|   FAQs - let's get on it. | francis
Sep 25, 2002 10:57 AM | | We're doing this on the SS board so it's time to make a little investment. Let's gather up all the frequently asked questions and attempt to answer them. If the answers are in the archives or in other sources, post them up on this thread.
What's at stake?
- well lots of interested 29ers have the same questions. Let's help them out.
- unless we have the FAQ posted prominently, youwill get the same questions asked every two days.
Post the questions as threads on this thread.
francis |
| Why do people ride 29-inch mtbs | francis
Sep 25, 2002 10:57 AM | | |
| Is this all marketing hype? | 2melow
Sep 25, 2002 12:00 PM | | |
| Pros vs. Cons of the bigger wheel | 2melow
Sep 25, 2002 12:01 PM | | |
| Pros vs. Cons of the bigger wheel | victorthewombat
Sep 25, 2002 2:58 PM | | Pro and con's of the bigger wheel.
Pro:
1) better inertia
2) ride with less pressure
3)
Con:
1) a little bit of strength reduction.
2) From what I have seen rear disc brakes are a no-no because 10% longer spokes just do not have the strength
3) takes a wee bit longer to get up to speed. |
| Pros vs. Cons of the bigger wheel | PAB
Sep 25, 2002 10:50 PM | | Disc brakes are not an issue with 29". I am using a Fisher and Magura Marta with no problem at all. |
| The Cons equal the Pro's! | Cloxxki
Sep 25, 2002 11:06 PM | | Pro:
3) Higher grip-
4) and traction levels, due to larger size and lower pressure
5) less fatique due to taking blows from the terrain, at the same speed
6) Higher placed hubs reduce the "endo-factor" under descending and extreme braking and also help prevent a wandering front wheel on steep climbs or agressive acceleration
7) With the same drivetrain (as on a 26"), you get a larger highest gear
8) People will see you go your own way and buy what you believe in
9) You will be content with a smaller amount of suspension travel. 80mm on a fork is enough for about everyone, and even before it was released, the Gary Fisher Sugar29 was said to "overkill", as a 29" rider would not often need such amounts of travel.
Con:
4) With the same drivetrain (as on a 26"), you get a larger smallest gear. Easy to correct by getting a taller cassette or smaller chainrings.
5) Your friends will now have proof that you're a geak
6) Your friends will be holding you up on group rides, better to lead the group on your niner :-)
7) You will start neglecting the other bikes in your stable, which is a sad sad thing to happen.
8) Reports are, grins will be very hard to wipe off your face after, let alone during a ride.
9) You get to carry a 180g WTB spare tube, but hardly ever need it, somehow it's hard to get a decent snake bite outta those tires! |
| The Cons equal the Pro's! | BruceBrown
Sep 26, 2002 12:04 AM | | Pro
7) With the same drivetrain (as on a 26"), you get a larger highest gear
Con
4) With the same drivetrain (as on a 26"), you get a larger smallest gear. Easy to correct by getting a taller cassette or smaller chainrings.
Just to get the terminology on the right page for everyone for highest and smallest gear - which one is the 32T (or 34T) cog and which one is the 11T (or 12T) cog? Depending on which way you figure, highest and smallest rear cogs could be counted in different directions depending on one's terminology.
Thanks.
BB |
| Errr, largest gear used at highest speeds? nm | Cloxxki
Sep 26, 2002 2:26 AM | | |
| Are 29"ers only for tall people? | 2melow
Sep 25, 2002 12:02 PM | | |
| What size rims does 29" require? Can I use my road wheels? nm | Cloxxki
Sep 25, 2002 12:39 PM | | |
| What size rims does 29" require? Can I use my road wheels? nm | PAB
Sep 25, 2002 10:54 PM | | 700 is the size. So road rims are the rims for 29". Just be sur they are stong enough !
29" the way to go ! |
| What parts are available? | Stonedead
Sep 25, 2002 1:34 PM | | |
| Who makes a FS 29"er SS tandem freeride bike? ;^P (nm) | shiggy
Sep 25, 2002 1:58 PM | | |
| I do. want one? it will cost you | 2melow
Sep 25, 2002 3:08 PM | | Ahhh...you real funny boy! you want one? fivethousanddolla!
you love it long time! |
| Do they have more traction (is the contact patch bigger)? nm | jpre
Sep 25, 2002 2:23 PM | | |
| Do they have more traction (is the contact patch bigger)? nm | Cloxxki
Sep 26, 2002 4:58 AM | | Running the same pressure as a 26" tire, science says the contact patch should be equal in size, just longer and narrower. This seems to explain reports of riders claiming their 29" tires feel more stable.
