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A wheelist
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11,324 Posts
Discussion Starter · #1 ·
Does anyone have a good simple way of measuring a fork's rake without resorting to custom made v-blocks and expensive height gauges?
 

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Decrepit Member
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1. Remove the front wheel

2. Remove handlebar

3. Lay frameset on butcher paper with front fork at right angle to frame and mark 1/2 the distance between the blades

4. Taking care not to move the frame, turn front fork so it's aligned with frame and mark center of dropout

5. Measure distance from the first mark to the second mark at a right angle to the steering axis. That's the fork rake.







 

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take it out of the frame and lay it on a table. make sure both the dropout axis (where the hub axle would be) and the steerer axis are exactly parallel to the table.

measure from the dropout axis to the table and from the steerer centerline to the table. subtract the 2nd from the 1st.

voila.
 

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A wheelist
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11,324 Posts
Discussion Starter · #5 ·
I'm dealing with this one right now Stan - mostly for the reason that I don't have to remove the fork from the frame.

I've taken many measurements and it makes a major difference if the fork is level and perpendicular when the two marks are made. I'm using a spirit level on the fork legs to make sure. I wish I had v-blocks and a Mitutoyo height gauge :(
 

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What Would Google Do.
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1,486 Posts
dont remove anything!
just drop a plumb line from the top of the steerer
measure the distance from where it stops to where the centre of the dropout is
measure the distance back up from the centre of dropout, up to the place you dropped the plumbline from.
you now have 2 distances, you can either get out the protractor and measure the angle or do a slope calculation to find the angle (in a similar way to using distance and altitudet to measure mountain gradient!)
 

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Decrepit Member
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Mike T. said:
I'm dealing with this one right now Stan - mostly for the reason that I don't have to remove the fork from the frame.

I've taken many measurements and it makes a major difference if the fork is level and perpendicular when the two marks are made. I'm using a spirit level on the fork legs to make sure. I wish I had v-blocks and a Mitutoyo height gauge :(
I built a half dozen variable V-blocks in a little more than an hour with a table saw, jigsaw, and drill. These are quite adequate for holding tubes off of a surface, although I wouldn't want to get an oxy-acetylene torch too close to them. I use a caliper between the "V" and the bottom to get the desired standoff distance. I let the widest part of the frame (almost always the rear dropouts) rest on the surface, and use the V-blocks under the seat tube, top tube, and down tube to get the rest of the frame parallel to the surface. I've found just that measuring from the surface to the centerline of each tube using a scale gives me very repeatable results (no height gauge needed).





 
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