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Thread: 29 fat

  1. #1
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    29 fat

    The 27.5 x 4.5 platform seems to be getting good reviews. I am thinking about what upgrades to do to the fatbike before the snow flies. I currently have the stock Bonty Barbi 26 x 4.7 and 80mm mulefuts on my Trek Farley 7. I also have a set of 29er wheels for it. WTB Freq i25 with 29x3 Fat B Nimbles. Judging by how much room I still have with the undersized 29+ setup, I'm thinking a smallish 29 x 3.8 on a 50mm rim would fit and have advantages in fatbike specific race classes where a 3.7" wide tire is required.

    Has anyone heard of any development work on such an animal?

  2. #2
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    Quote Originally Posted by slowride454 View Post
    Has anyone heard of any development work on such an animal?
    Nope.

    But based on the improvement I feel in float going from 26 x 5 to 27.5 x 4.5, I sure am interested.
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    This week, Classic Cycle is releasing a 32 hole double wall alloy 67mm 29+ rim (ISO 622 x 60).
    Being a closed rim, I expect that it will come in close to 1 kg requiring it to be drilled out if one desires to get it down into the Marge Lite weight range.

    Looks like it is time to fire up the milling machine.

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    Rims are apparently available, though from a off-brand source:

    https://fattirebikeparts.com/index.p...ht-560g-detail

    https://fattirebikeparts.com/index.p...ut-outs-detail

    I assume that since rims are available there must be tires available from someone?

    (The rims are mentioned in this post 100mm wide tubeless rims , never heard of them prior to that. )

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    Yup, another vote for wanting to try 29 x 3.5- 3.8 etc.

    Might be cool to see 24x6-7 too.....kinda like what you see on those all terrain motorcycles
    You could execute this using an IGH hub
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    I'll play devil's advocate... I hope they don't.

    I hate seeing parts go extinct. It would be a real shame if the 27.5 x 4 format were a fad and someone who bought one of those bikes was left with an obsolete wheel format with no new parts. I don't want that. I want to see this new wheel size thrive so that there's a whole slew of riders who prefer it.

    I will be the last to say "we don't need X" but I really don't think we need 29 x 4. 27.5 x 4 is already SO big. It pushes the limits of frame design. It has such a low angle of approach that there's almost nothing to be gained from an even bigger wheel. 27.5 x 4 is so big, it's big enough (I think).

    I would rather see saturation in one wheel size than extinction in two.
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    A 29x5" with shorter casing would be great. Not much need to air down too much when the contact patch is long and that wide.

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    I hear ya, in the thinking that something like 29 x 4 is too much.
    It very well may be.
    However the bicycle has not "needed" anything since it's inception
    But has been continuously improved upon over the past century.
    The reason I am interested is simply out of curiosity and possibillity.

    I just wanna experience it to know either wow that's awesome or yeah that sucks.
    However right now I think a true 29x3.2-3.4 has a place right now

    Does anyone know if the Vee bulldozer 29 x 3.2 is true to size? i know many of the vee tires have run skinnier than advertised

    Is there a Duro Crux 29 x 3.2 for sale? can anyone report these dimensions?
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    I personally would like a 29x3.8 or so very much. This is because, though I'm only moderately tall at 5'11" (180cm), the resulting wheel size seems like it would be my natural max. I also favor moderate Q-factor, so a style such as the Voytek or Suzi-Q with max diameter would basically be as much bike as I can fit and handle.

    But short of the roughly 32" diameter, the Rocky Mountain Suzi-Q would be pretty much perfect for me.

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    Quote Originally Posted by spruceboy View Post
    Rims are apparently available, though from a off-brand source...
    Me likey...well at least they are finally breaking the 50mm barrier.
    Classic Cycle is shipping a 32 hole, double wall, 75 x 622 rim that weighs at least 500g more than a Clown Shoe. They publish the same weight for the 26 and 29 rim so I don't trust their specs any farther than I can through a piano.

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    Quote Originally Posted by spruceboy View Post
    I assume that since rims are available there must be tires available from someone?
    They are running 2.35" Maxxis tires to get the chopper look.
    A 29+ Knard will perform very well on a 60mm rim...wish I could find one.
    I have run 3.5" Speedsters on a 99mm Clown Shoe. It looks cool and they roll fast but it comes with some serious off camber self-steer.

  12. #12
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    My vote is no, also. We're seeing SO MANY different options that production numbers for each tire are going to be so low that it'll keep prices high.

