anga

According to https://www.dcrwheels.co.uk/custom-wh...spokes-advice/ Sapim Force spokes have a life of 2 million revolutions.

On a 26" wheel, that comes to
2000000*pi*26*2.54/100/1000 = 4150 km or 2600 miles.

This seems to be lower than what I keep reading about the life of well-built wheels.

Please clarify.

reptilezs

do not take the marketing too literally. even crap oem spokes can last 2000 miles

Homebrew01

Sapim's numbers make no sense. Must be some uncorrected typo from years ago.
Here's an old discussion on the same topic:

https://www.cyclingforums.com/t/38408...tigue-estimate

HillRider

If they are correct, buy another brand. I've got wheels built with both DT and Wheelsmith 2.0/1.8/2.0 spokes with over 30,000 miles (48,000 km) that have never broken a spoke.

Actually, it's impossible to predict the life of a spoke based just on total revolutions. Bike/rider weight, road conditions and wheel construction (rim stiffness, spoke count) all play a major role in how long spokes will last.

Looigi

Right. You need to know the test methodology to interpret the results. Fatigue testing is often done at high stress to accelerate results in tests that would otherwise take impractically long to perform. It's almost certain this was done in this case and results are for comparative purposes between different spokes.

Wilfred Laurier

there are two possibilities i can think of

1
sapim has the most excellent quality control department
and they specify the exact number of stress cycles possible
before all the spokes will simultaneously break

if you ride 2599 miles you are fnie
but
when your odometer hits 2600.00
all spokes break and your hub hits the ground

i dont know if odometers have reminders or alarms
that go off at specified distances
but this would be a good idea

if you want to ride more than 2600 miles
you need bigger wheels

2
sapim spokes are tested to an arbitrary high number of cycles
like 2000000
to ensure there are no defects
which is a common strategy in testing fatigue limits of materials
and the wheel builder misinterpreted this
to mean
'spokes will last for 2000000 revolutions'

anga

Thanks guys for the informative responses.

AnkleWork

Not the first wheelbuilder to have published their material science and engineering misconceptions as fact.

joejack951

I have ~18,000 miles on DT Revolutions (2.0/1.5/2.0) and haven't had to replace a single one (rear wheel is half Revolution and half Competition 2.0/1.8/2.0). I did break my front hub (pothole at night in the rain) but relaced the new one with the same spokes.

FBinNY 

A decently built wheel can easily go 50,000 miles. It isn't necessarily overbuilt, because even light wheels can last that long.

IMO the perfect wheel is the lightest that is adequately rigid (laterally) and can go the distance. I try to build wheels like Holmes's One Horse Shay. My dream wheel will last for untold miles until the brake track wear is approaching the limit and the rim is just beginning to show stress cracks. The first spoke will break just before I drop it into a rain filled pothole and crack the rim. IMO if either spokes or rims materially outlast each other, one was over or under built.

BTW- my seriously abused commuter wheels built with 1.8/1.6 & 1.8/1.5 spokes are well past the 20k mark with no problems. The rear is near or passed the brake track wear limit, and I expect that it's be trouble free until the rim flange blows off. I think I might have over built them.

fietsbob

keeping the wheels tensioned and trued makes the whole wheel more reliable.

interested

I think the spokes where tested with extreme load in order to accelerate metal fatigue. Since a normal wheel (36H 3x) may last 100.000 or perhaps even 200.000 km before the spokes break from metal fatigue, it would have taken an awful long time to test them that way. The quoted numbers are quite old, and I don't think they can be found on Sapims homepage any more, probably because they can cause confusion. The numbers may give a relative feeling for the fatigue rating of Sapim spokes, but can't be used to compare them to other spoke brands, or even to "real life".

Sapim (Belgian company est. 1918) have now been bought bought by Ryde Int., but I know that they at least used to buy their spoke wire from SMT Sandvik, the same place as DT Swiss does. Ordinary spoke wire used to make spokes aren't that difficult to make, but good quality control is crucial, and that what Sandvik does really well. So Sapim spokes have always had a excellent reputation.

