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Old 03-18-2010, 12:45 PM   #1 (permalink)
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Fat Bob Question

I'm just wondering can you change the rake on a Fat Bob? Has anyone done this?
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Old 03-18-2010, 12:59 PM   #2 (permalink)
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you can change the rake on any bike but most involves cutting the frame behind the steering head . They make a raked tree but havent used one myself so i cant tell you how it will work .
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Old 03-18-2010, 01:06 PM   #3 (permalink)
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have read several things about raked tree's being a "huge" negative on the handling of the bike..

almost all of the articles i've read, suggest a re-angle of the frame neck, as opposed to switching out the tree's..

perhaps someone with a little more knowledge can chime in, and explain the pro's, and con's.......g
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Old 03-18-2010, 02:26 PM   #4 (permalink)
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For minor changes… trees are ok.

Example;
Changing an ultra to lean-able trike (this is hydraulics added to the rear wheel suspension and the frame is hydraulically leaned into a turn). We changed the rake slightly negative to help steer the thing easier, due to the added weight.

But if you want to extend the front end… math needs to be done to develop the proper rake for a given extension of the front wheel.

There is a set relationship between the angle of the neck and the position of the front tire from the neck. Basically the further you push the front wheel out the greater the angle.

This relationship is called “trail”.

You need to know how much extension you want to go (like 3 over, 6 over, 12 over or any dimension really)
And I can tell you the angle… if I know the off set in the trees you are going to use.
Note:
The off set in the trees is the dimension from the neck to the tubes… in the side view.
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Old 03-18-2010, 02:45 PM   #5 (permalink)
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this one is 47 degrees
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Old 03-18-2010, 03:23 PM   #6 (permalink)
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what about ofset bearing cups are they better than trees??
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Old 03-18-2010, 06:36 PM   #7 (permalink)
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The cups should be used with the trees... it's better than just trees... again depending how far you want to push the front tire.

I can do the math and check what you want to do. The math will give you a steady low speed, and a stead high speed...without any crazy wobble.
It will also give you a "no neck dip" or "no neck rise" while you are just standing still turning the wheel back and forth. (Do you understand what I mean here?) This gives you good corning (leaning) characteristics.
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Old 03-18-2010, 11:18 PM   #8 (permalink)
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You should send a PM to is JBone. He had a customized Fat Bob that I believe he changed the triple trees to gain some rake on the front end. He has done the research and has riden the Fat bob with a raked front end. Good contact for this info.
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Old 03-19-2010, 06:31 PM   #9 (permalink)
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My buddy from Harley at the Juneau Ave plant sent me the following concerning the issue of changing my SG narrow to a FB front end.
Quote:
I found out that HD can't advise on any modifications not listed in service or P & A due to liability. Your
other option is to cross reference parts books or talk to dealers who do modifications like what you are looking for.
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Old 03-19-2010, 09:52 PM   #10 (permalink)
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Your lookin' for trouble. As cool as rakin' out your front end would look, you will take away the handling. leave it be and just ride.
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