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    We are our own worst enemy. "We have brought you 1x drivetrains with gearing as low as you have been using, in fact lower than was the norm 10 years ago" Us: "It's not low enough!" Them: "Ok...um..Eagle?"
    "It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth

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  14. #14
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    Quote Originally Posted by mikeetheviking View Post
    I hear ya, in the thinking that something like 29 x 4 is too much.
    It very well may be.
    However the bicycle has not "needed" anything since it's inception
    But has been continuously improved upon over the past century.
    The reason I am interested is simply out of curiosity and possibillity.

    I just wanna experience it to know either wow that's awesome or yeah that sucks.
    However right now I think a true 29x3.2-3.4 has a place right now

    Does anyone know if the Vee bulldozer 29 x 3.2 is true to size? i know many of the vee tires have run skinnier than advertised

    Is there a Duro Crux 29 x 3.2 for sale? can anyone report these dimensions?
    I managed to get a pair of the Duro Crux 29x3.25 tires when they were available on the Jones site. Weight is 1180g, bead to bead measurement is 200mm. I have one mounted on an I35 rim, letting it stretch a bit before measuring. I'll update in a day or so.
    29 fat-img_3121.jpg

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    Ya know, if you guys hadn't been so mean to "Xtreme-Fat-tire-bikes-for-racing" (pronounced as one word I assume) maybe you'd already have a wide selection of low profile 29 fat tires at your LBS!

    Just gonna leave this here.

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    Quote Originally Posted by bikeny View Post
    I managed to get a pair of the Duro Crux 29x3.25 tires when they were available on the Jones site. Weight is 1180g, bead to bead measurement is 200mm. I have one mounted on an I35 rim, letting it stretch a bit before measuring. I'll update in a day or so.
    Click image for larger version. 

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    Waiting patiently for this one! Thanks!
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  17. #17
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    roll that beautiful bean footage

    29 fat-duro.jpg
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    for visual reference to 29 x 3.0

    29 fat-krampy3.jpg
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  19. #19
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    Watch Jeff go berzerk on the Duro CRUX 29 x 3.25 tires here


    https://www.youtube.com/watch?v=T4rx...ature=youtu.be
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  20. #20
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    I'd be fine with it. I don't think the smaller wheel sizes will become obsolete, because small humans will never be obsolete. It may prolong the high prices because of crummy amortization, but would it truly be indefinite such as Harold suggests? Maybe, and maybe not.

    I can think of plenty of local sand that would benefit from the float. And I only weigh a buck seventy.
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    I noticed the 27.5 x 3.8 advantage early last year in fatbike races before the snow came. I have some buddies who are close to 100lbs lighter than me rolling down hills faster than me on essentially the same bike. They were on Farley 9.8 and I was on Farley 7. They picked up speed much faster than I did where I normally would have a very distinct gravity assisted advantage. Taking that train of thought one step further and considering the 3.7" min rule, I thought an undersized 29x3.7" rated tire would have advantages. I would probably still run the 26x4.7 in snow because I am a fat ass.

  22. #22
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    Quote Originally Posted by spruceboy View Post
    Rims are apparently available, though from a off-brand source:

    https://fattirebikeparts.com/index.p...ht-560g-detail

    https://fattirebikeparts.com/index.p...ut-outs-detail

    I assume that since rims are available there must be tires available from someone?

    (The rims are mentioned in this post 100mm wide tubeless rims , never heard of them prior to that. )
    That website reeks of a gentleman known to many here as "TommiSea," who is a well known con artist and has done time for fraud. The reports and reviews on his products are less than glowing. Caveat emptor.
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  23. #23
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    Quote Originally Posted by Gigantic View Post
    That website reeks of a gentleman known to many here as "TommiSea," who is a well known con artist and has done time for fraud. The reports and reviews on his products are less than glowing. Caveat emptor.
    I spoke with Tommi yesterday and he told me that he will have tires by the end of the month. According to Tommi, these tires will have the same outer diameter and width as a 4.8 x 26 wheel but the lower profile tire will reduce the rolling mass of the wheel by 1kg when compared to a 26 wheel. The first run of tires will be supplied to racers as promotional pieces.

    I guess we will have to wait and see.

  24. #24
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    Quote Originally Posted by FatBike&SlenderWoman View Post
    I spoke with Tommi yesterday and he told me that he will have tires by the end of the month. According to Tommi, these tires will have the same outer diameter and width as a 4.8 x 26 wheel but the lower profile tire will reduce the rolling mass of the wheel by 1kg when compared to a 26 wheel. The first run of tires will be supplied to racers as promotional pieces.

    I guess we will have to wait and see.
    Lower profile? what's the point? More rim strikes? That pretty much defeats the purpose of fat; it's like the turkey bacon of bicycles, a big fat lie. But hey, at least that sh¡t is "extreme."

