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  1. #1
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    27.5 x 3.8 VS 29 x 3.0 for dirt use

    I have a 2017 Fatboy Expert Carbon which obviously has 26" wheels. When I bought it I only planned to use this bike in the snow so I swapped out the 26x4.0 Ground Control's for Bud/Lou 4.8's (which are awesome in the snow)

    I am interested in a new wheelset for use during the winter when I am in AZ and UT on some primitive roads that are loose and sandy, and probably some 4wd roads here in CO during the summer.

    Initially I planned to purchase a 29x3.0 setup but recently have been reading about 27.5 x 3.8's. From the overall diameter measurements I've been finding it appears that 29x3.0 and 27.5x3.8 should be similar diameter to my 26" Bud and Lou combo. Of course these measurements are from different sources so I'm not sure how accurate they are. Since the OE 4.0's are smaller in diameter than my current Bud/Lou's I can definitely go a little smaller than the Bud/Lou setup if needed.

    Aside from sizing my real question is what makes the most sense for my described riding. It sounds like the 27.5x3.8's roll pretty fast on gravel and dirt although I'm not sure how they compare to 29+. Common sense tells me that 29+ will be faster with less flotation on the soft stuff. I would like to hear from people who have ridden both setups on dirt and get their opinions as to the best all around setup for me. Also I'm not doing any racing with this bike, this is all about fun.

    I should add that I also have a Bluto with 120mm travel.
    Last edited by Projected; 2 Days Ago at 12:58 PM.

  2. #2
    fat guy on a little bike
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    Quote Originally Posted by Projected View Post
    I am interested in a new wheelset for use during the winter when I am in AZ and UT on some primitive roads that are loose and sandy, and probably some 4wd roads here in CO during the summer.

    Initially I planned to purchase a 29x3.0 setup but recently have been reading about 27.5 x 3.8's. From the overall diameter measurements I've been finding it appears that 29x3.0 and 27.5x3.8 should be similar diameter to my 26" Bud and Lou combo.
    I am a HUGE 27.5x3.8/4 fan. I ride it year round, except for the 15~20 winter rides that necessitate studs.

    post this same question in the plus bike forum, and they will say 29x3 0WNz aLL!

    Quote Originally Posted by Projected View Post
    I would like to hear from people who have ridden both setups on dirt and get there opinions as to the best all around setup for me. Also I'm not doing any racing with this bike, this is all about fun.
    i am all about fun, 100% of the time! well, 99.837%. when i am on the toilet in the morning, i am all business...

    in all seriousness, i had a stache 29x3 tired bike, and i did not get along with it. it did not match my style or the conditions/places i ride, so off she went.

    Quote Originally Posted by Projected View Post
    Common sense tells me that 29+ will be faster with less flotation on the soft stuff.
    tsk tsk my boy, this is the internet, common sense has no place here!

  3. #3
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    29x3.0
    Rigid SS 29er
    SS 29+
    Fat Lefty
    SS cyclocross
    Full Sus 29er (Yuck)

    Stop asking how much it weighs and just go ride it.

  4. #4
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    I own and ride both. I didn't fall in love with B-fat. Speaking only for myself, they floated only marginally better than 29x3.0, they felt slow and heavy. All that said perhaps it was just the tire I chose, Minion FBF front and rear. This all in bikepacking usage. I know this thread is about B-fat vs 29x3 but for my own curiosity I weighed the rear wheel of both the B-fat and 26x4. B-fat build is Mulefut 50 rims, sapim race spokes, brass nips and the afore mentioned FBF. 26x4 was My Other Brother Darryl rim, sapim race spokes, alloy nips, Husker Du tire. No cassette or rotor on either and B-fat tubeless, 26x4 tubed. Both have Bitex fat 12x197 hubs. Already forgot the actual #'s but the B-fat was 5 oz. (142 grams) heavier.

    Winter has come and all 3 wheelsets now reside on my wall waiting for spring while I ride my Dillinger 5/Wrathchild studdded combo. I'll probably give the B-fat another try in spring.

  5. #5
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    I have both sizes and use both depending on where and what I'm riding( which is New England).
    50mm carbon 27.5 rims with Hodags: gets used on my hard tail more because of the cush factor. Also used when it's wet or soft for traction and float.

    38mm carbon 29 rims with Bontrager Chuapa XR2. Use these more on my F/S bike...and on the hardtail when it's smoother stuff. When it's dry...these things rule.

    Tire choice and rim width make a huge difference.

