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Old 06-19-05, 07:04 PM   #1
ridehard
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Why not dual crown...

I found this on pink bike. I think it is a steelhead? Not to sure, but it looks like those forks put way too much pressure on that frame......

http://www.pinkbike.com/modules/phot...w&image=517590
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Old 06-19-05, 07:08 PM   #2
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Crown must have tasted good for whoever was riding that bike..
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Old 06-19-05, 07:10 PM   #3
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Ya...a dual crown fork can only work on smaller size frames, or frames that don't have a steep top tube.
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Old 06-19-05, 07:37 PM   #4
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The right tool for the right job...
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Old 06-19-05, 07:37 PM   #5
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Classic case of "make sure the bike can take it"

I am pretty sure that bike is only stress tested for a 5in sc. It could also be a case of NASTY casing on a jump. That will rip any headtube off regardless of the fork/frame configuration
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Old 06-19-05, 08:15 PM   #6
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nice

really nice

what a waste of money
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Old 06-19-05, 08:52 PM   #7
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Quote:
Originally Posted by ridehard
I found this on pink bike. I think it is a steelhead? Not to sure, but it looks like those forks put way too much pressure on that frame......

http://www.pinkbike.com/modules/phot...w&image=517590
not a steel head, a steelhead could have takin that.... but it was on pinkbike, so it was plobably a urban huck to flat.
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Old 06-19-05, 08:56 PM   #8
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hey at least the forks alright!
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Old 06-19-05, 09:00 PM   #9
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Quote:
Originally Posted by dirtjumpP.1
not a steel head, a steelhead could have takin that.... but it was on pinkbike, so it was plobably a urban huck to flat.
He's just about got all the bits to make a soft-tail uni- cycle
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Old 06-19-05, 10:38 PM   #10
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I think that's a DS1 frame.. not sure.
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Old 06-20-05, 09:57 AM   #11
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The single-crown alternative is usually just a broken steerer tube.

In any event, the length of the fork is a bigger factor than the number of crowns. A long singlecrown can snap a head tube off almost as readily as a doublecrown of the same length. It's all about the leverage.
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Old 06-20-05, 07:54 PM   #12
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Quote:
Originally Posted by ghettocruiser
The single-crown alternative is usually just a broken steerer tube.

In any event, the length of the fork is a bigger factor than the number of crowns. A long singlecrown can snap a head tube off almost as readily as a doublecrown of the same length. It's all about the leverage.
This is what I have been wondering about. As an engineer I cant see any reason why a double crown fork will affect a frame significantly differently than a single crown fork, given that the geometry of the bike and fork remains the same or not significantly different. Before you jump up and tell me that monster T's are 7" travel and Mx's are only 4", read what it is I've written again. Given 2 forks of equal travel and similar (very) geometry, one single crown and the other dual crown why should the dual crown transmit significantly more load to the bike than the single crown?. The load path for most geometries will mostly be up the fork, as the head angle decreases more load will be transferred to path that is trying to snap the frame and forks, but if the head angle remains the same for both forks then how is the dual crown going to transmit more load to this path? Responses ?
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Old 06-20-05, 08:38 PM   #13
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A DC fork is usually thought of as 7+ inches of travel, so we tell people not to put DCs on, say a Trek 4300. Now, there are 7" Single crown forks such as the 66RC, that are actually taller than a JR T (that should change for 06). A 7" 66 has a taller Axle to Crown length than a 7 "Jr T. The 6" 66 is very close to the height of a 7" Jr T, so even though it isnt DC, or 7" of travel, it should put as much stress on a frame as the Jr T.

Ill look for the correct AtoC measurements when I have time later.
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Old 06-21-05, 03:44 AM   #14
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Also dual crown forks are stiffer. When a long travel single crown is used, sometimes some of the force turns into flex at the crown.
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Old 06-21-05, 06:57 AM   #15
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Quote:
Originally Posted by ghettocruiser

In any event, the length of the fork is a bigger factor than the number of crowns. A long singlecrown can snap a head tube off almost as readily as a doublecrown of the same length. It's all about the leverage.
Indeed. The greater the axle to crown height, the greater the moment (or leverage) about the headtube. A tall singlecrown (like a Marzocchi 66) will stress the headtube junction more than a shorter dual crown.
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