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Old 03-27-08, 07:11 PM   #1
Raleigh71
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Is there any way this fork ISN'T bent?

See photo of a Raleigh hybrid bike (" Raleigh Eclipse") c. early 1990's. I notied there's a slight angle from the fork to the fork stem. It turns just fine. Is this fork bent, or is there any way it was made this way?
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Old 03-27-08, 07:30 PM   #2
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hmmmm......looks like the fork blades are straight. And not in line with the steerer tube, which appears straight. Does it look the same from both sides? I'm guessing that it was built the way it is.
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Old 03-27-08, 07:36 PM   #3
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Bent Fork?

It looks the same from both sides, and is absolutely symmetrical. No cracks in the welds or even the paintjob. Curious.
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Old 03-27-08, 07:37 PM   #4
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Other than the fact that I don't like straight forks, it looks fine.
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Old 03-27-08, 07:38 PM   #5
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It's using the angle of the weld at the top joint to achieve the same geometry as forks with curved blades. These straight blade forks are quite common with other brands of bikes.
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Old 03-27-08, 07:41 PM   #6
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It's a straight bladed fork and was built that way on purpose.

The desired fork rake can be obtained one of two ways;

1. Curving the fork tips forward near the dropouts.

2. Making the fork blades straight all the way and fastening them to the crown at an angle to achieve the same resuilt.

The pictured fork was built the second way and is fine.
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Old 03-27-08, 07:49 PM   #7
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See "Trail" in the Sheldon Brown glossary. Or: Note where the tire contacts the ground then draw a line from the headset through the center of the wheel to the ground. The line will hit the ground in front of the tire contact point. The space between the two points is the trail of the bike. A long trail increases straight line stability. Touring bikes tend to have large trails. A short trail is common in criterium bikes.
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Old 03-27-08, 07:54 PM   #8
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As long as we're on the trail issue an odd fact is that a strongly raked forward set of forks such as these has a smaller trail distance rather than longer. The more vertical forks will actually be more stable.

Odd but true.....

So likely this bike is quite a "fun" and quick steering bike to ride.
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Old 03-27-08, 08:00 PM   #9
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Quote:
Originally Posted by BCRider View Post
As long as we're on the trail issue an odd fact is that a strongly raked forward set of forks such as these has a smaller trail distance rather than longer. The more vertical forks will actually be more stable.

Odd but true.....

So likely this bike is quite a "fun" and quick steering bike to ride.
Not necessarilly. The exact same rake measurenment can be achieved with either design. A rake of, say 43 mm, will produce the same trail with a given frame no matter how the fork is built.
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Old 03-27-08, 08:29 PM   #10
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Fork looks fine. Fix your brakes.
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Old 03-27-08, 08:39 PM   #11
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Seems I got caught in the motorcycle vs bicycle deal here again. In motorcycles the steering angle is called the rake angle while for bicycles "rake" seems to be used most often in place of the fork offset which we were talking about above.

Hillrider, I was all set to say "Huh???" and ramble on but went and checked for some bicycle steering geometry sites. So yeah, we're actually talking about the same thing, fork offset or rake leading to reduced trail. How the fork gets there is immaterial to the steering feel. But as the rake or offset changes the stability of the bike alters.

..... darn semantics.... I'll have to remember the different uses of the R word when I'm jumping from the pedal to piston power forums now
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Old 03-27-08, 08:45 PM   #12
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With that rake, you should notice a distinct lack of toe overlap with the wheel.
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Old 03-28-08, 10:13 PM   #13
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Thanks for the erudite discussion, gents. Nice to know my fork isn't damaged. I just hope I don't get my toes overlapped with any wheels or have any run-ins with rakes.
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Old 03-28-08, 10:21 PM   #14
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Quote:
Originally Posted by BCRider View Post
It's using the angle of the weld at the top joint to achieve the same geometry as forks with curved blades. These straight blade forks are quite common with other brands of bikes.
exactly,...you get the same geometry as a curved blade fork, but it's a straight leg.

how does it ride? THATS the real question.

Quote:
Originally Posted by ken cummings View Post
See "Trail" in the Sheldon Brown glossary. Or: Note where the tire contacts the ground then draw a line from the headset through the center of the wheel to the ground. The line will hit the ground in front of the tire contact point. The space between the two points is the trail of the bike. A long trail increases straight line stability. Touring bikes tend to have large trails. A short trail is common in criterium bikes.
very nice description.

the trail on my 125cc streamliner speed record bike is more than 14", the thing will hardly turn at all,...but steady as a rock at speed.

now I have to go measure my GT road bike (I love the way it handles)

Last edited by j0e_bik3; 03-28-08 at 10:28 PM.
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Old 03-28-08, 11:06 PM   #15
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The steering geometry can be made the same with either straight or curved fork blades. The differences are in how much "suspension" they provide, and where and how the stress concentrates.
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