  6. #6
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    Quote Originally Posted by Rodney View Post
    I am a HUGE 27.5x3.8/4 fan. I ride it year round, except for the 15~20 winter rides that necessitate studs.

    post this same question in the plus bike forum, and they will say 29x3 0WNz aLL!



    i am all about fun, 100% of the time! well, 99.837%. when i am on the toilet in the morning, i am all business...

    in all seriousness, i had a stache 29x3 tired bike, and i did not get along with it. it did not match my style or the conditions/places i ride, so off she went.



    tsk tsk my boy, this is the internet, common sense has no place here!
    What bike do you ride ?

  7. #7
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    Opposed to running your 26" wheels? I run 26 x 3.8 or 4.0 in the summer with good results. On 80 mm rims.

  8. #8
    All Lefty's, all the time Moderator
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    29+ all day long.

    B-Fat is a silly marketing gimmick IMHO, but in this specific case, why carry more weight for less roll over and overall diameter, when the conditions don't even require float?
    This is a Pugs not some carbon wannabee pretzel wagon!!

    - FrostyStruthers



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  9. #9
    fat guy on a little bike
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    Quote Originally Posted by TheNatureBoy View Post
    What bike do you ride ?
    Lenz Fatillac & Surly Wednesday.

    Quote Originally Posted by MendonCycleSmith View Post
    29+ all day long.

    B-Fat is a silly marketing gimmick IMHO, but in this specific case, why carry more weight for less roll over and overall diameter,
    vanhelga 27.5x3.8 is the same OD at 29+. more cush, and currently my favorite 3 season tire. i wish it fit in the back of my fatillac, but it is not even close...

  10. #10
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    Quote Originally Posted by Rodney View Post
    I am a HUGE 27.5x3.8/4 fan. I ride it year round, except for the 15~20 winter rides that necessitate studs.

    post this same question in the plus bike forum, and they will say 29x3 0WNz aLL!



    i am all about fun, 100% of the time! well, 99.837%. when i am on the toilet in the morning, i am all business...

    in all seriousness, i had a stache 29x3 tired bike, and i did not get along with it. it did not match my style or the conditions/places i ride, so off she went.



    tsk tsk my boy, this is the internet, common sense has no place here!
    Haha! Thanks Rodney!

    Quote Originally Posted by DougA View Post
    I own and ride both. I didn't fall in love with B-fat. Speaking only for myself, they floated only marginally better than 29x3.0, they felt slow and heavy. All that said perhaps it was just the tire I chose, Minion FBF front and rear. This all in bikepacking usage. I know this thread is about B-fat vs 29x3 but for my own curiosity I weighed the rear wheel of both the B-fat and 26x4. B-fat build is Mulefut 50 rims, sapim race spokes, brass nips and the afore mentioned FBF. 26x4 was My Other Brother Darryl rim, sapim race spokes, alloy nips, Husker Du tire. No cassette or rotor on either and B-fat tubeless, 26x4 tubed. Both have Bitex fat 12x197 hubs. Already forgot the actual #'s but the B-fat was 5 oz. (142 grams) heavier.

    Winter has come and all 3 wheelsets now reside on my wall waiting for spring while I ride my Dillinger 5/Wrathchild studdded combo. I'll probably give the B-fat another try in spring.
    Great insight, thanks Doug!

    Quote Originally Posted by leeboh View Post
    Opposed to running your 26" wheels? I run 26 x 3.8 or 4.0 in the summer with good results. On 80 mm rims.
    Since I will be riding snow and dirt in the winter, sometimes every other weekend , I don't want to be changing tires that often. Especially if they are set up tubeless.

    So I decided I would rather buy another wheel set for dirt riding and my first thought was 29+. Since I'm buying a new wheel set I figured I should explore the 27.5 option as some people seem to really like it.


    Quote Originally Posted by MendonCycleSmith View Post
    29+ all day long.

    B-Fat is a silly marketing gimmick IMHO, but in this specific case, why carry more weight for less roll over and overall diameter, when the conditions don't even require float?
    I guess the main reason for looking at the 27.5 is that I "might" want to try riding down some washes, and a specifically a trail behind my parents house in AZ that crosses a few washes. But honestly the 29+ will probably float good enough for the percentage of time I see myself in any real sand. It may not be worth carrying around the weight of the 3.8's everywhere for the once in a while they may help out.

    That is why I wanted to get some opinions on how slow/fast/heavy the 3.8's feel compared to the 29+. Again common sense tells me they don't really compare, but just seeing what people think.

    Quote Originally Posted by the mayor View Post
    I have both sizes and use both depending on where and what I'm riding( which is New England).
    50mm carbon 27.5 rims with Hodags: gets used on my hard tail more because of the cush factor. Also used when it's wet or soft for traction and float.