HillRider

If you are lucky like I have been the rim will crack only a short way and you will find out by having the brake thump as the pads pass the crack and you will be able to limp home before the tube blows. If you are not lucky the rim will fail by loosing a large chunk of metal and you have to make either a long walk home or a cell phone call.

FBinNY 

Yes, I'm not sweating because I expect it to crack visibly or audibly before actually letting go. I worry most as I pump it, since that's when it first sees an increase in pressure since the last time.

Wilfred Laurier

...or an ambulance ride

i have had several rear rims wear through
and all happened slowly enough
that i noticed the spokes were losing tension
before i noticed the crack

but i have also seen a couple rims with foot long
jagged aluminum strips sticking out from the brake track

FBinNY 

I'll let you know how it plays out when it happens. Of course that's if nothing untoward happens first.

BikeWise1

The quality of the build and attention to detail, i.e. knowing when to use spoke head washers, having the spoke nipple come out of the rim pointed toward the flange so there's no bend at the spoke, spokes going sufficiently deep into the nipple, etc., will make far larger difference in spoke longevity than the brand of spoke used. Sure, there are some really bad OEM spokes on cheap bikes, but given the main reputable brands, the build, not the spoke, is what determines spoke life.

HillRider

Yep, both of my on-road rim failures were rear rims and a rear blowout is much less likely to cause an accident than a front. I knew the ones that cracked were badly worn so neither surprised me but neither lost spoke tension or went out-of-true before the failure occurred.

joejack951

Is there more to this than just properly lacing a rim with offset holes? I've never seen this addressed in any of the wheel building threads. Maybe I should actually read a good book on the subject

FBinNY 

It depends on the rim more than anything else. It's also a reason to reduce the number of crosses on flanges that are large diameter compared to the rim. Nipple angle becomes an issue on large drum brake or electric motor hubs, and also with 4" flanges on smaller wheels.

There's not much you can do because the nipple typically takes the line dictated by how the rim is drilled. However nipples vary, those with conical bottomed heads (like flathead screws) will be faithfull to the line dictated by the rim. But some have more of a spherical bottom to the heads, and therefore more float to follow the spoke (if the hole is big enough to allow it).

Many years ago, Mavic decided to improve rims by angled drilling, not only side to side, but forward and back. They were nice to build, but a nightmare for Mavic, since they never made clear that they were drilled this way, and therefore were accused of defective drilling. All in all it was a flop.

BikeWise1

Campy did this as well.... their rims assumed 3x 32 or 2x 28h in the way they literally aimed the spokes directly at the flange. It took a little care when lacing to make sure you had it right, but those builds generally never suffered spoke failure at the nipple...

Road Fan

FWIW, your 30,000 miles corresponds to about 10 million cycles. This counterexample should by itself show that the statement that Sapim's spoke is only good for 2 million cycles is probably a misinterpretation of the test results.

Any reasonable prediction of product life has to be based on some testing that actually created some failures. From that kind of data you can draw a curve of probability of failure for a given number of stress cycles given the specifics of the stress cycle is defined. From that you can make a prediction. It's still fraught with issues and uncertainties, however.

Craftsmanship is still king.

joejack951

Ok, I didn't think there was more to it than that. But I was sort of hoping there was some special technique to massaging nipples (now, now, fellas) into better alignment with the spoke other than relying on the nipple and rim design (and proper lacing and component choices).

For all those who deride radial laced front wheels for reasons other than appearance, nipple alignment is one performance factor radial lacing should help.

FBinNY 

As I said, it depends on the rim, and to an extent of the head shape of the nipple. On many rims the hole size is so close that there's no wiggle room for the nipple to take any angle except that of the hole. Others have holes that allow wiggle, and on those the shape of the nipple head determines whether the nipple will float to the spokes alignment or not.

You can fool yourself into thinking you can help, but tension will always pull the nipple as straight as it can go. So if you really care, you might enlarge the nipple hole a bit to create float. This is most helpful on aero rims drilled straight down the pointy centers. The rim is thick there so nipples can't wiggle at all unless the hole is a bit oversize.

OTOH, a slight bend at the nipple will not cause spoke breakage, unless you allow spoke twist as you tighten. Twist works the bend back and forth, setting up future failure, whereas a simple bend that isn't bent back and forth won't.