Still, 29" allows you to lower your pressure a bit, thus creating a larger contact patch. Yes, this provides more traction, and reviews are clear, 29" climbs steeper slopes than 26". Where even lightweight 26" dual suspension bikes lack the traction, a heavier stock 29" has a better chance reaching the top. Numurous riders have reported this. Where they'd normally walk up, they all at once could remain seated.
Traction works both ways, braking with be better as well.
Possible explanation for the 29" tire to grib so significantly better, is the shallower angle of attack of the knobs over the soil. |
| Do they have more traction (more thinking out loud) | drwelby
Sep 26, 2002 6:07 PM | | Now, I'm not picking on Cloxxki. I just want to to really think these things through. If we're going to have a FAQ it might as well be accurate.
1. I agree with the contact patch being the same at equal tire pressures. Simple physics - pressure = force x area.
2. I agree that the contact patch will be longer and narrower, based on data I have from Chester R. Kyle.
3. "The longer contact patch creates more stability". Why? How does the shape have anything to do with bicycle stability?
4. Lower pressures are possible - seems to be true, based on my experience.
5. 29ers climb steeper hills better - could this be also due to longer stays, which reduce the tendency to loop out in low gears?
6. The whole shallower angle of attack thing - this keeps coming up.
a) what does this REALLY mean? I can conceptualize it but I think it's a red herring. What is it doing for you? Explain please.
b) If your knobs are providing traction, they are probably pressed flat against the ground, so isn't "angle of attack" pointless?
More things to ponder - on a hard surface, the contact patch will be the same between wheel sizes. But what about a soft surface? I'm thinking of something like "floatation" and "wetted surface area" that you see in boat design, though I hesitate to use the terms because it might lead to mis-applying hydro theory. But given a soft surface, and the wheel pressing into it until there is equilibrium between the down force and the force from the soil, does the larger wheel "float" higher, based on geometry? I need to do some scribbling and think about it some more. |
| Do they have more traction (more thinking out loud) | Cloxxki
Sep 26, 2002 9:52 PM | | Early morning here, but I'll try to clearify what I was trying to theoretisize.
The longer, narrower contact patch. I didn't elaborate on why I expect this provide a feeling of stability, my poor English restricting me from expressing my thoughts.
Okay, lets say a 26" contact patch is more circel-shaped, whereas 29" is more like a line with round edges. Please do slam me when I'm wrong. To me, it makes sence the circel-shaped 26" contact provides less friction when I sit on my bike, not riding it, front wheel on any surface, me turning the handlebar like a kid pretending to propel a car steering the heck out of it. With the longer contact patch, the knobs on the front and rear will scratch over the soil, as they're futher away from the center of the contact patch than any knob on a 26" tire.
This higher friction, in my mind, makes it harder steer the handlebar of a 29" bike by one degree. This, I think, works the other way around as well, the terrain will have less influence on the wheel, while trying to push them off line, by throwing loose soil and rocks at it.
I agree, the centre knobs on the contact patch always press the ground at a flat angle. But on average, all knobs on the 29" will still have a shallower angle of attack, whatever that means to grip levels.
Let's compare bikes to a windmill driving a wooden wheel with buckets all around the edges. As the wheel turns, buckets at the bottom of the rotation fill themselves with water, and after a short trip around the axle, they empty themselves in another reservoir than where they got the water from, thus working as a pump.
Now up-scale that waterwheel, and place the bottom such, that the buckets can still fill themselves (read : adjust pressure on the 29" tire to get the same sag as on the 26"). The buckets are now dragged through the water over a longer distance, more buckets under water at the same time (longer contact patch), creating a more fierce current (grip!).
What would be grippier? 2 knobs next to each other, or two knobs smartly spaced behind each other?
Time to go to work, good luck getting to the bottom of this! |
| Do they have more traction (more thinking out loud) | Messassin
Sep 27, 2002 4:43 PM | | Just some musings on tire traction. In the situation of slicks on pavement, you have the relatively simple case of two types of materials in planar contact, and you could get pretty good empirical data (a coefficient of friction) for different types of rubber and for different pavement roughnesses, and it would be pretty consistent. Frictional force is related pretty directly to normal force in this case, but it would be interesting to see how varying wheel size (and contact patch shape) may or may not have an effect. Next step- knobbies on pavement. I bet you could still get good data, now it would be interesting to see how tread pattern affects Coef. Friction. Now, knobbies on dirt, that gets tough for the obvious reason that dirt comes in infinite variety. Everything from consistent particle size sand with varying compaction and moisture to aggregate overlaying hardpack to, well you get the idea. We are trying to quantify the very hard to quantify sensation of a tire "hooking up". How about this as to get us started, as far as what the shape of the contact patch does for straight line climbing traction on dirt--The tire is rolling and constantly compressing soil into its tread pattern to a greater or lesser extent, depending on particle size, moisture content, and probably lots of other factors. Maybe it would possible to measure a maximum shear stress for different soils, and go from there? Let's hear some thoughts! Thanks. |
| Now we're thinking... | Dr.Welby
Sep 27, 2002 5:33 PM | | If anyone reading this is in high school, this is a science fair experiment just waiting to happen.
