habe ich mal vor paar monaten zusammengestellt.
Question: Quick and dirty, give me a list of 29" vs. 26", which wins where, concept-wise?
Rolling resistance (by some 10%)
Bearing resistance and wear (by some 10%)
Tire wear (by at least 10%)
Roll-over stability climbing and descending
Overall comfort over a ride
Grip and cornering balance
26" Pro's :
Weight (300-400g lighter on the complete hardtail bike, all else being equal)
Due to this weigth advantage : faster acceleration, by around 2%
Wheelies are easier, the front lifts more easily.
Flickability in extremely tight corners (where walking would actually be faster)
Wheel stiffness, at least when using hubs of equal flange spacing
Why bother about wheel size?
What are the effects of wheel size?
Can I go faster with bigger wheels?
Is stability better with big wheels?
Is grip different?
Is energy better preserved with big wheels?
Is the need for suspension less with big wheels?
Are big wheels more comfortable?
Why is safety claimed to be higher with big wheels?
Are big wheels only for big people?
What type of riding are big wheels for?
What measure is the wheel size referring to?
Which bike parts are wheel size specific?
Are 29" wheeled bikes expensive?
Are big wheels heavy?
Does wheel size affect gearing?
Does wheel size affect braking?
Does wheel size affect maneuverability?
Are big wheels weaker?
Are all wheel sizes legal in races?
So, should I go 29"?
Q: Why bother about wheel size?
Your mountainbike's wheel size affects how you ride. It affects how efficiently you can ride in off-road terrain, and it affects the bike's handling. It affects your ride's entire feeling.
Most stock mountainbikes come in a handful different "sizes", by which all have the same wheel size. You can typically not change a bike's wheels to others of another size, since the entire frame geometry depends on the wheel size. Bigger wheels will generally not fit, and smaller wheels will have you strike the pedals to the ground. Therefore your very first step when choosing a mountainbike should be to decide which wheel size you want.
The effects that wheel size has to your ride can be described by their nature. It is then much up to you to value these effects, depending on your preferences and priorities.
Q: What are the effects of wheel size?
>From off-road, cross-country riding point of view, big wheels are different from small wheels in two important technical aspects: The angle of attack for the wheels against obstacles is smaller, and the contact area with the ground is longer.
Those two differences translate into a number of real riding benefits, depending on your type of riding and what is important to you. The benefits are higher speed capability, better stability, better grip, better energy conservation, less need for suspension, higher comfort, and a safer ride.
The main benefit with small wheels is that they make it easier to design a frame for a small person.
As a first illustration of the different benefits of big wheels and small wheels, you may try to imagine an adult riding with 12 inch wheels off-road, or a child learning to ride with 29 inch wheels.
Q: Can I go faster with bigger wheels?
Bigger wheels roll easier over rough terrain. That is probably the most important benefit with bigger wheels. Some go further and say "big wheels roll easier on flat ground also", but even if there may be some truth in that, it is not equally intuitive and general scientific evidence is yet to be seen.
One reason that bigger wheels roll easier over rough terrain is that their angle of attack towards obstacles, small as big, is less. Put in other words, they are not as hindered by stones, roots, and rough ground as small wheels are. Another reason to the lower rolling resistance may be that they due to the longer contact area with the ground are staying on top of the ground better - the deeper you sink, the more speed you lose.
With easier rolling, or lower rolling resistance, it becomes possible to ride at higher speed since more of your power output is available to increase speed when less is needed to overcome rolling resistance.
The benefit with low rolling resistance may very well be underestimated in off-road biking. There are few studies on rolling resistance for different MTB tire types, materials, knob patterns, air pressures, and wheel diameters, and even fewer that also takes into account real-life terrain types and variations. Weight, by comparison, has in the bike business a tremendous focus, which might be simply because it is so easy to measure, although the realistic effect of a weight difference at off-road riding is not by far equally straightforward to try to determine. Many riders are positive that the lower rolling resistance of big wheels helps them go faster much more than any weight savings do.
