PedalingWalrus

Just got asked this question on the wheel build for my tandem wheels: straight versus butted spokes, black versus silver spokes, or brass versus alloy nipples.

So I guess brass nipples sound better but I'm not sure if it matters
Black spokes sound fine to me

I'm unsure about the spokes. Straight is stronger, double butted flexes - does this matter for a tandem? I'm guessing the wheels should be as strong as possible so therefore : straight spokes?

PedalingWalrus

I suppose this is the answer:

Wheels are an order of magnitude stiffer than the tyres they roll on, so any stiffness differences will not be noticeable. A wheel built with butted spokes will be able to carry a heavier load before any of the spokes become slack. At this point the rim is no longer restrained and the wheel will be more likely to collapse.

Darth Lefty 

Straight does not make a stronger wheel, though this has been explained a million times by a million people so I won't add to the pile. Butted is better.

You can also get straight spokes with stronger elbows (DT Alpine, Sapim Strong). This reinforces a straight spoke right at the place it tends to break.

You can also-also get butted spokes with stronger elbows (DT Alpine III, Sapim Force), which in theory should be the best. But the extra improvement might not be needed if you have either of the above.

Doge

I just build 24rear, 20 front. ~380#. This is tandem 5, going on 40 years of tandem riding and racing.
I get arguments that the spokes are more important than the rims. The rims matter more.

IF you are an in-the-saddle rider, dbl butted are fine. If you stand and climb, or stand and sprint, the wider spoke center will be felt.
All the engineering in the world does not match the real world feel. I am both a rider (and former) engineer. Thicker spoke center is stiffer. The strong argument is meaningless. Spokes pretty much don't break anymore. Select for ride, handling and aerodynamics.

Anyway, I did Sapim Strong - 13g-14 round straight pull for the rear. cx-Ray 14-thin-14 front 20 hole. ENVE SES Tubular rims - why anyone rides clinchers on a tandem is a mystery to me, but most do.
I have an ENVE fork and it is not so stiff. This works, but in the day I would have wanted flat bladed and a stiffer fork.

I am totally good with the rear. The front, I'd go thicker.

Edit - add.
The hubs matter, the flanges matter, the dish (rear) matters.

Doge

Short answer - straight.

geoffs

As a wheel builder the only reason I ever use straight is for a cheap set of wheels which these days I just use for repairing the loaner bikes the club I'm in keeps for newbie riders.
Double butted are always more reliable but there are limits as to what will work or don't build tandem wheels with 14/17/14 and a 20h rim and expect a stiff wheel.
Alloy nipples are stronger than brass but they do corrode and don't last as long. Never use alloy nipples with carbon rims.
Main variables that determine what will work is Gross weight, Riding style and intended use such as fast road use, touring, gravel etc

scycheng

You really should read Jobst Brandt's book on the bicyle wheel if you haven't done so already. Butted spokes makes for a more durable wheel.

It all depends on where you ride. Over the years, our tandems always had butted spokes. Current tandem has 26" 48H wheels with single butted (swaged) spokes. It is likely overkill but when we go touring, I rather not have anything fail because I was saving 100g.

Brass nipples if you need to true the wheels after a few years.

Doge

I don't want to get into the "strong" debate. This is about feel and ride. I have both. Shoot - I have about 30 wheels I've ridden and raced on 5 tandems over the last 40 years.
I just took this. The carbon tubular is the best ride. The rim is strong. The alloy has bladed same cross sectional area (so like a straight gauge). It is worse in all areas but two (ENVE serrated brake track is stupid), it is stiffer - by a whole bunch. I used to spend much more time out of the saddle than I do now, so I went light and flexi and the tubular aspect makes a huge difference.


Old and new.


cs-Ray 20 hole less stiff


Rear is Sapim Strong - 13g-14g round butted. 24 hole


DT bladed

Krenovian

LV2TNDM

2.0/1.8/2.0 would be my choice for most tandems. Or 2.3/1.8/2.0 if loaded touring and/or durability is the highest goal. You want the larger nipple and thread interface of the 2.0 at the nipple on a tandem.

The tension wheel's strength is derived through spoke strength, fatigue resistance and elasticity. All high quality spokes meet the first two characteristics very well. Butted meets the third. Jobst Brandt's "The Bicycle Wheel" is indeed a worthwhile read and will explain the advantages of butted spokes. Butted spokes are used to improve strength and durabilty of a wheel. Weight savings is inconsequential and not the point. Butted spokes cost more because of the increased production costs. But well worth it, especially with high-quality, hand-built wheels.

Doge

What is being lost in this strength discussion is stiffness. On a tandem, particularly with few spoke holes and a team that stands, stiffness is very important. Breaking spokes is not even a concern, but I went 2.3-2.0 24 hole rear non dished for stiffness. The front 20 hole 2.0-thin-2.0 cx-ray just flexes too much. I am not concerned about it breaking, I just don't like it out of the saddle. I am likely to replace the cx-rays with the same as used on the rear - they are stiffer.