I would get a long piece of gutter, fill it with sand or gravel, and then either drag different sized wheels along it and measure the force or do some sort of coast-down test. You can work out the details.
Here's some real world cantact patch data from Chester Kyle, testing Clement tubular tires at 80psi at different sizes:
size, length, width
27",4.40,.46
24",4.13,.52
So for about a 10% change in size, the length and width change about the same (no surprise).
However, what does this mean? The area should stay the same. So from a traction standpoint traction should be the same, given the same size contact patch.
I think Cloxxki's (sorry Jan if I mixed up the x's) idea about the longer contact patch creating more stability is interesting and worth more discussion and investigation. |
| Maybe I should've compared Hockey skates vs. Speed skates? nm | Cloxxki
Sep 27, 2002 10:45 PM | | |
| Now we're thinking... | Messassin
Sep 28, 2002 8:05 AM | | Actually, this would make a decent undergrad project when you try to get down to a theory explaining tire/soil interaction...
Probably would want something deeper and wider than a gutter--the effect of particle compression probably runs deeper that a few inches in the softer soils...Draging a wheel along it would give you an idea of traction while sliding, but then that's when you're losing control...
I was thinking of measuring the force required to cause the tire to move, or break loose, while it's being pressed into soil. Take the instance of fine particle soil that's slightly wet...you know, the kind that makes perfect tire prints. The soil completely fills the tread, and when it slides, you have a combination of rubber on dirt Coef fric, and dirt on dirt coef of friction. I think it would be possible to show that one size of wheel has better traction than another with this test, but how about the claim for better stability (assuming during cornering) for 29ers? Can the actual shape of contact patch, and therefore the pressure distribution on the soil, affect the tires cornering ability? Think snow anchors for climbing--a wide thin blade holds better than a tubular picket. Thoughts on that? |
| Now we're thinking... | Cloxxki
Sep 28, 2002 11:09 PM | | I has the same thought, testing the force required for a tire to break loose, lose traction. With some ingenuity, it would also be possible to test traction throughout a climb or descend, by having some for of an engine propel a single wheel, or a complete bike at a continious powerimput up a slope that's too steep to hold traction for all it's length.
Hmm, I just came up with an honest test, using two rails that run along a dirt ramp. A wheel is placed on an axle that connects to both these rails. A weight, ingeniously hung from the axle is propelling the wheel with it's very weigth, some pulleys allowing the wheel to roll uphill as the weight goes down on a line. Should provide a very honest test, a tire is going to loose traction at a certain angle. Maybe an engine is better to use, though. Less hassle.
Or one could just gather up a bunch of riders and have them tell which tire climbs best, maybe make a small competition out if it, to make sure everyone tries it's on each bike and tire used.
Nature answers most of our questions though. There are reasons why swimming birds have different paws than birds of prey. How is a bike going to adapt/grow to become perfectly built to cross the offroads, with only a few decades to evolve? |
| different contact patch shapes | jpre
Sep 29, 2002 7:49 AM | | http://www.precisiontandems.com/artbillwheelsize.htm
This has been posted elsewhere before, and is not necessarily
directly about 29" wheel setups, but is interesting to read in
debate about different contact patch shapes.
-John |
| different contact patch shapes | Messassin
Sep 30, 2002 11:30 AM | | Thanks for that link, John. Interesting stuff. I've got book-Bicycling Science, I think--around here somewhere, and if I remember correctly there's a chapter or two on this subject. I'll try to dig it up and post the relevant things... |
| How are they in tight, twisty singletrack vs 26"? nm | jpre
Sep 25, 2002 2:29 PM | | |
| sometimes slower, sometimes faster | 2melow
Sep 25, 2002 6:29 PM | | depending on acceleration out of turns, if it is smooth, or if it is super rocky and technical.
