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The Effects of Mountain Bike Wheel Size on XC Performance

N8 v2.0

Not the sharpest tool in the shed
Oct 18, 2002
11,003
149
The Cleft of Venus
:devil:


The Effects of Mountain Bike Wheel Size on Performance in Uphill and Cross-Country Cycling
Authors: J.T. Herr and Holden S-H. MacRae
Department of Sports Medicine, Pepperdine University, Malibu, CA


Purpose: The purpose of this study was to assess the effect of wheel circumference on mountain bike performance during uphill and cross-country cycling.

Conclusion: Larger circumference wheels improve mountain bike performance during climbing and cross-country riding, with no detrimental effect on cardiovascular (heart rate) or muscle function (power output).

Summary: Our major performance outcome was time to complete each trial, since race performance is determined by who completes a given distance in the shortest possible time. The average times of the 6 cyclists tested were 4% faster (17 sec) on the uphill course, and 3% (26 sec) on the XC course when riding the 29” equipped bicycle.

If one extrapolates the duration of these trials to typical ride/race times of 1.5 or 2 hours, then it is likely that significant performance differences can accrue by riding a 29” equipped bicycle.

The practical significance of the faster course completion times of the 29” vs. 26” bicycle is illustrated by the effect size statistic for time completing the course. The effect size statistic is a calculation of the magnitude of the effect, in this case, that of riding the big wheel bicycle which was faster on both the uphill and XC trial. The number on the uphill course of 0.75, and on the XC course of 0.96, indicate a large effect from riding the 29” equipped bicycle. Most statisticians will say that a number greater than 0.5 is large. Thus, the effect here of riding the big wheel is likely very large, even though the trials were of short duration.

We attribute the faster course completion times on the 29” vs. 26” bicycle to the larger wheel traveling a greater distance per pedal revolution (average power outputs were not different between bicycles), and likely to a cumulative effect of the larger wheels rolling faster and more easily over obstacles during the uphill and cross-country trials.

The improvement in performance seen during climbing and cross-country riding with the 29” equipped bicycle, occurred without any detrimental effect on cardiovascular (heart rate response) or muscle function (sustained power output) even though the 29” bicycle was heavier that the 26” bicycle.

Presented at the South West Chapter of the American College of Sports Medicine Conference, Las Vegas, NV, November 2003
 

Westy

the teste
Nov 22, 2002
55,990
22,028
Sleazattle
I'd like to see them do the same test on some of my local trails where we have lots of things called turns and other things called sharp turns.
 

kidwoo

Artisanal Tweet Curator
Still looking for ways to pat yourself on the back regarding your purchase?

N8 said:
:devil:


We attribute the faster course completion times on the 29” vs. 26” bicycle to the larger wheel traveling a greater distance per pedal revolution (average power outputs were not different between bicycles), ]
BS.

Try switching wheels on a single speed and you see right quick the bigger wheels are tougher to turn for the same gearing. You get more gear inches out of bigger wheels with everything else the same but power output is also increased to maintain the same cadence.

N8 said:
:
and likely to a cumulative effect of the larger wheels rolling faster and more easily over obstacles during the uphill and cross-country trials.
True dat.
 

Angus

Jack Ass Pen Goo Win
Oct 15, 2004
1,478
0
South Bend
Westy said:
I'd like to see them do the same test on some of my local trails where we have lots of things called turns and other things called sharp turns.
Dude , really I can handle the twisties on a 29er, that bad cornering thing is just a myth, I have raged on some real tight technical single track that gave me trouble on 26"er....
 

N8 v2.0

Not the sharpest tool in the shed
Oct 18, 2002
11,003
149
The Cleft of Venus
MunkeeHucker said:
Dude , really I can handle the twisties on a 29er, that bad cornering thing is just a myth, I have raged on some real tight technical single track that gave me trouble on 26"er....
We have some extremely tight twisty switchbacks here and no 29er has a problem... perhaps it's lack of skills..???
 

cirKus

Monkey
I've ridden a moots 29r soft tail for a weekend last time I was in Flagstaff, Az. They actually ride well. Not so good on fast winedy decents. I had a cool two gear inter BB shifting cluch mecanism. Good, I still like standard 26 better
 

urbaindk

The Real Dr. Science
Jul 12, 2004
4,819
0
Sleepy Hollar
Westy said:
I'd like to see them do the same test on some of my local trails where we have lots of things called turns and other things called sharp turns.
Here you go: http://www.more-mtb.org/forum/showthread.php?t=3044 (I believe this is Elizabeth Furnace)

These guys (all on 29ers) tried riding the same switch back over and over again about a dozen times and none of them could do it. It was really pathetic.
 

kidwoo

Artisanal Tweet Curator
N8 said:
Who's actually spent time on one..?
I've ridden a few gary fishers. One sugar and one hardtail.