    Looking at his website of "Extreme Fat Tire Bikes," I can see that he's just taken a plus tire and put it on a wider rim. Hey TommiFraud, stop p¡ssing on our backs and calling it rain.
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  25. #25
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    Quick update on the 29 Duro Crux. I weighed them at 1180g and 1181g. They are mounted on a set of I35 rims and I took them up to 30 PSI. No, this is obviously not riding pressure, but measurements for the tire new at 30 psi on 35mm internal width rims are 77mm casing width and 82mm knob width. Just for comparisons sake, I pumped up a well used Chupacabra to 30 psi on the same rim, and it measures 75mm casing width and 77mm knob width.

    So after some ride time and stretching, I expect them to gain at least a couple of millimeters. And those big knobs should protect the sidewalls nicely. These things would probably be awesome on a wider set of rims, maybe even up to 60mm wide, but I don't have anything that wide in 29 inches. Jones actually has a really cool carbon 29er rim that's 56mm wide, but pricey!

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    Let us know what you think of those tires after some riding in various conditions.
    I a set of 29+ waiting to be built up, and new Chupies...those tires have me intrigued though.

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    I am in the process of updating my wheel spec list below and was wondering if anyone measured the 29 x 3.25 Crux Duro and Vee Bulldozer?
    Diameter?
    Bead-Bead?
    ETRTO?
    Tread Width on a 50mm or wider rim?
    Last edited by FatBike&SlenderWoman; 02-15-2017 at 08:49 AM. Reason: typo

  28. #28
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    Quote Originally Posted by Gigantic View Post
    Lower profile? what's the point?...
    Same width and traction as a Dillinger 4 but 1lb lighter with larger diameter hence, lower rolling resistance.
    The tire/rim combo is 2lbs lighter than a tubeless Bud/Clown Shoe and holds two Guiness world speed records for a mountain bike. If trail conditions are like they were last year, they will be racing on at least two bikes at the Fat Bike Birkie in March.

    Attachment 1120276

  29. #29
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    Quote Originally Posted by Gigantic View Post
    Lower profile? what's the point?...
    Same width and traction as a Dillinger 4 but 1lb lighter with larger diameter hence, lower rolling resistance.
    The tire/rim combo is 2lbs lighter than a tubeless Bud/Clown Shoe and holds two Guiness world speed records on a mountain bike. If trail conditions are like they were last year, they will be racing on at least two bikes at the Fat Bike Birkie in March.

    29 fat-img_7039.jpg
    Last edited by FatBike&SlenderWoman; 02-10-2017 at 12:19 PM.

  30. #30
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    Not the same traction, as the way they currently exist, they require substantially more air pressure than a high volume 26" or 27.5" tire, reducing compliance and available grip in order to prevent rim strikes.
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  31. #31
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    Quote Originally Posted by BATRG3 View Post
    I personally would like a 29x3.8 or so very much...
    Here you go...finally!
    29 fat-blackborow2.jpg

    Xtreme Warrior on an Xtreme 622 x 85mm Carbon rim.

    29 fat-blackborowwarrior1.jpg

    Specs at link below

  32. #32
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    So he settled up his real estate fraud case and is back selling terrible bike things on mtbr? Fantastic!

  33. #33
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    I saw this bike today at our fatbike race. Can't miss the funny looking saddle and the wheel/tire combo. Dude looks like he is drunk all the time.

  34. #34
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    Quote Originally Posted by FatBike&SlenderWoman View Post
    Here you go...finally!
    Click image for larger version. 

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    Xtreme Warrior on an Xtreme 622 x 85mm Carbon rim.

    Click image for larger version. 

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    Specs at link below
    According to your site, the bead to bead on your tire is 189mm, and the bead to bead on the Maxxis Chronicle is 188mm(Duro Crux is 198). You didn't make 29 fat, you put a 29+ tire on a really wide rim. You definitely get credit for making a 29+ tire with tread that wraps further around the casing, which will make it work better on wider rims. You should be pushing that aspect, as a 29+ tire, since there's a limited selection in that category.

  35. #35
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    Stupid saddles and poor use of the English languages spelling tenets for the brand name, pretty much insults the intelligence of anyone with a pulse.

    That said, yeah, low volume tire on wide rim just screams poorly thought out, or, someone who has no connection to the actual fat bike world, and is embodying the concept of, just because you can, doesn't mean you should.

    A rim that wide, purpose built larger diameter, really needs a tire with equal design qualities.

    Let me guess, extra attention was given to the placement of holes in the rim so as to prevent uneven spin balance.

