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Discussion Starter · #1 · (Edited)
Still a big fan of 26" wheels, and believe they are better than 29er's! Even though I've never ridden one and never will!

NOTE: This thread was broken off from one in the all-mountain forum. The statement above should be taken in context of all mountain and technical trail riding.

EDIT: So, I feel that this question has been answered. No one can make a coherent, fact based arguement on the measureable technical merits of 29" wheels for all mountain riding, while there are many more facts that tell us the 26" is better - weight, strength, stiffness. While the anecdotal evidence presented in favor of 29er's is interesting, personal opinion is too easily biased.
 

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Discussion Starter · #2 ·
Here's an interesting article discussing the weight vs. inertia of the various wheel sizes:

Educating the Debate ? Part I - NSMB.com

He calculates a 29er wheel taking about 12% more energy to accelerate to 10 m/s vs. an equivalent 26" wheel. You would have to drop roughly about a pound off the weight of the 29er wheelset to get back to a wheel that accelerates comparably to the 26". This seems like it would be expensive and/or decrease the strength of the wheel and the tire's capablities.
 

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29ers or 26ers?

You'll notice he doesn't claim any one size is superior or inferior. And that hasn't kept him from designing some well-regarded aggressive 29ers that have manners consistent with his designs for other wheel sizes.
 

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Here's an interesting article discussing the weight vs. inertia of the various wheel sizes:

Educating the Debate ? Part I - NSMB.com

He calculates a 29er wheel taking about 12% more energy to accelerate to 10 m/s vs. an equivalent 26" wheel. You would have to drop roughly about a pound off the weight of the 29er wheelset to get back to a wheel that accelerates comparably to the 26". This seems like it would be expensive and/or decrease the strength of the wheel and the tire's capablities.
He also says it takes the same amount of extra energy to stop the 29er compared to the 26". Harder to accelerate but retains momentum better. Give and take.

In fact probably the most important thing he says, over and over again, is that it's all subjective to the trail conditions, tyre choice and pressure.

Most rational people can agree that both 26" and 29" have pros and cons. Pick the one with the pros you want most and then set that bike up in such a way as to nagate it's cons as best you can, then ride the bloody thing till it becomes so natural to you that you forget what all the fuss was about in the first place.
 

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Here's an interesting article discussing the weight vs. inertia of the various wheel sizes:

Educating the Debate ? Part I - NSMB.com

He calculates a 29er wheel taking about 12% more energy to accelerate to 10 m/s vs. an equivalent 26" wheel. You would have to drop roughly about a pound off the weight of the 29er wheelset to get back to a wheel that accelerates comparably to the 26". This seems like it would be expensive and/or decrease the strength of the wheel and the tire's capablities.
The thing to remember about any metric filled anything is that it fails to take into consideration joy of user experience. I personally ride a fat front 29er and my front wheel/tire combo weights 1.5 times what my rear 29er wheel/tire combo but dammit do I love riding with it. It is such a fun thing to ride with that my brain just files away the obvious acceleration issues, as well as the manualling issues and the sheer effort of hefting it over rocks or fences or even off my car because I just love riding it. Every so often I put my other 29er front wheel on and for a short time I love the light weight and the fast acceleration and the manuals (oh how it manuals) but it isn't as much fun and since I measure my rides in smiles and not m/s and joules it really doesn't matter.

That is what you are missing here. It isn't about the physics it is about the fun and I can't think of a discipline that is more about fun then AM riding because it is what we used to call mountain biking before we got it all segmented and such.
 

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Discussion Starter · #6 ·
He also says it takes the same amount of extra energy to stop the 29er compared to the 26". Harder to accelerate but retains momentum better. Give and take.

In fact probably the most important thing he says, over and over again, is that it's all subjective to the trail conditions, tyre choice and pressure.

Most rational people can agree that both 26" and 29" have pros and cons. Pick the one with the pros you want most and then set that bike up in such a way as to nagate it's cons as best you can, then ride the bloody thing till it becomes so natural to you that you forget what all the fuss was about in the first place.
Right......this thread is about which wheel size is better for all mountain, and I'm presenting evidence that a 26" is easier to accelerate and deaccelerate. I would argue that having a bike that deaccelerates well is very important for all mountain, such as braking for a corner.

Very rarely have I ever said I needed a bike that "held it's speed in a straight line" better. Try riding a 45lb+ old school DH "plow bike" with 10 lb forks, 2.7 tires and 1 lb MX tubes (yes, walked into a MX shop and bought them)....brings new meaning to carrying speed through anything.
 

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Thank god we're finally openly debating this important issue. I can't wait for this discussion to be resolved, once and for all.
 

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Right......this thread is about which wheel size is better for all mountain, and I'm presenting evidence that a 26" is easier to accelerate and deaccelerate. I would argue that having a bike that deaccelerates well is very important for all mountain, such as braking for a corner.

Very rarely have I ever said I needed a bike that "held it's speed in a straight line" better. Try riding a 45lb+ old school DH "plow bike" with 10 lb forks, 2.7 tires and 1 lb MX tubes (yes, walked into a MX shop and bought them)....brings new meaning to carrying speed through anything.
You're not even trying to be realistic with your comparisons, are you?

Also, the "deceleration" as you put it, in the article is referring to the loss of momentum caused by trail features and has nothing to do with braking, of which the minor differences of rotational weight between a 29" and a 26" would be lost in the more than adequate stopping power of a modern disk brake.
 

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Discussion Starter · #9 ·
You're not even trying to be realistic with your comparisons, are you?

Also, the "deceleration" as you put it, in the article is referring to the loss of momentum caused by trail features and has nothing to do with braking, of which the minor differences of rotational weight between a 29" and a 26" would be lost in the more than adequate stopping power of a modern disk brake.
Sorry, I don't follow. Wheel moment of inertia is always a factor when riding a bike. How is it that extra moment of inertia now a "minor difference" when braking and accelerating (in contrary to 30+ years of MTB tech development, btw), and a "distinct advantage" when rolling across rugged terrain? I've ridden some VERY heavy wheels, and they do some things very very well, but I would not want to all mountain on them.
 

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The guys calculations are wrong. I will prove it in a post later, but read some of the comments after the article. Weight matters, but moment of inertia due to increased radius does not. 29er wheels rotate more slowly which cancels the inertia effect. The myth about "slower to spin up to speed" are a myth.
 

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Discussion Starter · #11 ·
The guys calculations are wrong. I will prove it in a post later, but read some of the comments after the article. Weight matters, but moment of inertia due to increased radius does not. 29er wheels rotate more slowly which cancels the inertia effect. The myth about "slower to spin up to speed" are a myth.
Nope. They are not wrong Steve. Please review them again.
 

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It's simple really.

29ers have a number of factors which make them better than 26ers at some things and
26ers have a number of factors which make them better than 29ers at some things.
Adding those factors up in a way that supports the way you ride is called personal preference.
Adding those factors up in a way that supports your chosen stance, on the other hand, is called politics.
 

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Sorry, I don't follow. Wheel moment of inertia is always a factor when riding a bike. How is it that extra moment of inertia now a "minor difference" when braking and accelerating (in contrary to 30+ years of MTB tech development, btw), and a "distinct advantage" when rolling across rugged terrain? I've ridden some VERY heavy wheels, and they do some things very very well, but I would not want to all mountain on them.
You are missing the point, it's the size not the weight of the 29" wheel that allows it to keep momentum over the rougher sections compared to the 26". But as I've tried to say already and the guy in the article says again and again, these are minor differences and are far less important than things like tyre choice and pressure and I'd add bike geo and design so stop trying to put me on the other side of your 29 vs 26 pointless debate as I've said most rational people can accept the pros and cons of both and use them to make the right choice for their needs.
 

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Re: 29ers or 26ers?

You are missing the point, it's the size not the weight of the 29" wheel that allows it to keep momentum over the rougher sections compared to the 26". But as I've tried to say already and the guy in the article says again and again, these are minor differences and are far less important than things like tyre choice and pressure and I'd add bike geo and design so stop trying to put me on the other side of your 29 vs 26 pointless debate as I've said most rational people can accept the pros and cons of both and use them to make the right choice for their needs.
The radius also increases the effect of weight.

Sent from my LG-LS995 using Tapatalk
 

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Nope. They are not wrong Steve. Please review them again.
I have some advice for you turbodog,
If you like your bike that's fine. If you want to convince yourself that nothing is better than your 20 year old mongoose your dad bought you, well, you are wrong. If you want to prove that there is a "best" wheel size, well, smarter people than you have determined that there is no one single best size.
So like what you like, and quit trying to fight a losing battle.

Also, Since you have insulted my new bike, and my Colorado front range trails, its time for you to post up pictures of your bike and your trails so we can see the awesomeness that is behind all your arrogance.

Pictures please!

Finally, I am an engineer and I know how to do the energy calculations referred to in that article you posted. So, don't try and tell me whether they are right or wrong when you have no idea.
 

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I said I will offer proof that wheel diameter doesn't effect energy to accelerate, so now I will provide it. By the way, this is from an old post of mine, as you can imagine this subject has been beaten to death a few thousand times on this forum in the past.

Put some energy into a wheel to make it roll and that energy is converted to translation and rotation.
The equation for translational energy plus rotational energy looks like this:

E = ½mv² + ½Iω²

I’m going to use moment of inertia I = mr², as for a hoop or hollow cylinder, and ω= angular velocity (rad/sec), which is related to translational velocity for a rolling wheel (not slipping) by ω= V/r (1 rotation = 2pi radians and circumference =2pi*r)

Substituting:
E= ½mv² + ½mr²ω²
E= ½mv² + ½mr²( v²/ r²)

Notice the r²’s cancel out in the second term and you are left with

E=mv²

So, you can see the energy it takes to get a wheel up to certain translational velocity depends on its mass! (There is no radius in the equation, because for bigger wheels, the r in higher moment of inertia canceled the r in the lower angular velocity).

More mass more energy. Higher velocity, more energy. The size of the wheel doesn’t matter!

As for the mass, the article used 90 grams more weight for 29er wheels. considering the mass of bike plus rider, that is only a difference of .2 or .3 percent weight. A water bottle makes more difference, as was pointed out in the comments following the article.

Physics aside, all you have to do is ride a 29er to know that these "slow acceleration" claims are false. Riding a 29er, by the way, is something that turbodog has never done :lol:
 

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Discussion Starter · #17 ·
I said I will offer proof that wheel diameter doesn't effect energy to accelerate, so now I will provide it. By the way, this is from an old post of mine, as you can imagine this subject has been beaten to death a few thousand times on this forum in the past.

Put some energy into a wheel to make it roll and that energy is converted to translation and rotation.
The equation for translational energy plus rotational energy looks like this:

E = ½mv² + ½Iω²

I’m going to use moment of inertia I = mr², as for a hoop or hollow cylinder, and ω= angular velocity (rad/sec), which is related to translational velocity for a rolling wheel (not slipping) by ω= V/r (1 rotation = 2pi radians and circumference =2pi*r)

Substituting:
E= ½mv² + ½mr²ω²
E= ½mv² + ½mr²( v²/ r²)

Notice the r²’s cancel out in the second term and you are left with

E=mv²

So, you can see the energy it takes to get a wheel up to certain translational velocity depends on its mass! (There is no radius in the equation, because for bigger wheels, the r in higher moment of inertia canceled the r in the lower angular velocity).

More mass more energy. Higher velocity, more energy. The size of the wheel doesn’t matter.
As for the mass, the article used 90 grams more weight for 29er wheels. considering the mass of bike plus rider, that is only a difference of .2 or .3 percent weight. A water bottle makes more difference, as was pointed out in the comments follwoing the article.

Physics aside, all you have to do is ride a 29er to know that these "slow acceleration" claims are false. Riding a 29er, by the way, is something that turbodog has never done :lol:
Cool man, sorry you're so bent out shape.

But that still doesn't make r = r or m = m.....! You are wrong.

Please review the web page in question again. We're talking about a 12% difference, or the 29's wheels needing to be about 1 lb lighter (in his example) to be equivalent.

I also find it amusing you think that you're better educated and more experienced than me.
 

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Cool man, sorry you're so bent out shape.

But that still doesn't make r = r or m = m.....! You are wrong.

Please review the web page in question again. We're talking about a 12% difference, or the 29's wheels needing to be about 1 lb lighter to be equivalent.

I also find it amusing you think that you're better educated and more experienced than me.
If r isn't in the equation than it doesn't matter if r=r.
And M does matter I already addressed that.

Still waiting for pictures of your cool bike on your cool trails. And throw in your in your resume of qualifications.


Pictures!
 

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Discussion Starter · #19 ·
If r isn't in the equation than it doesn't matter if r=r.
And M does matter I already addressed that.

Still waiting for pictures of your cool bike on your cool trails. And throw in your in your resume of qualifications.


Pictures!
Your math is wrong. Please review your equations. r =/= r!

Oh, and I can ride less than a mile from my house and be on terrain considerably more challenging than yours. Sorry.
 
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