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Discussion Starter · #1 ·
How long on a Gen 1 can you go before you feel underbracing is necessary? I have seen stupid long bikes without underbracing, but I feel that is just asking for trouble. If you were to be around 72 to 76 inch wheelbase, would you get underbracing on your arm?
 

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Power and arm material play a role. But I underbrace all my arms.
No need to worry if you need one or not if you have one. Last I checked a stock length factor arm had one so can't be a bad idea. Ones I see without them wheel can't be set straight in the chassis beyond a certain power level. The ones that do are more stable with the wheels set straight at the same power level. You can go quick with either one as long as you know how to adjust for the extra flex if that's what you're into.
 

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alot of the newer arms are inner braced. No need for a outer brace. Just because you dont see a brace, that doesnt mean that the arm isnt braced.
 

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Discussion Starter · #7 ·
I have been looking at getting either a Evil or Hardcore(tough decision), that is 14-18 over and then either swapping to a Gen 2 tail or figuring out how to put a big tail on my gen 1 with stock frame.

Both companies have told me their arms are inner braced either way being that long.
 

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I haven't done any flex studies on a tensile tester, but, logically, the underbraced should be stiffer than inner braced because the bracing doesn't share the same plane as the geometry it's supporting. Underbracing would stiffen that particular section of tubing but not the relationship of one side to the other. Under bracing ties them together amd maintains that relationship better IMO.
 

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Sorry that should say 'INNER bracing would stiffen that particular section...'
 

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Discussion Starter · #10 ·
For $100 I think it will be worth it to me to go ahead and get underbracing done. I don't want to do this more than once and I really don't want to have any flex or breakage issues. +14-18 is a big arm and I think if I get any real power down I'd run into issues. Thanks for the replies.


Now to figure out my tail section.
 

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This would be a good question for Hardcore or Evil.........to bad you can't tag over here, ask this question over on FB in the Psychobike group and tag both parties.
 

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Quickest no bar Busa when nice and straight and had an under braced swingarm. 6.50 at 227mph. Don't look like it's gambling to get a DME under braced arm. Until I see another arm go that quick and straight I'll keep buying them!
 

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image.jpg


Actually the record was on a non underbraced arm. And I'll run DME on everything I ever will own. I don't care if other arms are more affordable none of them beat DME period. DME makes the strongest non underbraced arms, until another bike goes that fast with another brand it's official
 

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I asked this question about a month ago, and a couple swingarm builders stated, if you weigh over 240lbs along with going over 70" they stated having the arm braced, whether inner or under braced. . . .
 

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Actually the record was on a non underbraced arm. And I'll run DME on everything I ever will own. I don't care if other arms are more affordable none of them beat DME period. DME makes the strongest non underbraced arms, until another bike goes that fast with another brand it's official
You are correct. I checked my photo's afterwards and it's the clone to this bike in the Middle East that has the under brace. The performance accomplished with DME components proves their parts beyond a doubt.
 

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I think alot of guys care too much about looks and it henders performance..Like stated before underbrace might weigh a 1lb so why not run it weather you "think" you need it or not.
Looks are very important to me. I think the bike looks better without the underbracing. If I can get the strength and performance with an inner-braced arm, then I would choose that over the traditional underbraced arm.
 

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I don't think you can get the same performance. It's force vectors and physics. There are laws that physical entities have to obey. Putting a tube inside a tube reinforces THAT tube. When you tie the 2 legs together with structure on a different plane, it stiffens the relationship between the 2legs. The only question is 'does it need to be that stiff?' Does the axle and stays maintain their position without additional bracing? Also, that dme arm is not the typical 1x2" box stuff most on this forum are running.
 
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