    Wake me when someone actually produces fat 29, please?
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    The good word from that proverbial little bird who is up to date on all sorts of developments is that no, fat 29 is not on the way.

    The biggest footprint you are going to get in the next two years is the 2XL. If yer current bike doesn't fit 'em, then get a new one.

  37. #37
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    Quote Originally Posted by sean salach View Post
    According to your site, the bead to bead on your tire is 189mm, and the bead to bead on the Maxxis Chronicle is 188mm (Duro Crux is 198). You didn't make 29 fat, you put a 29+ tire on a really wide rim.
    I obtained the Duro Crux partial measurements from an unknown source so I can not vouch for their accuracy.
    Any items in the spreadsheet that contain data in all of the fields are accurate.

    A little back story for you...
    Prior to the fat bike, my cycling consisted primarily of commuting via a couple road bikes 100-200 miles/week during the eight fair weather months in WI, then spending the next four months sitting on my ass getting fat while staring through a windshield. Eventually spring comes along and I spend the next six weeks struggling to 'reinstate' my summer legs.

    When I ride, I need to have a destination because I discovered years ago that I am too ADHD to spend 35-45 minutes/day on a cardio machine accomplishing nothing while going nowhere.
    Last March, I purchased a 2016 Blackborow XL on eBay from someone dumping the bike following a snowless winter in PA.
    Before the bike arrived, I had already determined that Bud & Low would never come in contact with dry pavement so the hunt was on for a 29+ fair weather wheelset that would drop 2 lbs of rolling weight/wheel while maintaining the same ride height and gearing as the stock wheelset.
    The 29 x 3 Knard was the lightest and fastest 29+ tire on tarmac until the 29 x 2.8 Vee Speedster started shipping in early summer. Having already purchased a set of Knards with no concern for clearance issues, I spent the next several months searching for a nonexistent rim in the 60 - 70mm range.
    Wanting to get the bike on the road, I decided to go with Speedsters on Hugo rims in the hope that some time in the future, there would be a wider rim to make better use of the Knards as a street tire in marginal conditions between plowed and blizzard.

    (More details & photos here)
    Notubes Hugo 52mm Rim

    After six months of searching, I came across Xtreme Fat Bike's web page and discovered their 622 x 85 rims. A little wider than what I was looking for but the Germans have been running 2.5" tires on 76mm rims so...
    I contacted them for more info and also learned about the Warrior tire which is manufactured by the same OEM as the Surly Knard. I brought some Warriors in for evaluation. Having both the Warrior and Knard in hand, it became obvious that the Warrior and the 120 tpi Knard share the same casing with the Warrior tread cap being more aggressive and 13mm wider (very similar to a Gravity Vidar only with the tread spread out a little more across the wider casing.)


    Quote Originally Posted by sean salach View Post
    You definitely get credit for making a 29+ tire with tread that wraps further around the casing, which will make it work better on wider rims.
    I am not the manufacturer. I am just an enthusiastic user stoked that someone finally came out with a light wide 622 rim. I am still running tubes on this wheelset and swapping out different tires on these rims just to satisfy my curiosity as to how they perform with a wider rim at different tire pressures on packed snow and ice.


    Quote Originally Posted by sean salach View Post
    You should be pushing that aspect, as a 29+ tire, since there's a limited selection in that category.
    I am down with you on the possibilities of using this tire for other appilcations besides sand and snow. I was thinking that they could possibly make for a nice downhill tire on a wider 45mm rim such as Mülefüt, Rabbit Hole or Scraper so I took a photo of the Warrior on a 29.5mm Velocity Blunt and sent it to Xtreme.

    (Click on photo to enlarge)
    29 fat-img_7029.jpg
    Last edited by FatBike&SlenderWoman; 02-15-2017 at 12:51 PM. Reason: grammer :)

  38. #38
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    29 Wide vs 26 Fat

    Quote Originally Posted by MendonCycleSmith View Post
    Stupid saddles...
    LOL, can't get your head around the Moonsaddles huh?
    Well, since my primary cycling activity consists of commuting from point A to point B, I have never had the desire to own or be seen in any form of cycling specific attire. 99% of my time spent in the saddle is wearing khakis or jeans.

    For off-road technical riding requiring center of gravity shifts and flicking the bike around, the lateral control that a traditional nosed saddle provides is the better fit.
    For commuting in street cloths and day long cross country treks, your 'boys' will be much happier if the saddle supports your skeleton rather sitting on your junk all day. The women that have ridden stoker with me on my tandem tell me that Moonsaddles make their 'hoo hoo' happier as well.