They do roll over things better. But going faster as a result of greater wheel circumference translating to greater distance traveled per pedal stroke without increasing power output is impossible. You're turning a bigger lever with the hub.
 

N8 v2.0

Not the sharpest tool in the shed
Oct 18, 2002
11,003
149
The Cleft of Venus
kidwoo said:
I've ridden a few gary fishers. One sugar and one hardtail.

They do roll over things better. But going faster as a result of greater wheel circumference translating to greater distance traveled per pedal stroke without increasing power output is impossible. You're turning a bigger lever with the hub.

Seems like some Monkey needing a college research project could tackle this one...
 

Westy

the teste
Nov 22, 2002
55,990
22,028
Sleazattle
29ers have their place. Big dudes, why not increase the size of the wheel with the bigger bikes, the power-weight won't be affected much anyway.

Wide open trails. I would have loved to have had a 29'er when battling the rock gardens at Seven Springs last year.

As someone who values quick handling and acceleration for 90% of my riding I'll stick to 26" wheels.

Actually you could have ****loads of data proving 29ers as better but until Fox makes an XC fork capable of running one I wouldn't even consider it.
 

kidwoo

Artisanal Tweet Curator
N8 said:
Seems like some Monkey needing a college research project could tackle this one...
A high school kid in a basic physics class is all that's needed.

The top part of your cog (or cassette) is working at a given radial distance from the center part of your hub......the short end of a lever. The radius of the wheel is the long part of the lever (center of the axle is the fulcrum) to be moved. Lengthen that and you need a greater force at the short end to produce the same radial velocity in revolutions per time for a given load. Your leverage is decreased by that extra length.

Saying you can keep that velocity the same between two different wheel sizes with no change in input force is just wrong. The author you quoted assumes this same rotational velocity which is where his/her assumption of greater horizontal distance per wheel revolution comes from. It happens if the velocity is the same but you won't get that with the exact same power input.
 

LordOpie

MOTHER HEN
Oct 17, 2002
21,022
3
Denver
since gear inches or efficiency is related to wheel size, yeah, bigger wheels are better and when it comes to mtbing, they roll over obstacles a little smoother.

That said, bigger wheels are heavy, ceterus paribus.

Maybe 29" is the ideal size for most riders?

I'd think 27" is the ideal since roadie Tour riders have the backing to produce something else, but don't. Yeah?
 

OGRipper

back alley ripper
Feb 3, 2004
10,735
1,247
NORCAL is the hizzle
cirKus said:
29er is basically a road wheel diameter with an mtb tire on it. 29er is the diameter of the wheel and tire incl.
Yeah they are basically just beefy cyclocross bikes. I read somewhere that it was a marketing thing - they decided to go with 29 instead of 27 or 700c to distance themselves from road weanies. Who knows but it didn't work so well - instead they just created a new category of weanie. :p
 

Angus

Jack Ass Pen Goo Win
Oct 15, 2004
1,478
0
South Bend
N8 said:
We have some extremely tight twisty switchbacks here and no 29er has a problem... perhaps it's lack of skills..???
N8, do you even read other people's post in your threads?
Your bashing me when I am supporting your statement, I am fully capable with skills that would probally shame you and I ONLY ride 29er's, so before you go a post a flame, read the post first, DINGLEBERRY
 

N8 v2.0

Not the sharpest tool in the shed
Oct 18, 2002
11,003
149
The Cleft of Venus
MunkeeHucker said:
N8, do you even read other people's post in your threads?
Your bashing me when I am supporting your statement, I am fully capable with skills that would probally shame you and I ONLY ride 29er's, so before you go a post a flame, read the post first, DINGLEBERRY
I am just messing with ya... :D

Sorry the humor didn't transmit that well... ride on!

Oh, and no, I don't read what others usually write... just dont have time!
 

BikeGeek

BrewMonkey
Jul 2, 2001
4,577
277
Hershey, PA
jdschall said:
These guys (all on 29ers) tried riding the same switch back over and over again about a dozen times and none of them could do it. It was really pathetic.
Two of them made it on the second filmed attempt and the third, on the blue bike, is riding fixed-gear. :confused:
 

Reactor

Turbo Monkey
Apr 5, 2005
3,976
1
Chandler, AZ, USA
First, I'm noticing this was a sports medicine paper. While there are some good sports medicine people, a lot of them have feathers and a green stripe around their neck. As an engineer, there is not much of difference between a 26 and 29" wheel, things like a clean chain, or a good hub will make more of a difference.

