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Thread: 29er fat bike

  1. #1
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    New question here. 29er fat bike

    Hello
    Fat bikes will roll also on 584mm rims= 27.5.
    Have you ever thought about getting a fat bike based on 622mm rims with 5" or more tyres?
    How would it ride vs 26x5" fat bike? Would roll over much better? How low would go with the tyre pressure on 29x5" fat bike?

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    Wut

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    Quote Originally Posted by Davidcopperfield View Post
    Hello
    Fat bikes will roll also on 584mm rims= 27.5.
    Have you ever thought about getting a fat bike based on 622mm rims with 5" or more tyres?
    How would it ride vs 26x5" fat bike? Would roll over much better? How low would go with the tyre pressure on 29x5" fat bike?
    For now there's only 27.5+ and 29+... 29er fat would just be a monster possibly very hard to ride... unless you're like 7 feet tall.

    And by the + sign, that means like 3.8" diameter. That's why they are also called "mid fat".

    Fat bikes now are more like 4.7" - 5".

  4. #4
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    Your troll fu is slipping, man.
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    Quote Originally Posted by Engineer90 View Post

    And by the + sign, that means like 3.8" diameter. That's why they are also called "mid fat".

    Fat bikes now are more like 4.7" - 5".
    No fat is 3.8 and up, under 3.8 is + sizes, and mid fat doesn't exist.

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    You could run 29's and low profile 5" tires though. Sittin on them thangz



    29er fat bike-bike-photo-homemade-bicycle-wheels-foil-spokes.jpg
    Fatbike / Monstercross / Hybrid

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    I'll take DC seriously. He flies some interesting kites.

    No doubt they'll come.

    I think their primary use will be on suspension bikes and the tyres will be low profile to remove some of the undamped suspension effect of a fat tyre.

    There won't be much difference in overall diameter if that's case though.

    But for a conventional fat tyre with a 700c wheel diameter we have practical restrictions though.

    Unless wheelbase is lengthened toe overlap will become an issue, and with a lugged tyre that can get a good grip on whatever it touches, it may be a serious safety issue. For the bike packers there will be less frame triangle.

    With a longer wheelbase, it will be a perfect size for the tall riders though, or if Surly ever make a fat Big Dummy.....

    One potential disadvantage will be heavier rims, but tyres that big are going to have to be run at very low pressures (unless riders like pogo sticks) and those low pressures will probably require a very different rim simply to retain the tyre. The possible reintroduction of tubulars or gluing the tyre to the rim may be a way to get very light rims, and eliminate the need for bead hooks etc. In this case a rim that was a simple rolled flat section might work and could be exceptionally light.

    The possibilities are endless, and we haven't seen the end of fatbike development by a long shot.

    Me? I reckon midfat 650b (27.5er) wheels with 3.2" to 3.5" tyres will make an ideal replacement for the current hardtail mtb, and fat will continue to get fatter at 26", and possibly go down to 24" when the 6" tyre comes along.
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  8. #8
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    Quote Originally Posted by Drew Diller View Post
    Your troll fu is slipping, man.
    Must be mellowing in his old age

    DC with 26" fat with 4.8's measuring around the 31" mark, I would expect a 4.8" on 29" to be pushing 34-35 inches. Roll over ? The wheelbase would be massive and would probably handle pretty ordinary.
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    I own a custom-proto 29er fat bike. It rolls so well i'm able to bike up staircases to the amazement of on-lookers. It gaps the stair treads perfectly. I have not found a stair case i have not been able to conquer. It rolls so well. I just need the gearing-low-end to make it up. I'm sure there are really, really steep stair cases i couldn't make it up, but it's more like i'd not have the low end torque

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    Quote Originally Posted by Velobike View Post
    One potential disadvantage will be heavier rims, but tyres that big are going to have to be run at very low pressures (unless riders like pogo sticks) and those low pressures will probably require a very different rim simply to retain the tyre. The possible reintroduction of tubulars or gluing the tyre to the rim may be a way to get very light rims, and eliminate the need for bead hooks etc. In this case a rim that was a simple rolled flat section might work and could be exceptionally light.
    On mud trucks, a common feature on rims is beadlocks. Anybody know of beadlocked mountain bike rims? I know it sounds wierd, and would definately weigh more than a simple tubless setup, but I can't help but wonder if someone has actually done it.

