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  1. #1
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    I was all about 27.5 and now Im like not so much

    ok so the 650b/27.5 bikes have intrigued me. I liked the idea until I really started trying to understand the science behind it. My pivot mach 5.7 has mountain king 2.4s in the front (measuring 27.25) and Xkings in the rear at 27.00. From what I have read most of the 27.5 bikes are measuring 27.00-28.00 inchs in diameter. Unless im missing something where is this benefit in going to the 27.5 inch option? Larger OD rim, with a smaller sidewall tire to net 27.5inchs? If this is the case I cant see how the 27.5 bikes are making much sense over a 26 inch bike.

  2. #2
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    Honestly, I think that you should not discount 27.5 until you try it. I also did notice that with high volume tires, the diameter on 26" rims is closer to 27". And certain 27.5 bikes have a diameter closer to 27 than 27.5.

    But still, let your butt tell you how it feels and if 27.5 is an improvement.
    Last edited by Vespasianus; 10-26-2013 at 08:19 AM.
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  3. #3
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    Quote Originally Posted by barry1me View Post
    ok so the 650b/27.5 bikes have intrigued me. I liked the idea until I really started trying to understand the science behind it. My pivot mach 5.7 has mountain king 2.4s in the front (measuring 27.25) and Xkings in the rear at 27.00. From what I have read most of the 27.5 bikes are measuring 27.00-28.00 inchs in diameter. Unless im missing something where is this benefit in going to the 27.5 inch option? Larger OD rim, with a smaller sidewall tire to net 27.5inchs? If this is the case I cant see how the 27.5 bikes are making much sense over a 26 inch bike.
    The difference in rim diameter between 26" and 650B is 18mm (.71") , so with the same model tire, the difference in wheel diameter will be that same measurement.

    Both wheel sizes, 26" and 27.5", are misnomers. With average tires, 26" wheels are bigger than 26", while 27.5" wheels are smaller.

    There is a slight, but noticeable difference in ride characteristics with 650B, but the reason I would go that way is to future-proof my ride, but I keep my bikes a long time. I really see the industry going to just two wheel sizes eventually, and one of them isn't going to be 26".
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  4. #4
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    OP: Have you ridden one? It seems like you're posting a lot of questions and suppositions. That's fine, this being the interwebz and all. But, really, just go ride a couple bikes and make your own decision.

  5. #5
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    Yo can't just compare 26 tall tires to 27.5 wheels/tires

    I really can't see how can a 2.4 tire would be fast roller, 27.5 wheelset and 2.1 fast rolling tires would make a huge difference.

    What if I get 27.5 wheels and get huge tires approaching 29", that wouldn't make much sense either
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  6. #6
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    Quote Originally Posted by Blatant View Post
    OP: Have you ridden one? It seems like you're posting a lot of questions and suppositions. That's fine, this being the interwebz and all. But, really, just go ride a couple bikes and make your own decision.
    I rode a SC solo or 5010 in the parking lot, but not a trail. I do need to spend some time on one, I am all for new technology but to buy into it, it has to make sense on the physics side of things for me.

    If I got a 27.5 bike it would be more of an AM bike then an XC bike, so I would run higher volume tires like I have on my mach 5.7. Im confused on how it would feel any better then my 26er with 27.25 inch tires on it right now.....both have similar diamater tires, difference would be a smaller side wall on the 27.5 and a .75" larger radius on the rim then the 26er. But if your overall tire diamater is the same how can it perform any different? Shouldnt the taller side wall tire on a 26er have a more compliant ride? a 26 inch rim would be more stiff then a 27.5 inch rim!? right?

  7. #7
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    Quote Originally Posted by barry1me View Post
    I rode a SC solo or 5010 in the parking lot, but not a trail. I do need to spend some time on one, I am all for new technology but to buy into it, it has to make sense on the physics side of things for me.

    If I got a 27.5 bike it would be more of an AM bike then an XC bike, so I would run higher volume tires like I have on my mach 5.7. Im confused on how it would feel any better then my 26er with 27.25 inch tires on it right now.....both have similar diamater tires, difference would be a smaller side wall on the 27.5 and a .75" larger radius on the rim then the 26er. But if your overall tire diamater is the same how can it perform any different? Shouldnt the taller side wall tire on a 26er have a more compliant ride? a 26 inch rim would be more stiff then a 27.5 inch rim!? right?
    You're hung up on the number, 27.5, which really has nothing to do with anything.

