Problems with Spoke Tension on New Tandem

[NoTrail]

We recently purchased a 2012 Cannondale Road Tandem 2 and have loved the few rides we've taken with it so far, but 2 rear spokes have recently become really loose. When we first purchased the bike, I had my mechanic go over the wheels to assure that spoke tension was correct. He made some minor corrections but overall said that everything looked good. Last night I noticed that the 2 spokes on the rear non-drive side on either side of the valve are dramatically loose.

Wheel Specs

• HUB: White Industries Mi6 Disc
• RIM: Sun ME14A w/eyelets, 40 hole
• SPOKES: DT Swiss Champion, 14g
• TIRES: Continental Ultra GatorSkin, 700x28c
• NIPPLES: Standard Brass
• Triple cross on both drive side and non-drive side.

Other Details

• TEAM WEIGHT: 420lbs (I'm 6'4" and she's 6')
• WHEEL MILEAGE: Only about 45 miles
• The rear wheel is still almost perfectly round and true.
• No major bumps, drops, or other noticable hits to the wheel.

I'm an avid cyclist and have been for years, but I've never been a wheel builder. Any thoughts on what might be causing this? Lack of loctite on the spokes? Spoke count too low? Cheap spokes? Some sort of random planetary alignment?

Thanks for your thoughts.

[TandemGeek]

Since there's no indication of a damaged rim from a rim-hit, most like the initial spoke tension was just too low and the spoke network is loosening up.

Have them retention the wheels under warranty to the upper end of the tension spec. per the appropriate spoke tension table for their shop's tensionometer.

Threadlocker might be a good idea, but is no substitute for getting the tension right on a tandem.

Make sure you get an invoice for the warranty work that notes the spoke tension was corrected in the event that any of the spokes were weakened while they were lose and begin to break in the future. If in the future you have a broken spoke it isn't a big deal; just have them replace it under warranty, referencing back to first warranty repair. If you have a second broken spoke shortly after the first, then you'll want to have all of the spokes replaced... again, citing the initial problem with the tension being too low.

[NoTrail]

Have them retention the wheels ... to the upper end of the tension spec. per the appropriate spoke tension table for their shop's tensionometer.

This was done before my first ride ... 45 miles ago. And they will be doing it again this afternoon.

Threadlocker might be a good idea, but is no substitute for getting the tension right on a tandem.

I completely agree, but I've never had a spoke nipple just loosen itself without some kind of wheel trama involved. Is this more common on a tandem due to the extra weight involved?

[rdtompki]

...but I've never had a spoke nipple just loosen itself without some kind of wheel trama involved. Is this more common on a tandem due to the extra weight involved?

We've had the original 40 spoke wheels on our daVinci for 8000 miles. The wheels have taken some good, unavoidable whacks and suffered through many stretches of bone-jarring road, but seem as true today as when we bought the bike. You've got a bit of weight on us, but we are not a light team. Other than posts about potential issues with boutique wheels, I just don't see many posts about folks having problems with properly tensioned tandem wheels. I'm far from expert, but I'd question whether the wheels were properly tensioned versus just, perhaps, uniformly tensioned.

[NoTrail]

We've had the original 40 spoke wheels on our daVinci for 8000 miles. The wheels have taken some good, unavoidable whacks and suffered through many stretches of bone-jarring road, but seem as true today as when we bought the bike.

That's nice to hear.

... I'm far from expert, but I'd question whether the wheels were properly tensioned versus just, perhaps, uniformly tensioned.

I'll make sure to have him check everything again. Thanks.

[waynesulak]

Tandem and singles with heavy loads do require high tension and some wheel builders and mechanics are not accustomed to using tension at the upper limit of the rim's capability. Some believe a lower tension provides a better ride. I agree that a properly tensioned rim should not have spokes loosing. Is your mechanic used to dealing with wheels carrying 450+ lbs?

[sculbertson]

We have a 2011 Cannondale RT 2 and had the same porblem with the rear wheel on the first long ride. We took it back to the shop and had them use spoke prep and rebuild and tension the wheel. Not a problem since. They are a pretty stout wheel once they are built and tensioned correctly.

[chris ss]

Is this more common on a tandem due to the extra weight involved?