Can we accurately quantify this advantage in rolling resistance? Probably not. Again, any derivation attempt quickly gets complex. Nevertheless, there have been some tests with tires rolling against one single surface (such as asphalt or steel), actual bikes rolling down a hill, or people riding with measuring devices for heart rate or oxygen consumption. These tests may all provide numbers, but those sure will be prone to be questioned.
Q: Is stability better with big wheels?
Bigger wheels have a longer contact area towards the ground, and they tend not to bounce as much on rough ground due to their lower angle of attack to obstacles. As a result, big wheels are perceived as more stable than small wheels, especially on rough terrain. Such higher stability provides better comfort and a safer ride, and may allow higher speed.
Q: Is grip different?
Again, bigger wheels have a longer contact area with the ground. Some feel that they get a better grip that way, enabling them to corner, brake, climb, and accelerate faster and more confidently.
Q: Is energy better preserved with big wheels?
The rider is going to be able to preserve energy better because bigger wheels roll with less resistance, less vertical oscillation, and less abrupt hits. Less rolling resistance spares your power output. Less vertical movement and less abrupt hits spares not only your arms but your whole body. This is particularly advantageous at long-time riding, such as in marathons and 24-hour events.
Q: Is the need for suspension less with big wheels?
Many riders are feeling that the smoother ride of bigger wheels allows less suspension. For example, among riders with 29 inch wheels, some are choosing hardtail instead of full-suspension, some are comparing an 80 mm 29" fork with a 120 mm 26" fork, and some are feeling that a rigid fork is a smoother ride with 29" wheels than with 26" wheels.
Q: Are big wheels more comfortable?
The ride is more comfortable with big wheels for the same reason as why energy is better preserved. The bigger wheels are not hitting rocks and roots as hard as small wheels do, because of the smaller angle of attack. Also, the bigger wheels are not finding their way as deep down between every rock and root and into every cavity, as small wheels do. As a result, the rider will not have to work as hard with arms and legs, acting as springs, for smoothening the ride.
Q: Why is safety claimed to be higher with big wheels?
Higher safety has been brought up as an advantage with 29 inch wheels. A couple of reasons why some feel safer with them, may be that the bigger wheels roll more stable and are less prone to be abruptly halted by obstacles, making it less likely for the rider to go over the handlebars.
Q: Are big wheels only for big people?
Everyone can experience the benefits with bigger wheels. That is what we all do several times during our grow-up, when we step up from 12" wheels to 16" wheels, from 16" to 20", and so on. The maximum practical wheel size is mainly determined by your body size. You must be allowed to sit in your preferred position and still have enough space for your desired front fork and enough clearance between feet and front wheel, to name a few aspects. The biggest size mountainbike wheel commercially available today is 29 inch. There is no exact minimum rider size for which 29 inch wheels fit, but there are size Small (around 16" frame size) production mountainbikes with 29 inch wheels, and short persons saying they fit them well, and custom frames in even smaller sizes.
Bigger people seem to be over-represented among riders with bigger wheeled mountainbikes. Consider that the height of a 180 cm (5'11") rider is proportionally to 26" as the height of an average height 165 cm (5'5") rider to 24" wheels, and then ask yourself how many average size riders choose 24" wheels for mountainbiking. Some claim that just looking at the proportions of an extra-large frame with 26" wheels says something.
In terms of body properties, not only the rider's height is important when choosing wheel size, but also the weight. Heavier riders have found the bigger wheel longer contact area with the ground give them better support, just like a heavier person benefits with longer skis.
Q: What type of riding are big wheels for?
Most of what is said here regards general off-road riding. Considering the properties of bigger wheels, they would certainly seem to have some benefits also in hardcore downhill riding, at least for the front wheel. For general-purpose street or commuter bikes, bigger wheels than 26" have since long been common, and in many parts of the world even the norm.