    Like I said right up there ^, the difference in diameter between 26" and 650B, WITH THE SAME MODEL TIRE, is .71" - so, if you run the same model tire that you are now, except in 650B, it's going to measure ~27.95".

    I don't get why you are trying to compare two different tires, on two different wheel sizes, just to arrive at an arbitrary diameter.
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  8. #8
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    I was all about 27.5 and now Im like not so much

    Quote Originally Posted by juan_speeder View Post
    You're hung up on the number, 27.5, which really has nothing to do with anything.

    Like I said right up there ^, the difference in diameter between 26" and 650B, WITH THE SAME MODEL TIRE, is .71" - so, if you run the same model tire that you are now, except in 650B, it's going to measure ~27.95".

    I don't get why you are trying to compare two different tires, on two different wheel sizes, just to arrive at an arbitrary diameter.
    Actually, the difference is 25mm/0.984"
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  9. #9
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    Quote Originally Posted by shiggy View Post
    Actually, the difference is 25mm/0.984"
    You're right. I was looking at ERD not BSD on a couple of rims.
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  10. #10
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    Quote Originally Posted by juan_speeder View Post
    You're hung up on the number, 27.5, which really has nothing to do with anything.

    Like I said right up there ^, the difference in diameter between 26" and 650B, WITH THE SAME MODEL TIRE, is .71" - so, if you run the same model tire that you are now, except in 650B, it's going to measure ~27.95".

    I don't get why you are trying to compare two different tires, on two different wheel sizes, just to arrive at an arbitrary diameter.
    I get why you are buying into the idea is to future proof your ride, makes sense. Besides that I cant make sense of this. Xking 2.2 26er is at 27.1" with 25psi in the tire, maxxis highroller 2 on a solo was 27.5" with 25psi in it. for .4" taller height I cant see how my novice abilities will notice that. It very well may well though. I think I would be better off putting a 650b rim/tire on my mach 5.7 to future proof this bike.

  11. #11
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    One of the mags recently ran an article which broken down all of the wheel sizes into comparisons of actual sizes and not just nominal. Sorry, can't remember which...maybe it was Switchback.

    Basically it said what other in this post have. There is really not that big a difference between 26" and 27.5" when you look at how manufacturers are kind of vague with their true sizes.

    I typically ride a 29er. I mostly ride XC and trail. For a long time I kept my 26" bike built up thinking I would ride it from time to time. After I made the switch, I rode my 26" one more time. It was clear it was much slower, blah blah blah.

    I recently rode a buddies 27.5" bike. It was more of an enduro setup than I am used to, but I don't feel like it felt as sluggish as my 26" bike. Maybe it was the setup or maybe it was the extra 3/4", not really sure. I think if I rode more downhill or enduro style riding, I could see how the 27.5" bike might feel a bit better.
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  12. #12
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    ya I have a 29er Epic and I love it, but I have the Mach 5,7 for more of a fun trail bike. I agree the 29er is faster and what not.

  13. #13
    Cleavage Of The Tetons
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    My 27.5 tires measure well over 28.
    There is math you can use.
    It's not just volume, but increased tire patch/contact patch.
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  14. #14
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    Quote Originally Posted by juan_speeder View Post
    The difference in rim diameter between 26" and 650B is 18mm (.71") , so with the same model tire, the difference in wheel diameter will be that same measurement.

    Both wheel sizes, 26" and 27.5", are misnomers. With average tires, 26" wheels are bigger than 26", while 27.5" wheels are smaller.

    There is a slight, but noticeable difference in ride characteristics with 650B, but the reason I would go that way is to future-proof my ride, but I keep my bikes a long time. I really see the industry going to just two wheel sizes eventually, and one of them isn't going to be 26".
    Your numbers are wrong
    The overall diameter of a 26" rim is 559mm.
    The overall diameter of a 650b rim is 584mm.
    The difference is 25mm which is pretty damn close to an inch (25.4mm).
    Please be careful what you post as some people will believe you.

    Riding a 650b with my wtb wolverine 2.2 is over 27.75". My nobby Nic at 2.35 is 28-13/16". - real close to 28".

