Strongest set of touring wheels.

[Vorpal]

When I was a kid, I had some rims fail. But I couldn't afford a proper bike, and my parts, including wheels, came from other kids, or the tip. Also, I fixed or maintained them on my own, with help from older kids, but not really any adults. So, I think wrecking some bits was to be expected.

Since buying my first 'proper' bike, the only rim that has ever failed me by any means other than the braking surface, it was because I hit a pothole hard on a 70s alloy racing wheel.

I have broken a fair number of spokes. Sometimes it has been because the wheel probably didn't get the maintenance attention it deserved. Sometimes, I think the combination of me, child, stuff, & pothole was too much.

I have a bit of a mystery with my tourer (not the bike that has the DT Swiss wheels). I tightened some spokes on it twice last year, had the bike serviced in May, then in early June, on a short tour, I had some loose spokes, got them tightened (free service at a cycling conference), then broke a spoke rolling at low speed off a kerb a couple of weeks ago. It's been to the shop again, but I'm starting to wonder if the wheel was correctly stress relieved when it was built

[MikeDee]

You might be referring to Boost, which widened the flange width on hubs a whole 6 mm. I don't think that did much, especially when 29er wheels have like 24 or 28 spokes. Do you think that more spokes in a wheel are a better approach?....

well there are lots of 'standards' to choose from in MTB rear hubs....



A 6mm increase in flange spacing has a very large effect on the lateral strength and lateral stiffness of wheels, which is badly needed in the case of 622 rimmed wheels; they fold up really rather easily (by MTB standards) if the flanges are spaced 'normally', or must be built rather too heavily for folk to actually want to ride them.

A ~10% change in the wheel diameter changes a load of other things by 10, 20 or even ~30% even if you attempt to scale the design somewhat; engineering with what are (effectively) cantilever loads is difficult; the numbers are an unforgiving mistress....

FWIW more spokes is always better but it may not greatly increase the lateral load required to pretzel a wheel. In fact it may even lower it, by pushing the rim loading closer to yield.

cheers

What does that do to the chainline and the Q factor of the cranks and heel clearance at the chainstay? After all, the bike has to be pedaled. Boost supposedly didn't change the Q factor, but those wider versions look like they would.

I guess I'm not that tough on my bike because I've ridden a 29er for a lot of years, and enough to crack two frames, but never had wheel problems and I don't have Boost.

[Brucey]

clearly you can be tough on your frame without being tough on your wheels.....

They argued that 148mm didn't alter Q if you used the right chainset, but that is of little interest to me anyway; I never liked those MTB chainsets because they already had a Q value that was way too high for my tastes. Like you say those even fatter hubs may compromise matters, even if you use just a single ring.

FWIW if you use a road triple (with a ~45mm chainline onto the middle ring) then it is centred pretty well on a 9s cassette that is installed on a 135mm hub. You can push the sprockets out at least 8mm if you intend to run a single chainring and that still leaves you with a Q value that is (with the right cranks) 140mm or so. Quite how we came to have MTB cranks with Q values in the region of 180mm is quite beyond me; I suppose that it allows more heel clearance if the cranks are, er, cranked or something, and if the Q value gets small enough you can't clear the monstrous chaintays either.

To get the chainring centred over a symmetric 157mm hub's cassette, I think that the chainline needs to be about 57mm; without a FD, I don't think this need increase the Q value much above the usual MTB chainset...?

cheers

[Manc33]

When I was adding up the cost (and weight saving) of going with double butted spokes (about 4.5g per spoke) I ended up just getting straight gauge (about 7.5g per spoke). I built my own wheels (36 front and rear) and it was the best thing I ever did for my bike. They have never need truing to this day and are strong wheels.

Straight gauge 2.0/2.0/2.0 spokes don't twist around when you do need to true them.

Over all 72 spokes, the weight saving by having the 4.5g spokes as opposed to the 7.5g ones is about 216g over both wheels, thats not even half a pound. I can't see any reason to use double butted, whether that be 2.0/1.8/2.0 or the more expensive 2.0/1.5/2.0.

When you're running Marathon Plus at something like 600g per tyre in their thinnest variant, 100g shaved off the spokes on a wheel becomes insignificant. To me it was an easy decision in the end, straight gauge - and the nice thing is, those are the cheapest spokes.

[Brucey]

14-16-14G DB spokes are more elastic than 14G PG ones. This means the wheels built with DB spokes are almost invariably better wheels, as well as being lighter.

I agree the weight saving probably isn't that important in wheels meant for load lugging, and that wheels built with PG spokes can be made to be quite satisfactory. However they are just not quite as good; in particular if there are spokes that must have low tension (eg because they are NDS spokes in a rear wheel, or the rim isn't straight and will only build with a few spokes that are not very tight) then these spokes are more likely to have the nipples back out if they are PG spokes than if they are DB spokes. There are some wheels that you can only build acceptably with PG spokes if you use threadlock on the nipples, whereas with DB spokes they may not need it.

