Fork rake and length on handling
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  1. #1
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    Fork rake and length on handling

    Just want to make sure I got this right before installing a new enve fork.

    New fork rake is 43mm compared to current 45mm. This should make a small difference in handling? A little less twitchy I believe

    However the new fork is a little shorter then the current fork. I think about 1cm or a little less. This would give a steeper head tube angle and make it more or a twitchy ride?

    Would the 2 differences above kinda offset? Are the differences so small I shouldn't worry too much or are the differences significant.

    Thanks

  2. #2
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    Length has nothing to do with rake and headtube angle measurements.

    Thus length has nothing to do with handling other that maybe tiny differences in weight distribution from you bars being lower (with a shorter fork). But presumably you'd just add a spacer to have the same fit as with the longer fork.

    I've never used a 43 and 45 on the same bike so can't really answer you specific question but whatever the difference is it won't be offset but one being longer/shorter.

  3. #3
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    Quote Originally Posted by sheepherder View Post
    Just want to make sure I got this right before installing a new enve fork.

    New fork rake is 43mm compared to current 45mm. This should make a small difference in handling? A little less twitchy I believe

    However the new fork is a little shorter then the current fork. I think about 1cm or a little less. This would give a steeper head tube angle and make it more or a twitchy ride?

    Would the 2 differences above kinda offset? Are the differences so small I shouldn't worry too much or are the differences significant.

    Thanks
    The link below answers the fork length question far better than I can (and with a lot less typing on my part!)

    As to changes to fork rake, it'll certainly change trail (as will length), but in my experience even going from 47 to 43 degrees was negligible. And yes, it'll 'slow' steering *some*. Link on trail below as well.

    https://www.sheldonbrown.com/rinard/forklengths.htm

    Bicycle Trail Calculator | yojimg.net

  4. #4
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    Length DOES affect the trail, so, yes, it does affect the overall handling of a bike. I know, I once made that mistake on an old frame which was initially designed for 27" wheels, and I fitted a 700c fork. My mistake was only corrected with a 4mm spacer.

    The real issue is this: How much will your rake (offset) chance affect the trail? What are you hoping for? It seems that about 55-60mm of trail is about correct for a road bike. Lesser trail will make the bike easier to handle in low-speed maneuvering (which would be great for a townie bike), but would make it less stable on super-fast downhill descents. OTOH, if you were into something extreme like motor-pacing, you would probably want a good bit more trail.

    Your 2mm reduction in rake (offset) combined with it being shorter might be a wash. It all depends on how much shorter the new fork is, and what that does for the headtube angle. If you can find out what the difference is, and also what your wheelbase is, finding the angle difference is just a simple trig equation away. Also, there may be online calculators for your use.
    Last edited by No Time Toulouse; 3 Weeks Ago at 09:09 AM.
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  5. #5
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    Quote Originally Posted by jay strongbow View Post
    length has nothing to do with rake and headtube angle measurements.

    Thus length has nothing to do with handling other that maybe tiny differences in weight distribution from you bars being lower (with a shorter fork).
    wrong.
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    I've got some bikes, some guns,
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  6. #6
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    Last edited by Jay Strongbow; 3 Weeks Ago at 12:52 PM.

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  8. #8
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    ugh, no! it's not a wash.

    Let's break this question down to "fork length" (axle-to-crown, or AC) and "fork offset" (rake).

    1. Fork length. Assuming the head tube angle of the bike doesn't change, then a decrease in AC will increase trail. In your specific case, i'm guessing an almost 1cm decrease in AC will result in about ~5.3mm increase in trail.

    2. Fork offset. Lesser fork offset will result in increased trail. In your case, going from a 45cm to a 43cm offset will increase trail by probably less than ~1mm.

    Combining both factors above, they contribute to increasing overall trail by ~6.3mm.
    Increase in trail has the effect of making the bike more stable in straight line but less stable in corners. If don't care to rail around corners, then this change in geometry is acceptable. But if you're looking to corner faster, then you need to go with a fork with greater offset (rake).

    In general, if you want to keep steering feel of the bike the same, then a fork with lesser AC also must have greater offset (and not lesser offset). Now roughly speaking, for a bike with ~72.5 deg head angle, and ~25mm tire, then a 1mm change in AC will impart a slightly greater change in trail than a 1mm change in fork offset. In your case, if you want to keep steering feel relatively the same as before, then i'm guessing you'll need a version of this Enve fork with at least 55mm offset (since a 10mm change in AC will require at least an opposing 10mm change in fork offset).

    see this thread for more details
    https://www.bikeforums.net/framebuil...nts-trail.html
    Last edited by aclinjury; 2 Weeks Ago at 03:42 PM.

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  10. #10
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    OP has not checked back. I wonder if he went ahead and put the Enve fork on?

  11. #11
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    Quote Originally Posted by aclinjury View Post
    OP has not checked back. I wonder if he went ahead and put the Enve fork on?
    No. Looks like the difference is great. I'll keep looking for a stock fork

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