DB spokes and weight question
 

Hi All, I talked briefly with another cyclist I'd met and long story short he remarked that the DB spokes on my bike "Saved a lot of weight.", to which I kept my mouth shut, because I really never considered that possible aspect of DB spokes. I just like that they help keep a wheel truer longer, IME.

So wheel gurus, is there enough weight savings to actually be of concern? How about TB spokes?

TIA,
Brad

From DT's web site the weights for 64 264 mm spokes are:

2.0 Straight gauge = 444 gms
2.0/1.8/2.0 butted = 382 gms

So for two 32H wheels the savings will be 62 grams.

Also consider that the saved weight reduces the rotational inertia of the wheels, theoretically allowing them to be easier to spin up. This is part of the reason why saving weight on your wheelset makes the most sense, rather than dropping negligible amounts of weight on something like your spacer stack. However, straight gauge spokes tend to build stiffer wheels in my experience, so that is something to keep in mind.

I went there also before posting my question and it made me more curious about his remark.

Brad

What don't you understand? If all you're concerned about is weight savings, go with the lightest spokes you can locate, however as others have indicated here, straight gauge spokes are cheaper and result in a stronger wheel.

Maybe he works in a spoke warehouse. I'd imagine a 15% reduction in the weight of 100,000 count pallets of spokes would make a substantial saving in handling costs.

- joel

I agree completely. Two of my roadies weigh nearly the same, with one having a lighter wheel set/tire combo making up for a heavier frame set and I can marginally accelerate more quickly with the lighter wheel set. The difference is more than a couple of ounces between the two wheel sets, however.

I guess it's the perspective of the cyclist that makes the difference of 64 grams "a lot" or not.

Brad

Reputable wheel builders that I have seen seem to universally agree that a DB spoke builds a stronger , more durable wheel . A straight gauge spoke has to flex at the ends , which is where spoke failures mostly occur.

You never hear of people saying how much better things are by adding a few oz. to their wheel weight.

I use 15/16 DB front & NDS rear on my (pavement only) bikes.

The OP also asked about triple-butted spokes.

I'm also interested about triple-butted weight savings. And further, what about quadruple and quintiple-butted spoke weights/performances?

your answer is Sapim CX-Rays = 282g (64@264mm)

Speaking of lightweight spokes, I've had great luck building wheels with DT Aerolites on a couple of wheelsets. I'd have to check the weight, but they are indeed light, the lightest offered by DT I believe. But they're expensive, relatively speaking.......like with most things bicycle-related, the main question is "are you willing to spend $x to save y weight. That's true even with the original example of DT straight gauge vs DT 2.0/1.8/2.0. 62 grams of weight savings on a wheelset costs $x more. And in that example, there is the issue of the double butted spoke having another advantage as well.

The statement by the friend in the OP, "double butted spokes save a lot of weight" is probably a little misinformed and over the top, but I have to admit I've done some pretty expensive things on bikes over the years to save 60 grams here, 60 grams there.

Aerolites are the same weight as Revolutions, but the claim is that due to the forging process to make them aero, the Aerolites are actually a stronger spoke. If you desire a little more stiffness from the wheel, DT also makes the Aero Comp spoke, which is an aero version of the Competition. The Aero Comp is still dimensionally able to fit through standard holes on hubs, unlike many larger aero spokes like DT's New Aero.

Good to know, thanks. I went weight-weenie on a wheel build for one of my own bikes, but I didn't want to go with minimal spoke count. I used Aerolites, American Classic road hubs (micro 58 front) and Stan's Alpha road rims. 32 rear/28 front. It's been an impressively bombproof wheelset, and actual weight is somewhere in the mid 1300's.

62g= about 11/2 Hershey's bars. Sure ain't much.

+1 but we have to define strength.

Wheel stiffness is proportional to the total amount of steel, so more or thicker spokes build a stiffer wheel

Likewise total load capacity is proportional to the amount of steel, so more or thicker spokes raises the static load capacity, BUT a chain is only as strong as it's weakest link. The strength of spokes at the elbow (in shear) is only 80% that of what it is in tension, so as long as the cross section of a butted spoke spoke is 80% or more than at the elbow the spoke is just as strong despite being thinner. A similar calculus applies at the threads, so any material in the spoke beyond the root diameter of the thread doesn't add strength.

