Easton EA 70 Case Study

[Johan Bornman]

Easton EA 70 - Spoke breakage

 

It seems that even the most revered boutique wheels also suffer from some common spoke maladies.

 

My good friend (and Yellow Saddle graduate) Gary from Margate sent me a parcel of stuff the other day for my bike museum - a nice DA rear derailer (circa 1970s), a couple of extinct sprockets, some extinct cleats for quill pedals and... a mangled spoke.

 

The note on the spoke says:  Spoke from Eason EA 70 - Drive Side.

 

A few weeks prior Gary spoke to me on the phone about his broken spoke and I found it quite strange that the spoke should have broken in this manner - from what sounded like a crack at the threaded end.

 

Easton prides itself on hand-built wheels, even tension, straight-pull designs and a couple of other must-haves for a really good wheel. Yet, here we have it, a broken spoke.

 

The spoke in my parcel was the very spoke Gary broke.

 

It is a straight-pull spoke, i.e without the J bend at the head end. The way Easton designed these wheels is to use straight-pull spokes in an a-symmetrical rear hub with a large right flange and small left flange. Lacing is 2X on the right and radial on the left.

 

The spoke Gary broke

 

 

The spoke shows evidence of a stress crack that traveled from the left to the right in the picture. The dull grey section is the slow part of the crack and the last little shiny tipsy bitsy bit is where the spoke finally broke in tension. The straw that broke the camel's back if you want.

 

Easton's one big party trick with its higher end wheels was a spoke that was threaded at both ends and screwed directly into the hub and fitted with a nipple at the rim. This eliminated the bend and its associated problems but also gave Easton the opportunity to keep the spoke perfectly linear, another design bonus.

 

The EA-70 is not designed like that and the spoke fixes to the hub by way of a standard mushroom head.

 

This spoke is from the right hand side and showed clear evidence of not being perfectly aligned with its nipple, hence the break at the first thread.

 

Easton EA 70s

 

 

Note the large right flange and small left flange on the rear wheel.

 

Without a wheel to measure, I estimate the right flange is about 70mm in diameter, the size of a PowerTap wheel flange.

 

It would appear that Easton underestimated the spoke arrival angle and overshot the rim's ability to swivel (about 9 degrees is the max for an aluminium wheel) and has a wheel with a built-in problem.

 

 

 

This is what I mean by arrival angle. If the angle is veers to far off from 90 degrees, the spoke bends where it meets the rim or nipple, putting stress on the weakest part.

 

 

 

Here is an example of a spoke that will break sooner or later. It is on a PowerTap wheel, 32 spoke, laced 3X.

 

Wihout drawing to conclusions, I'd like to know if anyone else has experience this on Easton 70s? Can  anyone confirm the hub flange size?

Can anyone tell me if their spoke angle looks problematic?

 

 

 

 

 

 

 

 

 

[singletrackmind]

A spoke kept coming loose on my old EA50s, think they are the same design. also drive side on the rear.

[tubed]

Johan

sorry never had a pair of those fancy wheels you are looking at, but this is a bit more applicable to my workshop, thought you may find some of the tools interesting, cheers

 

http://www.pezcyclingnews.com/?pg=fullstory&id=6725&status=True&catname=Latest News

[Johan Bornman]

Johan

sorry never had a pair of those fancy wheels you are looking at' date=' but this is a bit more applicable to my workshop, thought you may find some of the tools interesting, cheers

 

http://www.pezcyclingnews.com/?pg=fullstory&id=6725&status=True&catname=Latest News

[/quote']

 

Thanks for sharing this story.

 

Interesting... in a BS sort of way. It's all romantic and makes you want to sip cuppaccino and ride the Giro in the ghostly slipstream of Pantani and all that.

 

But I counted 25 nonsense statements in the piece. I wish they would assign these things to journo's with some scientific background. But I suppose that would kill the romanticism.

 

 

[Johan Bornman]

A spoke kept coming loose on my old EA50s' date=' think they are the same design. also drive side on the rear. [/quote']

 

That's a build fault, not design fault. The builder simply didn't put enough tension in the wheels. Easy to fix.

 

[ianfranklin]

You may have answered my problem. EA70's - 600 - 800 miles and I have already experienced, on separate occasions, two broken spokes on drive side. I have lost confidence in wheels but Easton UK have asked me to return to them so they can examine the wheel.

 

And to singletrackmind: Quote "That's a build fault, not design fault. The builder simply didn't put enough tension in the wheels. Easy to fix."  These are premium wheels supposedly all built to same standards by Easton - Not Joe Blogs - so presumably checked with a tension gauge.

[Johan Bornman]

You may have answered my problem. EA70's - 600 - 800 miles and I have already experienced' date=' on separate occasions, two broken spokes on drive side. I have lost confidence in wheels but Easton UK have asked me to return to them so they can examine the wheel.

