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  1. #1
    Cumbria, England.
    Reputation: D45yth's Avatar
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    Using the 'AC' with less travel?

    Hi, has anyone been using their AC with 120mm of travel front and back. If so, how much does it affect the geo/bb height?
    I'd be riding at maximum travel with a 150mm fork most of the time. Although I was thinking I could drop the travel, put some lightweight xc wheels on and remove dropper seatpost when it comes to doing races/events. This way I'd be able to get rid of one of my bikes to buy said wheels and a few other bits of bling!

    p.s. I know the new shock lever can't be set at exactly 120mm anymore.

    Cheers, DF.
    Last edited by D45yth; 12-28-2010 at 07:02 PM.
    - The seasons blow away, but the love is just the same -

  2. #2
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    As far as im aware changing the the rear shock position doesnt change the bb height at all, with regards the front, im sure there is a thread somewhere (All mountain or turner) that has a link that lets you input measuremen and then spits out a picture with results

  3. #3
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    D45yth - the only time it would change the geometry will be if you also don't change the fork height and the changes will then only be on the dynamic, i.e. the sagged, geometry and would be very minor.

    If you're running c.120mm versus 145mm then assuming you run the same amount of sag, the BB will be sitting higher at the120mm travel setting than in a longer setting. If also reduce the fork height, this should compensate.

    Changes at the front equate to roughly one degree at the head angle for every 25mm of axle to crown height and about 0.25" at the BB, but these figures are very rough.

  4. #4
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    As geetee says -

    Change in geometry with different rear travel is very minor - reducing travel from maximum to 120mm at the rear alters sag at 25% from 36mm to 30mm which is probably about 4mm additional height on the BB. However, most of us don't set our sag with mm accurate levels of precision anyway.

    Dropping the travel at the fork does make a signifcant difference. The CC is much more suited to adjustable travel as it starts with a higher bottom bracket and the geometry changes with dropped rear travel. This means it runs really well as a race bike with, say, 100mm front and 115mm rear (which means the HA is steeper than spec sheet) as well as at 130mm either end.

    The AC isn't intended to be run with a shorter fork than 140mm. At 130 the BB does become noticably low.
    Simon Still
    Momentum Distribution
    www.nicolai-uk.com

  5. #5
    Cumbria, England.
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    Thanks for that, Simon. Its starting to look like the AC may not be the bike for me.
    - The seasons blow away, but the love is just the same -

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