Q: What measure is the wheels size referring to?
"29 inch" is a mountainbike marketing denomination, a label, for tires and rims with 622 mm bead seat diameter. Another, much older and more common label for the same diameter is "700c", which is used in the road bike world. Yet another label used for the same bead seat diameter is "28 inch", which is used in some countries for street and hybrid tires. Thus, ISO 47-622 (47 is the width in mm), 700x47c, 28x1.85", and 29x1.85" are theoretical different denominations for the same tire, fitting "29 inch" rims. The labels "29 inch" and "700c" do not specify anything about a rim's measures other than the bead seat diameter, such as width, height, or intended brake type. You will need to find that information separately.
The "29" in "29 inch" refers to an approximate outer diameter of a typical mountainbike tire labeled about 2.1" wide. With a 2.1" mountain bike tire being about 55 mm tall from the bead seat, the actual outer tire diameter is (622+55+55)/25.4 = about 28.8 inches. Similarly, "26 inch" is a label for 559 mm bead seat diameter rims and tires. With the same tire height, actual tire diameter is (559+55+55)/25.4 = around 26.3 inches. So the difference between "26 inch" and "29 inch" is in reality two-and-a-half inches.
Q: Which bike parts are wheel size specific?
The parts that depend on wheel size are frame, fork, rims, tires, and tubes. Add spoke and rim tape length to be specific. Then gears and brakes may also be chosen different size, but they are not "wheel size specific" in the same sense.
Q: Are 29" wheeled bikes expensive?
Price is higher for 29" wheeled bikes, because the 29" specific parts are still made and sold in much smaller quantities than their counterparts for 26" wheeled bikes. So you are likely going to have to pay more for an equal-quality equipped 29er, or accept some lower-level components for a given amount of money.
Q: Are big wheels heavy?
Weight is a common objection to bigger wheels. So how much extra weight are we talking about, and how big effect does it have?
As an estimate, the weight difference between one 29" wheeled bike and one 26" wheeled bike with some kind of similar component quality level, can be over 1000 g for low-end bikes but doesn't have to be more than 500 g for high-end race bikes. The difference is expected to decrease, since there are yet no hyper-light versions of some of the 29" specific parts. The geometrical differences in frame, fork, rims, tubes, tires, and spokes, call for a theoretical, overall race-weight difference of about 300 g. To put this in perspective, the total weight for bike plus rider is around 90,000 g with an average 80 kg rider.
Another reason why 29 inch wheeled bikes tend to be heavier than the 26 inch counterpart is that the 29" specific parts are more expensive due to the smaller market and production volumes. Since they are more expensive, a given amount of money that could buy you a high-end, lightweight 26" part may sometimes only buy you a mid-end, heavier 29" part.
Some people are worried about the fact that most of the extra weight is in the wheels, increasing "rotational weight". All bike weight, rotational and non-rotational, affects your ride in two major aspects: acceleration and climbing. Additional weight in tires and tubes counts from acceleration point of view as an extra approximately 90% compared to "fixed" bike weight and an extra 70% for rims, but just as any weight from climbing point of view. But of course if you accelerate at a climb, there is still the acceleration penalty. For example, a 50 g heavier tire affects acceleration as much as 95 g on the frame does. Whether that heavier tire is 26" or 29" doesn't matter - it is the weight that matters, not the diameter itself. Another example: when climbing at constant speed, an extra 50 g in a tire feels exactly as much as an extra 50 g on the frame does (there is no constant speed riding is real life, but close).
So what practical effect does this extra 0.5% rider-and-bike weight have? The theoretical answer seems to be, from calculations on simplified conditions, that it would slow your race time down a number of seconds...if you didn't have the 29" wheels rolling advantages.
As a last note on weight, the same extra energy you need to put into a heavier bike to get it up to speed, may then help you keep that speed. It takes more to brake a higher momentum, which may then help keeping speed over rough ground and at downhill sections.