Bigger wheels will roll over technical terrain with more ease in tight twisties, but if it is tight, smooth singletrack - then the smaller, more nimble 26" will be quicker |
| How much slower do they accelerate? nm | jpre
Sep 25, 2002 4:05 PM | | |
| 1% difference on average, less if you are a Clydesdale | Cloxxki
Sep 25, 2002 10:48 PM | | This is with present availability of tires. Come time, tires will only be the necessary 10% larger/heavier as simular 26" tires, and the same for rims. Accelerating your bike, you don't just wind up your wheels' rotational weight, but all of your bike plus your bodyweight as well. Therefore, the difference in terms of acceleration isn't all that BIG.
Okay, so you lose 1% of the time you spend getting the bike up to speed. But on the other hand, you will LOSE LESS speed on every occasion that the wheel comes across a bump of any kind. Larger wheels roll over obstacles with greater ease, we all know that. Just, the advantage here is not 1%, but a multifold. I seem to recall the Trek people tested it to be 6%, could be more.
While climbing a smooth road, the extra grams in the 29" bike (some things are lighter, but overall 29" will weigh more) also influence climbing ability, the disadvantage is less than the 1% in acceleration, because you're not winding anothing up, just carrying it to the top of the mountain.
On the road, you do get lower rolling resistance, and if the climb is off-road, you get the earlier mentionned easier rolling over bumbs, effectively still making you a faster climber.
On most circumstances, a 29" bike will allow you to lap faster, because the advantages outway the disadvantages. |
| How come these big wheeled bikes are so fu%&#$@ fast | 2melow
Sep 25, 2002 6:25 PM | | |
| How come these big wheeled bikes are so fu%&#$@ fast | Cloxxki
Sep 25, 2002 11:25 PM | | Every wheelsize has it's use in biking :
20" - For BMX and recumbents. BMX needs the strength and swift acceleration, remubents need a wheels to fit on their bike, allowing them to stay low to the ground, getting all aerodynamical.
Kiddy bikes.
24" - For BMX that is more focussed on speed and long jumps.
Tiny grown up that don't fit a 26" bike.
Kiddy bikes.
26" - Primariry used for kiddy bikes, Paper Route bikes. Also very useful for overall XC riding, due to the larger wheels that roll over obstacles easier than 20" wheels. Also less nervous to manouvre.
29" - also the 700c rim size used in road bikes and CX bikes, for one reason only : speed. we all know CX bikes are faster on smooth surfaces, faster than 26" bikes with 1 3/8" tires knobbies. On straights AND through corners.
Put wide tires on 700c rims and you have something more XC worthy, able to take a beating from rough terrain without a snakebite every other rotation of a wheel. It's noticably faster in terms of rolling resistance than 26" on anything than glass-smooth surfaces, though a little slower (1%) to accelerate.
All other reasons to use 29" over 26" or vice versa are the same that apply to 26" vs. 24". Count the number of 24" bikes you come accross on your next ride (...)
Thing is, 29" was't available before, and now has to earn it's place in biking.
With the kinds of terrains we encounter XC and DH riding, bigger wheels are better, as long as they don't compromise the design of a bike with ideal XC angles and sizes. 29" wheels fit fine for riders over 5'6", and some smaller one love them as well.
If you don't believe 29" will make you a faster rider than on your 26", maybe you should consider 24". Ligher wheels, easier to change direction, more strength, it makes sence doesn't it? I just hope you won't come accross a root you fail to notice, 24" will just make a dead stop on it, 29" will smoothly roll over. |
| OK, Now all these questions need to get ANSWERED! | francis
Sep 25, 2002 9:32 PM | | in detail.
francis |
| re: FAQs - let's get on it. | BruceBrown
Sep 25, 2002 11:07 PM | | Is a 29" wheeled mountain bike a good consideration for a Clydesdale when selecting a XC bike to purchase? (Probably best to define what qualifies as a Clydesdale in terms of weight/height in the answer as well.) |
| Clydesdale Description | BruceBrown
Sep 25, 2002 11:48 PM | | According to the USA Clydesdale Athlete home page, a Clydesdale athlete is any male athlete that is over 200 pounds or any female athlete (called an Athena by some and called a Filly by some others) that is over 145 pounds.
Perhaps those parameters are too limiting when addressing the issue of height and finding a bike with proper fit for larger and taller riders. So the answer to my original question for the FAQ as to whether or not a 29" wheeled mountain bike is a viable consideration for the Clydesdale athlete should include information about the type of geometry concerns that a taller rider faces. Are there benefits of a 29" wheeled bicycle to be factored in when considering a bike purchase for the taller rider? Addressing those issues would help this portion of the FAQ.