    38mm carbon 29 rims with Bontrager Chuapa XR2. Use these more on my F/S bike...and on the hardtail when it's smoother stuff. When it's dry...these things rule.

    Tire choice and rim width make a huge difference.
    The 27.5 cush is something to consider on my hard tail. Even though I started on full rigid bikes when I was 14 and rode hard tails with 80mm of travel for many years my summer bike is a 155/160mm Transition Patrol so there may be some adjustment on my end

  11. #11
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  12. #12
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    29+ is the obvious answer as numerous posters have attested to.

    27.5x3.8 would be a complete waste of money. If you want a 4" tire, there are a gazillion 4" tires that fit on the wheels you already have. For summer use, the Jumbo Jim 26x4 tire is very popular.

    I second the above poster who said that "B-fat" is complete marketing nonsense. If you want a fat bike, ride a fat bike. If you want something with a little more grip that rides like a more conventional mountain bike, then ride a plus bike. "B-fat" is neither.

  13. #13
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    Quote Originally Posted by twodownzero View Post
    29+ is the obvious answer as numerous posters have attested to.

    27.5x3.8 would be a complete waste of money. If you want a 4" tire, there are a gazillion 4" tires that fit on the wheels you already have. For summer use, the Jumbo Jim 26x4 tire is very popular.

    I second the above poster who said that "B-fat" is complete marketing nonsense. If you want a fat bike, ride a fat bike. If you want something with a little more grip that rides like a more conventional mountain bike, then ride a plus bike. "B-fat" is neither.
    As I stated above I do not want to change tubeless tires once or twice a month so a 2nd wheel is what I'm looking at. As a result I'm not considering 4.0 tires on my current 26" wheels.

    I also had thoughts of possibly needing more float than 29+ so I thought, considering contact patch size, 27.5x3.8 might roll better and float about the same as a 26x4.0.

    Most likely I'll end up on 29+ but worth getting some opinions since I'm starting from scratch for wheel choice.

  14. #14
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    A taller fat wheel and tire combo is just heavier. The knobs on fat bike tires are not as big as the knobs on regular mountain bike or plus tires, and so the available traction on loose surfaces isn't that different. I actually think my 27.5x2.8" plus tires have more grip when leaned than my 26x4.8" fat bike tires on gravely loose over hard (higher ground pressure, larger knobs). In sand, it's no contest; any fat bike tire is going to have much more flotation than a plus tire. On the flat and flowy, once the heavy wheelset is going, it doesn't make much difference. Speeding up and slowing down is where the fat bike tires me out. Making the rim and tire combo taller and heavier for the same width tire is just going to make that situation worse. That's why a 27.5 fat makes no sense. It doesn't do anything 26 fat wasn't already doing, it just requires you to speed up and slow down a greater mass.

  15. #15
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    Quote Originally Posted by twodownzero View Post
    A taller fat wheel and tire combo is just heavier. The knobs on fat bike tires are not as big as the knobs on regular mountain bike or plus tires, and so the available traction on loose surfaces isn't that different. I actually think my 27.5x2.8" plus tires have more grip when leaned than my 26x4.8" fat bike tires on gravely loose over hard (higher ground pressure, larger knobs). In sand, it's no contest; any fat bike tire is going to have much more flotation than a plus tire. On the flat and flowy, once the heavy wheelset is going, it doesn't make much difference. Speeding up and slowing down is where the fat bike tires me out. Making the rim and tire combo taller and heavier for the same width tire is just going to make that situation worse. That's why a 27.5 fat makes no sense. It doesn't do anything 26 fat wasn't already doing, it just requires you to speed up and slow down a greater mass.
    Makes sense.

  16. #16
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    If you can only have one wheelset, make it 27.5 x fat.

    If you're going to keep your 26" set and add another set, 29+ makes the most sense. Fast, efficient, and fun -- a perfect counterpoint to your 26" x slow wheelset.

  17. #17
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    i own and ride both on a surly ICT. I find the 27.5x3.8 is great for flowing trails without a lot of rocks. When things get super rocky I like being able to fit my tire in tight spots without rubbing my sidewalls up, and I like a slightly higher bb, so I go with the 29+. Most of my riding is in relentlessly rocky areas so the 29+ stay on and the 27.5x3.8 set up sees very little use. I like to use the 27.5+ set up as a studded winter wheelset but I haven't found the money and there doesn't seem to be a good way to stud the hodags that I have.