Q: Does wheel size affect gearing?
The distance that you travel by one pedal revolution depends on the front ring, the rear cog, and the rear wheel diameter. A 29 inch wheel has about 10% bigger outer diameter than a 26 inch wheel, with average 2.1" tires, resulting in a "heavier" gearing if you would run the same front ring and rear cog. So with 29 inch wheels and a standard derailleur drivetrain, you will, maybe without thinking about it, either be using the granny ring a little more often and the big ring a little less, or tend to use a little bigger rear cogs. With today's 27 gears, the difference has little practical effect - you "lose" your lowest granny gear and get one even higher top speed gear. However, when you are getting into special setups like only one front ring or two, you will want to take the difference into account.
For singlespeeding with 29 inch wheels, you simply need a 10% smaller front ring or a 10% bigger freewheel to get the same gearing as compared to a 26 inch wheeled singlespeed bike.
Q: Does wheel size affect braking?
Braking depends on wheel size, because the wheel size affects the ground contact area, the braking leverage, and in some setups the heat-up and wear. Some say they feel a difference in braking characteristics between 29" wheels and 26" wheels, while some feel that the theoretical differences is overshadowed by aspects of brake type and setup.
The contact area with the ground is longer with bigger wheels, which some feel allows harder and more confident braking. This is hard to quantify, due to an infinite number of different combinations of surface, tire, and velocity, but might just be more significant than the difference in leverage.
Better leverage means that you don't have to pull the brake levers as hard to achieve the same braking effect, or speed reduction. Less leverage does not mean that you will not be able to brake hard enough, though. A rim brake is relatively a little closer to the wheel periphery on a bigger wheel, while a disc brake is relatively closer to the hub, given the same disc diameter. With 29" wheels and rim brakes, leverage is a few percent better as compared to with 26" wheels. With 29" wheels and disc brakes of same diameter, leverage is about 10% less. If you prefer, you could go up one disc diameter size, which would make up for the less leverage and as a bonus give extra-low disc heat-up and wear.
With the 10% higher mass of 29" rims, given same rim profile as a 26" rim, the heat-up and wear is 10% less. Heat-up and wear with disc brakes, on the other hand, is independent of wheel size.
Q: Does wheel size affect maneuverability?
Maneuverability is, besides weight, a common concern with those who hesitates going to bigger wheels. It is the bigger physical size, and perhaps also the longer contact path with the ground, that some believe would have an adverse effect on maneuverability. The contact path with the ground is indeed longer, and the wheels are about 10% bigger.
Some who are used to a 26 inch wheeled bike and have taken a test ride on a 29 inch wheeled bike, have claimed to have experienced a worse handling in tight terrain with the bigger wheels. Yet others claim the opposite - that their 29 inch wheeled bike is actually easier to handle in all types of terrain, let alone trials-style trick riding, due to better stability and support. Perhaps rider size again has something to do with it, and what you are used to.
Q: Are big wheels weaker?
Big wheels may be weaker than small wheels, especially if the number of spokes and overall construction is the same. For that reason, one would perhaps want to use 32 spokes instead of 28, 36 spokes instead of 32, and so on. However, big wheels take less hard hits due to their smaller angle of attack to obstacles, reducing the need for more spokes. In reality, many riders seem to use about the same number of spokes on their 29 inch wheels as would have been normal on a 26 inch wheel, and it has not seemed to be an issue.
Q: Are all wheel sizes legal in races?
All wheel sizes "no bigger than 29 inch" are allowed under UCI mountainbike rules. Until the end of 2003 only up to "26 inch" was allowed, for a reason that seems to be known by no-one.
Q: So, should I go 29"?
There is no guarantee that a 29" wheeled bike is the best for you. Everyone has got his or her own priorities and type of riding. It is up to you to ask yourself what is important to you, and to judge what you believe and what you do not believe, with or without test riding.