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69er's?

Old 06-30-07, 10:44 PM
  #1  
zephyr16
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69er's?

so who makes a good 69er bike? im looking for a complete or frame only, and so far the only one i've been able to find was the Trek 69er. i like the idea behind 69ers, but there doesnt seem to be an abundance or **** out there. is it possible to stuff a 29inch wheel in a 26inch fork, and if so what will that do to my ride?
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Old 06-30-07, 11:27 PM
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Carver makes the original. Next year there will be two more complete Trek 69ers. Ask questions at the 69er board on mtbr.com for more information.
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Old 07-01-07, 10:07 AM
  #3  
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Use a 29er fork. I dont think it will mess up the bike too bad. Its has been done before.
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Old 07-02-07, 10:01 AM
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Originally Posted by Little Leo
Use a 29er fork. I dont think it will mess up the bike too bad. Its has been done before.
If you put a 29er suspension fork on a 26er frame it will jack up your head tube angle. In an area where people debate about single degrees, this is a HUGE deal. Good handling 29ers actually have steeper head tube angles then 26ers intended for the same purpose. You're going in the opposite direction.

You can put a suspension corrected 26" RIGID fork on the bike and this should fit a 29er wheel. It won't jack the angles up nearly as badly (remember, you'll still have an extra 1.5" between the axel and the ground). But that is STILL pretty bad as you're going the opposite direction you should.

If you want to go 69er, buy a 69er frame. Though honestly, I see little benefit to a 69er beyond allowing for more suspension clearance. The "greater inertia" often cited by with just a little knowledge of physics (but not enough) is actually the difference in gearing between a larger wheel and a smaller wheel. I can ramp my XT/Rhynolite 29er front with 2.35 tires mounted up to 7mph with just a flick up my pinkie finger. The "slow acceleration" argument is just a fundamental misunderstanding of gearing.
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Old 07-02-07, 04:46 PM
  #5  
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not the pinky finger thing again .. I though that was disproved
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Old 07-03-07, 12:14 PM
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Originally Posted by DirtPedalerB
not the pinky finger thing again .. I though that was disproved
Really? Then perhaps you can explain how a muscle group hundreds of times weaker then those in your legs can easily accelerate a "heavy" wheel to typical MTB speeds in an instant while the much larger/stronger group apparently has great difficulty.

Please ... explain this my friend. Apparently the weight weenies are surrounded by a special aura that allows them to take everything completely out of context while maintaining a straight face.

Granted, this is not an empirical argument. But I've never heard one in which people did not take the system out of context by ignoring the entire mass of the system including the rider and non-rotating bicycle parts.
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Old 07-03-07, 10:54 PM
  #7  
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I'll have to look through the archive, but in the mean time I'll be pushing a car tire with my pinky.

the only place you can really feel extra weight on a bike is in the rear tire/wheel.. you have to pay for the weight there twice you have to spin it up and carry it with you the 26er has the advantage here.. after acceleration the rolling resistance comes into play. which may favor the 29er.

I'm not even going to look up the archive thread, because I'm sure you were proved wrong and have forgotten already.
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Old 07-04-07, 09:18 AM
  #8  
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Originally Posted by DirtPedalerB

the only place you can really feel extra weight on a bike is in the rear tire/wheel.. you have to pay for the weight there twice you have to spin it up and carry it with you the 26er has the advantage here..
Two times a really small number is still a really small number.

The energy required to accelerate the ENTIRE system including non-rotating bike parts and the rider dwarfs that of spinning the wheels. People "feel" all kinds of things that aren't there, especially when they're expecting to feel it (placebo effect).

A little bit of knowledge can be a bad thing. It's very easy to misapply a principle (rotational inertia) when you don't know how to work it into context. If a bicycle consisting solely of two spinning wheels with a phantom frame and ghost rider, you'd would be 100% corret. However, it isn't. I can get that heavy wheel up to 7mph with my pinkie, but my pinkie wouldn't help me accelerating the entire bike system (including my fat ass) up to 7mph. For that I need the big powerful muscles in my upper thighs and torso as the power required to get all that up to 7mph is quite a bit more then spinning a wheel.

Tell you what. Chew on this statement for a while:

There are no two 10# dumb-bells in any gym that weigh the same.

Debunk the claim above and you will have discovered why what you're saying is indeed technically correct, but effectively misleading.
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Old 07-04-07, 06:28 PM
  #9  
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I like the idea of the 69er. The bigger front wheel can roll over things easier and smoother. The rear wheel being smaller in diameter, will take less power to turn. MX bikes have used this setup forever.
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Old 07-04-07, 08:23 PM
  #10  
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The bigger rear wheel not only adds weight but you feel the extra resistance of the greater tire "foot print" because a tire with a larger circumfrence has a longer contact patch with the ground.
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Old 07-05-07, 05:43 AM
  #11  
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Originally Posted by pdq 5oh
I like the idea of the 69er. The bigger front wheel can roll over things easier and smoother. The rear wheel being smaller in diameter, will take less power to turn. MX bikes have used this setup forever.
Handling and steering may be slightly more difficult with a 29" vs. 26" front wheel, I don't know if I would like it.
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Old 07-05-07, 05:50 AM
  #12  
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Originally Posted by iwantakona
The bigger rear wheel not only adds weight but you feel the extra resistance of the greater tire "foot print" because a tire with a larger circumfrence has a longer contact patch with the ground.
Ahhh, I guess you've discovered why they use 622mm rims in road bikes. They all wanted the greater resistance associated with a longer contact patch. </sarcasm>

If you've tried it and found "greater resistance in the rear", what you were really experiencing is the difference in gearing between a 29er and a 26er.

Originally Posted by trek1
Handling and steering may be slightly more difficult with a 29" vs. 26" front wheel, I don't know if I would like it.

This all has to do with the geometry of each particular bike. I think if you tried them you would find a 29er wheel no more "difficult" to steer then any other as the task of turning a the wheel is VERY overwhelming compared to the strength in pretty much everybody's arms.
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Old 07-05-07, 08:02 PM
  #13  
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I give up ... any wheel you can push with your pinky is ok with me.
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Old 08-14-07, 09:20 PM
  #14  
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Originally Posted by zephyr16 View Post
so who makes a good 69er bike? im looking for a complete or frame only, and so far the only one i've been able to find was the Trek 69er. i like the idea behind 69ers, but there doesnt seem to be an abundance or **** out there. is it possible to stuff a 29inch wheel in a 26inch fork, and if so what will that do to my ride?
You can convert a classic 26 to a 69er. I did to my 1994 Gary Fisher Aquila. All I needed was a 26" suspension corrected rigid Bontrager fork to mount a 29 inch wheel in the front. It looks weird but it actually rides quite well. Its a whole different animal from a 26 or a 29 and combines the best of the two approaches.
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Old 08-14-07, 09:23 PM
  #15  
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just take the axle to crown length of a 26inch bike, then get a 29er rigid fork with a sligtly smaller axle to crown length and add a 29 inch wheel and you shoul then have a similar head angle, i am about to do that
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Old 08-14-07, 09:31 PM
  #16  
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Originally Posted by willtsmith_nwi View Post
There are no two 10# dumb-bells in any gym that weigh the same.
They all weigh the same if you're measuring them with your pinky finger.
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Old 08-14-07, 09:41 PM
  #17  
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Originally Posted by zephyr16 View Post
is it possible to stuff a 29inch wheel in a 26inch fork, and if so what will that do to my ride?
Maybe. What tire size/mud clearance are you after?

38x700C cross tires fit my 26" hardtail just fine. If I had disc hubs I'd use them, which may be my next project.
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Old 08-15-07, 08:16 AM
  #18  
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Originally Posted by willtsmith_nwi View Post
Two times a really small number is still a really small number.

The energy required to accelerate the ENTIRE system including non-rotating bike parts and the rider dwarfs that of spinning the wheels. People "feel" all kinds of things that aren't there, especially when they're expecting to feel it (placebo effect).

A little bit of knowledge can be a bad thing. It's very easy to misapply a principle (rotational inertia) when you don't know how to work it into context. If a bicycle consisting solely of two spinning wheels with a phantom frame and ghost rider, you'd would be 100% corret. However, it isn't. I can get that heavy wheel up to 7mph with my pinkie, but my pinkie wouldn't help me accelerating the entire bike system (including my fat ass) up to 7mph. For that I need the big powerful muscles in my upper thighs and torso as the power required to get all that up to 7mph is quite a bit more then spinning a wheel.
Ah, the old "scientists are idiots" aka "physics is for suckers" argument.

That being said, on a mountain bike it probably doesn't make a whole lot of difference.
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Old 08-15-07, 08:30 AM
  #19  
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No, the opposite ...

Originally Posted by GV27 View Post
Ah, the old "scientists are idiots" aka "physics is for suckers" argument.

That being said, on a mountain bike it probably doesn't make a whole lot of difference.
No, those are the opposite (contradiction) of my arguments. What I would say using you words is:

"idots are not scientists" and "physics is not for suckers".


I'm not saying that anyone here is an idiot. I'm saying that they are mis analyzing systems by considering the part without the whole. It's easy to over-apply a limited understanding.
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Old 08-15-07, 10:46 AM
  #20  
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Actually, in most cases I think they're just overestimating the magnitude of the problem. So I think you're both wrong, really. It definitely DOES make a difference. It's just a matter of how much of a difference.

On a road bike you can really feel it if you go from lightweight climbing wheels to a deep section aero wheel. The climbing wheels just feel a lot snappier. But it's fairly subtle. It's not a matter of "I can climb that on climbing wheels but not on aero wheels", just a subtle "the bike feels a little more nimble on the climbing wheels".

That being said, the pro road racers use a wide variety of wheels - not just the super light climbing wheels. Why - well, that goes back to the old "it depends". It depends on the terrain, what sort of race it is, etc. If you're on a flat time trial, not only does the aero advantage of a full-disc wheel outweigh the weight penalty, but once you get that full disc up to speed it has it's own momentum helping to keep it up to speed and roll over undulations in the road. Then theirs the gear issue. I have about the lowest granny available on my bike and I need all the help I can get!


Now on an XC mountain bike it's a little more complicated but the same principles apply. Yes, the 29" wheel is going to be a little heavier and that weight is going to be a little further from the hub. But you still have big balloon tires, big knobs, etc. So either way you have quite a bit of "mush" in the system. Then you're going over rocks, ruts, logs, etc where a heavier wheel might be more desirable for rolling over and through that stuff - just like a TT disc can be desirable on an undulating TT course. So in some situations the 26" might be desirable, in some the 29".

I don't get how the bigger footprint is a disadvantage for the 29" wheel - in a lot of situations that's going to be an advantage - more tread on the ground = more traction. Plus footprint is going to be impacted a lot more by the type of tire you run and how much pressure.

I'm not sold on 29" wheels by any stretch. I don't see them being much of an advantage and probably the advantages and disadvantages balance out. I'm fine with my 26" wheels. But the bottom line is I just don't think it makes a heck of a lot of difference.

Last edited by GV27; 08-15-07 at 11:00 AM.
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Old 08-15-07, 11:03 AM
  #21  
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I'm pretty sure my legs aren't strong enough to even move a 29" wheel.
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Old 08-15-07, 06:21 PM
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Originally Posted by gastro View Post
They all weigh the same if you're measuring them with your pinky finger.
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