Results 1 to 23 of 23
  1. #1
    mtbr member
    Reputation:
    Join Date
    Mar 2008
    Posts
    1,071

    650b Conversions vs 650b Designed Frames

    Just wanted to know how much different 650b designed frames are compared to 650b conversions. For instance, some 29er frames are kind of compact from bottom to top and longer than 26 inch frames to compensate for the larger tires. I know I'm generalizing here, but if a frame is designed to be a 650b frame, how does the geometry compare to a 650b conversion? Are there any disadvantages of a 650b conversion compared to a 650b bike that is designed to be that way? For example, I imagine the bottom bracket might be higher on a conversion compared to a regular 650b frame - if this is the case, how might this or other factors effect performance?
    Last edited by getagrip; 12-05-2012 at 01:09 PM. Reason: Correction

  2. #2
    mtbr member
    Reputation:
    Join Date
    Jul 2005
    Posts
    824
    Some of the differences between 26" conversions to 650B vs 650B designed bikes, assuming you use similar sized tires (ie you don't go from using 26 x 2.4 tires down to 650B x 2.0).

    Conversions have:

    1) Increased trail on front fork. Despite same head angle, slower steering.
    2) Less clearance for mud.
    3) Higher bottom bracket and higher centre of gravity. Conversions won't have any bb drop associated with 650B wheels.650B bicycle could theoretically have bb drop designed in.
    Higher BB could be good and improve ground clearance.
    4) Possibly shorter wheelbase on conversion than on a 650B bike. Again, like bb height/drop, depends what 650B bike designers are doing. I haven't checked to see if 650B bike designers are using larger 650B wheels to slightly lower bb in relation to axles on 650B designed bikes, or increase wheelbase vs a 26" design.
    5) You have a relatively short chain-stay for the size of wheel tire you have. Possibly good for climbing.

    Then there's modded conversions. If you had to mod your 26" to make 650B wheels fit and/or work, you may have reduced rear shock travel. If you modded your bike to increase the head angle in order to compensate for the increase in fork trail, either by using offset shock bushings on the rear shocks of a full suspension 26'er, and/or used a headset that alters the head angle, you will slightly change wheelbase and/or increase seat tube angle.

    Many of these differences aren't huge, and it all depends on the bike. From my reading here many people here love their conversions.

    One difference between conversions and a 650B bike is, if you like the way the 650B from 26"conversion bike rides, you've made yourself a new bike experience One bike has become two bicycles! You have another wheel size bicycle experience without having to buy a whole other bicycle.
    Last edited by morkys; 12-06-2012 at 07:36 AM.

  3. #3
    mtbr member
    Reputation:
    Join Date
    Mar 2008
    Posts
    1,071
    Thanks morkys! Great technical response!

  4. #4
    mtbr member
    Reputation: OneEyedHito's Avatar
    Join Date
    Jun 2009
    Posts
    292
    Morkys,
    Line item #3, if my remedy says 13.9" BB height and then lists a .43" BB Drop, does your statement mean that there is not any BB drop at all if I put 650b wheels on the bike?!


    EDIT:
    Answered my own questions with a google, looks like BB Drop isn't a measurement from sagged suspension at all like I thought, but is a measurement from ("bottom bracket drop", it's the distance below the axle centerline to the bottom bracket centerline.), we damn looks like my BB is going to be a little higher than I wanted afterall......

    Thanks,
    Hito

  5. #5
    NedwannaB
    Reputation: JMac47's Avatar
    Join Date
    Apr 2004
    Posts
    8,604

    Same drop

    Quote Originally Posted by OneEyedHito View Post
    Morkys,
    Line item #3, if my remedy says 13.9" BB height and then lists a .43" BB Drop, does your statement mean that there is not any BB drop at all if I put 650b wheels on the bike?!

    Thanks,
    Hito
    Higher bb. Geometry is within the individual frame, whether it's sitting on a bench, or up on 12" blocks, or hanging in a stand.
    Wait,who did he tell you that?....