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    Quote Originally Posted by watts888 View Post
    On mud trucks, a common feature on rims is beadlocks. Anybody know of beadlocked mountain bike rims? I know it sounds wierd, and would definately weigh more than a simple tubless setup, but I can't help but wonder if someone has actually done it.
    Wonder no more:
    Beadlocks for tubeless.
    in the fat forum no less....

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    Schwalbe Procore is the same concept.

    PROCORE - RIDE PROGRESSIVE | Schwalbe North America

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    Not exactly what I was looking for, but closer with the second page of the forum link. I was thinking of a true beadlock ring that gets bolted to the rim. Maybe a carbon fiber rim with an aluminum outer ring for rim strike protection. The forum link brought up a good point about not being able to do any trailside work on it though. Complete pain to get a beadlock ring removed on the trail.

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    Quote Originally Posted by Fat Urkel View Post
    I own a custom-proto 29er fat bike.
    The Cake Eater?

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    We did discuss the bolt-on rings back in the day. Thought that 2nd one was the thread, but maybe you've got to go deeper down the rabbit hole than that. There were also a handful of threads where "glassing" an other footprint measurement ideas from ORV's came up. Ground pressure vs PSI, sidewall deformation, rim width vs tire width.........
    IRC, 3 piece rims and trail side fix was brought up, but more so that it would be relatively heavy compared to the mass of the vehicle and difficult to hand fabricate. Others offered similar suggestions from the motorcycle world but then there was the tire compatibility issue and weights of moto tires.

    There used to be lengthy thought-ful/provoking threads where ideas were vetted and various knowledgeable people participated with ideas. That ship has pretty much sailed.

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    Well this thread turned out better than expected. (Accurate, yet grim assessment there, bme107..)

    I would totally try making some three piece rims. Heck yes. I thought there was simply hardly any interest due to the weight of the external fasteners involved.

    I have the capabilities to make something like ProCore but obviously I don't want to infringe on their stuff. Just wanna make bike stuff, not legal battles.
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    I would contend that there isn't a real need/ market given the weight penalty vs benefit if any.

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    My nextie rims hold the beads on tires so tight you have to deflate then stand on the tire to get it off.
    Why would moving from 26" to 29" make this not enough force to hold the tire?

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    Quote Originally Posted by tfinator View Post
    My nextie rims hold the beads on tires so tight you have to deflate then stand on the tire to get it off.
    Why would moving from 26" to 29" make this not enough force to hold the tire?
    Not all rims are Nexties.

    We're talking about ultralow pressures too, so there will not be so much force holding the bead against the rim.
    As little bike as possible, as silent as possible.
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    Quote Originally Posted by Velobike View Post
    Not all rims are Nexties.

    We're talking about ultralow pressures too, so there will not be so much force holding the bead against the rim.
    I know not all rims are nexties. I think though, that if nextie can design a rim that holds most brands of tires so tightly, why would we want another entire wheel tire system?
    Wouldn't it be easier just to use the one we have already.
    Keep in mind I said they hold ultra tight with no air... Are you going lower than 0 psi?

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    It would take a lot less than a beadlock to solve the problem (if the problem exists)
    A wider bead/rim interface, possibly with a cloth component on that bead and some sew up cement - done. A lot less trouble to design, a lot less cumbersome and a lot less weight than a beadlock.

    Also as tfinator has pointed out, even less is probably necessary. Just a tight bead/rim tolerance with the right bead hook and you're probably set. Tire and rim combo goes a long ways. When I was a mechanic I used to hate, HATE fixing flats or removing for any reason Trek tires from Trek rims, they just didn't want to budge and some hand pain was always involved.

