Do I need two sets of rims?- Mtbr.com
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  1. #1
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    Do I need two sets of rims?

    Getting closer to pulling the trigger on an Otso Voytech. I want to use it is a winter fat bike as well as an alternative 3 season trail bike (to my current 29er). Based on where I live I will do some snow riding, but if I'm lucky it will be 10 rides a year. It will get a lot more use as a 3 season bike. Based on a test down on bikerumor.com, the Voytek will fit 27.5 x 4.5 tires. So it is actually two questions.

    1) The main one is can I fit 27.5 x 4.5's, and 27.5 x 3.0 on the same rims? I'm assuming no, or it would work but would be a severe compromise. What about going down to 27.5 x 3.8's?

    2) So if I need two rims, should I do 26 or 27.5 as my winter choice? I do understand the differences in diameter, the potential effect on bottom bracket height, etc.--though the Voytek mitigates some of this with the adjustable rear dropout.

    And then a bonus question. I'm thinking about building up a winter wheel set (if I need two wheel sets) with less expensive hubs, aluminum rims, etc. But my three season wheel set would be dream hubs, carbon rims, etc. I'm thinking that the typical winter riding I will do won't demand the high end hubs, but I'd appreciate thoughts on that as well.

  2. #2
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    I have a Voytek. A true 27.5 x 4.5 will be a tough fit. My bike will not fit a 26" D5 on 65mm rims without the chain rubbing the tire in the two largest cogs. Could I make it fit by shimming the crankset and a little offset dish of the rear wheel, I expect so.

    The tuning chip (rear drop out adjustment) will do nothing significant to impact bottom bracket height. It certainly does not make up the difference between a 26 and 27.5" rim. I would be concerned about that going from 27.5 x 4.5 to 3.0.

    The Voytek is a great frame and I run mine 26 fat and 29+.

    Since you have a 29'r why not just set the Voytek up Bfat and call it a day. It will still be fun in the summer.

  3. #3
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    I've been in contact with Otso, and they have said that they can set the bike up to run 26 x 4.6. I assume that means that they shim/dish accordingly. I would assume that trying to fit a 27.5 x 4.5 would also work, because the width is similar enough, and the issue isn't the tire fitting in the frame, rather it is chain rub. Clearly the fit is somewhat tight in terms of frame clearance. I would sort all this out with Otso before buying--but I haven't asked if they'd be willing to try 27.5 x 4.5. Also, since I couldn't run slimmer tires on rims for those, then I'd have to think about just do 26's, and I could base that decision on the cost/weight difference between similar rim set ups.

  4. #4
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    Bug lug wide tires for snow
    Narrow fast rollers for fall/packed/spring.

    Wheel size as you need.

    Personally i would run 3.8x27.5 and being gnarwhals sound like they would be tight 26x4.6 knobbies... can even have studs like wrathchilds


    Sent from my iPhone using Tapatalk
    Fatbike, XC bike, Gravel Bike....

  5. #5
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    I've run 4.8's on 47mm rims, and I run 2.4" tyres on the same rim on my summer bike. Those extremes will obviously alter the profile and tread wrap of each tyre, but they both work reliably.

    Look at the Blizzerks for a lower cost, excellent tubeless aluminum fat rim. Experience with the 90's, but ppl like the 70 as well.

    Not sure about the fatbike hub thing. I've broken more fatty hubs(197mm) than regular mtb hubs in many fewer miles. A couple broken axles, cracked ratchet rings, and freehub failures. Multiple brands. As far as I can tell, fat hubs are built with the same materials and thicknesses as normal hubs, but span a much longer distance. Snow riding should require less, but I've had very poor 'luck' with fat hubs.

  6. #6
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    As BlueCheeseHead says, I think the problem going to a 4.5ish tire(26 or 27.5) is going to be the chain rubbing the tire in the easiest gears. You will need to either remove a couple of small cogs and space the cassette out, or use a different offset chainring, or possibly both, to fix that issue. That's just the way it is with a 170/177 spaced rear. Since you won't be running this setup a lot, if you can get away with a different offset chainring only, that's the way to go. That would pretty easy to accomplish using an SRAM or Race Face crank with direct mount rings. Chainline won't be ideal, but you're not putting a ton of miles on it like that.

    If I were choosing between 26x4.6 and 27.5x4.5, I'd always pick the 27.5x4.5.

    For your 3 season wheelset, I'd consider 29+ instead of 27.5+. Diameter would be closer to the 27.5x4.5.

    This is all assuming the 27.5x4.5 will actually fit the frame with a decent width rim.

    I do something similar, but one size smaller. I have a custom frame with 157mm rear spacing and an 83mm bottom bracket. For 3 seasons I run 27.5x3.25 or 29x2.6 with a normal chainring that's offset 6mm toward the center. For winter, I have a set or 27.5x3.8 tires on 65mm rims, and then I mount a 0mm offset chainring so the chain will clear the tire.

  7. #7
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    Just 2 sets of rims?
    I have 26 in 65, 80, 90 and 100( and probably going to sell the 80s)
    27.5 in 50 and 85
    And 29+
    With matching tires for conditions......

  8. #8
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    Just my opinion, but I'd rather do the 27.5 x __. I have two fatbikes - one with 26" wheels and the other with 27.5. If I could only keep one, it's an easy choice for me - the 27.5. It just "feels" better.

  9. #9
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    Quote Originally Posted by scottyferrari View Post
    1) The main one is can I fit 27.5 x 4.5's, and 27.5 x 3.0 on the same rims? I'm assuming no, or it would work but would be a severe compromise. What about going down to 27.5 x 3.8's?

    2) So if I need two rims, should I do 26 or 27.5 as my winter choice?

    If you do pick one rim to run 3.0's *and* 4.5's, you're compromising on the performance of at least one, and probably both. That's an enormous difference in sizing.

    As to your second question, need to know more about what your winter conditions are to understand which of 26 or 27.5 is ideal.

  10. #10
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    mikesee, my winter conditions are typically wetter snow, not infrequently rain on top of snow, and some ice (the Pacific Northwest, home of "cascade crud".

  11. #11
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    Quote Originally Posted by scottyferrari View Post
    mikesee, my winter conditions are typically wetter snow, not infrequently rain on top of snow, and some ice (the Pacific Northwest, home of "cascade crud".

    Sounds like float is low on the list and traction, possibly even with studs, is high?

  12. #12
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    Float need is probably medium. Traction is more important. I've ridden rental fat bikes without studs and not had a big problem, but for certain there are some times that if you want to ride, you need studs (or a trail at a much higher elevation).

  13. #13
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    Quote Originally Posted by scottyferrari View Post
    Float need is probably medium. Traction is more important. I've ridden rental fat bikes without studs and not had a big problem, but for certain there are some times that if you want to ride, you need studs (or a trail at a much higher elevation).

    Gotcha.

    If I were in your shoes and leaning toward a Voytek, I'd get one set of 27.5" wheels, and I'd use a ~50mm rim. Run the Bontrager Gnarwhals in 4.0 for float and traction (can be studded if needed), run something like the 3.8" Hodag for fast and fun.

    Or, if you want to just have one set of tires on that wheelset that can do it all, get a set of the Terrene Cake Eater's in 4.0.

    Compromises abound with any one-size-fits-all wheelset.

    After a season or two ridden that way, you'll have enough info to decide *if* you need a second wheelset, and if so, which direction to go on sizing to complement what you already have.

  14. #14
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    While the 27.5x4.5 Gnarwhal "fits" the rear of the Otso Voytek,there is less than 3mm clearance after stretching. It will rub on the chainstays in the longest setting while riding. Not a functional setup. We really need an actual 4.0" tire to be an ideal all rounder for the Voytek.

  15. #15
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    Quote Originally Posted by blackflys64 View Post
    While the 27.5x4.5 Gnarwhal "fits" the rear of the Otso Voytek,there is less than 3mm clearance after stretching. It will rub on the chainstays in the longest setting while riding. Not a functional setup. We really need an actual 4.0" tire to be an ideal all rounder for the Voytek.
    27.5 x 4 Gnarwhal.....Mikesee has them.
    Or a CakeEater or , my personal fave, Hodag

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