Bicycle Mechanics - Spoke Meesurements

The bike shop I ordered my new rims from told me that the rim measurement for my spokes is 289MM, but every site I go to doesn't carry the spokes I'm trying to buy (DT Alpine III) in a size 289MM. Would going with a size 288MM be fine? Or does it need to be exact? If it doesn't need to be exact, is it better to go with a higher or lower number (i.e.: 288MM or 290MM) than the given measurement? Or does that not matter either?

You'll need to round up or down to an even number which doesn't create any problems as there's a bit of latitude to work with. To decide which way, you could toss a coin, but the wisest thing to do is ask the people who gave you the dimension how high in the nipple they predict the spoke will end up.

You want them to end just short of the top of the nipple, so if they say they expect them to end near the top, round down. If they say short of the top, round up.

If they won't give you guidance I'd suggest rounding up because most people are calculating a minimum spoke length, rather than a maximum, and I'm a firm believer in the importance of good thread engagement within the head of the nipple. (but I'm sure the very next poster will tell you to round down, and it might come down to a coin toss after all).

Thanks so much for the detailed reply.

Is this information:


...if they say they expect them to end near the top, round down. If they say short of the top, round up.

...something they'd be able to provide without having the spokes on hand to physically check? Reason I ask is because I believe the guy used some kind of computer program to check the measurement for my specific rim.

Round down to reduce the chance of running out of threads when reaching high tension. This is more critical on the drive side rear.
Try out the spoke calculator at www.DTSwiss.com.

Buy 292mm...have someone with a spoke machine cut and roll to size.

Like doulbe butted spokes...there's probably at least 10mm of extra round end to work with.

=8-)

On second thought...that'd probably work with a Morizumi or Kowa spoke machine - but maybe not with a Phil because the 5mm of body to the left of the dies might interfere with the rotating aero blade.

Look up the specs for Alpines, how long is the section where the blade ends and the round end ends in millimeters...if it's 30mm+ then it'd probably work on a Phil machine as well.

=8-)

Is this information something they'd be able to provide without having the spokes on hand to physically check? Reason I ask is because I believe the guy used some kind of computer program to check the measurement for my specific rim.

They probably use the same calculator on a regular basis, and having built wheels themselves are familiar enough with where spokes usually end up to give you the right advice.

As I predicted the very next post said round down out of concern for running out of thread. It's a valid concern, and could certainly become an issue if 289mm is already near the maximum length. OTOH, if 289mm is towards the low end, and you round down you risk spokes not engaging the head of the nipple with enough thread, possibly leading to nipples cracking.

It's like navigating, in order to know which way to go to end up where you want to be, you need to know where you're starting from.

BTW- Matched spokes and nipples usually have enough thread to bring the head 1-2mm over the top of the nipple, so I feel my concern is usually the more critical one. FWIW, I use a popular calculator and add 1-2mm to every calculation, and the spokes just barely reach the top of the nipples.

On second thought...that'd probably work with a Morizumi or Kowa spoke machine - but maybe not with a Phil because the 5mm of body to the left of the dies might interfere with the rotating aero blade.

Look up the specs for Alpines, how long is the section where the blade ends and the round end ends in millimeters...if it's 30mm+ then it'd probably work on a Phil machine as well.


Blades?? He's planning to use Alpine III. They're triple butted round.

Why the triple butted spokes?

Double or triple butted spokes that can stretch are another good reason to round down the spoke length. When building wheels there is nothing worse than running out of threads.

Why the triple butted spokes?
Triple butted spokes have a larger cross-section at the "J" bend where most spokes break. I'm assuming the OP knows that the holes in his hub are big enough.
Alpine III's are 2.0-1.8-2.34.

Blades?? He's planning to use Alpine III. They're triple butted round.

Thought those were the bladed spokes...my bad.

If triple butted...then slight cut down on a spoke machine is a piece of cake....

=8-)

The bike shop I ordered my new rims from told me that the rim measurement for my spokes is 289MM, but every site I go to doesn't carry the spokes I'm trying to buy (DT Alpine III) in a size 289MM. Would going with a size 288MM be fine? Or does it need to be exact? If it doesn't need to be exact, is it better to go with a higher or lower number (i.e.: 288MM or 290MM) than the given measurement? Or does that not matter either?