  22. #22
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    Quote Originally Posted by tfinator View Post
    I know not all rims are nexties. I think though, that if nextie can design a rim that holds most brands of tires so tightly, why would we want another entire wheel tire system?
    Wouldn't it be easier just to use the one we have already.
    Keep in mind I said they hold ultra tight with no air... Are you going lower than 0 psi?
    I'm quite happy with what we have at the moment, other than I'd like a 6" tyre for some of the bogs I ride (try to) ride over.

    However progress is happening and fatbikes are very much in the developmental phase of their existence, so we are going to see all sorts of solutions, some for problems that don't exist, other we will adopt readily.

    Suspension will alter the game for some fatbikers, and we'll see fatbikes being hurled down rock strewn hills at speeds we never contemplated. The need for full control over suspension will lead to a need to reduce the undamped component contained in the tyre. The way to do that is to reduce the tyre profile. The corollary of that is to retain the same overall wheel diameter, the rims will have to be larger diameter and potentially heavier.

    We will never get a perfect match between rim and tyre until standards are introduced that leave less tolerance in the manufacture of each. Some tyres are very loose on some rims, other are **&&^%$%&*&* to get on or off. Current standards are good enough for the high pressures used in all other bikes, but we need closer tolerances for fatbikes IMO. Bearing in mind most folk cannot afford $300 rims we are going to have to put up with status quo on standards a bit longer I suspect.

    As for pressure, I have used 2psi, but bead retention was a problem.

    We already have had the argument that what is currently available is good enough when we went from 2" tyres to 2.35".
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  23. #23
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    New question here.

    Regular 26er 32 psi equals roughly 25-27 psi on a comparable 29er.
    The natural corollary is that 29er fat bike pressure are going to be lower vs 26" fat bikes. By how much? Take an average 26x5" tyres' pressure and extrapolate them into 29x5". Lower by 8 psi? 5 Psi? Just curious.

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    not quite that much pressure drop, but you might get an extra 1-2 psi drop. It's not because of the increased volume of the tire, but the tire/ground contact patch for a 29er is a litle bit longer than 26". If I dropped from 32psi to 27 psi, I'd snake bite all day. If you're talking fat bike pressures, dropping half a psi can be the difference between perfect and snakebike. Ultimately, tire pressure will change from hour to hour and dirt to sand to snow to mud. I set it a litle high and just go with it. Never perfect, but always fun. It's fat after all.

  25. #25
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    Quote Originally Posted by watts888 View Post
    It's not because of the increased volume of the tire, but the tire/ground contact patch for a 29er is a litle bit longer than 26".
    If you air up let's say 2,4" 26" and 29er tyre up to 30 psi, the 29er one will feel harder and behave like a ~34-6 psi 26" tyre. If you load both tyre with 100 kilograms, the 29er one will deflect less owing due to more air volume inside the bigger tyre.
    If you air up a 20" 2,4" tyre with 30 psi it will feel like underpumped. If you air up a 36er 2,4" tyre it will feel much harder. If you want to achieve the same feel- tyre deflection in all four 20,26,29 and 36 inches you will need to apply differentiated air pressure, thus there is no point in comparing the same pressure for all tyre standards.
    A 36er with 35 psi will have a much longer tyre contact patch than the same tyre in 20" kid bike, which will be almost like flat with 100 kilograms onboard. To avaoid that you need to add air into smaller tyre in order to get a desired feel.
    Like 26"x2.4" X-king 32 vs ~25-27 on a 2.4" 29er version. I did that with my 29er. You always run a lower tyre pressure on a larger rim.
    It is physics.

    That's why I am curious how much lower could one reduce the tyre pressure on 29x5" tyre vs 26x5" one to achieve the same sensation and tyre deflection?

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    Good luck pedaling that wheel!

    I have a ridden 26 x 4-5" on a bike and uni, a 36 x 2.25 on a uni, and a 29+ on a bike and a uni, the idea of riding a 4-5" tire on a 29" wheel begs the question: Why?