  6. #6
    mtbr member
    Reputation:
    Join Date
    Jul 2005
    Posts
    824
    Ur bb drop remains the same, but it's designed for 26". So there is no further bb drop in consideration of larger 650b wheels. Technically, if u imagine your bike redesigned with 650b wheels in mind, the designer may add up to a 1/2" more bb drop to compendate for the approx 1/2" higher that the 650b wheels raise your bike vs 26".

    Then again, instead of designing in a bb drop according to wheel size to give lower centre of gravity, ur higher bb height may give u more ground clearance, fewer pedal strikes. That is one difference I forgot to mention. It all depends on how ur bike is to begin with.

  7. #7
    mtbr member
    Reputation:
    Join Date
    Feb 2006
    Posts
    1,394
    Making generalizations or comparing apples to oranges does not answer your questions. Some stock 26" bikes have low BB's some have high, some have lots of clearance , some don't ,some have steep HA's........and so on......Buying a 27.5 specific frame may not get you the numbers you want either, unless you buy custom or are lucky, and have lots of cash....The good news is 27.5 is now coming fast so choices are growing.

  8. #8
    NedwannaB
    Reputation: JMac47's Avatar
    Join Date
    Apr 2004
    Posts
    8,604

    As I mentioned above

    Quote Originally Posted by morkys View Post
    Ur bb drop remains the same, but it's designed for 26". So there is no further bb drop in consideration of larger 650b wheels. Technically, if u imagine your bike redesigned with 650b wheels in mind, the designer may add up to a 1/2" more bb drop to compendate for the approx 1/2" higher that the 650b wheels raise your bike vs 26".

    Then again, instead of designing in a bb drop according to wheel size to give lower centre of gravity, ur higher bb height may give u more ground clearance, fewer pedal strikes. That is one difference I forgot to mention. It all depends on how ur bike is to begin with.
    Not rocket science. Same way they design geo "drop" for a 29, 32 or 36er for that matter.
    Wait,who did he tell you that?....

  9. #9
    mtbr member
    Reputation:
    Join Date
    Mar 2008
    Posts
    1,071
    Thanks for all of the responses. I was thinking about buying a Breezer 26er and converting it into a 650b. I wonder, though, if it would just be better to hold off and pick up a complete 650b bike. My main concern is how much converting a 26er into a 650b effects overall performance compared to an outright 650b. I don't like the fact that a lot of 650b bikes with entry level components are selling for $1400! Seems like you can get a better deal by doing a conversion, but I suppose that will vary by manufacturer, but you sacrifice frame design when you do that. Honestly, though, you can get a good entry level 29er for about $700, which has equal or better specs than most 650b models selling for over $1000, but if you are a shorter rider like me (5'7")...you might have a better experience on a 650b than a 29er. Decisions, decisions!

  10. #10
    mtbr member
    Reputation:
    Join Date
    Sep 2005
    Posts
    830
    Honestly it depends a lot on the bike. The Rush is a fantastic candidate for a conversion, other bikes, not so much. With a conversion, you'll always have compromises. On mine, the tire rubs the derailleur. I've tuned it so it's pretty minimal, but there's a fine line between rubbing and not working well. The BB height started super low, so adding a half inch is really a non-starter. On any other bike, it may not be so.

    If you convert, you have to ask- is mud clearance important? It'll be reduced pretty dramatically if you do.
    Is a higher BB a deal breaker? Out here on the NE coast, a high BB is a boon, and the cali-style super low BBs turn into pedal mashers, so adding a half inch can actually make a bike handle better.
    Are you flexible on steering? Finding an appropriate fork might be a challenge. Adding trail (by increasing wheel size) will slow the steering. If you swap to a 650b fork with decreased trail, you may end up with a longer axle to crown, slowing your steering back down. If you don't think you'll notice, then go for it!