Lastly is life expectancy, which is the kind of strength that most of us are most concerned with, and butted spokes win hands down. Butted spokes move the majority of deflection away form elbows into the thinner sections, increasing the fatigue life at the elbow. Since metal fatigue is the most common non-crash cause of wheel failure, it's safe and accurate so say that butted spokes build a stronger wheel.

They weigh the same as Sapim Lasers, DT Revolutions, DT Aerolites, or any other 2.0/1.5mm or 14/17 gauge spoke before or after flattening from round to oval shape.

( To be pedantic DT quotes 283g for 64 264mm DT Revolutions ).

IIRC I paid $0.69 each for my last set of DT Revolutions which is a few dollars a spoke less than the bladed options.

Provided that you properly correct spoke lines, use high uniform tension, stress relieve and avoid issues like elbow length + flange thickness combinations conventional high-quality steel spokes are strong enough unless you put them in a testing machine for marketing purposes which creates higher amplitude stress cycles than actually riding them.

Retro grouches like Jobst Brandt continually rebuilding the same wheels as rims and bearings wear out have put over 300,000 miles on the same set of spokes (IIRC those are 15/16 gauge) which is to say for most people spokes last forever.

A few bikeforums.net users have also clocked over 100,000 miles on the same spokes.

While technically true you have to consider the magnitude of the effect.

With force = mass * acceleration or acceleration = mass / force increases are proportional to the ratio between total before and after weights.

Weight where the rubber meets the road counts double (it's accelerated with the bike and to the same speed about the wheel's axle), weight halfway between axle and road 50% more (it's traveling half the bike's speed around the axle), etc. where a piece spanning between two points acts as if its weight were concentrated halfway between them.

Consider a 140 pound rider plus a 15 pound UCI minimum weight bike which total 70,307 grams (the effects will be less for bigger riders).

Disregarding all other rotational inertia (rims usually weigh 400g+ each, tires 200g+) and putting the spokes' center of gravity halfway between axle and rim the rider would accelerate 0.21% faster dropping 100g to the UCI minimum via lighter spokes versus 0.14% from loosing the same weight elsewhere.

When running the same tires (rolling coefficient of friction is significant and can vary by a factor of two between the fastest and slowest slick road tires) perceptions of faster accleration are more about trying harder with the new equipment and the placebo effect.

+1

Folks tend to over think weight factors. IMO, most of the reported magic improvements in speed are due to a placebo effect.

That "placebo effect" changed my daily best distance from 50 miles to 70 miles.
Of course on the latter, I was still recovering from the effects of my intermedullary nailing of the tibia, which must have been a SUPER "placebo effect"!

Subjectively based on their frame of reference, these wheel builders may believe this; however there are so many factors that affect wheel durability that this universal "knowledge" is suspect. Number of spokes, strength of rim, and proper spoke tension are more important than whether they're butted or not.

I have a bit over 11,000 miles on the wheels on my commuter bike. These were built straight gauge and have never needed re-truing, despite my practice of flying over speed humps. If I say that this proves that straight is better than butted, should folks believe me?

You're showing your bias in believing that even tension trumps all, and there's no reason to believe this either. There's a long term consensu world wide, based on both practical experience, and theoretical analysis, that butted spokes build more durable (long lived before spoke failure) wheels. This is tough to refute, but folks will blieve what they will.

There's also no debate, except among non-experts, that butted spokes have better strength for a given weight (or are lighter for the same strength) than their plain gauge counterparts. The calculus changes somewhat with straight pull spokes, but comparing apples to apples, there's no debate among experts about the superiority of butted spokes.

Of course, as you say, other factors come into play, but that's true of everything in life, and those factors don't negate the benefits of DB spokes properly selected for the needs of the wheel.

I don't sell spokes (any more) and have no interest in twisting anybody's arm, and many will do fine with plain gauge spokes. But if you do have spoke breakage issues, one of the best things you can do to address them is to switch to DB spokes.

I started using my touring bike for distance rides when our drought wrecked havoc with the rural road beds... big cracks where bicycles ride. I had the sensation that it's heavier tires, primarily, and wheel set provided a flywheel effect that made constant speed rides easier. This is over mostly flat land and some gentle rolling terrain.

Brad

Compared to the total inertia of a bicycle and rider, the inertia the wheels is negligible, even factoring that they're rotating weight. Heavier wheels do feel different because you tend to rock the bike so you're feeling the effects of side to side motion and gyroscopic precession, but this has little impact on total forward inertia.

The illusion of differences in weight is important because it affects how the bike feels to you even when it has little actual impact.