Ok I know I will get some poo thrown my way as we all know that USD are leaps and bounds ahead and superior to conventional forks in every way shape or form. There I lied for you all.
Now seriously this came up on a different forum about how superior the USD forks are in comparison to conventional in regards to stiction or lack of on USD forks.
First let me say I am in no way opposed to USD forks or am I saying that conventional are better. I am just trying to relay the information I found to those that read different things on the web that may be false.
If you have seen where a conventional forks bends as opposed to the USD fork they are pretty much both the same in that it is right below the lower triple clamp, Makes sense since that is the point where the most leverage is and the most supported right at the base of the lower triple. If you take your bike that has USD forks and very gently put the front tire up against a wall and then gently apply the throttle and feather the clutch you will see that the USD do indeed deflect, Do the same to a conventional fork and it will deflect as well. Now here is where the issue lies with the USD fork, The bushings are fixed and as in the image below at 307mm apart. Since the bushings are fixed in the outer tube and the fork tube itself sliding inside any deflection of that outer tube will give you more stiction than a conventional fork would have.
Even if there was a movable bushing on the USD fork you would still have the same issue as the housing where the bushings are sliding is no longer straight. It only takes a few thousands of a inch to cause stiction. Now with the conventional fork the fork tube itself will deflect at the bottom of the lower triple so there is not any binding down in the lower leg to cause a stiction issue.
Here is the image you can see where both will bend and just as a note the conventional is a CBR600 F3 and the USD is off a R6. With the conventional as badly bent as it is I can still push down on the fork tube and it will slide freely but even with the slight bend that the USD fork has the tube is stuck in the bore.
If you agree or disagree post on back if you want to discuss this more.
Tmod
Now seriously this came up on a different forum about how superior the USD forks are in comparison to conventional in regards to stiction or lack of on USD forks.
First let me say I am in no way opposed to USD forks or am I saying that conventional are better. I am just trying to relay the information I found to those that read different things on the web that may be false.
If you have seen where a conventional forks bends as opposed to the USD fork they are pretty much both the same in that it is right below the lower triple clamp, Makes sense since that is the point where the most leverage is and the most supported right at the base of the lower triple. If you take your bike that has USD forks and very gently put the front tire up against a wall and then gently apply the throttle and feather the clutch you will see that the USD do indeed deflect, Do the same to a conventional fork and it will deflect as well. Now here is where the issue lies with the USD fork, The bushings are fixed and as in the image below at 307mm apart. Since the bushings are fixed in the outer tube and the fork tube itself sliding inside any deflection of that outer tube will give you more stiction than a conventional fork would have.
Even if there was a movable bushing on the USD fork you would still have the same issue as the housing where the bushings are sliding is no longer straight. It only takes a few thousands of a inch to cause stiction. Now with the conventional fork the fork tube itself will deflect at the bottom of the lower triple so there is not any binding down in the lower leg to cause a stiction issue.
Here is the image you can see where both will bend and just as a note the conventional is a CBR600 F3 and the USD is off a R6. With the conventional as badly bent as it is I can still push down on the fork tube and it will slide freely but even with the slight bend that the USD fork has the tube is stuck in the bore.
If you agree or disagree post on back if you want to discuss this more.
Tmod
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