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  1. #1
    Senior Member illdthedj's Avatar
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    Does longer rake change top tube angle?

    was just thinking about forks and their relationship to the frame....

    now obviously, if you take two forks of same rake but one is longer than the other, the longer will result in making the top tube of the frame a bit more sloped.

    however, what im wondering is this:
    if two forks of the same length (i guess axle to crown) but of different rake were on the same frame, would the top tube stay the same on both, or would the one with bigger rake slope the top tube forward? like say, you had a fork with a 30mm rake. the top tube is perfectly level with this fork. you then replace fork with an exactly same length fork but has a 45mm rake. would the top tube then dip slightly forward? i guess opposite of sloping, like pursuit esque...

    i guess im thinking since the front axle is farther forward, the frame would dip down a bit....
    "Never argue with an idiot. He'll only bring you down to his level, then beat you with experience..."

  2. #2
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    Top tube angle is a frame measurement. The angle of your top tube relative to the ground changes.
    Quote Originally Posted by Santaria View Post
    because physics has more street cred than tarckstars.

  3. #3
    Senior Member illdthedj's Avatar
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    Quote Originally Posted by ianjk View Post
    Top tube angle is a frame measurement. The angle of your top tube relative to the ground changes.
    so are you saying longer rake changes the top tube angle?
    "Never argue with an idiot. He'll only bring you down to his level, then beat you with experience..."

  4. #4
    Veteran Bastard Scrodzilla's Avatar
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    Pretty sure that's what he meant. Yes, it will change the angle at which your entire frame sits in relation to the ground. Very, very slightly.

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    Veteran Bastard Scrodzilla's Avatar
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    Quote Originally Posted by ianjk View Post
    Top tube angle is a frame measurement. The angle of your top tube relative to the ground changes.
    Pretty sure that's what he meant. Yes, it will change the angle at which your frame sits in relation to the ground. Very, very slightly.

    If you come across a fork capable of changing your frame's actual geometry, please let us know.

  6. #6
    Senior Member Kayce's Avatar
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    The entire bike will be at a different angle relitive to the ground. The seat tube and headtubes will be less steep, the top tube will slope back, as will the chainstays. None of those things would effect the performance of the frame outright, but it will be a totally different handling bike due to the change in trail, and the movement of the bottom bracket.

  7. #7
    Senior Member illdthedj's Avatar
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    oh haha yes thats what i meant, relative to the ground.

    basically, i got a traitor ringleader frame only for a super good deal. however no fork. the fork the frame usually comes with results in level top tube. a fork i am looking at is very slightly longer, but has slightly more rake.
    was told by traitor dude longer fork would mean slightly sloped top tube on the complete bike, but i was thinking the longer rake would subtract some of that slope.
    "Never argue with an idiot. He'll only bring you down to his level, then beat you with experience..."

  8. #8
    Senior Member illdthedj's Avatar
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    Quote Originally Posted by Kayce View Post
    The entire bike will be at a different angle relitive to the ground. The seat tube and headtubes will be less steep, the top tube will slope back, as will the chainstays. None of those things would effect the performance of the frame outright, but it will be a totally different handling bike due to the change in trail, and the movement of the bottom bracket.
    wait you are saying the top tube would slope BACK with longer rake? wouldn't it slope FORWARD? me confuse.
    "Never argue with an idiot. He'll only bring you down to his level, then beat you with experience..."

  9. #9
    THE STUFFED Leukybear's Avatar
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    Quote Originally Posted by Scrodzilla View Post
    If you come across a fork capable of changing your frame's actual geometry, please let us know.
    Low rider bike fork.

  10. #10
    Veteran Bastard Scrodzilla's Avatar
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    That would still only change the angle of the frame relative to the ground.

  11. #11
    Senior Member osiris419's Avatar
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    when the front wheel is more forward of the head tube it will lower the front end of the bike but if you have longer fork legs the drop is not as much. It's like motorcycle building, a chopper has extreme rake and really long fork legs but the front of the bike is actually higher, if you shorten up the forks you will lower the front end.
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  12. #12
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    David Moulton did a pretty good job at explaining how fork rake/trail works with the frame.

    Also, a change in axle to crown length will affect the head tube angle too. It's not necessary a change in geometry, but more or less, change in handling as Kayce have stated.

  13. #13
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    Senior Member AEO's Avatar
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    if you use different sized tires on the front and back, it'll change the top tube angle.
    Food for thought: if you aren't dead by 2050, you and your entire family will be within a few years from starvation. Now that is a cruel gift to leave for your offspring. ;)
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