To me it's more important to have a ready supply of good components. 29'er tires are scarce, often special order items, 29'er wheels aren't built as strong , to reduce the weight from having a larger wheel. I like having a good selection of tires, wheels and forks. And to be perfectly honest, a 3% or 4% difference, even if it were true, wouldn't help me win a race. I can count on my crossmax or XM819 wheels to hold together if I take a brutal line.

If you like the 29'er ride it with pride, during the super bowl, of course.
 

blue

boob hater
Jan 24, 2004
10,160
2
california
I'm with Westy's Fox assertion...and it really doesn't matter. It's sort of like shaving 200 grams off your bike's weight by buying the $400 pedals instead of the $100 ones...It's far more worth it to make yourself faster than deal with the hassles of bigger wheels. Fast, long descents through tight singletrack here are death on 29ers...I've tried...
 

ridetoofast

scarred, broken and drunk
Mar 31, 2002
2,095
5
crashing at a trail near you...
heres a thought

ride'm both and have fun on either

last time i checked its still just a bike and the objective is to...are you ready for this...have fun

concering the fox thing, ive got a reba on my fisher and it works just fine for me. im not a huge proponent (sp?) of rox shox, but so far i couldn't be happier and i ride that bike hard, im not huge at 220, but im sure as hell not little, and that fork works just fine.

as long as im riding and the bike works well, i could care less if its 26 or 29 or 24.
 

ito

Mr. Schwinn Effing Armstrong
Oct 3, 2003
1,709
0
Avoiding the nine to five
blue said:
I'm with Westy's Fox assertion...and it really doesn't matter. It's sort of like shaving 200 grams off your bike's weight by buying the $400 pedals instead of the $100 ones...It's far more worth it to make yourself faster than deal with the hassles of bigger wheels. Fast, long descents through tight singletrack here are death on 29ers...I've tried...
That's just because you aren't technically proficient.

:p

Meh, big wheels are fun, but they suck to jump on. Good for singlespeeding and rigid, but my race bike will be 26er. I'm short and can't get the geometry I want without toe overlap on a 29er. I imagine I will be just as fast on either of them.

The Ito
 

brungeman

I give a shirt
Jan 17, 2006
5,170
0
da Burgh
I am part in agreement and part in disagreement with this whole thread.
#1 29'er is not for everyone... the first thing I noticed on mine was I needed to exert more effort to get the thing up to speed. I feel myself getting faster though. and after getting used to a completely new bike with foriegn frame geometry etc. I am just as fast as before if not faster.
#2 as for Technical riding, there isn't anything that I cant ride on my 29'er. as a matter of fact I can make it over larger logs now cause the angle of attack, and dismount is minimalized.
#3 I am a person that relies on a quick burst of energy to get up or over tricky stuff. I am as able now after riding the bike for 8 to 10 rides to get that burst with it.

and yes it does roll over stuff REAL well!!!
not for everyone though!!!

JUST RIDE WHAT YOU LIKE:)
 

manhattanprjkt83

Rusty Trombone
Jul 10, 2003
9,660
1,237
Nilbog
Listen to the brungeman, he is wise people...Last time we were out riding he was acting like he was on a trials bike but infact he was aboard the too nyne.
 

DNA

The human raccoon
Jan 31, 2003
1,443
0
NH
N8 said:
We have some extremely tight twisty switchbacks here and no 29er has a problem... perhaps it's lack of skills..???
:rolleyes:

* Cough * bull * cough *

I distinctly remember someone on his 29er NOT making some of the switchbacks that someone else did on his regular ol' mountain bike when riding the Monkey Trail.

:blah:
 

N8 v2.0

Not the sharpest tool in the shed
Oct 18, 2002
11,003
149
The Cleft of Venus
DNA said:
:rolleyes:

* Cough * bull * cough *

I distinctly remember someone on his 29er NOT making some of the switchbacks that someone else did on his regular ol' mountain bike when riding the Monkey Trail.

:blah:

That's cuz I've got no skillz...

:p
 

DNA

The human raccoon
Jan 31, 2003
1,443
0
NH
N8 said:
That's cuz I've got no skillz...

:p
Or is it because I have MAD skillz? No, that's not it.

To paraphrase Eydie Gorme, I blame it on the 29er. :D