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12/29/2016
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Ronkonkoma, NY
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PracticeChamp141
12/13/2017 10:25am
12/13/2017 10:25am
How hard is it to determine frame flex with frames made of the same material? I consistently hear keefer, vital and various other test riders talk about frame flex during shootouts. I can distinctly feel a difference in suspension clickers, valving and bar flex, but don’t think I would be able to isolate frame flex specifically. What kind of numbers are we talking about here? I know rake angles change on frames over time but can you really feel damping in your frame?
If you want to feel how sensitive a frame can be (for example) 2017/2018 CRF450R. Change the torque settings by 10-15% on all of the motor mounts and swingarm pivot. Ride the bike stock then reduce the torque settings and ride the bike again (don't change any other settings) feel the difference.
It is all about flex flex and flex. Triple clamps flex and clamp pinch bolt torque settings can change how a bike flexes. Axles flex, everything has to flex a little. Some factory bikes don't run Ti axles because they might not flex enough, or some run them because they don't flex - just depends.
A good test rider can isolate each item and deduce in the end if the flex is suspension related or a frame that has too much or not enough flex and feels harsh. OEM's have spent a lot of time with the latest bikes to allow the frames to be stiffer rotational - yet flex over a greater span front to back so they don't feel harsh.
If a frame is too soft they can feel mushy or twist and store energy and then when they flex back it does all sorts of stuff to the chassis like swapping or not tracking straight. Slower vet riders like a frame that flexes, that is why the YZ450F has been such a popular bike, fast pros did not like the flex.
The average rider does not do enough or any testing, they ride a bike, make basic changes they read somewhere or they just send their suspension off and think the shop has all of the answers. Testing and setting up a bike can be a battle. There is a fine line between a decent bike and an awesome bike and the only cost is testing and a log book to track what works and does not work.
Every rider can feel flex, most just think because the wheels are the only things moving up and down, that is all they are feeling, not always true.
The Shop
Also, just because someone is fast on a bike does not mean, in the slightest, that they can feel subtle changes. Corner speed does not equal set up ability.
Anyone who knows anything about steel frames is that they feel different after breaking them in, 5hrs or so. They feel better to me, don’t stay rigid like Aluminum. Factory riders are picky AF. Only thing that’s gone soft is your noodle.
http://www.vitalmx.com/forums/Moto-Related,20/Another-snapt-KTM-frame,1…
I guarantee you will know which bike has less frame flex. Then you will have a better understanding of how frame flex affects handling.
(Doesn’t stop me buying a Ti bolt for my clutch perch!)
I've also experimented and noticed a difference (could be placebo effect) with removing one of the upper engine frame mount bolts on both sides of my RMZ. This in theory allows the engine/ frame mount to pivot, as it is now held on with 2 opposing bolts as opposed to 3 in a triangle pattern.
I guess it all depends how in tune you are with your bike and also how fussy you are in terms of comfort and set up.
Pit Row
Every. Single. Year.
I wonder why the manufacturers are so stubborn with the high riding linkage arms....
Sorry guys!
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