29ers

[Crackle]

Loving these replies. Drago can be relied on to talk about mud and the small rider, yellow saddle to talk about how the damn things don't fit into cars. I got mine in a Fiat Panda no problem, along with a load of other gear. The worst thing about that was, I didn't realize I'd hired a Fiat Panda, damn stupid hire website.

I'm quite happy with mine. I use it at trail centres and x-country. Every time I ride it it brings a smile to my face. I haven't particularly noticed the common held beliefs about not being as manoeuvrable, this is quite possibly because I'm too shoot a rider to notice. I find it easier in deep mud to keep going, I do find it smoother to ride, sooo much smoother, no real problems with wheels (Superstar) or components or geometry, I think a lot of the worst of those things were solved some time ago. I spent some time riding different bikes before I chose it, a Maxlight ff29 and they are not all the same. You can't say a 29er really, you must talk about the bike, in a way the wheel size is irrelevant. I urge you to try and compare different bikes as what you choose will depend upon what kind of rider you are and where you ride.

Are they more suited to road: Possibly. Again I don't think there's a single answer to that. My wife uses hers for commuting but I wouldn't use mine, it's set up for off road and the bars are too high and wide for road.

They do seem to polarise opinion though, as you may have noticed.

 

[Drago]

Not mentioned small riders once.

My very first post was, in essence, "it ain't all that simple, so ride one and see what you yourself think." What's so remarkable about that?

 

[Crackle]

Not mentioned small riders once.

My very first post was, in essence, "it ain't all that simple, so ride one and see what you yourself think." What's so remarkable about that?

I beg your pardon, you're quite right, it was quite reasonable a post.

 

[DEFENDER01]

Hmm thanks.
The general feeling seems to be they have no real advantage over a 26ins.
I see one the other day in my L.B.S and i must say the do look a bit monstrous.
The only advantage as i see it is once you get roiling they maintain the momentum better but you pay for that in slower get aways.

 

[marzjennings]

Have you attempted quantify the so-called "attack angle" or perhaps even attempted to define it. I would like to hear your definition.

I would also like you to explain to me (in simple English) how the inertia in a larger wheel does what you say it does.

Just to help you out I=M.R^2, a simple equation that highlights the impact of the wheel's radius on its inertia. Now I will agree that the inertia in a spinning wheel only reflects a small fraction (~2%) of the total inertia of bike and rider, but I stand by my observations that it's a fraction that can be realized while riding, especially off road.

Angle of attack is even simpler to define, see if you can get this, the bigger the wheel the easier it rolls over small obstacles on the trail. Hence why nobody mtb's with wheels from a skate board. But as mentioned there's a trade off, otherwise we'd all be on 36" monster truck wheels. 29er wheels for a given quality/material will be heavier than 26er's, making them slightly harder to accelerate, either in sprinting, braking or cornering.

I have and will keep 26ers for hard fast sprint days in the woods and likewise i will keep a 29er for long marathon rides where the advantage of straight line speed is helpful.

I'm torn about picking up a 27.5 as I'm not sure if it'll be the best or worst of 26 and 29ers.

 

[marzjennings]

I think one of the better comparative video's.
Part 1

Part 2

 

[Yellow Saddle]

just to help you out I=M.R^2, a simple equation that highlights the impact of the wheel's radius on its inertia. Now I will agree that the inertia in a spinning wheel only reflects a small fraction (~2%) of the total inertia of bike and rider, but I stand by my observations that it's a fraction that can be realized while riding, especially off road.

Angle of attack is even simpler to define, see if you can get this, the bigger the wheel the easier it rolls over small obstacles on the trail. Hence why nobody mtb's with wheels from a skate board. But as mentioned there's a trade off, otherwise we'd all be on 36" monster truck wheels. 29er wheels for a given quality/material will be heavier than 26er's, making them slightly harder to accelerate, either in sprinting, braking or cornering.

I have and will keep 26ers for hard fast sprint days in the woods and likewise i will keep a 29er for long marathon rides where the advantage of straight line speed is helpful.