    Quote Originally Posted by MendonCycleSmith View Post
    and poor use of the English languages spelling tenets for the brand name, pretty much insults the intelligence of anyone with a pulse.
    That practice has it's roots in the early 70's when Miller came out with their shitty 'Lite' beer so I'll give you that one.


    Quote Originally Posted by MendonCycleSmith View Post
    ...low volume tire on wide rim just screams poorly thought out...
    Tell that to NASCAR and the Grand Prix racers. (I know...apples to oranges. I'm just being a smart ass)


    Quote Originally Posted by MendonCycleSmith View Post
    or, someone who has no connection to the actual fat bike world, and is embodying the concept of, just because you can, doesn't mean you should.
    For the sake of argument, I will refer to the Xtreme tire/rim combination as '29-wide'
    Fact is that with all other things being equal, racing on sand, the 29-wide wheel has proven itself to be at least 6% faster than any 26-fat wheel in production.
    Bikes running the 29-wide wheels now hold two Guinness world speed records.
    Last month, my race peeps tested a 29-wide wheelset at an event and told me that it is just as sure footed along with being significantly faster than a Dillinger 4 on groomed snow.
    I have had the same experience riding unplowed snowmobile tracks with my bikes.

    Quote Originally Posted by MendonCycleSmith View Post
    A rim that wide, purpose built larger diameter, really needs a tire with equal design qualities.
    Engineering is the art of compromise. One has to choose priorities and decide what trade-offs they are willing to make in order to achieve the goal. A taller tire begets heavier wheels, heavier frame. It all depends on the application.
    Tall fat tires will keep you rolling through deep snow.
    Low profile wide tires will get you on the podium at the Birkie.

    Quote Originally Posted by MendonCycleSmith View Post
    Let me guess, extra attention was given to the placement of holes in the rim so as to prevent uneven spin balance.
    ...only if you have a speedo magnet to counter balance the valve stem. JK
    After setting up a set of these tubeless for the race team to try out, we did the math and determined that the rim strip necessary to seal those holes ended up adding twice as much mass when compared to the mass subtracted by the holes in the first place so, I passed that bit of info on to Xtreme.
    Looks like the next batch of rims will no longer have holes resulting in a lighter, stronger wheel set. All that is required for tubeless is 7g of tape over the spoke heads or maybe a FattyStripper. I am going to miss the bling strip.
    Last edited by FatBike&SlenderWoman; 4 Weeks Ago at 02:13 PM. Reason: grammer :)

  39. #39
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    My mistake! I thought you were the manufacturer(obviously).

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    Quote Originally Posted by slowride454 View Post
    I saw this bike today at our fatbike race. Can't miss the funny looking saddle and the wheel/tire combo.
    Aside from the previous weeks Bike Across Bago, the Fat Cupid Ride was the first chance I've had ride a bike on an actual groomed trail. I used it as an opportunity to test the performance of different wheel/tire combinations in what turned out to be 'soft' snow.
    I rode each wheel set for two laps stopping to adjust tire pressures along the way. Then I would ride back to the van, perform a NASCAR like wheel swap and do another two laps.
    My rear brake was acting up out of the gate...pad damage probably from the hasty wheel swaps so I rode most of the event with no rear brake. I discovered significant differences among the four wheel sets but then there where also significant differences in trail conditions from the first to last lap as well.


    Quote Originally Posted by slowride454 View Post
    Dude looks like he is drunk all the time.
    Too funny! There must have been something in that green smoothie that I drank on the way to Appleton.
    Last edited by FatBike&SlenderWoman; 4 Weeks Ago at 02:14 PM.

  41. #41
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    The point here is that as you increase the rim diameter the casing does not need to be 6" tall. Decreasing the casing back down to a more manageable size like the first fat tires makes it lower weight and more predictable over greater variables.

    29"x5" (OR 29"X6" which is what my friends and I really want) will have more float and traction. A manageable 10 to 15 psi replaces 2 to 5psi. No rim strikes, burping or crazy bouncing. Thus eliminating the negative factors of increasing casing size on 26" rims and adding the properties that we want more of in deep snow. Traction and float.

    Another "invisible elephant in the room" we are not discussing is BB width verses frame clearence. Easily fix by switching to pinion gearbox drive platform. The roloff hub types have not been proven to meet fatbike expectations. A gearbox will give us a manageable Q factor, chain line and reliability.

    Those touting that this is too niche oriented, have narrow future vision. Fat bikes have exploded in winter and summer. Multiple wheelsets make it possible to make many terrains work and money in sales for the industry. I now see fat bikes and 29+ everywhere. A bike platform that takes us farther, easier and gives the industry an excuse to sell us more products is a win win situation.