  11. #11
    www.derbyrims.com
    Reputation: derby's Avatar
    Join Date
    Jan 2004
    Posts
    6,788
    Yes, morkys covered this very well. Thanks!

  12. #12
    Doesntplaywellwithmorons!
    Reputation: DeeEight's Avatar
    Join Date
    Jan 2004
    Posts
    10,578
    You can also consider BB drop/height as a factor in how easy the bike is to manual/wheelie. Bikes without any drop for example, like 26" wheel trials bikes... are amazingly easy to lift the front wheel on (whether you can balance once its up there is up to your own skill level) while bikes with a lot of BB drop (as many 29ers end up being designed) are very hard to get the front end lofted because your weight is much lower on the bike. I've noticed this myself on my 29ers and I've heard that comment from others trying 29ers for the first time coming from always riding 26ers. Here in Ottawa, we have a guy working at one shop who raced the men's olympic race in Atlanta and still owns his DBR Titanium team bike from back then (I saw him, and it only a week ago). Last month he and others took a drive down to vermont to ride the kingdom trail network. They stopped enroute at the Xprezo bikes factory in quebec and borrowed some demo bikes, including a 29er. The atlanta-games veteran, who'd raced professionally for years, complained about how hard it was to lift the front wheel on the 29er. Now if a pro-rider with tens of thousands of miles of riding experience, and likely tens of thousands of hours spent on a bike, has a hard time with a 29er, its no wonder many rank & file recreational riders never wanted to make the switch.
    I don't post to generate business for myself or make like I'm better than sliced bread

  13. #13
    Cleavage Of The Tetons
    Reputation:
    Join Date
    Jan 2004
    Posts
    4,830
    Exactly my Experience, Dee.

  14. #14
    dwt
    dwt is offline
    mtbr member
    Reputation: dwt's Avatar
    Join Date
    Jul 2009
    Posts
    3,891
    Quote Originally Posted by getagrip View Post
    Thanks for all of the responses. I was thinking about buying a Breezer 26er and converting it into a 650b. I wonder, though, if it would just be better to hold off and pick up a complete 650b bike. My main concern is how much converting a 26er into a 650b effects overall performance compared to an outright 650b. I don't like the fact that a lot of 650b bikes with entry level components are selling for $1400! Seems like you can get a better deal by doing a conversion, but I suppose that will vary by manufacturer, but you sacrifice frame design when you do that. Honestly, though, you can get a good entry level 29er for about $700, which has equal or better specs than most 650b models selling for over $1000, but if you are a shorter rider like me (5'7")...you might have a better experience on a 650b than a 29er. Decisions, decisions!
    A lot depends on the bike; a lot depends on the rider. I can't imagine at this point in my riding career buying a mtn bike without a demo first, especially when it has taller wheels and/or more suspension. I have a converted Chinese carbon HT, which is a good 5 lbs lighter than than my 5" travel Jamis 650B2. The lighter bike is more nimble, of course, but the dual suspension purpose built bike is just more comfy and fun for me to ride. Having said that, I do like the fact that pedal strikes are all but eliminated on the conversion. I do prefer having the problem eliminated than having to ratchet the cranks and overly finesse rocky terrain, as I must on the dually.

    So see if you can borrow a conversion, then demo it and the 29'ers and the 27.5'ers. It should be self-evident that there is no substitute for your personal demo. All of these bikes will be much different than your 26'er.
    Old enough to know better. And old enough not to care. Best age to be.

  15. #15
    Team Chilidog!
    Reputation: Stripes's Avatar
    Join Date
    Aug 2004
    Posts
    7,267
    Quote Originally Posted by dwt View Post
    A lot depends on the bike; a lot depends on the rider. I can't imagine at this point in my riding career buying a mtn bike without a demo first, especially when it has taller wheels and/or more suspension. I have a converted Chinese carbon HT, which is a good 5 lbs lighter than than my 5" travel Jamis 650B2. The lighter bike is more nimble, of course, but the dual suspension purpose built bike is just more comfy and fun for me to ride. Having said that, I do like the fact that pedal strikes are all but eliminated on the conversion. I do prefer having the problem eliminated than having to ratchet the cranks and overly finesse rocky terrain, as I must on the dually.

