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Who Needs USD Forks?....

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firstyammerha

I've always felt the RSU forks can be tuned to match or surpass the USD fork. The stiffness question doesn't sell me because aren't the USD forks sliders 41MM? Same diameter as the RSU fork stanchion tube.

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mossrider

Chris was seriously fast on that thing. He's made some improvements too, damn.

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kylerhsm
3 hours ago, firstyammerha said:

I've always felt the RSU forks can be tuned to match or surpass the USD fork. The stiffness question doesn't sell me because aren't the USD forks sliders 41MM? Same diameter as the RSU fork stanchion tube.

Based on what logic would tell me, and my engineering background, it's easy to see why USD forks would provide more stiffness (less flex) than conventional. Flex within the forks happens in the location of the stanchion (tube) and not within the actual structural part of the fork. On convential forks, the location where any flexing would occur within the stanchion is further from the wheel when compared to USD forks. Bending forces are higher the closer you get to the pivot point, which in front forks would be the bottom triple. Therefore, the stanchion in a conventional fork is subject to much higher bending forces than in a USD fork, and therefore is more prone to flexing.

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twf

In conventional forks you also have one bushing that moves with tube while most USD have both bushings fixed.

Chris has K-tech cartridges in his forks.

And stiffer forks don't always mean better, it all depends what bike they are on. Flex is good :)

We run stock forks on our bike as well. Flexing is not issue.  

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firstyammerha

Some time ago,I read an article on the web regarding USD forks weight and the article mentioned Kawasaki(I believe) went up to like 48 mm diameter RSU forks to bring fork weight down. I guess that the manufacturers have solved the weight issue with the early USD forks and now they are the predominant front suspension. I suspect that fork action can be tuned to best performance in either system. I'm curious as to how the weight of the complete slider/stanchion combination compare between a 41mm RSU and a popular 43mm(?) USD fork.  Maybe one of the racers has this information. Forks loaded with springs and oil but no triple clamps.

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twf

They are pretty much same in weight. 

Unsprung vs sprung weight may be different. 

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