    I saw all the same negative comments when 29ers first raised its ugly head and look now. Most of us are on them. Bypass all these tiny incremental steps towards what we will end up with anyways.

  42. #42
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    Quote Originally Posted by OilcanRacer View Post
    The point here is that as you increase the rim diameter the casing does not need to be 6" tall. Decreasing the casing back down to a more manageable size like the first fat tires makes it lower weight and more predictable over greater variables.

    29"x5" (OR 29"X6" which is what my friends and I really want) will have more float and traction. A manageable 10 to 15 psi replaces 2 to 5psi. No rim strikes, burping or crazy bouncing. Thus eliminating the negative factors of increasing casing size on 26" rims and adding the properties that we want more of in deep snow. Traction and float.

    Another "invisible elephant in the room" we are not discussing is BB width verses frame clearence. Easily fix by switching to pinion gearbox drive platform. The roloff hub types have not been proven to meet fatbike expectations. A gearbox will give us a manageable Q factor, chain line and reliability.

    Those touting that this is too niche oriented, have narrow future vision. Fat bikes have exploded in winter and summer. Multiple wheelsets make it possible to make many terrains work and money in sales for the industry. I now see fat bikes everywhere. A bike platform that takes us farther, easier and gives the industry an excuse to sell us more products is a win win situation.

    I saw all the same negative comments when 29ers first raised its ugly head and look now. Most of us are on them. Bypass all these tiny incremental steps towards what we will end up with anyways.
    More casing = more float. When run at lower pressures, a bigger casing has a greater potential to spread out into a much larger footprint. Lower pressures will also deform more and have less likelihood for the leading edge of the contact patch to break through and take the rest of the tire with it. Look at the wheeled (motorized)vehicles designed for snow. The have a much bigger R&D budget than all fat bike manufacturers combined due to the economic pressure of finding the most efficient way to work in that environment. They almost universally go with huge, supple casings at very low pressures. The ones that don't are using tracks. They're not going with large diameter, low volume.

  43. #43
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    Quote Originally Posted by sean salach View Post
    More casing = more float. When run at lower pressures, a bigger casing has a greater potential to spread out into a much larger footprint. Lower pressures will also deform more and have less likelihood for the leading edge of the contact patch to break through and take the rest of the tire with it. Look at the wheeled (motorized)vehicles designed for snow. The have a much bigger R&D budget than all fat bike manufacturers combined due to the economic pressure of finding the most efficient way to work in that environment. They almost universally go with huge, supple casings at very low pressures. The ones that don't are using tracks. They're not going with large diameter, low volume.


    Of course flattening the tire of a larger casing tire will give you a bigger footprint. But a 29"x5" (or 29"x6") already gives you a bigger footprint without having to use lower psi. Thats the point. More positive less negative tendencies. Lower psi is not needed.
    .
    your analogy with car tires is flawed. They are also trying to keep down manufacturering costs and cars cannot run taller wheels. Like us they would need a whole new car (bike for us). The cost is vastly higher. Their constraints makes for a poor correlation to our plight.
    Out riding, leave a message

  44. #44
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    Quote Originally Posted by OilcanRacer View Post
    Of course flattening the tire of a larger casing tire will give you a bigger footprint. But a 29"x5" (or 29"x6") already gives you a bigger footprint without having to use lower psi. Thats the point. More positive less negative tendencies. Lower psi is not needed.
    .
    your analogy with car tires is flawed. They are also trying to keep down manufacturering costs and cars cannot run taller wheels. Like us they would need a whole new car (bike for us). The cost is vastly higher. Their constraints makes for a poor correlation to our plight.
    If the two tires have the same outside diameter, the one with the higher volume casing will make a bigger footprint at lower pressures. If you have a low profile 29 x 6" tire with the outside diameter of a 29+, it will be similar to the outside diameter of 26 x 4.8". You could go to 24" x 6", get the same outside diameter and, theoretically, drastically more float.

    I wasn't talking about cars. I was talking about Arctic exploration trucks and Arctic oil field equipment.

    Even the Russians know this.

    https://www.youtube.com/watch?v=c58xlx5AGA8

  45. #45
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    Quote Originally Posted by OilcanRacer View Post
    Of course flattening the tire of a larger casing tire will give you a bigger footprint. But a 29"x5" (or 29"x6") already gives you a bigger footprint without having to use lower psi. Thats the point. More positive less negative tendencies. Lower psi is not needed.
    .
    your analogy with car tires is flawed. They are also trying to keep down manufacturering costs and cars cannot run taller wheels. Like us they would need a whole new car (bike for us). The cost is vastly higher. Their constraints makes for a poor correlation to our plight.