BB |
| The Answer | Bigwheel
Sep 26, 2002 7:47 AM | | While it is noble of MTBR to try and get to the bottom of these most FAQ's it is this 29" riders opinion that there is no true answer to any of the questions, except for each individual depending on their needs.
The only way to answer each question based on individual needs is for the rider to go and try a 29"er in his/her environment. Because of the lack of 29" wheeled bikes that have been available since the "tire" (52/47 WTB Nanoraptor) evolved four years ago this has not been easy, so many of the questions and answers have been based on theory. Now there are 29" bikes available and anyone that is truly intrigued by the concept, whether they are small or tall, or thin or thick should be able to get ahold of one to ride to see "for themselves" if the concept works for their individual style.
I have seen enough evidence in the last 4 years by lending my bikes to people at trailheads and demo days and for rides to know that it is the true test. Some get it and some don't. If you have to ask the questions, then ask them. You will get different answers for the most part from all parts of the globe, that is what forums are for. But to get the true answer for yourself, you gotta ride to decide. |
| The Answer | Cloxxki
Sep 26, 2002 12:43 PM | | You're right, before buying or even judging, people should try one out, it tells more than a book full of theoreticizing.
Still, even before someone is intrigued enough to go find a shop or rider to go test their 29" bike, an FAQ section is a good way for a newby to gather knowledge on what (s)he's getting into. we are well able to write objective answers to FAQ's, we don't have to sell them. Sharing our personal experiences is of course okay. |
| The Answer | BruceBrown
Sep 29, 2002 12:36 AM | | Bingo! I thought the idea of a FAQ had merit, but certainly agree with the power of a test ride providing you can find one in your size. I simply posted a couple of questions I felt would be of benefit residing in a FAQ.
I have only been able to try the medium size frame of the 2002 Mt. Tam which didn't tell me much since I need an XL size. I sure do want to hop on an XL Sugar 292 or 293 to make some more accurate determinations before making a decision. Perhaps the LBS circuit will carry more inventory of Fisher 29" bikes this year with the advent of 2003 selections available from Fisher. Not to mention, not every mountain biker has access to easily find or test a 29" at this point in time.
BB |
| Hey | Bigwheel
Sep 29, 2002 5:52 AM | | Bruce, I wasn't trying to squash the idea of a FAQ thing, I just was trying to point out that one question does not always equal one answer for everyone? Curious minds always want to know, but theory and numbers so far have only retarded the progress of the 29"er IMHO and now there will be more and more bikes available for you and others to try. Sometime, if you feel strongly enough in your mind that it could be right, you just have to bite the bullet and put down the $$ and get one on spec? I did years ago and have never regretted it--- |
| Hey | BruceBrown
Sep 29, 2002 6:30 PM | | I wasn't trying to squash the idea of a FAQ thing, I just was trying to point out that one question does not always equal one answer for everyone?
I agree. I also imagine that if the 29" market continues to grow, there will be a lot less need to ask questions as the ability to just "hop on one and see for yourself" will increase with the growth in the market and space on the showroom floors. That was not the case in the past year as showroom floors were not well stocked with options. I have no idea how many units were produced for the two 2002 Fisher 29" models. I only had the chance to test a Mt. Tam medium size frame as that is all the LBS had in stock to test.
Sometime, if you feel strongly enough in your mind that it could be right, you just have to bite the bullet and put down the $$ and get one on spec? I did years ago and have never regretted it---
I understand, but my mind has been more incorrect than correct on many big ticket items in the recent past - even with proper research and good selection.
It is hard for me to make such a leap of faith without at least being able to demo something close to the end product. In my case, I have an interest in one of the new Sugar models that should be arriving on showroom floors this quarter. I have tested my size frame in the 2002 26" wheeled Sugar 3+ well enough to know I like or could adapt to like the performance from the full suspension of that bike. How the Sugar will feel and perform with 29" wheels for the price I have to pay where I live is more a leap of faith than I want to make without a test on that actual bike. Whether it is a L or XL frame used for the test doesn't really matter. (Heck, I could even crank the seat up enough on a M size frame to get an idea I could run with....)
BB |
| Hey | jpre
Sep 29, 2002 9:40 PM | | I wonder how much it costs a company like specialized to put on demo
days at popular riding destinations for their new 26" full sus Epic.
http://www.specialized.com/SBCWhatsNewDetail.jsp?market=us&article=696
If the cost is not that extreme, I would then wonder how many potential
buyers are reached via this method. If the cost/benefit is worthwhile
I wonder if Gary Fisher or someone of similar resources would do
something like it for 29"ers, as riding around a parking lot or up and
down the street doesn't necessarily tell one much about off road handling. |
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