  18. #18
    fat guy on a little bike
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    Quote Originally Posted by twodownzero View Post
    29+ is the obvious answer as numerous posters have attested to.

    27.5x3.8 would be a complete waste of money...

    I second the above poster who said that "B-fat" is complete marketing nonsense. If you want a fat bike, ride a fat bike. If you want something with a little more grip that rides like a more conventional mountain bike, then ride a plus bike. "B-fat" is neither.
    spoken like a true hater...



    Quote Originally Posted by mikesee View Post
    If you can only have one wheelset, make it 27.5 x fat.

    If you're going to keep your 26" set and add another set, 29+ makes the most sense. Fast, efficient, and fun -- a perfect counterpoint to your 26" x slow wheelset.
    excellent advice. / thread

  19. #19
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    Quote Originally Posted by twodownzero View Post
    The knobs on fat bike tires are not as big as the knobs on regular mountain bike or plus tires.
    Sorry, that is just patently false. Name me a non-fat tire with knobs as big as a Wrathchild, Vanhelga or Wazia (I'll stop there)?

  20. #20
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    Quote Originally Posted by BlueCheesehead View Post
    Sorry, that is just patently false. Name me a non-fat tire with knobs as big as a Wrathchild, Vanhelga or Wazia (I'll stop there)?
    Nate, Bud, Lou, Flowbeist, Dunderbeist
    Rigid SS 29er
    SS 29+
    Fat Lefty
    SS cyclocross
    Full Sus 29er (Yuck)

    Stop asking how much it weighs and just go ride it.

  21. #21
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    Quote Originally Posted by *OneSpeed* View Post
    Nate, Bud, Lou, Flowbeist, Dunderbeist
    Now that's just spiking the ball.

    Heck, the popular XR2/Chupa knobs are not as big as a Knard.
    Last edited by BlueCheesehead; 1 Day Ago at 09:39 AM.

  22. #22
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    Quote Originally Posted by mikesee View Post
    If you can only have one wheelset, make it 27.5 x fat.

    If you're going to keep your 26" set and add another set, 29+ makes the most sense. Fast, efficient, and fun -- a perfect counterpoint to your 26" x slow wheelset.
    I think Mike makes the most sense. For what it's worth, I have 26 & 27.5. I really like 27.5 and only put on the 26 to wear thru my tire stock and get a touch extra float in the soft stuff. 27.5 is faster and more nimble for me - but they are close enough that trying something totally difference (a la 29+) is a better spread. Can't help you on the 29+ specifically but the people I see rocking them seem to do pretty good blasting head on thru the chunk.

  23. #23
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    27.5 x 3.8 VS 29 x 3.0 for dirt use

    We had these discussions when the 29er came out. It was heavier, slower, gimmick, fad, bla, bla. Same arguments with the 27.5 format.

    Anyway, my advice for dirt only, is to get the 27.5 3.8 format only if you insist on seeing a fat tire under you.


    Sent from my iPhone using Tapatalk
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  24. #24
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    I got one of the last steel Chumba Fat bikes and had it built up 27.5 X 3.8 with 80mm rims. Loads of fun, carves real nice and I'm no slower/faster because of the size.. I have had probably every size wheel over the years and as mikesee mentioned this is my only wheel set for this bike. Great guys at Chumba to deal with BTW.

  25. #25
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    IMO I'd go 29+

    Simply because, as others have stated, there isn't as dramatic of a difference between 26 4.0 and 27.5 3.8

    The extra roll-over is what I'd be looking forward to. I run 29 X 3.0 on a fat bike and it's excellent for what it's intended for.

  26. #26
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    Missing from this conversation is the rims that go with your tires.

    If you have 27.5 x 3.8 with 80mm rims, you still have a fat bike. A bike which can handle sand or snow.

    For dirt, I run 27.5 x 3.8 with 50mm rims. The weight difference is tiny compared to 29+ and I would love to see some real data showing they roll slower than 29+. Tire choice is always a bigger factor than width anyway. In fact I might be willing to place a bet my 27.5 hodags are faster than 29+ with minions on gravel/hardpack. I do know that every time I've gone out with guys on standard bikes (27.5 or 29) I roll faster than they do when coasting on gravel or hardpack. They might have the weight advantage, but the roll over of the big diameter rubber is a real thing.

    In any case, I ride where most buddies are on full suspension, so I liked the idea of the extra volume and lower pressures front and back to soften the ride.

    So back to your original post, I'd say you can't go wrong with either choice, especially if you use light and narrower rims with the 27.5 option.
    Last edited by Teton29er; 16 Hours Ago at 10:17 AM.

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