    The Vee 2XL's are already over 31" tall by 5.25" wide. Even at 0.0 psi they don't offer enough float. I don't disagree with your assertion but we're going to need bigger than 29 x 6 to be able to ride, period, and a LOT bigger than that to be able to ride at pressures in the teens.
    Handbuilt wheels: www.LaceMine29.com

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    Quote Originally Posted by sean salach View Post
    If the two tires have the same outside diameter, the one with the higher volume casing will make a bigger footprint at lower pressures...
    This is true but to avoid confusion, I would change one word in your statement... 'the higher volume casing CAN make a bigger footprint at lower pressures.

    For all pneumatic tires, area of the footprint is result of weight divided by tire air pressure.
    Weight ÷ psi = footprint
    My bike with me sitting on it has approximately 150 lbs on the rear wheel.
    A 29 X 3 Knard or a 26 x 4.8 Knard (same diameter) both inflated to 10 psi will have a 15 square inch footprint. At 5 psi the footprint doubles to 30 square inches.
    The 4.8" casing will have a shorter, wider footprint compared to the 3.0" casing but the area of both will be equal.

    The often overlooked factor is that the relationship of rim width to casing width can become the limiting factor when it comes to the size of foot print.

    Air pressure forces acting on the inside of the rim is what supports the weight of the bike so if the rim width is reduced to half, the lift is reduced to half.
    If at a given weight, a 100mm rim bottoms out at 3 psi then a 50mm rim will bottom out at 6 psi.

    The other factor here is rim size or more accurately, rim area. A 622mm (29") rim has 11% more circumference than a 559mm (26") rim giving the 29er 11% more load capacity at a given rim width.

    So to keep things apples to apples, let's say that we mount the 3" tire on a 622 x 85mm rim and the 4.8" tire on 559 x 96mm rim. At some point while decreasing pressure with our 150 lb load on the wheel, the 3" tire is going to run out of casing and either bottom out or burp the bead. So Yes, the larger 4.8" tire on a rim large enough to support the bike at lower pressures will be capable of an even larger footprint as the pressure is lowered further.

    A 3.0 x 29 Knard on a 29mm Velocity Blunt rim is capable of running at lower pressures without burping while achieving a larger footprint when compared to it's 4.8 x 26 counter part on a Velocity Blunt rim.

    Bottom line is that the differences in maximum achievable footprint between different size tires quickly diminishes as rim width is reduced.
    Last edited by FatBike&SlenderWoman; 4 Weeks Ago at 09:13 AM.

  47. #47
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    Quote Originally Posted by mikesee View Post
    The Vee 2XL's are already over 31" tall by 5.25" wide. Even at 0.0 psi they don't offer enough float...
    That is because the rims are not wide enough take full advantage of the casing. Performance at lower pressures is a product of rim size more than anything else. A 3" tire on an 85mm rim can be run at lower pressures without burping than a 5" tire on a 50mm rim. More at post #46 above...
    Last edited by FatBike&SlenderWoman; 4 Weeks Ago at 11:39 AM.

  48. #48
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    Quote Originally Posted by FatBike&SlenderWoman View Post
    This is true but to avoid confusion, I would change one word in your statement... 'the higher volume casing CAN make a bigger footprint at lower pressures.

    For all pneumatic tires, area of the footprint is result of weight divided by tire air pressure.
    Weight ÷ psi = footprint
    My bike with me sitting on it has approximately 150 lbs on the rear wheel.
    A 29 X 3 Knard or a 26 x 4.8 Knard (same diameter) both inflated to 10 psi will have a 15 square inch footprint. At 5 psi the footprint doubles to 30 square inches.
    The 4.8" casing will have a shorter, wider footprint compared to the 3.0" casing but the area of both will be equal.

    The often overlooked factor is that the relationship of rim width to casing width can become the limiting factor when it comes to the size of foot print.

    Air pressure forces acting on the inside of the rim is what supports the weight of the bike so if the rim width is reduced to half, the lift is reduced to half.
    If at a given weight, a 100mm rim bottoms out at 3 psi then a 50mm rim will bottom out at 6 psi.

    The other factor here is rim size or more accurately, rim area. A 622mm (29") rim has 11% more circumference than a 559mm (26") rim giving the 29er 11% more load capacity at a given rim width.

    So to keep things apples to apples, let's say that we mount the 3" tire on a 622 x 85mm rim and the 4.8" tire on 559 x 96mm rim. At some point while decreasing pressure with our 150 lb load on the wheel, the 3" tire is going to run out of casing and either bottom out or burp the bead. So Yes, the larger 4.8" tire on a rim large enough to support the bike at lower pressures will be capable of an even larger footprint as the pressure is lowered further.

