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Why are asymmetrical rims not more popular?

12219 Views 18 Replies 11 Participants Last post by biketuna, Jun 20, 2009

spookygeek

Discussion Starter · Jun 16, 2009

I grabbed a cheap set of Ritchey OCR discs off ebay a few months ago and just last weekend got around to building them up. While this is my first wheel build, and I am by no means an expert, it seems that the asym rim solves one of the most important and age-old problems with spoked wheels - even tension. Per Spoc Calc If my wheels were built with a regular symmetrical rim the left side spokes would have 33% less tension than the right spokes. Using the Ritchey OCR rim this discrepancy drops to only 19%. With an even greater off-set one could achieve even tension. My question for the wheel building populace is that if even spoke tension is the holy grail of wheel building why is the solution (asymmetry) not more popular?

Thanks,

-Brent

1 - 19 of 19 Posts

mtnbiker72

· #2 · Jun 16, 2009

The only thing I can tell you (having been a mechanic at a Trek dealer for many years and been around Bontrager Asym Rims) is that while in theory it creates a stronger wheel...I just never really saw that in reality. My experience was that handbuilt wheels using quality rims (like Mavic) were just as durable. The fact that Mavic (or DT, Sun, WTB, etc.) never jumped on the Asym bandwagon tended to back this up.

Nothing wrong with asym rims, but I just don't think they make that much of a difference.

Uncle Six Pack

· #3 · Jun 16, 2009

spookygeek said:
I grabbed a cheap set of Ritchey OCR discs off ebay a few months ago and just last weekend got around to building them up. While this is my first wheel build, and I am by no means an expert, it seems that the asym rim solves one of the most important and age-old problems with spoked wheels - even tension. Per Spoc Calc If my wheels were built with a regular symmetrical rim the left side spokes would have 33% less tension than the right spokes. Using the Ritchey OCR rim this discrepancy drops to only 19%. With an even greater off-set one could achieve even tension. My question for the wheel building populace is that if even spoke tension is the holy grail of wheel building why is the solution (asymmetry) not more popular?

Thanks,

-Brent

I would imagine that it is an even trade-off-the more offset, the more you balance spoke tension... but then with more offset, the rim itself will not have forces evenly distributed.

I am no expert, so take it for what it is worth.

Mike T.

· #4 · Jun 16, 2009

I've had asym rims and I've had lots of non asym rims. Asym rims cured nothing because I've never had a problem with rims due to them NOT being asym. Maybe it's a solution looking for a problem.

This is what happened to my asym rim. And this has never happened to one (of mine) that wasn't asym -

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Monte

· #5 · Jun 17, 2009 (Edited)

Mike T. said:
I've had asym rims and I've had lots of non asym rims. Asym rims cured nothing because I've never had a problem with rims due to them NOT being asym. Maybe it's a solution looking for a problem.

This is what happened to my asym rim. And this has never happened to one (of mine) that wasn't asym -

Sorry Mike, I can't leave it be. You aren't implying what it sounds like you are implying, are you? :nono:

Nah, I didn't think so. :thumbsup:

Mike T.

· #6 · Jun 17, 2009

Monte said:
Sorry Mike, I can't leave it be. You aren't implying what it sounds like you are implying, are you? :nono:
Nah, I didn't think so. :thumbsup:

I'm not sure what I was implying!

Dan Gerous

· #7 · Jun 17, 2009

mtnbiker72 said:
The fact that Mavic (or DT, Sun, WTB, etc.) never jumped on the Asym bandwagon tended to back this up.

Well, Mavic do have asymetric rims on some prebuilt wheels. My rear Ksyrium rim on my cross bike is offset and apparently the disco-machined Crossmax SLR are too, front and rear... But, like most, I think offset rims sound good in theory but in the real world, they don't seem to change anything. I know that never happens in the cycling world but I suspect it could very well be more of a marketing thing than anything.

JmZ

· #8 · Jun 17, 2009

spookygeek said:
I grabbed a cheap set of Ritchey OCR discs off ebay a few months ago and just last weekend got around to building them up. While this is my first wheel build, and I am by no means an expert, it seems that the asym rim solves one of the most important and age-old problems with spoked wheels - even tension. Per Spoc Calc If my wheels were built with a regular symmetrical rim the left side spokes would have 33% less tension than the right spokes. Using the Ritchey OCR rim this discrepancy drops to only 19%. With an even greater off-set one could achieve even tension. My question for the wheel building populace is that if even spoke tension is the holy grail of wheel building why is the solution (asymmetry) not more popular?

Thanks,

-Brent

I'm a fan. YEARS ago I went through two wheels in a season. (One was stock on the bike, the other was a mail order deal). I was riding XC, on a hardtail, in Ohio, so even my 200 lb arse shouldn't have been that much of a problem.

I had a wheel custom built that summer with ASYM, and I'm still riding that wheel at over 10 years later. It's now on a back-up bike, but it's still around.

I was tweaking and bending rims pretty regularly back then, and talking to the builder, he suggested an asym rim for a more even and higher tension than the other wheels had. I bought into it, and bought it. My wheels lifespan increased on that day. Part of it was due to being handbuilt vs machine built - I'm positive of that, but also sure that the ASYM helped out. I figure my riding style didn't change overnight to become easier on my wheels.

I've gone from having issues with rear wheels staying round and true to the front wheels. The fronts have been from crashes or overriding (mental note, when the guy on the free ride bike talks about some neat jumps, don't try to keep up on a bike with 1500g wheelset.)

I've built my own wheels for the most part since the early 2000's and have had pretty good luck with both regular and asym wheels. For rear's I still prefer the asym rims. Normally it has little or no weight penalty and it does help to equalize the tension. Used Bontragers, Ritchey, and Velocity.

I'm finally going to need to relace a rear wheel, but it's due to rock strikes, not out of round or true. It's been several years since I had to do that, and the last one was a front wheel (see comment above about following freeriders).

JmZ

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mtnbiker72

· #9 · Jun 17, 2009

Part of it was due to being handbuilt vs machine built - I'm positive of that

I would argue that ALL of it was due to being a handbuilt wheel

meltingfeather

· #10 · Jun 17, 2009

Mike T. said:
Maybe it's a solution looking for a problem.

I agree. Without a problem to solve, the theoretical benefits are questionable.

JmZ said:
Part of it was due to being handbuilt vs machine built - I'm positive of that, but also sure that the ASYM helped out.

I'd venture to say that all of it was due to the quality hand build vs. machine-built stock stuff.

spookygeek

Discussion Starter · #11 · Jun 17, 2009

So if the argument is made that asymmetrical rims create no stronger a wheel than any comparable quality symmetrical rim then does it disprove the idea that even spoke tension is essential to a well-built wheel? Or it may just mean that the loss of strength due to unevenly tensioned spokes is negligible at best or perhaps simply not a controlling factor in creating a strong long-lasting spoked wheel?

My only concern with this line of thought is that the long standing argument of "hand-built" wheels being superior to machine-built wheels is 100% based upon the premise that a hand-built wheel has more of an even tension, after all what other difference could there be with identical components? Maybe the relative tension of a spoke to all other spokes on its half of the rim is a much more important factor in wheel strength, than relative tension in spokes from left-to-right.

-Brent

Mike T.

· #12 · Jun 18, 2009

spookygeek said:
So if the argument is made that asymmetrical rims create no stronger a wheel than any comparable quality symmetrical rim

I don't think anyone is claiming that assymetrical rims don't make a stronger wheel.

then does it disprove the idea that even spoke tension is essential to a well-built wheel? Or it may just mean that the loss of strength due to unevenly tensioned spokes is negligible at best or perhaps simply not a controlling factor in creating a strong long-lasting spoked wheel?

I wonder what the ratio of non-assymetrical wheels to assymetrical wheels is? Millions to one? And for most situations most of the time they're strong enough. Collapsing wheels isn't a plague.

My only concern with this line of thought is that the long standing argument of "hand-built" wheels being superior to machine-built wheels is 100% based upon the premise that a hand-built wheel has more of an even tension, after all what other difference could there be with identical components?

There could be the relief of stresses, windup, bedding of parts (elbows, nipples).

Maybe the relative tension of a spoke to all other spokes on its half of the rim is a much more important factor in wheel strength, than relative tension in spokes from left-to-right.

I think you got it!

meltingfeather

· #13 · Jun 18, 2009

spookygeek said:
So if the argument is made that asymmetrical rims create no stronger a wheel than any comparable quality symmetrical rim then does it disprove the idea that even spoke tension is essential to a well-built wheel?

No. I think you are taking one point and confusing it for the sake of argument. In wheels with dish, the left- and right-side tensions are always different. The evenness of the spoke tension per side is generally what people talk about when they talk about even spoke tension. I also don't think anyone said asymmetrical rims don't (in theory) create a stronger wheel... only that symmetrical rims build strong enough wheels, so the extra strength (if it is there... see below) is not a material benefit (for those of you who have read my posts on spoke strength, does this sound familiar?

).

spookygeek said:
Or it may just mean that the loss of strength due to unevenly tensioned spokes is negligible at best or perhaps simply not a controlling factor in creating a strong long-lasting spoked wheel?

No. Again, I think you have confused two things: the uniformity of tension on each side of a wheel and the balance of tension left-to-right. Wheels with even tension stay true longer, that is a well known fact.

spookygeek said:
My only concern with this line of thought is that the long standing argument of "hand-built" wheels being superior to machine-built wheels is 100% based upon the premise that a hand-built wheel has more of an even tension, after all what other difference could there be with identical components? Maybe the relative tension of a spoke to all other spokes on its half of the rim is a much more important factor in wheel strength, than relative tension in spokes from left-to-right.

Yes. Your last sentence got it. There are also a few differences that make good, hand-built wheels are far better than machine-built.
I think this is another case where the theory has gotten well out in front of reality on a sort of myopic tangent. First, if there were a problem with symmetrical rims failing all the time and it was attributable to unbalanced tension right-to-left, it would make sense to look at asymmetrical rims as a part of a solution. However, there is no plague (nice word) of failing symmetrical rims, so as has been pointed out, there is no need for a solution.
Another crucial point that has been (almost) completely neglected here are the inherent problems with designing a rim to take an eccentric (off center) load. As the picture Mike posted points out, the 'longer' side of the rim becomes more vulnerable the further it is from support. That can't be neglected and has to be balanced against any gain in overall wheel strength as a result of the asymmetry using engineering analysis.

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spookygeek

Discussion Starter · #14 · Jun 18, 2009

OK, I'm convinced, my next set of rims will be symmetrical rims.

I'm jumping on the bandwagon that while asym rims create a "technically" stronger wheel, in actual use they do not really solve any current problem. I think it was hit upon earlier that asym rims are a solution looking for a problem, hanging their hat on a negligible incremental increase in strength (while introducing moment stresses to the rim itself). Sometimes you have to just talk it out to get your head around an issue.

Thanks.

highdelll

· #15 · Jun 18, 2009

I like round rims
asymmetrical is too bumpy and lumpy
and its a b!tch with all the different spoke lengths

mtnbiker72

· #16 · Jun 18, 2009

Highdell...your confusing asymmetric with eccentric :thumbsup:

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highdelll

· #17 · Jun 18, 2009

mtnbiker72 said:
Highdell...your confusing asymmetric with eccentric :thumbsup:

does that wheel go on this bike?

:yikes:

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reformed roadie

· #18 · Jun 19, 2009

HAY-OH!

That is awesome!

biketuna

· #19 · Jun 20, 2009

My bontrager asym rear has lasted over ten years. I will order a Velocity asym next.

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