The weight saving is most significant in lightweight road wheels; the weight saving in a pair of wheels in using DB vs PG spokes is about the same as the mass of a lightweight tyre.

If you don't need the weight saving, you can build much stronger wheels using DB spokes at about the same weight; for example you can build a set of 36 spoke wheels with DB spokes and they will be lighter than a set built using 32 PG spokes, but waaaay stronger.....

cheers

[531colin]

Most of the responses assume that the initial build of a wheel entirely dictates it's longevity.
Whilst broadly I agree with this, it does ignore the possibilities of bad luck and carelessness.
The majority of broken spokes I have experienced have broken mid length and show clear fatigue pattern on the fracture surface.Reports I see of broken spokes are at the elbow or at the thread route. These probably are indicative of poor stress relief during initial build. However I cannot see mid length fracture as in any way related to the builder's talent; far more likely the spokes I have broken were scratched (through my riding on any surface as it pleases me - just as the OP seeks to, or from too intimate contact with pedals of my too many bikes when I am careless in storing them) and the scratch gave an initiation site for fatigue to progress.
My most recent experiences of such failure were a spa rear wheel originally built by Colin (I cast no aspersions at Colin's wheel building; I attribute failure entirely to my use of the wheel) which broke one spoke, which I replaced, then several more in chain reaction such that I rebuilt with new spokes. The other was my tandem disc front, originally built by Harry Rowlands, which similarly broke mid length with fatigue type fracture surface; again a first class wheel built by a first class builder, but failed due to my bad luck and carelessness.
It feels ironic that, to date, I have not suffered similar failure on any wheels I have built myself. I certainly don't compare my experience to those listed above and simply assume that my parental pride in my own invested effort causes me to take better care of those wheels.

I have never seen any mid-spoke failures which I was convinced were the result of stress-raising damage to the spokes. I have seen plenty of wheels with the spokes chewed up by contact with the chain, but never leading to spoke failure, as far as I recall.
Now 71, I have been retired for longer than I worked at Spa, so recollection is a little hazy....but in my 5 years at Spa we had (at least) a batch of "stainless" spokes which rusted....a batch of PG spokes so soft that you couldn't build up a Chrina rear rim and stress-relieve it, the spokes failed (ductile failure; but at least they didn't get out of the shop!) ....and a batch of DB spokes which failed mid-shaft on 36H 700c Sputnik rears.....there may have been others. If a wheel with several spokes failed mid-shaft had been returned, it would have been re-built free.
I don't know the mechanism for mid-spoke failure, but I do know its spoke batch related. I suspect there is something wrong with the wire, maybe too many/too big inclusions.

I say again....spokes should outlast rims....even Sputniks you can get 2 rims to a set of spokes, by then the hubs may be wearing.
Any spoke which fails hitting a rock (etc) was already fatigued. A new spoke will generally pull through the rim before it fails.

[531colin]

……...yeah but you dont weigh much if the pictures of you are true and accurate?

Just like framebuilders make a disproportionate number of very small and very large frames, anybody with a reputation as a wheelbuilder will get to build a disproportionate number of wheels for heavy use. You get the 20 stone men, the tandemists, the trike riders.

[Brucey]

Most of the responses assume that the initial build of a wheel entirely dictates it's longevity.
Whilst broadly I agree with this, it does ignore the possibilities of bad luck and carelessness.
The majority of broken spokes I have experienced have broken mid length and show clear fatigue pattern on the fracture surface.Reports I see of broken spokes are at the elbow or at the thread route. These probably are indicative of poor stress relief during initial build. However I cannot see mid length fracture as in any way related to the builder's talent; far more likely the spokes I have broken were scratched (through my riding on any surface as it pleases me - just as the OP seeks to, or from too intimate contact with pedals of my too many bikes when I am careless in storing them) and the scratch gave an initiation site for fatigue to progress.
My most recent experiences of such failure were a spa rear wheel originally built by Colin (I cast no aspersions at Colin's wheel building; I attribute failure entirely to my use of the wheel) which broke one spoke, which I replaced, then several more in chain reaction such that I rebuilt with new spokes. The other was my tandem disc front, originally built by Harry Rowlands, which similarly broke mid length with fatigue type fracture surface; again a first class wheel built by a first class builder, but failed due to my bad luck and carelessness.
It feels ironic that, to date, I have not suffered similar failure on any wheels I have built myself. I certainly don't compare my experience to those listed above and simply assume that my parental pride in my own invested effort causes me to take better care of those wheels.

I have never seen any mid-spoke failures which I was convinced were the result of stress-raising damage to the spokes. I have seen plenty of wheels with the spokes chewed up by contact with the chain, but never leading to spoke failure, as far as I recall.
Now 71, I have been retired for longer than I worked at Spa, so recollection is a little hazy....but in my 5 years at Spa we had (at least) a batch of "stainless" spokes which rusted....a batch of PG spokes so soft that you couldn't build up a Chrina rear rim and stress-relieve it, the spokes failed (ductile failure; but at least they didn't get out of the shop!) ....and a batch of DB spokes which failed mid-shaft on 36H 700c Sputnik rears.....there may have been others. If a wheel with several spokes failed mid-shaft had been returned, it would have been re-built free.
I don't know the mechanism for mid-spoke failure, but I do know its spoke batch related. I suspect there is something wrong with the wire, maybe too many/too big inclusions.

I say again....spokes should outlast rims....even Sputniks you can get 2 rims to a set of spokes, by then the hubs may be wearing.
Any spoke which fails hitting a rock (etc) was already fatigued. A new spoke will generally pull through the rim before it fails.

Colin's comments tally closely with my own observations. FWIW I have seen stainless steel spokes corrode (typically with salty debris from a winter road) and this is more likely to cause a spoke failure than (say) a scratch. Spokes may be more likely to corrode at the mid section because nearer the hub the spokes are usually already dirty/oily (so are protected to some extent) and the dirt is less likely to stick near the rim because the G forces are higher when the wheel is turning. With DB spokes the stresses are high in the centre part and this is a potent combination when you add a corrosive element. Note that stainless steels are not 'corrosion proof' but they are corrosion resistant. If you subject any stainless steel spokes to the strongest brine and high stress, they will break. You get the strongest possible brine every time you ride the bike in winter and store it in a dry(-er) shed without washing it first.

if you want to improve the corrosion resistance of any stainless steel spoke, polishing it helps more than you might expect. Polished stainless steel is noticeably more corrosion resistant than the same stainless steel when it is not polished. It is to do with how easily the surface is 'passivated'.

cheers

[goatwarden]

Thanks Colin and Brucey for your considered opinions; they are interesting.
I hadn't really thought about other spokes I have damaged which didn't go on to break; I have graunched loads with chain interference and never seen one break at the damage site.
The cases I described (not my only experiences of mid spoke breakage, but the most recent) are the two bikes which I tend to do the biggest days and all weather on, so are probably the least likely to get a proper clean immediately after a ride. The fracture surfaces always look like a fatigue fracture and the spokes have generally gone with a bang; I don't have anything which magnifies sufficiently to identify any corrosion/mechanical damage evidence at the crack initiation sites.
I am also 95ish kg (170 kg total rider load on the tandem) so my wheels are probably stressed above average.

[Manc33]

Brucey you shouldn't have said that, now I want to rebuild my wheels with DB spokes

[Brucey]

.... The fracture surfaces always look like a fatigue fracture and the spokes have generally gone with a bang; I don't have anything which magnifies sufficiently to identify any corrosion/mechanical damage evidence at the crack initiation sites....

you would probably need a scanning electron microscope to see the corrosion damage; all that (or an unusually large inclusion in the steel, etc) does is initiate a crack; the crack then propagates via fatigue and then the final fracture occurs when the remaining part of the spoke is not strong enough to bear the load any more. The final fracture is usually about 1/3rd of the original cross sectional area but of course it can vary.

There is a school of thought that says that if you re-stress-relieve your wheels, you may get an extended life out of them. The logic is that any nascent cracks will yield and then have a more favourable local stress distribution afterwards. Whether this actually stops cracks or just slows them down, once they are past a certain size, is unclear.

Once thing I do know is that (with a load on) it can only take about 600 miles for a defect in a spoke to initiate and grow a crack so that the spoke breaks. You can take it that there were no (large) cracks in the spokes at a given time, if you manage to ride (say) a couple of thousand unladen miles or a few hundred laden ones subsequently, and that any stress-relief you might have done was effective.

cheers

[Des49]

I have never seen any mid-spoke failures which I was convinced were the result of stress-raising damage to the spokes. I have seen plenty of wheels with the spokes chewed up by contact with the chain, but never leading to spoke failure, as far as I recall.
Now 71, I have been retired for longer than I worked at Spa, so recollection is a little hazy....but in my 5 years at Spa we had (at least) a batch of "stainless" spokes which rusted....a batch of PG spokes so soft that you couldn't build up a Chrina rear rim and stress-relieve it, the spokes failed (ductile failure; but at least they didn't get out of the shop!) ....and a batch of DB spokes which failed mid-shaft on 36H 700c Sputnik rears.....there may have been others. If a wheel with several spokes failed mid-shaft had been returned, it would have been re-built free.
I don't know the mechanism for mid-spoke failure, but I do know its spoke batch related. I suspect there is something wrong with the wire, maybe too many/too big inclusions.

I say again....spokes should outlast rims....even Sputniks you can get 2 rims to a set of spokes, by then the hubs may be wearing.
Any spoke which fails hitting a rock (etc) was already fatigued. A new spoke will generally pull through the rim before it fails.

Totally agree. No spoke should fail mid length in a well built wheel, unless there is some material deficiency. I suffered from one of these same batches of bad spokes, Sapim spokes in my case bought loose from Spa a few years ago.

See this thread:-

viewtopic.php?f=5&t=94784