separated airflow
• The Aerocoach disc and 75mm deep section front wheel showed quite interesting results. This wheel was essentially an aluminium wheel with a clip on fairing. At low to moderate speeds, the wheel performed reasonbly but as the speed was increased the wheel started to perform quite erraticaly. The front wheel construction is agriculturual and large gaps exist between the spokes and the non structural fairing. These gaps generated pressure disturbances and caused the flow to behave erratically. As the speed was increased, it’s performance became quite poor in comparison to the immediate competition and this was mainly due to the poor front wheel design. A picture of the problem is shown below

this site is also a fun read>

https://blog.silca.cc/part-5-tire-pr...d-aerodynamics

did you know that a worn tire can be a drag?

cjenrick

starting to understand how over inflation can actually slow you down,

as the tire becomes harder, your body starts to bounce around more, with rough pavement compounding the effect,

https://blog.silca.cc/part-4b-rollin...-and-impedance

"Impedance

Tom Anhalt was one of the first to take tires used in roller testing into the field to try and replicate data. What he found was quite a shock!

While the data matched at lower pressures, the real world data diverged somewhat dramatically from the roller data at higher pressures!

This divergence is the result of impedance losses overwhelming the system as the tire is over-inflated. Most interestingly, this initial test was done on 'good' asphalt, which really brings up questions about lower quality surfaces.

The new theory on Rolling Losses is that both Surface Impedance AND Casing Losses were adding together to create total rolling loss. "

cjenrick

no wonder they like the big tires and lower pressure at Paris Roubaix

"This theory predicts that below the Breakpoint pressure the system will be dominated by Casing Losses (though still affected by impedance) and at higher pressures the system will be dominated by Impedance Losses, though still affected by Casing Losses.'

Deepcherry

Large wheel diameter would effect aerodynamics too- longer spokes create more drag.

Therefore a BMX wheel would be the best option

Troul 

wheel dish will change the efficiency based on purpose & environment conditions. ITE, I'd rather roll with the weight penalty of having more spokes than fight potential hazardous crosswinds.

asgelle

Wheel dish is fixed by hub design; it can not be chosen to fit conditions. There are only two choices for wheel dish: correct or incorrect, and as long as it's correct has no effect on "efficiency" (whatever that is).

urbanknight

I have been away for a long time, but do I recall correctly as you being an engineer? That might explain why you're a stickler for using the proper terms.

asgelle

I would think that anyone, regardless of occupation, who communicates in either their professional or personal life would be in favor of clear language.

urbanknight

"Clear" is not always the same as correct or precise. I am a music teacher, and much of what we explain is conceptual. Even if I knew precisely how many hundredths of a mm a trumpet player needed between their tongue and their upper palate in order to play a high C versus a low C, specifying that would do nothing for them. Telling them to "say Tee for the high C and Tah for the low C", and to "breath in to your stomach" will go much further, yet the player isn't actually speaking anything, nor are they taking air into their stomach.

Likewise, I think cyclists sometimes use terms that make sense conceptually, even if they are not exactly correct. "Pedal circles" is a common technique for pedaling efficiency (yes, I just had to use the term... couldn't resist), but no matter how good or bad your form is, you're pedaling circles because the cranks won't spin the pedals in any other pattern.

To a layman, "efficient" just means what we can sustain for a longer time period, or optimum for a level of exertion. We don't necessarily realize that the actual amount of energy consumed isn't the factor there, and honestly, we don't care. Regarding that other thread, I would be annoyed if someone told me, "60 RPM is the most efficient cadence... but you don't want to do that".

Steamer

Correct, but power required to overcome wind resistance increases with the cube of speed. (P = FxV)

Troul 

My fault for the wrong word used, but I'm referring to the rim thickness. An 80mm rim will "cut" the air better when going straight when compared to a 30mm rim. That's comparing like materials used & quantity of spokes.

rydabent

I would still like to know the difference between a 32 spoke wheel and a 36 spoke wheel. Does anyone know.

tomato coupe

4.