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Thread: SIR 120mm?

  1. #1
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    SIR 120mm?

    I have always ridden a niner carbon fork on my 2011 sir. Now I have a 2013 and i am thinking about buying a fox ctd remote 100 mm tapered fork. I was wanting to know if it would be okay to run a 120mm fork so I could swap it to a jet 9 rdo if I wanted to put a carbon fork back on it.

  2. #2
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    Maybe you should consider a talas fork? You can run it at 120 on the jet and 95 on the sir.

  3. #3
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    Not interested in that.

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    Quote Originally Posted by AaronJobe View Post
    I have always ridden a niner carbon fork on my 2011 sir. Now I have a 2013 and i am thinking about buying a fox ctd remote 100 mm tapered fork. I was wanting to know if it would be okay to run a 120mm fork so I could swap it to a jet 9 rdo if I wanted to put a carbon fork back on it.
    Most forks can have the travel reduced with a spacer. It does involve partial disassembly in the workshop. So why not buy a 120mm and get it reduced to 100mm. This is what I did with my Jet9, I bought a 120mm Reba XX and got it reduced to 100mm. I can always get the spacer removed and have a 120mm fork again (if for instance I ever got a black/white Jet 9 RDO (drools)).

    I also considered a Talas 95/120. I have read that it should not be ridden at length in 95mm mode as this is meant for climbs only. I was considering riding it in 95 normally and switching to 120 for descents.

  5. #5
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    Do you think 120 would cause extreme stress on the frame?

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    At the end of the day you should take the manufacturers advice on that one.

    Here is some info from WebHelp to help.

    32 mm Forks Axle-to-crown Heights (5 mm)

    29"

    100 mm 500.9 mm

    120 mm 520.8 mm

    The original SIR9 ran a 490mm rigid steel fork. The latest steel and carbon forks are 470mm. So at 120mm you are going up by 50mm in axle to crown dimension over the rigid fork.

    It's going to slacken your steering geometry by a degree or two and slow the steering of the bike.

    Generally a suspension fork is going to put less stress on the frame than a rigid fork until you bottom it out as it absorbs all the impact (shock) loading.

    Personally I wouldn't put anything more than the 100mm Fox fork on a SIR9.

    I did put an 85-115 Reba U Turn on my Epic which was designed for an 80mm fork and I had no troubles with that. But that is only going 35mm above the design.

  7. #7
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    I second going with a 120mm and space it down to 100mm. The spacers are cheap, it's simple to swap in, and it won't be running out of spec geometry.

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