    Hope that helps.
    Medz

  15. #15
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    barry1me - per above, you really need to demo a 27.5 bike on one of your home trails to form an opinion you'll be comfortable with. The ride difference is subtle (unlike your 29er); you'll notice the bigger wheels at first, then you get into your groove and it feels like a 26, just faster, a little bit more grab in the corners, and a tad bit more stable over the chunder. I've demo'ed a few now and liked them quite a lot. My take it is if you love your current 26 (like I love my 5.7C), ride it until you either need to get a new rig or are ready to upgrade. If one doesn't love their bike, then sell it now and order up a Mach 6. :^)

  16. #16
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    I was all about 27.5 and now Im like not so much

    I have been a long time user (Fanboy) if Conti tires and have been contemplating a 650 wheel build for my Firebird. I run a Rubber Queen 2.4 in the front on a Mavic rim. This tire measured 27". The 2.2 xKings that I use over our dry summers measure right at 26". I have a 2.4 XKing and it measures out just under 27" on the same 26" rim. Can you post pics of your tire sizes.

  17. #17
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    My wife's 27.5 is just about 28" with Nobby Nics.

    I thought I wanted a 27.5 too, until I rode a 429.

  18. #18
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    Quote Originally Posted by Mederz View Post
    Your numbers are wrong
    The overall diameter of a 26" rim is 559mm.
    The overall diameter of a 650b rim is 584mm.
    The difference is 25mm which is pretty damn close to an inch (25.4mm).
    Please be careful what you post as some people will believe you.
    That's not quite correct. Please be careful what you post...

    BSD refers to Bead Seat Diameter. This is not the overall diameter, rather the diameter of the location where the tire bead lands on the rim. Here's a diagram.

    Name:  bead-seat-diameter.jpg
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    BSD for -

    26" = 559mm
    650B = 584mm
    29" = 622mm
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  19. #19
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    despite the numbers... most people who have actually ridden 27.5 notice a small, but significant difference. I am one of them..

  20. #20
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    Agreed.
    I spent two days at a NEMBA fest demoing bikes, with the intention of confirming my desire for a 650B. I was also convinced that 29ers were for people who didn't appreciate the joys of flicking their 26er over and around things. After more than 12 hours of demo rides, my fantasy of what a 650b should be was broken.
    I ended up buying a 429c xx1, it is very flickable, rolls over everything, and grips demonstrably better than any of my old 26ers.

  21. #21
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    I own a 26" Firebird. The idea of converting it to 27.5 seems like a big waste of money. If I didn't already own the Firebird, then buying the 27.5 would make sense. Why not right? Any little advantage is great. As a result, I have concluded the following:
    1. Converting a 26" to 27.5 is not worth the financial investment, given the slight advantage.
    2. Buying a new bike I would choose 27.5 over 26"
    3. A long travel 29er will trump all, and hopefully Pivot is working on something in this category.

  22. #22
    Cleavage Of The Tetons
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    Quote Originally Posted by aevanlloyd View Post
    3. A long travel 29er will trump all, and hopefully Pivot is working on something in this category.
    Not necessarily. That's a false assumption. Depends on you, your riding preferences, terrain choice, and suspension needs.
    Pivot has the 429 already, but for some, the chain stays are too long, bike is sluggish in tight terrain, and is hard to wheelie....for others, it's just right.
    There are reasons beyond conspiracy theories that we are going through this wheel size 'revolution' (heh...). It's because everyone is a little different, which is good.
    "We LOVE cows! They make trails for us.....

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  23. #23
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    If it "depends on you, your riding preferences, terrain choice, and suspension needs" then how can my assumption be false? My assumption, after 3 years of riding a 29er, is that once Pivot figures out the geometry, a long travel 29er will be the ultimate trail bike. I demoed a Specialized Enduro 29er and they are on to something. That bike is breaking new ground. I have no doubt that with Chris's knowledge and the DW technology, a nimble long travel 29er is possible. For now, I'll stick with my Firebird and a couple of 29er XC bikes.

  24. #24
    Cleavage Of The Tetons
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    Logic isn't your major.
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    And then we eat them."

  25. #25
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    Quote Originally Posted by rideit View Post
    Logic isn't your major.
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