FWIW - I generally tied and soldered my crosses. I will likely do that next. If not - a re-build.

MikeAndJean

Exactly. In 45 years of tandem riding we never broke a spoke in the middle. The tensile strength of an 1.8 gauge stainless steel wire is more than enough to lift the entire weight of the bike with riders. Spokes fail from fatigue, either at the bend or the threads. The advantage of butted spokes is that they can be loaded enough to actually stretch a little. The load on a spoke varies cyclically while the wheel rolls. That elongation assures that the load on an individual spoke is not reduced enough for the spoke to flex at the bend or thread. This matters as lot with wheels with high spoke count. Loading 48 spoke wheel enough to achieve that elongation will collapse the rim.

Jobst knew a lot about wheel building (that's him on the right).

kingston 

I think your sensitivity in this regard is very unique. I'm confident I couldn't tell the difference in any kind of spoke by the way they feel.

Doge

I think I qualified this a few times that is in standing up. We I live tandems come in and out of fashion on a seven or year cycle. When they are "in" we can have 2-4 on a group ride and that always ends up in some out-of-the saddle sprint. Or just jamming up hill.
For the group I ride with, I doubt I am unique at all in my perception.

I just finished a ride along the CO river near Moab. There are lots of rollers and it is nice to hold the gear and stand and roll over. With 130PSI 27mm tubular in front, there is a lot of squish standing and powering. As I posted, I'll tie and solder these next, but on a 2X 20 hole the cross is pretty close to the flange.

Holes and cross and where the spokes cross, if the are weaved (touch) or not also matters a bit. I like the 24,32,40 hole patterns better. On my rear 24 hole straight pull I can weave twice. That is a stiff, responsive wheel - 2.3-2.0 Sapim Strong.

Doge

A lot of things were different then from frame material and configuration - double double laterals as pictured - and those wheels~. When Jobst wrote his book (the one I read in the early 80s) the high profile carbon rim did not exist. He wrote of concept of standing on the spoke was introduced and the deformation of the rim as it contacts the ground. Because the rims deformed so much more, more spokes were used. I doubt I could tell a dbl-butted vs straight in those wheels (weight), with quite low tension and many of them. While engineering concepts are the same the builds are not. The rims deform much less, the tensions are double. I am running almost half the spokes I used to in a 20/24 where I used to have a 40/48. I later settled on 32/36 in deep alloy in the 90s.
The spoke tension now is in the 140kgf range. That would have warped most alloy rims or pulled the spoke through the rims after a few months. I used to build so tight I would have to replace after a couple years.

Current carbon wheels with half the spokes and over double the tension vs wheels as pictured when Jobst wrote his book behave a bit differently.

The same 300#-400# tandem is now on half as many spokes.
What 70kgf on a 2.0 vs a 1.8 may not feel any different. Double that tension and stand up - I can feel it.

kingston 

I see where you're coming from now. Since we don't race our tandem, or even go very fast, we haven't graduated to any modern wheel materials. Old fashioned box section aluminum 40h rims are fine for us. As I said, I'm sure I couldn't tell the difference between straight or butted spokes on wheels like that.

LV2TNDM

140kgf exceeds Chris King's max of 120 by a considerable margin. Going above 120 will expand the hub shell enough to affect the bearing interface. I wouldn't recommend using these tensions on any wheels unless specifically approved by the rim and hub manufacturer. Plus, bringing spokes to such high tensions leads to such high thread friction, nipple failure is a concern. Personally, I'd prefer to not build wheels that require tensions so high, a vital component of the wheel is at or above its limit.

Doge

I'm not sure I could either.
Look at the picture above with the 48 (I think) hole and my comment on Jobst book.
Then look way above where I post those carbon rims - 20 hole and 24 hole. And I think way back I posted and older picture of me on a white Co-Motion (1994) and I'm a big guy.

So to the OP:
Build alloy box rims with high spoke count and lower tension (by carbon standards) - dbl-butted is lighter and you won't notice the flex.
Build aero profile stiff rim with lower spoke count and high tension IF you do out of the saddle riding and are on the mid->upper tandem total weight, I think you will find thinner mid sections too flexi.

In neither case is strength (breaking) that big a deal from the spoke perspective.

Doge

I was explaining my build and why I think straight - or in my case the Sapim single butted 2.3-2.0 was better than butted. And why I get flex in the cx-ray. I think the DT aerolights may be stiffer. I have those on climbing wheels - 140kgf

I have purchased 3 ax-lightness sets including the 25 Ultras that come 140kgf ds on a 25mm profile 200g rim.
https://www.starbike.com/en/ax-lightness-selection-25t-disc-tubular-road-wheelset/

The ENVE rims that are OK with that tension too. PowerTap is OK with 140kgf (a verbal), Extralite is OK with 140kgf. The flange design is not the same as Chris King's.
I thread past the nipple. The ax forms (laminated) the nipple bed and spoke holes.

MikeAndJean

I agree that deeper rims have added considerable strength to wheels. Back in the late 70s, when I built up the tandem we rode for the next 40+ years, the only good rims where Super Champions. These came with 48 spoke holes so I added flanges, drilled for 48 holes, to an Atom drum brake and made my own 48 hole front hub. A few years later we stripped the freewheel threads so we had a friend build a steel insert that had freewheel threads on one side and a male double-lead thread on the other side that matched a double-lead female thread cut into the aluminum hub. Except for breaking axles every few years, this setup worked well for the next 35 years. By "worked well" I mean that the added flanges on the rear hub put the spoke holes outside the diameter of the freewheel so we could change spokes on the road. We still broke spokes every few hundred miles, but it no longer was a big deal. Five years ago, I found myself unable to replace those old Super Champion rims so I switched to Velocity Deep V rims and haven't broken a spoke since. We climb less now that we are in our late 60s but we still climb several thousand feet on a typical week, mostly out of the saddle.

Doge

Pretty bike.

The carbon wheel changed the standing on spoke idea a bit. The rims are very much part of the structure, vs the Super Champion soft rims. A tri-spoke is a good example (see link). The rim is what is holding up the bike and the hub is suspended.
See the build in this thread https://www.bikeforums.net/tandem-cy...-re-build.html

The 1995 Co-Motion is tandem 3. I built those wheels and they were 32/36. The rims were not deep enough, and the sidewalls would blow out (meaning the metal brake track would blow apart. I'd expect a broken spoke on those ENVEs may mean I have to loosen the calipers a bit. I'd finish the ride. I
The other things is cx-rays don't normally break. They elongate kind of like when you pull a plastic straw. This I have seen from crash and chain in spokes (not me). The wheel is messed up, but not broken.
I've only broken a spoke once on a tandem ~50K miles. I was riding the Nimble fly - 16 spoke radial 15-16-15 on the front just testing it. It broke in the middle. I stopped, took it out and road home.

bakerjw

Nothing to add other than this thread provides a lot of good information and differing viewpoints.

Our road tandem has 40 hole straight spoke wheels built on Sun Ringel rims. We're not racers and it's a bit of a heavy frame. The wheelset was cheap enough and is solid although probably not the softest ride but it is what we have for now. We have accidentally hit a pot hole or two and the rims have never deformed. Once our new custom frame comes in and finances settle, I'll be building up a new wheelset on Onxy hubs due to the Sprag clutch.

Now our mountain tandem built for bikepacking is a bit of a different beast. I built the wheels on Onyx 36 hole hubs with Sun Ringel rims similar to what our road tandem runs. I went with Swiss Alpine 13-15-14 spokes. The wheels tensioned and trued up very nicely and have remained that way after a handful of shakedown and mountain rides.

FWIW, on my road bikes, I've only had spokes break near J bends. I've never had one break on our tandems.

Darth Lefty 

OP hasn't been back in a week to tell us whether he has C&V 48-spoke wheels with aluminum rims or hi tech 24 spoke wheels with CFRP rims. If we were judging just by his bike list it's a MTB

Carbonfiberboy 

Always double butted if it's round spokes. We bought a used tandem with 36H Cris King hubs. Nice, huh? So we've always used 36H rims and rim brakes. The important thing is the rim, not the spoke, especially if you use rim brakes. We blew off several tires before I figured out that we needed deep alu rims, at least 28mm to absorb and dissipate the heat. Never blew another tire off. So if you have deep rims, and no reason whatsoever not to, then spokes aren't much of an issue because they won't unload much in the contact patch. Probably anything will work for such rims. We use Sapim CX-ray, which I think are 18 gauge, never broke one even touring. 285 lb. team.

If one is using shallow rims, use the 2.0-1.8 double butted to keep the spoke tight when it unloads. The most important thing with spokes is to check the tension with a tension gauge and keep it even and in the correct range for the rims one is using. Most broken spokes are from using too little tension, not too much. OTOH if you're pulling them through the rim, then it's either a poorly designed rim, or way too much tension. Because of all this, straight spokes will break more frequently than butted because tension changes at the ends lead to fatigue.

If one were using fewer than 36H, all the more reason to use butted, since the loading changes will be greater.

IMO there's no reason to think about spoke weight when speccing a tandem wheel. It's ridiculous. Use as many or as few as you want, but for some reason other than weight, like the number of holes in your desired hub or rim.

Doge

Unless you are a weightweenie and like a Tandem tipping the scale in the high 25#s...

I knocked 5lbs off mine with bakes (disc to rim), bars, seat post and it was very noticeable.
The most noticeable thing is the tubular/s. That lead to a different rim, spokes, hubs. Pretty hard to beat the ride of a 320g 27mm 130PSI tubular - and the speed picked way up.