And to singletrackmind: Quote "That's a build fault, not design fault. The builder simply didn't put enough tension in the wheels. Easy to fix."  These are premium wheels supposedly all built to same standards by Easton - Not Joe Blogs - so presumably checked with a tension gauge. [/quote']

 

Are you going to send them all the way back there? If the schlepp and cost prevents you from doing so, consider a rebuild. I have a little trick to overcome that problem. However, you have to perform it when the spokes are not yet screwed into the rim.

 

As for your faith in tensiometers: a tensionometer gives you an absolute reading. An analagy would be a horse power reading machine. Cars cloaked in black cloths come into the lab and the technician puts the car onto his machine and gives a horsepower reading (without knowing what car it is) and then makes a judgement as to the car's performance.

 

It would be silly. It could be an F1 car on the machine producing only 100kw or a Fiat Uno producing 200kw, who knows?

 

Tension meters are the same. They produce a meaningless reading unless you know a few things about the wheel. You need to take into account how many spokes, how much torque is transmitted through the hub to the other side, the relative stiffness of the rim, the intended load and the lacing pattern, amongst others.

 

From the few reports we've heard here, this consideration (I doubt it was a calculation) was incorrect, since spokes are coming loose. Spokes only come loose if they have insufficient tension, if the load is too big or if the rim is failing and thus slackening the spokes.

 

No doubt Easton used a tensiometer. You'll find that all their wheels have exactly the same (insufficient) tension and were built to close tolerances within the specified tension. Unfortunately these tolerances were wrong to start off with.

 

Easton now needs to up the tension and sort out the spoke arrival angle.

 

 

 

 

[ianfranklin]

I live in UKand Easton asked me to send the wheels back viathe dealer. They were rebuilt/tensioned and touch wood no problems since. Just did 300km some of which were on very poor road surfaces without problem. I'm prepared to accept that there are odd problems with any products but these seem to have been sorted.

[Johan Bornman]

If you look at the description of the problem, a rebuild won't do the trick. But time will tell.

[Harryn]

I wish I had seen this thread yesterday  - I have just taken delivery of a new set of these. Was real happy with my purchase until I read this!

 

Johan, my technical ability is just about zero, so I do not pretend to properly appreciate all that you have said here.

 

That said, do I undertand you correctly to say that there may, in your opinion, be an inherent design fault with these wheels. If so, is it not reasonable to assume that:

 

1. The incidence of this occurring would have been very widely reported; and

2. These wheels should have been subjected to a worldwide recall by Easton?

 

[oldie]

I have a set of EA 70's and have broken a drive side spoke. However not at the start of the thread, but about 30mm from the nipple. Also have a set of EA 90's and broken a front spoke at the start of the thread. Have noticed that the nipples crumble when attemting to true the wheel. Could this be oxidation between the two metals(spoke and nipple)

Know of at least 3 other similar cases where drive side spokes on the EA 90's have broken.

[Harryn]

Grawsh, but we need JB back in his thread.

 

There might be this huge class action suit  lying dormant on which to make a gazillion dollars.

[Johan Bornman]

Occasional spoke failure on a wheel is not cause for concern and certainly not cause for the manufacturer to recall the wheel.

Spoke failure is generally a matter of metal fatigue and not all spokes will fail concurrently, therefore one here and one there is not a safety problem.

 

Spokes that prematurely break from fatigue is a wheelbuilding and wheel design problem and only occasionally a material or manufacturing fault.

 

The spoke that broke on the right hand side, away from the bend or nipple, as reported above, was almost certainly the result of a nick or scratch in the spoke at that point. This caused a stress riser and like a Simba chips pack that will not tear until you've bitten a nick out of it, tears easily once there is a nick. That's how your car windscreen's crack travels.

 

The spoke that broke at the start of the thread is a fatigue problem. However, this shouldn't happen if the wheel was designed and built correctly. By design I mean the wheelbuilder should have chosen a crossing pattern that doesn't bend the spoke at the nipple and ensures an absolute straight nipple entry. By build I mean the builder should have stress relieved the wheel.

 

Properly designed and stress relieved wheels have a service life (in the spokes, the rims less so) of hundreds of thousands of kilometers. Rims fail earlier since they are also a braking surface and, aluminium fatigues quicker than steel.

 

However, rims that crack, supposedly from too much spoke tension is a topic on its own and when presented here will cause a huge barney. I'm too tired for that tonight.

 

 

[Harryn]

Thanks Johan, for the clariication. Guess I will just sommer ride and enjoy my new wheels!

[Schwynn]

If I may, I would like to add that I have a set of EA90SL's. I weigh in at 90kg's and have done +- 5000km on them. No Problems so far. A Friend has a set of EA90SLX's and broke 2 spokes. They were replaced and again, so far no problems. Use it, lose it...