Always round down. A little too long spokes means new spokes. Way too short spokes can be salvaged by using longer nipples.
Some spoke length calculators gives "raw" numbers (ideal geometric length), other adjust for the fact that spokes elongate and rims compress under tension. (typically they subtract 0,5 mm from the spoke length). Since you don't know whether the 289 mm figure is a "raw" or "adjusted" value, it is safer to assume that it is "raw" and you therefore need spokes shorter than 289 mm. (like 288 mm)

For arguments sake; if your shop made a serious mistake and the spokes turns out to be way too short, then one can use 14 mm or 16 mm DT Swiss brass nipples to effectively lengthen the spokes by 1 or 2 mm. Such nipples are quite cheap.
But it requires some serious miscalculation to get too short spokes; standard spokes have around 8-9 mm thread engaged in a standard 12 mm nipple when the spoke is flush with the nipple slot. Even spokes 3 mm shorter than ideal would still have ample 5 mm thread engagement on average. A whopping 5 mm spoke length miscalculation can even be salvaged by using 16 mm nipples.

Too long spokes can't really be salvaged in the same easy and cost effective way. And even small miscalculations can mean that the spokes are too long since standard spokes and nipples will start to crush thread if overshooting the length by a mere millimeter. Let me give an example; lets say that the 289 mm length is a "raw" figure. If you then round up and use 290 mm spokes, then you would start to crush thread (0,5 mm) since the actual spoke length under tension would be 290,5 mm. Perhaps still doable, but not a nice way to build wheels, and probably quite close to the limit.

Quite another thing is that several well known wheelbuilders like Brandt and Musson says that thick spokes like Alpine III is a misunderstanding that doesn't build better wheels. You will probably get better, cheaper and lighter wheels by using standard double butted 2.0/1.8mm DT Swiss spokes.

--
Regards

Having just been through this and replaced all the 288 mm DT alpine III s with 290mm, I'd say round up.

BTW "interested" as far as I can tell everything in your post is wrong. The longer nipples have the same thread length the same distance from the nipple head, it's just the length of the shank that is different (to allow access for the spoke wrench). You cannot compensate for short spokes this way. All you are doing is taking advantage of the fact that there is 8mm of threaded length in the nipple and using less of it.

On DT Alpine IIIs up to 3mm excess length is easily accommodated with standard 12mm x 2mm nipples (I've measured this).

What Musson etc have ignored is that DT Alpine IIIs are stiffer than comps and using them on the DS with thinner spokes on the NDS reduces the difference between the elastic strain in the spokes on each side. This results in a wheel which is marginally heavier (a little over 10 g for 32H) but stiffer and better balanced.

Having just been through this and replaced all the 288 mm DT alpine III s with 290mm, I'd say round up.

BTW "interested" as far as I can tell everything in your post is wrong. The longer nipples have the same thread length the same distance from the nipple head, it's just the length of the shank that is different (to allow access for the spoke wrench). You cannot compensate for short spokes this way. All you are doing is taking advantage of the fact that there is 8mm of threaded length in the nipple and using less of it.


No I am exactly right. 14 and 16 mm DT Swiss nipples works as I say. This is clearly seen on the cut away photos in Musson book (page 96 in 5th ed.) and is explained in the text too. It can also be deduced from the fact that DT Swiss' own spoke length calculator changes the required spoke length depending on choosing 12, or 14 or 16 mm brass nipples.
Other nipples from eg. Sapim may work as you describe, but not the DT Swiss nipples I explicitly named.
So when using DT Swiss 14 mm nipples, the ideal spoke length is one mm /below/ the nipple slot.




On DT Alpine IIIs up to 3mm excess length is easily accommodated with standard 12mm x 2mm nipples (I've measured this).


Depending on what you are even talking about here, this is wrong. What I say is that it is commonly accepted that the ideal spoke length to go after, is a spoke length that means the spoke is flush with the nipple slot (assuming standard 12 mm nipples). When the spoke is flush with the slot, that means that the nipple can still turn for a further 1 mm without running out of thread. To put it in another way, by aiming for making the spoke flush with the nipple slot, one has an error margin of +1 mm, or that the spoke can protrude 1 mm above the nipple slot before it starts to crush thread.
What you seem to claim is, that (Alpine III) spokes can easily protrude almost 3 mm above the nipple slot. If so, then you are wrong, since it is a simple fact that every millimeter above the 1 mm error margin means that thread is crushed.



What Musson etc have ignored is that DT Alpine IIIs are stiffer than comps and using them on the DS with thinner spokes on the NDS reduces the difference between the elastic strain in the spokes on each side. This results in a wheel which is marginally heavier (a little over 10 g for 32H) but stiffer and better balanced.

Jobst Brandt is an engineer that knows what he talks about. Musson's reasons are more practical; after making wheels for e.g. professional Downhill bikers for years with 2.0/1.8 mm spokes (or thinner) his conclusion is that thicker spokes solves no practical real world problems with bicycle wheels. Modern day quality db spokes from Sapim and DT Swiss are so good that people probably die of old age before they ride their spokes to the metal fatigue limit, if the wheel is correctly build and designed to begin with.
So why optimize for features that have no or very little practical meaning, but comes at cost like price, wind resistance, weight, availability in both lengths and at the LBS, incompatibility with many hubs etc.

I know this sound somewhat prattish, but I have reread both my own and your post, and I fail to see where I was wrong, or where you have found anything wrong with what I said.


--
Regards

On your first point: you are right, I hadn't checked my facts properly. The DT swiss nipples do work in the way you said. I wish I'd known that before I replaced my spokes; shear stupidity on my part since I'd already bought and read Musson's book.

On your second point,it goes both ways. I accept that there is only 1 mm before you start to go above the nipple, but you originally said that the threads would bottom out and this doesn't happen unitl 3mm. Yes having excess spoke above the nipple is "incorrect" but the last 2 mm can be cut off easily.

On your third point, I disagree that equalising elastic strain is not a worthwhile design goal. IMO it is more important than aerodynamic considerations in a spoked rear wheel.

Lastly I should apologise for being so curt in my first post.

Thanks for the help, everyone.


They probably use the same calculator on a regular basis, and having built wheels themselves are familiar enough with where spokes usually end up to give you the right advice.

Thanks again, FBinNY.


Alpine III's are 2.0-1.8-2.34.

The gauge is 13 / 15 / 14, but what measurement is "2.0-1.8-2.34?"


Always round down.

Okay, I'll go with the 288mm. Thanks a lot! :)

Another quick question, tho': Al1943 mentioned if I knew whether or not the holes on my hubs are big enough. Well...I don't, actually. I just bought two Shimano XT M770 hubs, do I have to insure that they (the hub holes) are big enough? If so, how do I do that? Is the size of the holes on listed in the manual? And if so, what then? Would I match them against the gauge (13 / 15 / 14) or the number Al1943 provided: 2.0-1.8-2.34?

Since DT Swiss are not septics, they use the metric system, therefore their spokes are sized in mm. The bend is 2.34mm, the shaft is 1.8mm and the thread is 2.0mm.

You will need spoke holes of at least 2.5mm to use these spokes: this should be listed in the hub specs by the manufacturer.

Can't seem to locate it. I took a picture of the specs - perhaps the size is not listed?

http://img693.imageshack.us/img693/2154/img3317k.jpg (http://img693.imageshack.us/i/img3317k.jpg/)

A quick look around indicates that Shimano specs hub holes at 2.6mm but I can't find any hard evidence for those particular hubs.

Is it not ridiculous that the specifications sheet does not list the flange diameter, flange spacing or the spoke hole diameter? Every other manufacturer I know of lists these specs, almost like they expect people to actually build wheels from them.

On your second point,it goes both ways. I accept that there is only 1 mm before you start to go above the nipple, but you originally said that the threads would bottom out and this doesn't happen unitl 3mm. Yes having excess spoke above the nipple is "incorrect" but the last 2 mm can be cut off easily.


Well, I actually didn't use the words "bottoming out", but stated that anything above 1 mm would mean that one started to crush thread. Given enough force and lubrication one could probably crush the entire thread of a spoke. When people experience "bottoming out", it is when the friction of the crushed thread becomes too big to overcome, not when the spokes actually run out of thread.

Technically, standard spokes and nipples "bottom out", when the spoke protrudes roughly 1 mm above the nipple, since this is the point where unthreaded part of the spoke is being forced into the thread of the nipple.
This is easily seen on the photo on page 96 in Musson's book. Notice how the there is around 1 mm of spoke thread below the point where the nipples thread begins when the spoke is flush with the nipple slot. Imagine that spoke is moved up upwards so it protrude 1 mm above the nipple slot, and you can see that any further movement would mean that the unthreaded part of the spoke is forced into the nipple thread.
So a spoke protruding 3 mm above the nipple slot would mean that 2 mm nipple thread is crushed.

There are many reasons why one should avoid having the spoke protruding 1 mm or more above the nipple slot, while "undershooting" the spoke length so it is several mm below the nipple slot isn't a problem at all. It is therefore better to always round down when in doubt.




On your third point, I disagree that equalising elastic strain is not a worthwhile design goal. IMO it is more important than aerodynamic considerations in a spoked rear wheel.


I am not saying that it isn't a worthwhile design goal, though I would really like to see some hard numbers on how much practical difference it would make between DS and NDS, because I suspect that the difference is small. What I was saying was, that when one optimizes for one particular parameter, other parameters may gets worse. The alleged advantage of the Alpine III spokes comes at a cost in other ways.



Lastly I should apologise for being so curt in my first post.
[/QUOTE]

Nah, no need to apologize. You gave an honest opinion without any malice. Debates move along because of stated honest opinions, if we where too polite to contradict each other there wouldn't be any discussions.

--
Regards

The gauge is 13 / 15 / 14, but what measurement is "2.0-1.8-2.34?"


2.0-1.8-2.34 refer to the three metric diameters of the spoke.

The 2.34 may not fit into standard hubs drilled to accept 2mm spokes, which are usually drilled slightly bigger than the 2.2mm thread diameter of 2.0 spokes. Also even if the hub is drilled 2.4mm it may be difficult to work the elbow through depending on the flange thickness, though the tightest workable fit is the best.

I suggest that before buying the spokes you see if the shop has a 13g spoke to check with.

For future reference, here's a link to a chart for the dimensions of spokes of various gauges. (NOTE- spoke gauges are different from and unrelated to the American Wire Gauges used for things like copper electrical wire).

The HB-M525 and HB-M770 and HB-M775 will accept 2.34mm elbows and heads...actually it's better...snugger fit. Using 2.0mm will result in a slight slack which is okay if the tension is where it belongs.

If you want an exact 289mm Anthony buy 292mm-296mm roughly and cut and re-roll in a spoke machine at an LBS. (Bring extras for testing...)

Rounding down to 288mm is okay IF you were aiming for a spot in the nipple a thread or two above the screw driver flat. If you were aiming at or below - you'll have 1-2 threads showing when done.

Either way...remember...your goal is to ride...not to be a perfectionist endlessly looking at the mirror.

=8-)

Guy's it's 1 @#$%& millimeter, so it isn't going to make more of a difference than that. In reality it'll be less than that because the 289mm calculation was rounded in the first place. That's why I sent the OP back to where he got the calculation. If, for example the calculated measure was 289.3 than rounding up would be closer to the ideal, if it was 288.6 than rounding down would be closer.

In any case, anyone with a decent amount of wheel building experience is used rounding to the nearest even length, and doing so presents no unusual problems. Going to the extra work of buying longer spokes and cutting them is totally uncalled for.

Guy's it's 1 @#$%& millimeter, so it isn't going to make more of a difference than that. In reality it'll be less than that because the 289mm calculation was rounded in the first place. That's why I sent the OP back to where he got the calculation. If, for example the calculated measure was 289.3 than rounding up would be closer to the ideal, if it was 288.6 than rounding down would be closer.

In any case, anyone with a decent amount of wheel building experience is used rounding to the nearest even length, and doing so presents no unusual problems. Going to the extra work of buying longer spokes and cutting them is totally uncalled for.


Whoah...I think you need to chill out a little here.

1. If the 289mm was rounded down already...rounding down to 288mm again is not a good idea.

2. I have a spoke machine, and I cut in .5mm increments...is it necessary? Of course not...but I do it just because it's fun and I can do it.

3. More importantly buying longer and cutting is not totally uncalled for. For a combo front and rear wheelset - 99% of the time it allows you to buy ONE box of 100 of ONE length and then cut into the THREE lengths needed. You save money on the ONE box bulk which THEN gets negated by the spoke machine charge - you come out pretty much even.

Not everyone is willing to sell 20 of one, 20 of another and 40 of another WITHOUT an additional markup just for the convenience.

But all the above ignores the bigger picture and easily get's away from thinking big as this thread has already done.

The goal is to ride. Pick the simplest and least painful way that'll work - and get the wheels done.

=8-)

Whoah...I think you need to chill out a little here.