    So see if you can borrow a conversion, then demo it and the 29'ers and the 27.5'ers. It should be self-evident that there is no substitute for your personal demo. All of these bikes will be much different than your 26'er.
    Being someone who rides small frames, it can be really hard to find a bike to test ride in my size to get the right feel.

    I'm happy on a 26er and not in a market for a new bike, but I'm hoping when I am in a few years, it'll be for a 650b. I've test ridden a few 29ers and they all feel funky in different ways. Glad to see 650b is taking off.
    MTB4Her.com: mountain bike site for women, by women

  16. #16
    dwt
    dwt is offline
    mtbr member
    Reputation: dwt's Avatar
    Join Date
    Jul 2009
    Posts
    3,891
    Quote Originally Posted by Stripes View Post
    Being someone who rides small frames, it can be really hard to find a bike to test ride in my size to get the right feel.

    I'm happy on a 26er and not in a market for a new bike, but I'm hoping when I am in a few years, it'll be for a 650b. I've test ridden a few 29ers and they all feel funky in different ways. Glad to see 650b is taking off.
    Short stature rider, small frame and 29" wheels are not an ideal mix. Especially if you don't like toe/front wheel overlap. If and when you do want to try taller wheels, 27.5" may be better fit than 29". But demo. The 27.5" is still less flickable than your 26", though better in that dept. than 29". The 29" advantage is rolling over obstacles better than the other 2 sizes. But if nimble and easy to handle is your benchmark, you may never want or need to move up in wheel size.
    Old enough to know better. And old enough not to care. Best age to be.

  17. #17
    Team Chilidog!
    Reputation: Stripes's Avatar
    Join Date
    Aug 2004
    Posts
    7,267
    Quote Originally Posted by dwt View Post
    Short stature rider, small frame and 29" wheels are not an ideal mix. Especially if you don't like toe/front wheel overlap. If and when you do want to try taller wheels, 27.5" may be better fit than 29". But demo. The 27.5" is still less flickable than your 26", though better in that dept. than 29". The 29" advantage is rolling over obstacles better than the other 2 sizes. But if nimble and easy to handle is your benchmark, you may never want or need to move up in wheel size.
    Exactly. Being 5'5", but with a short torso means short frames for me. Need a pretty short top tube.

    However, finding small frames to demo is difficult--no matter what the wheel size is, which is why I've gone the boutique bike route.

    I'm not a fan of 29ers, but if I was looking for bigger wheels, it would be the 650b and not the 29er. But yeah, I'll definitely test ride what I can--but right now, I'm happy with the frames I have and not looking to switch out wheels or even do a conversion right now. Might try a B66er with my Ventana Ciclon at some point since the bike is designed around a taller AtoC than the standard Ciclons, but that's definitely way down the road.
    MTB4Her.com: mountain bike site for women, by women

  18. #18
    dwt
    dwt is offline
    mtbr member
    Reputation: dwt's Avatar
    Join Date
    Jul 2009
    Posts
    3,891
    Quote Originally Posted by Stripes View Post
    Exactly. Being 5'5", but with a short torso means short frames for me. Need a pretty short top tube.
    Everybody is different. I have a son who is 5'5" who loves his 29'er. He can swap wheels with his 700c cross bike is one reason.
    Old enough to know better. And old enough not to care. Best age to be.

  19. #19
    mtbr member
    Reputation:
    Join Date
    Mar 2004
    Posts
    415

    headset to fix it?

    I've got an idea........

    I'm really in the fence right now.

