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Exactly 1/2 of 2-Epic
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Discussion Starter #1
I posted this over on the 29er board, will probably get a proper public beating, but what the hell. My inquisitive nature won't be denied.

This talk of 29ers being more efficient, faster in most circumstances...well, every single argument I've heard is purely subjective. That's a problem because 29ers are so damn fun to ride. One caveat is the study cited on the GF site, but they aren't exactly impartial ;)

I'm taking matters into my own hands. I've got a 26er and a 29er, both with power tap hubs (thanks MC). Anyone that has trained with power knows that alls you can do is alls you can do - so one potential test is to choose a ~ 1 hour course and blast away with one bike, recover a day or two, then do it on the other bike. Power Tap provides the data of exactly how many kJ it took to ride that loop. Comparing kJ for similar power outputs over identical routes should reveal something...

Anybody ever try this? Any recommendations on experiment setup?

After riding the 29ers for half of the '05 season, my hunch is that there is a good bit of variability between courses/bikes. The 29ers rocked at 24hoMoab, but sucked at the Durango 100. I've already compared a fireroad climb between all bikes: 32' on the Fuel, 35' on the Dos, and 38' on the 292, but these rides were before I had the PM for the 29er so no power comparisons. In all fairness, the road was driest/fastest on the day of the Fuel trial - results inconclusive.

More to come, stay tuned.
 

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Harmonius Wrench
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Different horses for different courses

hairball_dh said:
I posted this over on the 29er board, will probably get a proper public beating, but what the hell. My inquisitive nature won't be denied.
Ha! No beating from me! Sounds like a perfectly fine test to me

After riding the 29ers for half of the '05 season, my hunch is that there is a good bit of variability between courses/bikes. The 29ers rocked at 24hoMoab, but sucked at the Durango 100.
It looks like this is where you're going to end up. Some instances will favor the big wheels, and some the smaller. I think the scales tip toward the twentynine inch wheels the larger you are. At a certain height/ weight, twentysix inch becomes rediculus, no matter what you ride. Don't ask me to draw that line, though! That will really get you beaten! ;) I know that for me, twentynine inch wheels are WAY better than the smaller wheels ever were. I can't really find any reason to go back, and I have plenty of 26 inch wheel mountainbikes sitting in the basement that aren't going to get ridden anymore! I have only one 29"er now, and I hope to get my grubby hands on more. I'm convinced it's better- for me, your mileage may vary! Good luck on that test! I'll be watching for your results!
 

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My gloves stink
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It's about time!

hairball_dh said:
I'm taking matters into my own hands. I've got a 26er and a 29er, both with power tap hubs (thanks MC). Anyone that has trained with power knows that alls you can do is alls you can do - so one potential test is to choose a ~ 1 hour course and blast away with one bike, recover a day or two, then do it on the other bike. Power Tap provides the data of exactly how many kJ it took to ride that loop. Comparing kJ for similar power outputs over identical routes should reveal something...

Anybody ever try this? Any recommendations on experiment setup?

More to come, stay tuned.
Kudos to you for trying to be scientific and objective about it! The fact is that almost everything we read and hear about bikes is entirely subjective. About the best we get are comparisons by one person who has experience with several competing products. But even in those cases, a useful, objective evaluation metric is usually missing. I wish the MTB press would try to take a more rational approach to product and design evaluation, rather than the usual "this bike rocks, dude!". Be sure to let us know what you come up with.

On an entirely subjective note, I've been riding a 29er HT for about 3 years. A little while back I took my son's I-Drive out for several rides, and had so much fun I now have a 26 FS on order. I sure like the way I can rev up those little wheels so quickly. My plan is to ride the 29er in races or hardcore training, and ride the 26 for fun.
 

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Hup, Hup
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Eddie O said:
Waiting patiently for the results.

Eddie O
I'll almost second that. You have definately got my interest since I am on the edge of purchasing a new ride for 2006 and am undecided on a new 26er or going with a 29er. Excited and impatiently waiting fo results.
 

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Exactly 1/2 of 2-Epic
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Discussion Starter #6
Enthusiasm is appreciated

But results will be slow in coming. It'll take quite some time to gather enough data to make any sort of "strong" statements.

