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Steering/Geometry Effects of Changing Forks?

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Steering/Geometry Effects of Changing Forks?

Old 12-09-13, 11:57 AM
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Steering/Geometry Effects of Changing Forks?

i've recently aquired an 80mm travel suspension fork - marzzochi z2 bam

so now i've got to decide on a frame to put it in
how will bike handling be effected by using a frame not intended for said fork ?

considering using :
rigid frame
hardtail meant for 100mm travel

so either going longer or shorter , what kinds of handling change will there be each way/whats less detrimental ?


anyone know specs on a Soma Groove?
2011 (most recent) model wants a 80mm travel , but a 2006 i was looking at seller claims 100mm
not listed on bikepedia
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Old 12-09-13, 12:01 PM
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Trail, the distance on the ground between a Perpendicular line thru the Hub Axle down

and the head tube angle centerline, [that falls ahead of the vertical line]

is what will be measured to get some Idea of what you are changing.

raising or lowering the head tube changes the angle.. a rake change in the fork also effects trail .

Get out a straightedge, and a Tape measure.

Last edited by fietsbob; 12-09-13 at 12:05 PM.
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Old 12-09-13, 01:49 PM
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Honestly, you'd be hard pressed to tell the difference between a 100 mm travel fork and an 80 mm travel fork, from flat road handling characteristics alone. The 20 mm of extra travel translates to maybe 12-15 mm difference when the fork is compressed (you only care about it when you're riding it), which causes only a couple mm difference in trail by changing the head tube angle infinitesimally (longer fork, longer trail, "slower" handling). On those big squishy tires and with a sloppy suspension fork, you'd have to be the proverbial princess to feel the difference. I can't even tell the difference between a 40 offset fork and a 45 offset fork on the same stiff road frame.

What's more important is that a 100 mm travel fork can go over a slightly bigger obstacle without bottoming out, which means that you can go a little faster than on an 80 mm travel fork. Also the effective height of the handlebar is different- you might need to change the rise of the bars to make everything fit the same.
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