The direct answer to your question about loosing up is "no" -- but with the important caveat that "everything is right to begin with." I'm not currently working in a bike shop but have in the past, and have 20+ yrs riding tandems. I hand-built the wheels for our 2 tandems, and never done anything except once a year touch-up trueing.

Tension DOES need to be higher. If the spokes become UNLOADED (that is, tension goes to zero) as they revolve "around the bottom" of the wheel as it turns, this will
(a) eventually create a fatigue failure, and
(b) allow the opportunity for nipples to loosen up.

Wheels on tandems have far less margin for error than wheels on singles, and this means you see the consequences quicker and with more problems, of underlying things like spoke tension or other "latent" conditions, which might not affect a single bike so harshly or so quickly.

One downside to threadlock- it obviously prevents loosening of the nipples in a situation where the spokes are loose enuf to become unloaded "around the bottom." In this way threadlock can MASK the unloading condition. This load+unload cycle is exactly what creates fatigue failure - greatly increases the odds of a failure at some point - most commonly broken spokes and-or cracks in the rim around the spoke holes where the spoke tension has remained high.

For consideration: At your weight a 48 spoke wheel might make sense. It's not a gotta-have. But if you ride strong, and on rougher surfaces than "usual" (however one might define that...) it could make sense. If you ever end up rebuilding the wheel, IMO you might consider 48 spokes. If you do, you should also consider increasing the "cross" - as much as cross-5 for 48 spoke. Wheels obviously serve under HIGHLY dynamic loads so there are NO hard and fast rules, but even that said, 48 spoke x5 obviously gives you much more "headroom" and whatever loads occur get spread over more spokes, nipples, and rim holes. It kinda depends on your riding style and your own desires for weight vs stiffness vs maintenance vs robustness in case of hits, etc. Which you probably understand from your single riding.

So yeah - best to get this addressed correctly, and sooner rather than later.

Good luck

[NoTrail]

Thanks for the quick replies everyone. I've had my regular mechanic look it over again and he suggested to just retighten them and it should be good. But after reading through your posts, I'm planning to take both wheels to the shop where I bought the tandem and have them look everything over again. I agree that they should be tighter than a non-tandem wheel.

As for the 48 spoke 'upgrade' ... do you think keeping the 40 spoke hub and switching to a more deep dish rim (like he Velocity Dyad) would help?

[TandemGeek]

As for the 48 spoke 'upgrade' ... do you think keeping the 40 spoke hub and switching to a more deep dish rim (like he Velocity Dyad) would help?

If they get the tension right and distress the spoke network on your current wheelset there's no need to change anything: 40h are fine for your stated weight and they spec'd good components.

It just seems as though the build is lacking.

[conspiratemus1]

... If you ever end up rebuilding the wheel, IMO you might consider 48 spokes. ...

Well, if you want 48 spokes, you can't exactly "rebuild" the wheel. You're looking at new hub and new rim, plus 48 new spokes (because the spoke length will likely be different from the 40-spoke wheel it replaces).... I guess you could re-use the rim strip. But point taken.

One other thing to consider is that the wheel builder may not have properly compensated for spoke wind-up. When the nipple is turned, the friction with the spoke makes it want to twist the spoke as well as moving up the spoke. If you just leave it like that, the spoke will want to untwist as soon as the friction of the nipple threads falls enough to allow them to unwind -- this happens when the spoke becomes compressed (de-tensioned) when the wheel goes over a bump at that spoke. When building a wheel, it's very important to over-twist then back off to the desired point. You have to do this with every spoke, every time you touch the nipple once it's fairly tight. So going around and around the wheel, building up tension a 1/4 turn at a time, you twist a half-turn (more if the spokes are thin or double-butted), then back off 1/4 turn. Repeat x 40 x the number of rounds it takes to get to desired tension. If you leave a few with residual twist, they will loosen as the wheel is ridden. If two loose spokes are adjacent in the rim (going to opposite hub flanges), the wheel will stay laterally true and probably won't have an obvious hop, ... yet.

As an amateur wheel builder, I ride all my new wheels downhill on a really frost-heaved road to shake loose any twisted spokes that I missed, then I re-true and re-tension. If I was a pro I wouldn't have to do this -- the wheel would be fine coming right off the workstand.