Stay tuned though, it'll be worth it. Just don't wait for the results to make a decision - it may not be until spring as I live in Colorado and winter is just around the corner, making testing difficult. I can certainly do some pavement testing...but that might not tell us anything valuable.
 

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Exactly 1/2 of 2-Epic
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Discussion Starter #7
Score: 26": 1; 29": 0

I finally got around to comparing two identical rides ridden on different bikes. The route was 4 Peaks road in AZ, hwy 87 to hwy 88 & back. Pretty much dirt road climbing, a little sand and some rocky sections & plenty of ATV dust.

As you might imagine, the results are not overwhelmingly in favor of either - but the edge goes to the 26" wheels. Full details are at http://teamhealthfx.com/blogs/dave_harris/archive/2006/01/02/309.aspx.

If you want to dig in to more of the details yourself, let me know and I'll make the power files for both rides available.

I'm not posting this to the 29er board, cause, well they probably don't care. 29ers are a blast - but that's not what's at issue here. On this board I'm assuming its performance (ie speed) we're after.

More techy singletrack testing to come in due time.
 

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Roadies have already been through this a decade ago

In road circles the question was 650C or 700C wheels. These aren't exactly the same as 26" and 29" wheels, but they are close and the principle is the same.

650C wheels put the rider down lower and present a smaller profile of wheel. They are more aero. However, they carry less momentum and are generally considered worse for climbing, they wear out tires faster, and they have higher rolling resistance.

The triathalon scene is definitely departing the 650C and are switching en mass to 700C. The fad is over and they have determined that 700C is generally better.

One thing about your experiment. I think that seeing what wattage you could put out on both wheelsets would be misleading at best. Your wattage is your wattage. If you can put out X watts on a 26" wheel you will also be able to put out X watts on a 29" wheel. The question is what does X watts get you. I would suggestan comparing identical wattages and resulting speeds. Ie, over the same course and the same wattage see what your speed was. This would tell you your efficiency in terms of MPH/watt, the real question here.

Another question is whether 29" is the ideal. What about 30"? 31"? 50"? I doubt anyone has done any scientific testing has been done that shows what the ideal balance of rolling resistance, strength, and maneuverability is. 29" is just a MTB tire strapped onto a 700C rim. If 29" is better than 26", all we know is that bigger is better. There has to be an upper limit, but where? Someone needs to get a high roller and strap some knobby tires to it and take her off road. . .
 

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hairball_dh said:
I finally got around to comparing two identical rides ridden on different bikes. The route was 4 Peaks road in AZ, hwy 87 to hwy 88 & back. Pretty much dirt road climbing, a little sand and some rocky sections & plenty of ATV dust.
.
Very interesting test.

The only problem is that Kj of output do not tell the whole story for the human anatomy, as our output is highly non-linear. For road racing it is less of a factor, as you can just set the right cadence. For MTB, the power spikes when rolling over obstacles may be a much larger factor.

That what seems to be the selling point of 29r - rolling over obstacle easier means smaller spike in force - not less work performed.

It would be interesting to see the RMS variability of the power output. Raw time series available? :D

Also - 2% of difference can easily be explained by slight variations in riding position. Did you try to optimize? If you do a lap with a 15mm longer stem for example, what would be the difference?

P.S. Personally - I am sold on 29r as a hardtail - for something rougher then what a cyclocross bike can handle. Also gives an option to put on road/CC tires. Not sold on FS 29r.
 

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Is it play time yet?
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Interesting

I know you are looking purely at efficiency, but the improved traction and stability still make me grab my 29er. These are again somewhat subjective traits and I happen to think they are real. When the ride gets long I like to lean on my equipment a little bit more :D .
 

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Exactly 1/2 of 2-Epic
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Discussion Starter #11
This isn't my final word...

Please don't take this as a wholesale knock on 29ers. I've been riding them exclusively since July while the Fuel gathered dust...the 29ers are a blast, no doubt about it.

Also, this test only looks at climbing steep dirt/sandy roads. It doesn't deal with the traction part, or obstacle clearance, or singletrack for that matter.

KJs are essential to endurance racers. You can put only so many for the long haul.

The 29er vs 26er isssue is not comparable to 700 vs 650 road wheels - although it might be for this particular test.

What the test did show, however, was that climbing steep dirt roads is slightly better on the 26er. Absolute speed/watt was higher for the 26 inch wheels *even though the 29er was lighter*.