    At a certain point the benefits are outweighed (literally) by the costs: issues with starting and stopping, issues with steering, issues with weight and durability.

    You can make an engine more powerful in a truck, but there are limits to what we can do with the human body.

    If you want clearance, just get a bike built with a higher BB.

    I really like the kid posting with his tinfoil accented wheel

  27. #27
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    Quote Originally Posted by Nurse Ben View Post
    Good luck pedaling that wheel!

    I have a ridden 26 x 4-5" on a bike and uni, a 36 x 2.25 on a uni, and a 29+ on a bike and a uni, the idea of riding a 4-5" tire on a 29" wheel begs the question: Why?
    I have found the basics about 26vs29 differences:

    https://www.youtube.com/watch?v=HLirh0gJrps
    How does it translate into a Fat Bike world?

  28. #28
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    Quote Originally Posted by Velobike View Post
    I'm quite happy with what we have at the moment, other than I'd like a 6" tyre for some of the bogs I ride (try to) ride over.

    However progress is happening and fatbikes are very much in the developmental phase of their existence, so we are going to see all sorts of solutions, some for problems that don't exist, other we will adopt readily.

    Suspension will alter the game for some fatbikers, and we'll see fatbikes being hurled down rock strewn hills at speeds we never contemplated. The need for full control over suspension will lead to a need to reduce the undamped component contained in the tyre. The way to do that is to reduce the tyre profile. The corollary of that is to retain the same overall wheel diameter, the rims will have to be larger diameter and potentially heavier.

    We will never get a perfect match between rim and tyre until standards are introduced that leave less tolerance in the manufacture of each. Some tyres are very loose on some rims, other are **&&^%$%&*&* to get on or off. Current standards are good enough for the high pressures used in all other bikes, but we need closer tolerances for fatbikes IMO. Bearing in mind most folk cannot afford $300 rims we are going to have to put up with status quo on standards a bit longer I suspect.

    As for pressure, I have used 2psi, but bead retention was a problem.

    We already have had the argument that what is currently available is good enough when we went from 2" tyres to 2.35".
    Your really stuck on the nextie rims huh?
    My point is that the interface they use hold the majority of current tires down to 0psi
    You're looking for rim manufacturers to create an entirely different type of system.
    I'm saying it's going to be easier for everyone to just tweak what is existing instead of that.
    Maybe all the manufacturers would just grab some nexties and just make the tire bed like theirs.
    That's going to be easier for them, and it's sure as hell going to be easier for everybody who already rides.
    In short, I think it's a bad idea, it seems neither of us will change our minds. In a world of constantly changing standards, is a 'be careful what you wish for' thing.

  29. #29
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    Quote Originally Posted by tfinator View Post
    Your really stuck on the nextie rims huh?
    My point is that the interface they use hold the majority of current tires down to 0psi
    You're looking for rim manufacturers to create an entirely different type of system....

    In short, I think it's a bad idea, it seems neither of us will change our minds...
    I thought Nextie had a proprietary interface protected by patent? (I could be wrong)

    Unless rim manufacturers pay a licence fee they are going to have to come up with their own designs, and traditionally you make sure that's high enough to prevent a competitor from undercutting you.

    Otherwise they'll need to come up with their own designs.

    I have no interest in suspension, so I doubt I'll be looking for 29" rims with low profile tyres anytime soon, but it's something I predicted for fatbikes quite a few years back.

    There are full suspension fatbikes available now, something I thought completely unnecessary, but they are attracting a new group of more trail park oriented riders, so obviously I was wrong. That's where the demand for bigger wheels with low profile tyres will eventually come from.

    The 29" (622mm ERD) rims are available Classic-Cycle | Alu Rim DHL 80, 28 inch., 80 mm, high polished | online kaufen

    However like the 27.5+ trend, first you need someone to take the chance and supply the tyre.
    As little bike as possible, as silent as possible.
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  30. #30
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    Any update synopsis guys?

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    Any news on Sea Otter?

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