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  1. #1
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    How important is a new fork when switching 29->27.5+ ?

    I have a 2017 Santa Cruz tallboy 29er. It has a 120mm travel fork. The frame is designed to allow for 27.5+ wheels as well, but when they sell the bike in that configuration, it comes with a 130mm fork. Can I get away with my 120mm fork with 27.5+, or do I really need that 130 fork?

  2. #2
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    You can get away with it. But youíll steepen the head angle a little and lower the BB. 27.5+ isnít as tall as the 29. Thatís where the increased travel fork comes in to get the geometry as close to original as possible.
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  3. #3
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    I don't think the head angle will change since both wheels will be the same size. The bottom bracket will be lower however, and it may or may not be too low. You can try it and see how it works, depending on which fork you have swapping in a longer air shaft shouldn't be a problem for a good shop.

  4. #4
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    Absolutely not true, your are changing both wheels to smaller, it has ZERO effect on any angles, the only thing that will change is BB height if he runs anything under a 3.25" B+ tyre (they're about as tall as a 29x2.25" tyre) and you can't fit one of them in a TB.

    Quote Originally Posted by almazing View Post
    You can get away with it. But youíll steepen the head angle a little and lower the BB. 27.5+ isnít as tall as the 29. Thatís where the increased travel fork comes in to get the geometry as close to original as possible.
    100% correct, only difference will be BB height. I would suggest if you're thinking of getting one of these bikes and using both wheel sizes, that you go with the B+ configuration and longer fork and just deal with the taller BB when using the 29" wheels. Since the OP already has the 29er version of the bike, as said, an air spring swap to make it 130mm travel would work and is probably the best option.
    Quote Originally Posted by jgdblue View Post
    I don't think the head angle will change since both wheels will be the same size. The bottom bracket will be lower however, and it may or may not be too low. You can try it and see how it works, depending on which fork you have swapping in a longer air shaft shouldn't be a problem for a good shop.
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  5. #5
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    Yeah, you'll probably want to adjust the air spring. I've found that on most of the bikes that can swap between 27.5+ and 29, you absolutely do not want to lower the BB unless you ride smooth trails.

    I run a 150 fork on my Hightower in both configurations since it's easier than swapping back to 140.

  6. #6
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    If your fork is Boost 110x15 you'll have the width for the wider tires.

  7. #7
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    Stick a 10mm spacer under the bars and see if you like it.

  8. #8
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    Thanks for the advice. I didnít even know that I might be able adjust my fork (Fox 34) to give it a longer travel.

  9. #9
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    Quote Originally Posted by LyNx View Post
    Absolutely not true, your are changing both wheels to smaller, it has ZERO effect on any angles, the only thing that will change is BB height if he runs anything under a 3.25" B+ tyre (they're about as tall as a 29x2.25" tyre) and you can't fit one of them in a TB.


    100% correct, only difference will be BB height. I would suggest if you're thinking of getting one of these bikes and using both wheel sizes, that you go with the B+ configuration and longer fork and just deal with the taller BB when using the 29" wheels. Since the OP already has the 29er version of the bike, as said, an air spring swap to make it 130mm travel would work and is probably the best option.
    I also have a brand new Tallboy 3 29er. I don't have any experience on a FS trail bike, so I opted for a set of 27.5+ wheels with 2.8" tires. Took my first ride on the 29x2.3 tires and it was great. Next time I'll swap wheels and see what the ride is like on those. It's supposed to be like a different bike. So I need to make an air spring swap and this gives me 10mm more travel?

  10. #10
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    If one runs it with 120 mm fork, 27.5+ wheels, and you flip the chip on shock to H, yes the result will be a slightly steepened head tube angle compared to 29er with chip on L.

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