This is really validation of my hunches. I bought into the 29er movement hook, line and sinker (and two bikes :)), but lately have begun to think they don't climb as well. That's a biggie for me as most of my racing is in the Rocky Mountains.

Now if the course in question was one sandpit after another (like MCs domain), I'm fairly certain there'd be a different conclusion.
 

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climb
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hairball_dh said:
Also, this test only looks at climbing steep dirt/sandy roads. It doesn't deal with the traction part, or obstacle clearance, or singletrack for that matter.

KJs are essential to endurance racers. You can put only so many for the long haul.

What the test did show, however, was that climbing steep dirt roads is slightly better on the 26er. Absolute speed/watt was higher for the 26 inch wheels *even though the 29er was lighter*.

This is really validation of my hunches. I bought into the 29er movement hook, line and sinker (and two bikes :)), but lately have begun to think they don't climb as well. That's a biggie for me as most of my racing is in the Rocky Mountains.
Dave,

The only think I can summerize from your findings is that you were able to 'output' more KJs on the Fuel vs the Dos. Let's say 1.75% on average :)... I was feeling the same way last year (2005) when I switch to a 29er. I felt slower on the 'big' climbs.

For me I think it was because of what you have observed, I wasn't willing to put out as much energy on the 29er as the 26er, probably because of the 'acceleration' of the larger rims.

So this is what I did to compensate, I moved to a harder gear, I swapped the 12-34 cassette for a 11-32 cassette. This has kept me from getting 'lulled' to sleep in granny gear. I can also ride the same amount of terrain, and my 'feeling' of being slower has diminished.

I made these changes based on my experience racing on a team at the 24-hours of steamboat. The next races I did I felt much more inline with my 26er climbs. Keep in mind that I have no intentions of ever standing on a podium, and I'm not looking to shave off seconds to place... Just an observation from someone else who likes riding the 29ers...

They are the best for Moab :)...
 

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Exactly 1/2 of 2-Epic
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Discussion Starter #13
jl said:
Dave,

The only think I can summerize from your findings is that you were able to 'output' more KJs on the Fuel vs the Dos. Let's say 1.75% on average :)... I was feeling the same way last year (2005) when I switch to a 29er. I felt slower on the 'big' climbs.
Interesting...but this isn't the case. The first ride (on the 29er) was my first ride at lower elevation since coming down to AZ from CO, and I just didn't want to put myself in the hurt locker on ride#1. I had more available power - just didn't use it. For that matter I didn't pin it on the Fuel run either - but did ride harder in general as it was the last day of a training block. FYI: overall ride time on the Fuel was 14 minutes faster.


jl said:
For me I think it was because of what you have observed, I wasn't willing to put out as much energy on the 29er as the 26er, probably because of the 'acceleration' of the larger rims.

So this is what I did to compensate, I moved to a harder gear, I swapped the 12-34 cassette for a 11-32 cassette. This has kept me from getting 'lulled' to sleep in granny gear. I can also ride the same amount of terrain, and my 'feeling' of being slower has diminished.

I made these changes based on my experience racing on a team at the 24-hours of steamboat. The next races I did I felt much more inline with my 26er climbs. Keep in mind that I have no intentions of ever standing on a podium, and I'm not looking to shave off seconds to place... Just an observation from someone else who likes riding the 29ers...

They are the best for Moab :)...
Thanks for the comments. That's an interesting perspective. My reaction was the opposite. When I got a 292 it felt waaaay overgeared (duh - first event was DGO 100 MTB) and I went scrambling for a crankset that would accept 20/30/40 combos to more closely mimick the XTR 26er gearing I was accustomed to. Made a huge difference for me...I'm a spinner type of rider.
 

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Why not compare 26"/29" to 650C/700C?

hairball_dh said:
The 29er vs 26er isssue is not comparable to 700 vs 650 road wheels - although it might be for this particular test.
Why?

Two sizes of road wheel, two sizes of MTB wheel. Seems like an apples to apples comparison to me.
 