I'm torn about picking up a 27.5 as I'm not sure if it'll be the best or worst of 26 and 29ers.

See if you can get this: it is far, far less than 2% because you are only looking at the difference in inertia (between 26 and 29" wheels) as a percentage of the inertia of the rider and his wheels. It seems as if Google didn't have a specific example for you.

Further, a skateboard wheel is of course absurd. Why don't you do the angle of attack calculation for the two sized wheels in discussion and then get back to us with this supposedly significant figure you so vividly imagine? I'll even allow you to toy with a reasonably large obstacle - a brick.

 

[Sandra6]

I'm no mathematician, although I do have an A grade GCSE, and I'm far from a MTB pro, but what I do know is that I took two cube analogues over the same course, a standard 26 and a 29er, and I found the 29er to be the better bike for me.
I don't know how exactly it rolled better,but it did. It also felt more stable, less twitchy and easier to take round the course. It was slightly heavier on the short, steep uphill (I tend to find myself unexpectedly dismounting over the back wheel) but with a bit of push it picks up speed and maintains it with less effort.
I use it on road with suspension locked and I'm consistently faster than on my daily hybrid.
The only way to know for sure is to do as I did and try both.
I would also like to point out 650b, or 27.5's have been around for some time, but do seem to be becoming more mainstream, as they appeal to the undecided or unconvinced.

 

[T.M.H.N.E.T]

First time ever seeing a wheelsize debate Why not test ride bikes and pick the wheelsize you like best? Ultimately nothing else matters.

 

[DEFENDER01]

First time ever seeing a wheelsize debate Why not test ride bikes and pick the wheelsize you like best? Ultimately nothing else matters.

Theres a first time for everything.
Looks like its horses for courses at the end of the day.

 

[PhilDawson8270]

But just to help you out I=M.R^2, a simple equation that highlights the impact of the wheel's radius on its inertia.

Depending on how you model the wheel,

If you model it as a hollow disc then that would be correct, but the hub and spokes account for probably half of the weight. So more accurate to model it is a solid disc rather than a hollow one.

So it would be I=1/2M*R^2 So the change of inertia by a bigger wheel will be even less.

Looked on wiggle and picked 2 pricier wheels, that seemed identical other than size.

http://www.wiggle.co.uk/sram-rise-60-29er-rear-mtb-wheel/
http://www.wiggle.co.uk/sram-rise-60-mtb-rear-wheel/

It only gives the weight as a wheel set, so lets assume that front and rear are equal and half the weights.

29er rear is 710g
26 is 665

Without tyres, 29 radius is 0.3683m
26 is 0.3302

Inertia for the 29 is 0.048 kg m^2
and for the 26 0.036 kg m^2

So while the numbers may seem small, it's actually just over a 30% increase of inertia PER WHEEL, and not a difference I would call negligible.

BUT,

See if you can get this: it is far, far less than 2% because you are only looking at the difference in inertia (between 26 and 29" wheels) as a percentage of the inertia of the rider and his wheels.

Inertia of the wheels is relevant to acceleration, deceleration, and turning. That all acts independently of momentum.

Though the momentum p = mv
Lets assume a 10kg bike without wheels, and a 70kg rider. And, a speed of just over 12mph to give an easy 5.5m/s

For the 26 you have a total weight of 81.33kg with momentum of 447.32 kg m/s
For the 29 a total weight of 81.42kg and momentum of 447.81 kg m/s

So about 0.1% difference in momentum by changing. So, in some situations it will like to have an effect. Changing direction is unlikely to be any different between the 2 wheel sizes.

Climbing hills? Climbing a steep hill at just under 8mph or 3.5 m/s?
26 is 284.66 kg m/s
29 is 284.97 kg m/s

A difference of less than 0.05% so sticking 29s on going up a hill isn't going to slow you down much.

A quick descent at 20mph ish or 8.5m/s?
26 is 691.31 kg m/s vs
29 at 692.07 kg m/s

A difference of 0.1% again.