[CaptainHaddock]

One other thing to consider is that the wheel builder may not have properly compensated for spoke wind-up. When the nipple is turned, the friction with the spoke makes it want to twist the spoke as well as moving up the spoke. If you just leave it like that, the spoke will want to untwist as soon as the friction of the nipple threads falls enough to allow them to unwind

Spoke windup being one of the reasons it's nice to run bladed spokes, you can see the wind up and then compensate with a spoke tool.

[CaptainHaddock]

I will say, that it's rather alarming that you've had this issue. My wife and I've primarily been riding our RT2 as an XC bike due to the weather conditions and we've got about 150 miles on in the last month. I actually went checked our wheel-set (as in theory, we have the same wheel-set from the same builders) to see how tight they felt and have not noticed a loosening of the tension. While we're not as hefty a team as you, given your minimal riding, and our higher miles combined with rough riding, it makes me wonder if your wheels were in-fact at a deficit to begin with.

[specbill]

Quite surprised with your wheel issue. We have a '10 RT 2 with the same wheels and well over 5000 miles on it with not a hint of an issue. I am not easy on those wheels. We ride some very rough and hilly roads on a regular basis and I regularly use the disc brakes aggressively right before corner turn-in. However ... we are a 290 pound team with modest power. At your team weight and power I would give that rebuild only one shot....they should get the job done, but then I'd be on to a high quality 48 spoke wheel and hub built by a tandem pro. Nothing takes the fun out of riding, particularly a tandem, than questionable wheels or tires...there is way too much at stake. Good luck.
Bill J

[NoTrail]

Yeah, that's why I'm surprised too. I've seen so many other people with the same wheels have zero problems with them.

This weekend I took them into the shop where I bought the bike. I explained the problem that I had and that I have had another wheel builder retighted them, but that I wanted to make sure they were properly tensioned for a tandem and for riders of our weight. They took the wheels in the back and I watched from the showroom as he simply went around the wheel and tightened each one. Not once did he use a spoke tensiometer (I think that's what it's called). I was a little annoyed but have come to a great conclusion.

I am a really good bike mechanic. I worked in the industry for a few years in my early 20's and have built every bike I've owned since them ... with only two exceptions. My one missing talent is wheel building. So I think I'm going to learn that skill so that I can fix this problem myself. And of course, it's another reason to upgrade wheels on some of my other bikes too.

[jimmuller]

They took the wheels in the back and I watched from the showroom as he simply went around the wheel and tightened each one. Not once did he use a spoke tensiometer (I think that's what it's called). I was a little annoyed but have come to a great conclusion.

You can find arguments in BF that a spoke tension meter is or isn't required to build a great wheel. I happen to think it isn't because there are other non-metric'ed ways which a good builder can use to judge spoke tension. But the builder has to be good whether s/he uses one or not. That you found a loose spoke at all suggests that it wasn't built up right to start with, and that's what you should be annoyed about. In any case, you probably have a good wheel now. Just check that it is true and stays true.

[NoTrail]

... In any case, you probably have a good wheel now. Just check that it is true and stays true.

Here's hoping. I'll be keeping a close eye on them for quite some time.

[CaptainHaddock]

Here's hoping. I'll be keeping a close eye on them for quite some time.

If you find yourself thinking about parting ways with that wheelset, give me a shout, maybe we can work something out.

[NoTrail]

If you find yourself thinking about parting ways with that wheelset, give me a shout, maybe we can work something out.

I will keep that in mind.

[Brad Bedell]

Wheel building is an art. I suspect (95%) of all wheel problems are related to the builder not stretching the spokes or balancing the wheel correctly. To determine if it's a mechanical failure, mark the loose spokes. If they are the same ones coming loose, you could have a bad spoke(s). You could also have bad nipples or the rim failing somewhere. (spokes pulling through) If you're on aluminum spoke nipples, get rid of them.

I got away from DT Swiss spokes about two years ago after having some issues. I forget why, but I seem to think it was how they formed the end. I'm on Sapim CX-Ray spokes for the Tandem. After I did the initial wheel build and spoke balance, I've yet to touch the wheels on my tandem, road bike or mountain bike.