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Old 07-17-08, 06:35 PM   #1
bklein
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Reducing fork offset

I'm looking to make my road bike a bit more aggressive by replacing the fork with one that has less offset. The current fork curves forward toward the bottom. Hoping a straighter fork will make for a more responsive bike and allow for a safer feeling while making tight turns.
The bike is an older Basso Ti frame with an EMS Kestrel carbon fork. Bike was assembled and purchased in 1992/93 Just looking to lessen the laid back feel without replacing the bike.
Any ideas here?
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Old 07-18-08, 12:01 PM   #2
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You have the fork offset thing backwards; more offset reduces trail which increases steering speed. Also, straight blade forks have offset just like a curved one; the offset is built into the crown angle and doesn't require curved blades.
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Old 07-18-08, 04:04 PM   #3
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Aren't we saying the same thing? Less offset reduces trail, so the bike will steer faster?
If I find a straight fork with little to no offset I should be reducing the offset, right? I know that I'm not changing the head angle, but if wheel axil is brought closer to down tube, won't I get a more responsive bike?
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Old 07-18-08, 04:16 PM   #4
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Originally Posted by bklein View Post
Aren't we saying the same thing? Less offset reduces trail, so the bike will steer faster?
If I find a straight fork with little to no offset I should be reducing the offset, right? I know that I'm not changing the head angle, but if wheel axil is brought closer to down tube, won't I get a more responsive bike?
No; you've got it backwards. Everything else (HTA, fork length, etc.) being equal, reducing offset (or rake) increases trail. Increasing offset reduces trail.

Dave Moulton on Trail, Fork Rake, and a little bit of history.
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Old 07-18-08, 10:36 PM   #5
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Also, will a faster stearing bike feel safer through fast turns, not sure about that.

The way to visualize things (and you don't have to because there are trail videos and calculators online) is that the first line is drawn through the center of the stearing collumn and projected to the ground. On a normal bike this is the forward point on the baseline. The second line is dropped through the axel to the ground, and will touch down something like 50 mm behind the first line. trail is the difference between these two intersections on the ground and can be negative or positive, but is as described above with bikes. If you shorten fork ofset that line is further back and trail is greater.

http://www.wisil.recumbents.com/wisil/trail.asp
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