    Used to have a 26in transAM SS with a 160 fork and loved that bike

    Well, I moved to an area much less rocky and thought it was overkill, so I sold it. I'm LOVING my blur TRc - no 650's on it yet, its a blast no matter what! But I still want a SS again.

    Part of me wants to buy a 29er TransAM (I have a 29er fork laying around), part of me is considering the following:

    buy the 26in transAM(which fits 650's) - but get the 2012 version with the 44m headtube. Run a works engineering headset for a -1 deg adjustment.
    This way I can fit 650s in the rear, it will slacken the front end back to where I liked it with my old fox 36, and I'll have a 8mm lower BB than going with a standard headset.

    Thoughts?

  20. #20
    Doesntplaywellwithmorons!
    Reputation: DeeEight's Avatar
    Join Date
    Jan 2004
    Posts
    10,578
    Speaking of short + 29... my gf is 5'5, she's on the smallest size niner frame, with a flat bar and running a negative 7 degree stem with one 5mm spacer under it, an traditional external cup headset, and an F100RLC fork. Without sag, the bar height is basically level with the top of the saddle. Emily Batty who rides for Trek-Subaru is 5'2, and on her Superfly 29er she's using a negative 25 degree stem, flat bar, internal taper headset, no stem spacers, and that JUST puts her into the traditional XC racer body position. Which was also a great position to go over her bars at the olympics and crack a rib last summer... so I will not be surprised to see her on a Trek 650B bike by the time Sea Otter happens.
    I don't post to generate business for myself or make like I'm better than sliced bread

  21. #21
    Stubby-legged
    Reputation:
    Join Date
    Jun 2006
    Posts
    779
    Stripes, if you are ever in Maine, you can try my 1x1. 14 in frame, 650b wheels. I tried this bike as a 96er, 29er and now as a 650b.
    Best move yet. Inexpensive way to try wheel sizes. The 1x1 can do it all. (Hmmmm..maybe not the 36er!)

  22. #22
    dwt
    dwt is offline
    mtbr member
    Reputation: dwt's Avatar
    Join Date
    Jul 2009
    Posts
    3,891
    Quote Originally Posted by DeeEight View Post

    Emily Batty who rides for Trek-Subaru is 5'2, and on her Superfly 29er she's using a negative 25 degree stem, flat bar, internal taper headset, no stem spacers, and that JUST puts her into the traditional XC racer body position. Which was also a great position to go over her bars at the olympics and crack a rib last summer... so I will not be surprised to see her on a Trek 650B bike by the time Sea Otter happens.
    Given Nino's success on 27.5", it just makes intuitive sense that short stature riders, including women, would fit better and have good results on tweeners, assuming their Team/Sponsor makes them. Do you have inside info re: Trek?This question also applies to the bike mag articles about Aaron Gwin experimenting with "bigger wheels" for DH. In his case it would be opposite of Batty. The fit on the 27.5" would be mostly the same as 26". The question is whether bigger wheel would help or hinder DH racing.
    Old enough to know better. And old enough not to care. Best age to be.

  23. #23
    mtbr member
    Reputation:
    Join Date
    Jan 2004
    Posts
    918
    Quote Originally Posted by DeeEight View Post
    Speaking of short + 29... my gf is 5'5, she's on the smallest size niner frame, with a flat bar and running a negative 7 degree stem with one 5mm spacer under it, an traditional external cup headset, and an F100RLC fork. Without sag, the bar height is basically level with the top of the saddle. Emily Batty who rides for Trek-Subaru is 5'2, and on her Superfly 29er she's using a negative 25 degree stem, flat bar, internal taper headset, no stem spacers, and that JUST puts her into the traditional XC racer body position. Which was also a great position to go over her bars at the olympics and crack a rib last summer... so I will not be surprised to see her on a Trek 650B bike by the time Sea Otter happens.
    However on the 29er, even with the front end as low as it could go, she was still less likely to go over the bars than on a 26. So I am pretty sure the same crash would have happened on a 26 or 650 bike if her bar drop was the same.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •