CXP33 - Spoke count?

[fish156]

I don't know where you got this idea from, but the spokes only need to be tight enough to not go slack under riding loads. Any tighter than this and you will drastically decrease the fatigue life of the wheel. I've seen rims on over-tensioned wheels start cracking within a few thousand miles of riding. That's not what I would call strong. As for "relative" tension, if you get your wheel trued, rounded, and centered and there's a variation is spoke tension it means that the rim was bad to begin with.

Ok, maximum tension - for the third or fourth time in this thread - is spec'd by the manufacturer of the rims. That's where I get that. If you like to drink Jobst Brandt's koolaid, you tension until the rim begins to warp and then back off a little - and spec's be damned. I do not, and never did, suggest over tensioning. I would define that as past the maximum recommended by the rim manufacturer. Please try to make an effort not to twist my words. Over tensioning is your term - not mine. Let's be perfectly clear about that. As far as relative tensioning goes, that comes directly from Barnett's. Are you claiming that you know more about wheelbuilding than Barnetts? There is no question that there are variations in rims, and that is undoubtedly why Barnetts specs proper relative tensioniong as within 5%. I have discussed this specifically with Peter White and his opinion is that rims would have to cost over $300/per to make any noticeable difference in quality.

 

[fish156]

I don't know where you got this idea from, but the spokes only need to be tight enough to not go slack under riding loads. Any tighter than this and you will drastically decrease the fatigue life of the wheel. I've seen rims on over-tensioned wheels start cracking within a few thousand miles of riding. That's not what I would call strong. As for "relative" tension, if you get your wheel trued, rounded, and centered and there's a variation is spoke tension it means that the rim was bad to begin with.

more on where I got this idea from :

There are two books on wheelbuilding that are readily available and widely accepted as the standard references on wheelbuilding. Not everyone will agree with all that is put forward in these two books and they clearly differ from each other on some subject. That being said, they both agree on how to get optimum tension when building a wheel. The two books are:

'The Bicycle Wheel' by Jobst Brandt
and
'The Art of Wheelbuilding' by Gerd Schraner

I highly recommend both of these books for anyone who has a real interest in building wheels. There is a lot of great information and these two authors put a tremendous amount of time and effort to give good explanations for what they feel is the right way to build wheels. It's obvious that these two men have spent most of their lives researching and learning from experience.

Both books are fairly inexpensive and can be obtained at:

http://www.biketoolsetc.com/index.cgi?id=72536211751&c=Books Videos&sc=Wheel Building
for about $20 a piece.

On with the quotes... Since this forum app does not handle quotation marks in an elegant fashion, I will spell it out with the words quote and unquote


From Schraner's 'Art of Wheelbuilding':
quote (pg44)
The majority of wheels today have insufficient spoke tension.
unquote

He goes on to say that the majority of broken spokes can be attributed to insufficiently tensioned spokes.

quote (pg46)
High spoke tension helps to balance the wheel when it is under load. The
spoked structure will hardly move at all...

The higher the spoke tension, the more effectively the overload is distributed over
several spokes ...

The perfect spoke tension is determined by the quality of the rim. For this reason,
the hightest possible tension for flat rims is lower than that for high V-cross section rims. And on cheap rims made from soft aluminum, you can forget any kind of respectable spoke tension altogether.
unquote

While there is much more from Schraner, he clearly feels that the best wheels are built at maximum tension.

Now, from Brandt's 'The Bicycle Wheel' :

quote (from pg104 - Final Tensioning)
To achieve greatest strength, spokes should be tensioned near the maximum that the rim permits.
unquote

He goes on to describe his method for finding just exactly what a rim will permit. He does this by tensioning the rim until it begins to warp and then backs off. In almost any case, this method will exceed the maximum tension spec'd by any manufacturer, so, if you use the maximum tension - as stated by the rim manufacturer - you will still be short of the tension recommended by Jobst Brandt.


I hope this will remove any questions about where I am getting my information. I stick to widely accepted and published sources. I, personally, am NOT an expert on these things. I do make sure I do my homework and their is more than a little experience mixed in with my comments. If something is my opinion and unbased on any easily quotable reference, then I state it as my opinion (=IMHO).
I also have enough respect to read the entire thread before I start firing off criticism of other people's postings.

 

[fish156]

I don't know where you got this idea from, but the spokes only need to be tight enough to not go slack under riding loads. Any tighter than this and you will drastically decrease the fatigue life of the wheel. I've seen rims on over-tensioned wheels start cracking within a few thousand miles of riding. That's not what I would call strong. As for "relative" tension, if you get your wheel trued, rounded, and centered and there's a variation is spoke tension it means that the rim was bad to begin with.

more on where I got this idea from :

There are two books on wheelbuilding that are readily available and widely accepted as standard references on wheelbuilding. Not everyone will agree with all that is put forward in these two books and they clearly differ from each other on some subjects (such as tying&soldering). That being said, they both agree on how to get optimum tension (which they both define as maximum) when building a wheel. The two books are:

'The Bicycle Wheel' by Jobst Brandt
and
'The Art of Wheelbuilding' by Gerd Schraner

I highly recommend both of these books for anyone who has a real interest in building wheels. There is a lot of great information and these two authors put a tremendous amount of time and effort to give good explanations for what they feel is the right way to build wheels. It's obvious that these two men have spent most of their lives researching and learning from experience.

Both books are fairly inexpensive and can be obtained at:

http://www.biketoolsetc.com/index.cgi?id=72536211751&c=Books Videos&sc=Wheel Building
for about $20 a piece.

On with the quotes... Since this forum app does not handle quotation marks in an elegant fashion, I will spell it out with the words quote and unquote


From Schraner's 'Art of Wheelbuilding':
quote (pg44)
The majority of wheels today have insufficient spoke tension.
unquote

He goes on to say that the majority of broken spokes can be attributed to insufficiently tensioned spokes.

quote (pg46)
High spoke tension helps to balance the wheel when it is under load. The
spoked structure will hardly move at all...

The higher the spoke tension, the more effectively the overload is distributed over
several spokes ...

The perfect spoke tension is determined by the quality of the rim. For this reason,
the hightest possible tension for flat rims is lower than that for high V-cross section rims. And on cheap rims made from soft aluminum, you can forget any kind of respectable spoke tension altogether.
unquote

While there is much more from Schraner, he clearly feels that the best wheels are built at maximum tension.

Now, from Brandt's 'The Bicycle Wheel' :

quote (from pg104 - Final Tensioning)
To achieve greatest strength, spokes should be tensioned near the maximum that the rim permits.
unquote

He goes on to describe his method for finding just exactly what a rim will permit. He does this by tensioning the rim until it begins to warp and then backs off. In almost any case, this method will exceed the maximum tension spec'd by any manufacturer, so, if you use the maximum tension - as stated by the rim manufacturer - you will still be short of the tension recommended by Jobst Brandt.


I hope this will remove any questions about where I am getting my information. I'm not just shooting from the hip, as some people seem to have a penchant for in this forum. I stick to widely accepted and published sources. I, personally, am NOT an expert on these things. I do make sure I do my homework and there is more than a little experience mixed in with my comments. If something is my opinion and unbased on any easily quotable expert reference, then I state it as such (=IMHO).

I also have enough respect to read the entire thread before I start firing off criticism of other people's postings.

 

[dhk]

I don't know anything about wheel building either, but like Art, I've had personal experience with an over-tensioned rear wheel which failed in a few thousand miles due to the spokes pulling through the rim.

From my limited knowledge of how things work, if the spokes are tensioned to the ultimate static limit, then there is no margin for the dynamic loading on the road. IE, every bump and pothole you hit is going to cause one or more spokes to exceed the limits of the rim, and failure will soon result.

Would seem to me that there is an optimum range for spoke tension, which would be well-below, ie, perhaps 50% of the ultimate tension that the rim could tolerate. That way, you'd have a good working margin on either side, tension and compression.

Like you, I'd look to either the rim manufacturer or an expert wheelbuilder to tell me what that optimum tension should be. I certainly wouldn't use the J. Brandt method as you described it.

 

[fish156]

Like you, I'd look to either the rim manufacturer or an expert wheelbuilder to tell me what that optimum tension should be. I certainly wouldn't use the J. Brandt method as you described it.

JB's method is not what I would use. While I have no way of proving it, it would seem to me that the manufacturers would be shooting themselves in the foot if they stated specs that would lead to premature failure of their rims. Based on that I believe that even the maximum tensioning spec that you would get from a manufacturer is most likely to be on the conservative side. Mavic says that 110kgF is the maximum for their rims but I have seen plenty of people state that they have far exceeded this without problems. YMMV. My point is as it has been from the start - if you use the maximum tensioning spec as stated by the rim manufacturer you should not have any problems. Peter White and many well known wheelbuilders guarantee their wheels to stand without the need for further work. These guys would go out of business in short order if they had these wheels keep coming back to their shops. Ship a wheel and see what it costs.

One question I have for you, dhk. You say you have seen over tensioned wheels fail prematurely. I am just curious when it was determined that the spokes were over tensioned? I have to speculate that either it was known to be built as such, or was measured to be so, after the failure. In the first case, a known violation of the manufacturers spec just proved what the manufacturer was telling you in the first place. In the latter, you discovered that the wheel was not built correctly to start with. Do you agree with this?

