ball joints

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wanablaze
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Joined: Wed Mar 10, 2021 10:41 pm

#11 Post by wanablaze »

Or it's time to replace the a-arms...
For how much it would cost to have these rebuilt, maybe I'll just throw down for some +3's.

haydug
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#12 Post by haydug »

QUOTE
Originally posted by wanablaze
Or it's time to replace the a-arms...




Time for Rated-X!! :clap:

ktmlew
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Joined: Wed Mar 10, 2021 10:41 pm

#13 Post by ktmlew »

Changing the angles of the control arms relative to each other raises or lowers the roll center. A lower roll center (taller spindles and/or longer ball joints) will load the outer wheel more heavily when turning but induce more chassis roll. Raising the roll center will keep the chassis flatter but it will be more likely to "push" when the turn is initiated. smile.gif

claas900
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Joined: Wed Mar 10, 2021 10:41 pm

#14 Post by claas900 »

..So ktmlew witch is better? Iv been sitting here trying to act out how it works,with funny hand movment..lol..I think i understand it?

ktmlew
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#15 Post by ktmlew »

Which is better? That's the $1.99 question! I doubt a woods rat would notice the change but a TT type rider might. The roll-center is only "adjustable" to a certain point on a quad due to the solid rear axle. On a fully suspended vehicle you have 2 roll-centers, front and rear, both "adjustable" and inter-related. Think of a pig on a spit.

If you watch any Nascar, no flaming please, when they say they are adjusting the track bar thru the back window they are changing the rear roll-center. That means they are changing how the weight transfer affects wheel loading. The term is called roll-couple. If you add the "roll-stiffness" of the front and rear of course you get the total but how is it split? That is what adjusting R/C at one end does, it changes how the total is spit front-to-rear. On dirt, again on a 4-wheel suspended vehicle, the end with the lower R/C carries more "vertical load" on the tires. On a car the engine is in the front so the front roll-stiffness will have to be "stiffer".

Uhhhhh.......sorry i'm rambling........ok? For a quad the effective spindle height, ball-joint pivot point-to-pivot point, determines how much camber gain you will get. Camber gain is a GOOD thing for dirt! If you measure the the length of the control arms, both upper and lower, distance between mounting points both vertically and horizontally, then plot it on graph paper you can find out where the R/C is located.

Just look at the quad from the front. Draw a line thru the pivot points of the bushings and ball-joints. Where those lines come together is the roll-center height. Essentially for our purposes lower is better unless you can control chassis roll with a swaybar. A higher roll center requires stiffer springs, moving the shocks/springs closer to the ball-joint or a swaybar.

Because the upper arm is usually 2/3 the length of the lower it swings a different arc. That is what creates camber gain. You don't want the camber to go positive! Now I'm generalizing to a degree because a "quad" tire functions quite differently that a "normal" tire. Try measuring your camber at different ride heights. As the suspension "squats" the camber may go toward the positive direction but it better max out, still be negative before half-travel. Imagine diving into a corner with one corner almost bottomed-out and the other side at only 1/3 travel. The camber, due to chassis roll, with go positive and try to roll the tire off the rim.

So.......a taller "spindle", i'm including the ball-joints, is better!

Guess you learned better than to ask me a question?:deal: rolleyes.gif

claas900
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#16 Post by claas900 »

..thats some very good info thanks..

Brad Oakley
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#17 Post by Brad Oakley »

Awesome answer, but... The reason that the moto upper ball joints are taller is because the standard size ones bind in that location (they are asked to flex a few more degrees than they are capable of moving!) The longer spindle changes the angles just enough so that they don't bind when arm travel reaches its extreme limits.

I carry a replacement set-up for the upper moto a-arm ball joints. Actually works better than the original part - and is quite a bit less expensive.

ktmlew
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Joined: Wed Mar 10, 2021 10:41 pm

#18 Post by ktmlew »

QUOTE
Originally posted by Brad Oakley
Awesome answer, but... The reason that the moto upper ball joints are taller is because the standard size ones bind in that location (they are asked to flex a few more degrees than they are capable of moving!)  The longer spindle changes the angles just enough so that they don't bind when arm travel reaches its extreme limits.


But that's too short an answer!tongue.gif biggrin.gif

Brad Oakley
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Joined: Wed Mar 10, 2021 10:41 pm

#19 Post by Brad Oakley »

Your reply really made me laugh!!!

You really know your stuff! When I start tweaking the chassis for the Blackwidow I want you to have a look at the suspension - to make sure I'm getting things right!

claas900
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Joined: Wed Mar 10, 2021 10:41 pm

#20 Post by claas900 »

..Hey Brad how is the "Blackwidow" comeing along anyways?

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