    Bottom line is that the differences in maximum achievable footprint between different size tires quickly diminishes as rim width is reduced.
    Some of your ideas are based in truth, but you are not taking everything into account. First, the relationship between safe pressure and rim is not linear. Doubling the rim width does not allow you to run half the pressure. The other problem is that a tire basically acts like a balloon, looking at the cross section. With your theoretical approch to reducing sidewall height with a bigger rim, you just end up with a narrower tire overall, which requires more pressure and results in less float.

    The only answer to getting more float is more volume. The rim size plays a much smaller role as far as I can tell, but's it's still noticeable. An example would be going from a 26x3.8 tire to a 27.5x3.8 tire. The one on the larger rim will give you more float because of the attack angle of the larger setup and also because it can be run at slightly lower pressures to increase the footprint. But if you try to increase the rim size without increasing the outside diameter, you just end up with a setup that needs more pressure and does not provide the same amount of float.

    Now if you are talking about speed on groomed or packed snow, that's whole different discussion. Your wide 29+ setup might well be faster there.

    Quote Originally Posted by FatBike&SlenderWoman View Post
    A 3.0 x 29 Knard on a 39mm Velocity Dually rim is capable of running at lower pressures without burping while achieving a larger footprint when compared to it's 4.8 x 26 counter part on a Velocity Dually rim.
    That statement is just not true. If you were comparing a 29x3 knard to a 26x3 Knard then it would be true.

  49. #49
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    Quote Originally Posted by FatBike&SlenderWoman View Post
    That is because the rims are not wide enough take full advantage of the casing. Performance at lower pressures is a product of rim size more than anything else. A 3" tire on an 85mm rim can be run at lower pressures (larger footprint) without burping than a 5" tire on a 50mm rim. More at post #46 above...
    Again, not true. Any he is talking about running that 5.05 tire on a 100mm or wider rim, not a 50mm rim.

  50. #50
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    [QUOTE=bikeny;13044770]...Now if you are talking about speed on groomed or packed snow, that's whole different discussion. Your wide 29+ setup might well be faster there.

    Exactly...I have run the 29's in mashed potatoes at 4 psi but it's a struggle. Bud/Lou/CS are much better in that situation.

    I do have to make a correction, the rims we tested were a 29mm Velocity Blunts.
    We mounted a 4.8 x 26 tire to the front fork of a bike, put the front wheel in a tray full of sand then I climbed and stood my 210 lb carcass on top of the handlebars.
    Just so you know, the layer of sand was 5mm deep, just enough to get an imprint of the casing that is flat on the surface. I realize that in deep sand or snow, the center of the tire would sink in deeper and create a larger imprint but I was looking for how much load could be put on the rim before it bottomed out like when you jump a curb.

    The tire was deflated until the rim bottomed out. By that time, the bead had flipped and the casing was actually beginning to wrap itself around the rim. If it wasn't for the inner tube, the tire would have burped before the rim bottomed out. What we found interesting is that the outer most row of knobs barely made contact with the sand.

    Same test procedure with a 3.0 x 29 tire but when the tire was able to be deflated a half pound lower before bottoming out. The contact patch measured 98mm wide which included some sidewall since the tread imprint was only 79mm wide. So I will agree that the 4.8 had a larger tread imprint in the sand but total footprint of both tires was essentially the same. I realize that running a 4.8" (260mm bead-to-bead) tire on a 29mm rim is an extreme example but as the rim width approaches 12% of the tire bead-to-bead, it becomes the limiting factor.

    A real world example:
    One can estimate tire/rim volume factor for comparison purposes by adding the tire bead-to-bead measurement with the rim inner bead width and then subtracting the bead overlap (15mm). This gives you the total section circumference.

    My Salsa Beargrease came with a Dillinger 4 on a Marge Light rim so...
    Dillinger 4 b-b: 227
    Marge Lite b-b: 59
    227 + 59 - 15 = 271 Section Circumference

    622mm Xtreme 29 wheel set
    Xtream Warrior b-b: 188
    Xtream Carbon b-b: 85
    188 + 59 - 15 = 258 Section Circumference
    Factor in that 29 wheels have roughly 11% more volume than a comparable 26 so..
    258 * 1.11 = 286 Effective Section Circumference

    Just for comparison, D4 on a 76mm Rolling Daryl comes in at 288

    As you can see, the Xtreme 29 tread width and volume is comparable to the D4 but with 300g less mass along with the ability to run at lower pressures without burping.

    There are plenty of 29+ tires out there that are competing and winning races against the 26 fatties on sand and snow but it doesn't happen on 50mm rims.

    Isn't physics fun?

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