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  1. #1
    cyclopath vik's Avatar
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    Grand Bois Tire/Wheel Axle Height?

    I was wondering if anyone that has one or both of these tire/wheel combos could measure the height of the axle above the ground for me?

    - Grand Bois Hetres 42mm [650B]
    - Grand Bois Cypres 32mm [700C]

    Thanks in advance!
    safe riding - Vik
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  2. #2
    Randomhead
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    I would be interested in the 650b number too, particularly if it is mounted on a Velocity Synergy

  3. #3
    Reeks of aged cotton duck Hydrated's Avatar
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    Quote Originally Posted by unterhausen View Post
    I would be interested in the 650b number too, particularly if it is mounted on a Velocity Synergy
    I'm running the Hetre/Synergy setup on my Kogswell. I'll measure it after work today for you guys.
    It is the mark of an educated mind to be able to entertain a thought without accepting it.-Aristotle

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    Senior Member Hairy Hands's Avatar
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    I'm running the new 700-38 compass tire that came out last month. If u need this measurement let me know
    ~John~

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    7-speed doomsday prepper ThermionicScott's Avatar
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    I would imagine that the tire pressure and load make a tiny impact as well...
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  6. #6
    Member dciskey's Avatar
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    On my wife's Cross Check, with whatever rims the bike came with in 2012, I measure 345mm from ground to axle center for the Cypress 700x32c. The tires themselves only measure about 29mm tall, but they've only got about 50 miles on them.

    Edit: bike was unloaded; I'm the only one home right now.

  7. #7
    cyclopath vik's Avatar
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    Thanks!
    safe riding - Vik
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  8. #8
    Reeks of aged cotton duck Hydrated's Avatar
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    Sorry it took me so long to get the measurements posted, folks...

    My Hetre/Synergy wheels measure 343mm to the hub center. Tire inflated to 60psi and the bike unloaded.

    And I must admit that I took no special steps to be incredibly accurate... I just threw a tape measure up to the side of the wheel and eyeballed it. If someone needs real accuracy, I will do it again and ensure that I'm measuring absolutely square to the ground.
    It is the mark of an educated mind to be able to entertain a thought without accepting it.-Aristotle

  9. #9
    cyclopath vik's Avatar
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    No worries. I was just trying evaluate the conversion of a 700c frame to 650B wheels. The utmost accuracy was not required.

    As it turns out the BB drop was too great so I won't bother proceeding and will keep my eye out for a dedicated 650B frame that meets my needs.

    Thank you for all the replies.
    Last edited by vik; 03-26-14 at 02:11 PM.
    safe riding - Vik
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  10. #10
    Randomhead
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    I don't think 2mm is going to make that much difference in pedal strike, or am I missing something?

  11. #11
    cyclopath vik's Avatar
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    Quote Originally Posted by unterhausen View Post
    I don't think 2mm is going to make that much difference in pedal strike, or am I missing something?
    I collected data from other sources as well and came to the following conclusions:

    - 650B x 42mm axle height = 330mm BB H = 258mm [10.2"]
    - 700c x 32mm axle height = 345mm BB H = 273mm [10.8"]

    I then compared to a reference bike I commute on and the 10.2" BB height is lower than I care to go.
    safe riding - Vik
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  12. #12
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    Quote Originally Posted by vik View Post
    I collected data from other sources as well and came to the following conclusions:

    - 650B x 42mm axle height = 330mm BB H = 258mm [10.2"]
    - 700c x 32mm axle height = 345mm BB H = 273mm [10.8"]

    I then compared to a reference bike I commute on and the 10.2" BB height is lower than I care to go.
    I think you're making too much of this and have overestimated the difference in tire size. By my estimate, going from GB Cypres 700x32 to GB Hetre 650x42 drops the BB by .3 inches.

    I have four bikes that I've converted to 650B (and two of those have been converted back to 700 because I only have three sets of 650B wheels). I've never noticed any significant difference in pedal strike. The bikes in question: A Gunnar Sport, was on 700Cx32 (Cypres or Paselas) now running as 650B with Hetres; an '84 Trek 610, was 700Cx32 then 650Bx42 now reconverted back to 700Cx32; an '82 Trek 728, was 700Cx32 then 650Bx42 now reconverted back to 700Cx32; my wife's '86 Trek 400, was 700Cx25 now 650Bx38. The third set of wheels is now on my Soma Grand Randonneur with Hetre's.

    Nick

  13. #13
    cyclopath vik's Avatar
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    Quote Originally Posted by thebulls View Post
    I think you're making too much of this and have overestimated the difference in tire size. By my estimate, going from GB Cypres 700x32 to GB Hetre 650x42 drops the BB by .3 inches.
    I have a bike I commute on. I know how high that BB is and it's already not as high as I would like for the terrain I ride [rough, dirt w/ potholes] and the pedals I use [MTB flats]. On my current setup I have to stop pedalling in corners where I would otherwise keep cranking because I'll clip the ground.

    So it makes zero sense to me to spend $$ on a new frame that is going to have a lower BB than what I currently ride and is at the minimum I can accept.

    It makes far more sense to take my $$ and buy a frame that better meets my needs.
    safe riding - Vik
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  14. #14
    Senior Member
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    Quote Originally Posted by vik View Post
    I have a bike I commute on. I know how high that BB is and it's already not as high as I would like for the terrain I ride [rough, dirt w/ potholes] and the pedals I use [MTB flats]. On my current setup I have to stop pedalling in corners where I would otherwise keep cranking because I'll clip the ground.

    So it makes zero sense to me to spend $$ on a new frame that is going to have a lower BB than what I currently ride and is at the minimum I can accept.

    It makes far more sense to take my $$ and buy a frame that better meets my needs.
    That makes sense but it's a different question than you asked. If you had started with "My bike already suffers from pedal strike because the BB is too low for the terrain I'm riding. Will switching to 650B make this even worse?" then the answer is definitely yes, though only slightly!

    But for most bikes that are already set up correctly for the terrain they're being used on, using "normal" 700c tires, switching to 650Bx38 or 42 is not going to be a problem.

  15. #15
    cyclopath vik's Avatar
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    Quote Originally Posted by thebulls View Post
    That makes sense but it's a different question than you asked. If you had started with "My bike already suffers from pedal strike because the BB is too low for the terrain I'm riding. Will switching to 650B make this even worse?" then the answer is definitely yes, though only slightly!
    ***sigh****

    I did not ask the question you suggest because that is not the situation I am in.

    The question I asked was what were the axle heights of 2 different wheel+tire combos. I have no intention of converting my current commuter and it's not a 700C bike in any case.

    I got the info I needed. Thanks.
    Last edited by vik; 03-27-14 at 01:58 PM.
    safe riding - Vik
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