 

[artmichalek]

Ok, maximum tension - for the third or fourth time in this thread - is spec'd by the manufacturer of the rims. That's where I get that. If you like to drink Jobst Brandt's koolaid, you tension until the rim begins to warp and then back off a little - and spec's be damned. I do not, and never did, suggest over tensioning. I would define that as past the maximum recommended by the rim manufacturer. Please try to make an effort not to twist my words.

I did not say that you were suggesting over tensioning, but rather don't understand what the phrase means. Tension specs provided by manufacturers are pretty much useless. Exactly how the manufactuers come about these specifications is typically not disclosed. The manner in which forces are transfered to the rim vary with different spoke gauges and lacing paterns. If you were to build a wheel by cranking the tension up to the recomended maximum, but were using a heavier gauge spoke than the manufacturer had in mind you would in fact be over tensioning. The other thing that you're missing is that all alloy rims are eventually going to fatigue. It's a question of when rather than if. If you tension the spokes to the absolute maximum recomended by the manufacturer, then you are giving that wheel it's minimum possible life span.

 

[fish156]

I did not say that you were suggesting over tensioning, but rather don't understand what the phrase means. Tension specs provided by manufacturers are pretty much useless. Exactly how the manufactuers come about these specifications is typically not disclosed. The manner in which forces are transfered to the rim vary with different spoke gauges and lacing paterns. If you were to build a wheel by cranking the tension up to the recomended maximum, but were using a heavier gauge spoke than the manufacturer had in mind you would in fact be over tensioning. The other thing that you're missing is that all alloy rims are eventually going to fatigue. It's a question of when rather than if. If you tension the spokes to the absolute maximum recomended by the manufacturer, then you are giving that wheel it's minimum possible life span.

Well, we now all know exactly what aspect of cycling that you actually do have expertise in, and that would be backpedalling. Seems that you also seem to know more than the rim manufacturers, as well as the bona fide experts. Congratulations on your fine accomplishments. Geez, I must just be totally stupid - I thought that rims lasted forever. You learn something new every day. And, for all of you out there that are using 13 gauge spokes on road wheels, we now know that this is not what the manufacturer has in mind (duh!). Ok, I'm done wasting my time with this nonsense.

 

[dhk]

JB's method is not what I would use. While I have no way of proving it, it would seem to me that the manufacturers would be shooting themselves in the foot if they stated specs that would lead to premature failure of their rims. Based on that I believe that even the maximum tensioning spec that you would get from a manufacturer is most likely to be on the conservative side. Mavic says that 110kgF is the maximum for their rims but I have seen plenty of people state that they have far exceeded this without problems. YMMV. My point is as it has been from the start - if you use the maximum tensioning spec as stated by the rim manufacturer you should not have any problems. Peter White and many well known wheelbuilders guarantee their wheels to stand without the need for further work. These guys would go out of business in short order if they had these wheels keep coming back to their shops. Ship a wheel and see what it costs.

One question I have for you, dhk. You say you have seen over tensioned wheels fail prematurely. I am just curious when it was determined that the spokes were over tensioned? I have to speculate that either it was known to be built as such, or was measured to be so, after the failure. In the first case, a known violation of the manufacturers spec just proved what the manufacturer was telling you in the first place. In the latter, you discovered that the wheel was not built correctly to start with. Do you agree with this?

Yes, I agree. I never measured the tension on the straight 14 ga spokes after I had the wheel built by an LBS, but only noted that the spoke pitch was high on the drive side. I remember at the time I was pleased the tension was so high, thinking I'd gotten a really strong wheel build. Anyway, the rim (an MA-40) became distorted around the spoke nipples pretty quickly. Then, after around 2000 miles, it developed a crack at the outside corner, right opposite one of the distorted spokes. By the time I noticed the crack, it was already about 1/2" long, so I tossed the wheel then.

Realize from a scientific viewpoint I've got no data here, but rather just an opinion about what caused my rim to fail so soon.

 

[fish156]

Yes, I agree. I never measured the tension on the straight 14 ga spokes after I had the wheel built by an LBS, but only noted that the spoke pitch was high on the drive side. I remember at the time I was pleased the tension was so high, thinking I'd gotten a really strong wheel build. Anyway, the rim (an MA-40) became distorted around the spoke nipples pretty quickly. Then, after around 2000 miles, it developed a crack at the outside corner, right opposite one of the distorted spokes. By the time I noticed the crack, it was already about 1/2" long, so I tossed the wheel then.

Realize from a scientific viewpoint I've got no data here, but rather just an opinion about what caused my rim to fail so soon.

Thanks for your reply and, especially, thanks for being honest about it. There are others in this forum that would be well served to follow your example.

I would guess that your wheel was built by feel and a tensiometer was never used.
Gerd Schraner makes a very revealing statement in his book that, after years of building wheels by feel, he learned just how far off he was when he checked his own work with a tensiometer. Just that one statement of his earned my respect.

 

[Deanster04]

I have a set of MA40 rims on my 1969 Cinelli. They are the first clincher wheels that I ever built in 1985. I have over 25K on these wheels with no problems. I'll have to check all the spoke holes next time I do my winter tuneup. I never paid much attention, but the tension I used on these wheels was somewhat less than what I now use on my Mavic OP wheels. I just checked the relative tension after I read your post. The big difference is probably the fact that until 5 years ago I built all my wheels by "feel" (you know "ping" A440 and all that stuff). Now I am using the Park tensiometer and build the wheels at the top end of recommended Mfg tension which is pretty tight by "feel." My experience is that it makes for a better build.
The MA-40 has the steel eyelet hole but I don't remember if it is double like the Mavic OP (I'll have to check next tire change). The only problem I ever had with a spoke pulling is when I used a light rim without any steel eyelets. The wheel failed at less than 4K miles. Don't even remember the brand (Campy Montreal???). I just build with Mavic OP these days since durability is the name of the game for me.
The difference in wt between my wheels with Record hubs, DTSwiss 14/15 spokes with brass nipples and Kryserium or Cosmos wheel sets isn't worth quibbling about. But the durability differences for me at 220# are huge. I ride typically 4Kmiles each year (down considerably from my younger days) and I don't like flats nor broken spokes (I can't remember my last broken spoke).
The only thing that I see is that wheel building has made some great strides going to lighter wheels with assymetric low spoke counts by building the rim "heavier" for strength and spoke tension that is scary. There are tradeoffs in terms of angular velosity and all that physics stuff which tend to even out the weight argument. I have a friend who just bought a set of Zipp carbon rim wheels (talk about light) and he won't even let me sit on his bike for what that is worth. Lately I have been riding in some pretty wicked cross winds here in Boulder (gusts of 30 to 40mph) and I ain't sure that the Zipps (or any of the deep aero rims) would be my choice of wheel to ride.
A point of discussion in the thread is the differences between alloy and brass nipples. On a conventional build the weight difference is miniscule enough that VERY few riders would ever note any differences and most of those guys (petite) get free wheels on an annual basis so durability is a moot point.
Lots of opinions in this thread and some good thoughts and suggestions. Wheels are like anything else when it comes down to it know your design criteria and that will lead you to the best decision. And for everyone take the time to build a wheel at least one to demystify the process. Get a used wheel from someone who has a junker in the garage (offer them a sixpak) cut out the spokes and get the tools (part of every wheel builders tool kit should be a bottle of good wine and a soothing CD for background). Lots of mechanical skill and some art make a good wheel. I always say if I can do it so can you. I ain't no mechanical genius.

 

[hd reynolds]

A point of discussion in the thread is the differences between alloy and brass nipples. On a conventional build the weight difference is miniscule enough that VERY few riders would ever note any differences and most of those guys (petite) get free wheels on an annual basis so durability is a moot point.

Semi deep dish rims require long nipples. My CXP30s (32h) are built up with 'generic' alloy nipples - I don’t know the brand cause they came in unmarked plastic bag, possibly made in china and cost $7 for 36pcs. The same wheels use to have brass nipples in them and I remember being astounded by the weight difference between the 32 brass nipples and the 32 alloys. Having shaved the weight penalty imposed by the brass nipples made for a lively ride immediately felt when I first tried the wheels, obviously because this is due to the lower inertial mass.

For all intents and purposes, the wheels are solidly built in a cross 4 pattern using straight gauge DT spokes. I regularly use them for training and the occassional crit for over a year now since I converted to alloy nipples and have recently fitted them to a new bike I built up specifically for climbing. They remained true ever since.

 

[Deanster04]

yeah, I should have specified standard Mavic OP rims. You are right on the others where the nipple size is much longer. I have a set of 36H 4X 14/15 Mavic OP wheels that are my regular off road set for the brutal country roads. They are bullet proof. I know you can use 4X on 36H wheels but not 32???

Wheels and spoke tension seems to generate the most heat of all the forums I have seen to date. Interesting.

 

[hd reynolds]

I know you can use 4X on 36H wheels but not 32???

You're right Dean, they're laced cross3 and not 4x.