The "it's just a @#$%& millimeter" was a bit of Hyperbole to make a point. The thread started with the OP asking if it was OK to round by 1mm and which way would be best, then right away went off on a bunch of tangents.

Of course he could buy longer and cut down, but for a causal builder the cost of getting equipped to do this would dwarf the up charge for buying less than a box of spokes, and would preclude mixing gauges to offset the effects of dish on the rear wheel.

From the tone of the OP, I'm guessing it's his first, or near first build, and IMO it would help him more to stay on point and give guidence on how to make an intelligent decision, up or down, rather than make wheel building some kind of super precise rocket science, which it clearly isn't.

...some kind of super precise rocket science, which it clearly isn't.

Could've fooled me. lol

And thanks for the help, but I haven't any brain cells left to compute what's happening in this thread and so I'll just ask my LBS to see what they have to say first, and if I get nothing there, I'll just go with the 288mm and hope for the best. Plus, the shop has a return policy in the event that my LBS deems the spokes "not good enough" for whatever reason.


Rounding down to 288mm is okay IF you were aiming for a spot in the nipple a thread or two above the screw driver flat.

Not sure what you mean, but would my LBS know whether or not what you say is the case?


If you were aiming at or below - you'll have 1-2 threads showing when done.

What does, "1-2 threads showing" mean? What exactly are "threads?"

Could've fooled me. lol

And thanks for the help, but I haven't any brain cells left to compute what's happening in this thread and so I'll just ask my LBS to see what they have to say first, and if I get nothing there, I'll just go with the 288mm and hope for the best. Plus, the shop has a return policy in the event that my LBS deems the spokes "not good enough" for whatever reason.



Not sure what you mean, but would my LBS know whether or not what you say is the case?



What does, "1-2 threads showing" mean? What exactly are "threads?"



Anthony...you know how you calculated...and this is your thread. If you are having a hard time keeping up with adjustment discussions and basic references in wheel building - perhaps you are in over you head. In other words - maybe it's better that you let the LBS build the wheels for you OR restart with some more basic "training" oriented wheel building before doing "production" stuff like that which you are trying to do now.

I know the above is discouraging, but I don't feel like restarting this thread all over again.

=8-)

Anthony...you know how you calculated...and this is your thread.

=8-)

I'm confused: I know how I calculated what? The measurements provided for the spokes (289mm) were calculated by the shop I bought the hubs from, as I mentioned, not me. And I never said I was going to build them myself - thought I was pretty clear in relaying that my LBS was going to build them for me. If not, apologies for the confusion.

I'm confused: I know how I calculated what? The measurements provided for the spokes (289mm) were calculated by the shop I bought the hubs from, as I mentioned, not me. And I never said I was going to build them myself - thought I was pretty clear in relaying that my LBS was going to build them for me. If not, apologies for the confusion.

Not criticizing you here, you asked hoping to learn, but I don't understand what kind of wheelbuilder sends the client out to buy the parts, especially without giving him clear direction. It's like going to a restaurant and the chef sending you out to buy your own steak. Tell the builder that the 289mm spokes he requested are unavailable, and let him decide. Otherwise you're setting yourself to be caught in the middle if things don't work out perfectly.

Ah, okay, now I understand where the confusion lies.

There are three bike shops. lol

Shop 1: Bought the rims, tires, hubs, tubes from this shop - good prices, cheaper than LBS, so I figured, "why not?" Same place that provided the 289mm measurement.

Shop 2: Reputable local bike shop that is going to build my wheels that knows nothing about me or the merchandise that I've bought.

Shop 3: The shop (located overseas - I'm from the states) I'm going to buy the spokes from.

Only reason I'm buying the spokes from an overseas shop and then giving them to the LBS in the states is because neither he (LBS guy) nor any US stockist carries the DT Alpine III in silver - which is what I want.

Hope that clears it up a bit. :)

In that case, tell the builder what rims and spokes you're bringing him, and let him do his own calculation for spoke length. That way he'll be responsible for the whole job and you won't be caught in the middle. You brought the chef the steak as asked, but it didn't cook up right because it was the wrong cut.

Got it! Thank you, sir! :)

In that case, tell the builder what rims and spokes you're bringing him, and let him do his own calculation for spoke length. That way he'll be responsible for the whole job and you won't be caught in the middle. You brought the chef the steak as asked, but it didn't cook up right because it was the wrong cut.

+100

Fillet Mignon, well done please!

:thumb: