Fullcount

…each one in the center of spoke. Why is this happening?

The bike is a Sun EZ Sport AX and most of my weight is over the rear tire. Wheel has 36 spokes. Granted, I am 220 lbs, but figured that would not cause spoke to break in center, but rather at the nipple with flex. I am running tires at 90 psi. 26 x 1.75” tire.

Help.

HillRider

Did anything knock the rear derailleur into the spokes? It sounds like something must have hit and scratched the spokes for them to break in that location.

Fullcount

All four spokes have broken individually over time in the last year. All four have been on the drive side. This was a used bike purchase for me and I really do not know age of bike.

I love the way this bike rides compared to my DF bikes. If I can get this recumbent dependable, like to try a couple of Rando rides. Is it possible that all spokes are approaching fatigued state and need to be replaced? Do LWB rear tires stress more easily than a short wheel base?

cpach

It is more common for spokes to fail in the center, though generally failures are more common on the nondrive side. When they have enough radial load the spokes will detension and flex in the center. If you have that many spoke failures it's likely that the rest are all fatigued. A recumbent can be harder on spokes because it's harder to unweight the bike like you can on an upright bike and tends to have even more of a rear weight bias. Still, a 36 spoke wheel on a 26" rim should be more than plenty strong for your application. Get a good wheelbuilder to rebuild your wheel with double butted spokes.

MyRedTrek

Some trauma that occurred to the spokes before you got the bike?

etherhuffer 

If your spokes are not correctly tensioned, they can fatigue more quickly. Straight gauge spokes? I had the same issue on a factory rear wheel. I built a new wheel with butted spokes, have not broken any spokes since. A wheel can look true but have poor tensioning.

Mosquitolt

Spokes are very prone to rust. Even a small amount of winter/salty riding will reduce their lifespan significantly. Also check if they are tension correctly and equally.

Fullcount

Not sure, but possible. I cannot see anything apparent.

Fullcount

I think your advice is sound. Time to get the wheel reworked and put the correct tension on the spokes and upgrade all spokes to a sturdier material. When I went to look up what a double butted spoke was, I found the following comment on www.wheelbuilder.com ; Tire pressure: Increased tire pressure has the effect of causing lower spoke tension, which increases fatigue sensitivity.

I think this may have contributed to the last two breaks. I ran the pressure up from my normal 80 psi to 90 psi, thinking this would help...., but it was actually counter productive. From what I have read, thinking that 36 spokes is a good number and that is what is on my touring bike (Trek 520). I am thinking I just need new spokes as the ones on the rim may just have gotten old and fatigued. Thanks for all your help.

JohnDThompson 

Having four spokes break suggests this will continue to be a problem. At 220#, you may better be served by a hand built and tensioned wheel. If the rim and hub are in decent condition, those may be re-used to save some $$$.

pdlamb

I've broken a number of spokes over the years. Probably 80% were at the head, with the remaining 20% just above the nipple. (Then I bought a tensiometer, and later started to run out of broken spokes for various "tools".)

Then a couple years ago a misaligned or misadjusted derailer went into a wheel. A few weeks later, I started breaking spokes in the middle where the chain had scratched them. All head-in, so the spokes were on the outside of the rim.

If you want to keep your wheel, try the Brandt stress relief method. First make sure the wheel is trued and tensioned. Then put on some heavy leather work gloves, grab each pair of near-parallel spokes, and squeeze the tar out of them. You want to squeeze hard enough that any flawed spoke breaks right then. Get back out on the road and ride some more.

If you buy a new wheel, make sure the person who last touches it knows what they're doing. Many people don't.

ThermionicScott 

What they say is broadly true, but I highly doubt adding 10 psi to your tire did anything to cause those last two failures. Low spoke tension usually causes breakage on the left side, not the right side.

cyccommute 

I disagree. Midspoke failures are very rare. I’ve broken hundreds of spokes and seen hundreds of broken spokes at my local co-op over 10 years of volunteering. The vast majority of spoke breakage is at the elbow and on the drive side in my experience. Seldom do I see spokes broken midshaft and those have experienced some kind of damage. I’ve seen a fair number of broken spokes just below the elbow but those are all caused by over shifting into the spokes.

Additionally, when spokes detension and retension during rotation, the part that flexes isn’t mid-shaft. It flexes at the elbow as most spokes have a sloppy fit in the hub. As the rim deforms upward, the tension on the spoke is released and the elbow moves upward. As tension is placed back on the spoke the elbow moves back down. It’s like bending a paper clip over and over again. The thinner center section of butted spokes probably allows for a slightly slower retensioning over a straight spoke resulting on a slower tug on the head.

With that I agree.

Although I partly agree that it’s harder to unweighted the rear wheel, I don’t see that as the major problem with this kind of recumbent. I see the problem more due to sidewards flex of the wheel. For any bike, the act of pedaling causes the rim to flex from side-to-side. This bike has a much higher rear wheel bias than most diamond bikes so the sideways stress is higher. It’s more like a touring bike that is carrying a heavy rear load than a race bike, for example. That puts a lot more stress on the spokes.

36 spokes is better than 32 for this applications but either many more spokes are needed or stronger spokes are needed. Rather than double butted spokes, I’d suggest triple butted ones like DT Alpine III 2.3/1.8/2.0mm spokes. They stronger than double butted and significantly stronger than single butted. Using them is like adding 4 (my estimate) to 10 spokes (Ric Hjertberg’s estimate). Here’s Hjertberg’s explanation on why using them is a good idea.

DiabloScott

My thoughts too - the spokes had a nick or gouge that started the fatigue. Once you got a crack, fatigue will go to work on it. Fatigue at the elbows or threads is to be expected under normal use given enough cycles, fatigue in the middle of the spoke needs something to get started.

Fullcount

Bike made the long journey to Williamsburg to see Matt at Contes. He is good and will make my wheel strong again.

As is the case with a lot of bike shops in this age of COVID, it may be a few weeks before I see the bike again. He was going to take a close look at alignment of rear derailleur and replace a few other items on the Tour EZ Sport. Thank you all for your input.

adamrice 

In my experience, spokes tend to break at the bend, on the drive side. Also, once spokes start breaking, they keep breaking—I'm pretty sure this is because of uneven spoke tension in the wheel. I would not be surprised if all the broken spokes were at 90° to each other.

Loosening and retightening all the spokes to restore even tension would be one way of dealing with this problem (this assumes that the wheel was correctly built in the first place, with inside and outside spokes where they should be). Buying a new wheel might actually be cheaper.

etherhuffer 

What, no pie plate comments? I thought for sure there would be a pie plate rant in here by now!