So it seems what you gain downhill is similar or equal to what you would lose going uphill. The difference in acceleration between them would be negligible. The idea that the wheels spin up easier is flawed in that the wheel is independent of the bicycle. Stick it on a spindle and sure it will spin up and slow down quicker, but having to transmit that motion into the whole bicycle the 29" wheel isn't likely to have a massive effect.

They shown some considerable differences, but with such a small study, as he said it's statistically negligible. There are too many factors that could have accounted for the difference, course familiarity for one, more familiar with the course later on in the day when the 29" wheel was used? They didn't say in what order each run was done in? Course changes, becoming cleaner and faster throughout the day? It happens in all forms of gravel racing too.

Did they change the gearing between the different wheels? As the larger wheels will roll faster for the same gearing and cadence. A true test should have made sure that the gearing of the bike was adjusted for each wheel size.

The angle of attack works out around 2degrees ish less for the 29" wheel (I really can't be bothered typing out the differentiation, much easier on paper )

So there is an advantage for 29" wheels there, though it only works out to be an advantage of around 15mm or so. Hitting something 115mm on a 29" wheel is roughly the same as hitting something 100mm on a 26" wheel. Again, I don't think that is enough to cause a massive difference in speed, especially with suspension systems too.

It honestly doesn't seem to have any significant advantage, other than a psychological one, as with anything involving human performance. If you think you're quicker with it, you most likely will be.

 

[marzjennings]

See if you can get this: it is far, far less than 2% because you are only looking at the difference in inertia (between 26 and 29" wheels) as a percentage of the inertia of the rider and his wheels. It seems as if Google didn't have a specific example for you.

Further, a skateboard wheel is of course absurd. Why don't you do the angle of attack calculation for the two sized wheels in discussion and then get back to us with this supposedly significant figure you so vividly imagine? I'll even allow you to toy with a reasonably large obstacle - a brick.

No, I'm not wasting my time attempting to show you where you're wrong. If your position is that wheel size is immaterial and that no rider is able to perceive differences in wheel size, then your wrong. Riders can tell the difference between 23 and 25mm tyres and can then pick the appropriate tyre size for how they want to ride. Same for 26, 27.5 or 29er, there are real and tangible differences in how these wheel sizes ride and pro's and con's for each. Whether one is better than the other totally depends on the rider and where they ride, but just to repeat so you get it, differences are real and can be experienced while riding.

 

[Yellow Saddle]

Though the momentum p = mv
Lets assume a 10kg bike without wheels, and a 70kg rider. And, a speed of just over 12mph to give an easy 5.5m/s

For the 26 you have a total weight of 81.33kg with momentum of 447.32 kg m/s
For the 29 a total weight of 81.42kg and momentum of 447.81 kg m/s

So about 0.1% difference in momentum by changing. So, in some situations it will like to have an effect. Changing direction is unlikely to be any different between the 2 wheel sizes.

Even if you factor in a thin film wheel with all the mass at the circumference, the difference as a percentage of the total momentum is still negligible. And that's the most extreme example possible.

I agree that changing direction won't be different. The mass of the wheel is relatively low down compared to your COG, which is probably somewhere at your hip.

 

[PhilDawson8270]

Even if you factor in a thin film wheel with all the mass at the circumference, the difference as a percentage of the total momentum is still negligible. And that's the most extreme example possible.

I agree that changing direction won't be different. The mass of the wheel is relatively low down compared to your COG, which is probably somewhere at your hip.

My sentence structure is a little weird there. It is of course entirely negligible, I was expecting there to be a larger difference, so was preparing to prove you wrong But instead, I proved you correct, and missed that paragraph out while proof reading.

Sometimes, our own in depth analysis proves our own logical thoughts incorrect. As a mechanical design engineer, I can do nothing but believe in the numbers, maths doesn't lie.

 

[Yellow Saddle]

I can do nothing but believe in the numbers, maths doesn't lie.

The story of my life. Believing in numbers instead of anecdote gets me into a lot of trouble at dinner parties.