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Harmonius Wrench
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With All Due Respect

hairball_dh said:
Interesting...but this isn't the case. The first ride (on the 29er) was my first ride at lower elevation since coming down to AZ from CO, and I just didn't want to put myself in the hurt locker on ride#1. I had more available power - just didn't use it. For that matter I didn't pin it on the Fuel run either - but did ride harder in general as it was the last day of a training block. FYI: overall ride time on the Fuel was 14 minutes faster.
These comments from you seem to cast serious doubt on your findings. I find it hard to be convinced either way at this point.
 

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climb
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hairball_dh said:
Interesting...but this isn't the case.
This is the case. I looked at your blog, and your power was 2.03% greater with the Fuel on the first climb, and 1.53% higher on the second climb. So why was you power output greater on the Fuel than the Dos--that's the question you should be asking. A 14 minute difference sound more 'mental' to me than 'physical.'

hairball_dh said:
Thanks for the comments. That's an interesting perspective. My reaction was the opposite. When I got a 292 it felt waaaay overgeared (duh - first event was DGO 100 MTB) and I went scrambling for a crankset that would accept 20/30/40 combos to more closely mimick the XTR 26er gearing I was accustomed to. Made a huge difference for me...I'm a spinner type of rider.
Durango is a killer ride, I haven't even tried it because the climbs look so brutal. Anyway, I wasn't talking about the 'crankset' I was talking about the cassette. I geared up the rear cassette to keep me from getting too lazy... I figured I should be able to handle 2 teeth...
 

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jl said:
This is the case. I looked at your blog, and your power was 2.03% greater with the Fuel on the first climb, and 1.53% higher on the second climb. So why was you power output greater on the Fuel than the Dos--that's the question you should be asking. A 14 minute difference sound more 'mental' to me than 'physical.'
Again, someone's power is not going to be effected by their wheel choice. It will be determined by their fitness, how tired they are, what they ate the morning of, whether they are motivated for the day, etc. The only significant bike related aspect to power is the rider's position on the bike. Assuming the geometry of the 26" and 29" bikes are identical, wheels are irrelevant to how much power the rider can put out.

In fact, if someone put out more power on a given ride but had the same overall speed, it would indicate that more watts were needed to maintain the same speed. In other words, that the setup was less efficient. For the same speed more watts is bad, not good.

Watts are indirectly like horsepower. If one car takes 20 horsepower to go 65 mph, and another car takes 30 horsepower, you would assume that the car which required 20 horsepower was lighter and more aerodynamic. It took less effort to maintain the same speed.

And it takes energy to keep up the horespower. A car that requires 20 horsepower to maintain 65 mph is very likely going to use less gas per mile than a car which requires 30 horsepower. Think Geo Metro vs Suburban. The Geo Metro has a smaller engine which works less hard and consumes less fuel per given distance.

So if you are riding along and need 2% more watts to maintain the same speed on the bike, it isn't that the bike's wheels are somehow energizing your legs to put out more watts. It is that the bike's wheels are REQUIRING more watts from your legs to maintain the same speed. You worked harder for the same result.

Again, the way to measure this is to take a given terrain and maintain speed, measuring watts needed to maintain. Grass/rocks/hill/etc at 100 watts on 26" wheels, same terrain at 100 watts on 29" wheels. Which had a higher speed. The wheel with the higher speed but identical wattage would be the more efficient. Wattage should not be a variable in this test, but should be fixed. Speed is the variable.
 

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Pardon my arrogance...

But aren't 26-ers most of the time better at climbing than 29-ers? 26" wheels are essentially lower gearing. One would think that thats what you want when you're climbing. I don't understand how bigger wheels equate to climbing better...anybody want to explain this to me?

-PB
 

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Morlahach said:
Speed is the variable.
Thinking about it, it seems to me that tires rolling resistance may be a deciding factor here.

Schwalbe has a interesting graph on their site indicating that wider tires at the same pressure have up to 10W lower rolling resistance then a narrower tire. Also, Specialized tires are quite bad in the rolling resistance department, judging from a bunch of tests mentioned around these forums.

I would venture to guess 2.0 (is that right) Specialized can easily have 5W more rolling resistance then Panaracer and Weirwolf.

My (only somewhat educated) guess though, is that 29er and 26 should need about exactly the same power to cover the same distance with the same speed on the same type of tires, and the difference for me is in the comfort/suitability for conditions department. I would not buy a hardtail with 26 wheels anymore - but would gladly have more travel achievable on an 26" bike with the same geometry constraints.
 
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