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Old 02-02-2009, 10:16 AM   #1
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Default Roll center what to do when.....

Hello I am pretty recent to RC racing and I am having trouble understanding roll center and I am constantly wondering what to do when my car does "THIS", are there any books out there that would be useful or anyone that just has time to explain. I bought my WEC cyclone from a local racer a couple months back and have been making changes to to the things that I know but I really want to understand more. The only thing I have not changed is are all of the little shims on the car under pivot blocks etc...
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Old 02-02-2009, 10:29 AM   #2
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XXXmian chassis setup guide book. It has information on roll center, caster, toe .ect, and how to correct any issues you might have.
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Old 02-02-2009, 10:41 AM   #3
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XRAY or SERPENT setup book covers those issue......you can download them from their website. I saved them on my phone so when I am bore, I can study them...
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Old 02-02-2009, 10:44 AM   #4
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On Xray's forums you will find some great info.

http://forum.teamxray.com/viewtopic.php?t=2872
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Old 02-02-2009, 11:23 AM   #5
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I have been trying to get a feel for this as well, and here is what I personally feel the links do on the cars that I've changed them on. I find that it's easiest (albiet not 100% accurate) to envision each link as a camber curve (or camber gain). Shorter links are more gain, longer links are less. Angled links feel more stable, and feel like they generate more traction, straight can take away some initial bite, good when you are traction rolling. Height needs to be taken into consideration relative to the lower arm, since you can raise or lower independently, they will produce different results. Leaving the lower pin the same and raising the upper link will result in less gain, raising the lower pin, without changing the upper will result in more gain (thus traction).

Now this is only one part of the equation, since changing the links/pins also changes how the car rolls, depending on your shock/spring combo it's very possible to get different results.

I personally like the descriptions in the Phi and type-r manuals regarding these changes. I tend to run angled links to some degree until traction gets very high, I prefer the way the car drives.

*usually Haynes will chime in here and tell me I'm an idiot and wrong, so take it for what it's worth LOL.
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Old 02-02-2009, 02:39 PM   #6
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Quote:
Originally Posted by MikeXray View Post
I have been trying to get a feel for this as well, and here is what I personally feel the links do on the cars that I've changed them on. I find that it's easiest (albiet not 100% accurate) to envision each link as a camber curve (or camber gain). Shorter links are more gain, longer links are less. Angled links feel more stable, and feel like they generate more traction, straight can take away some initial bite, good when you are traction rolling. Height needs to be taken into consideration relative to the lower arm, since you can raise or lower independently, they will produce different results. Leaving the lower pin the same and raising the upper link will result in less gain, raising the lower pin, without changing the upper will result in more gain (thus traction).

Now this is only one part of the equation, since changing the links/pins also changes how the car rolls, depending on your shock/spring combo it's very possible to get different results.

I personally like the descriptions in the Phi and type-r manuals regarding these changes. I tend to run angled links to some degree until traction gets very high, I prefer the way the car drives.

*usually Haynes will chime in here and tell me I'm an idiot and wrong, so take it for what it's worth LOL.
This is all good.

As for roll center.... This adjustment changes the effective amount of weight that forces your chassis to roll during a corner. By lowering your rollcenter (lower hingepin setting on your lower arms), you have more weight above the rollcenter so the chassis will be forced to roll further during cornering (light a van or bus). When raising the roll center the opposite happens and the chassis rolls less. Basically lower rollcenter means more mid corner bit as you are applying more grip with increased roll but the chassis will be less responsive. Higher roll centers make a very lively car (more response) but decrease mid corner bite.

And to complecate this further there is also roll axis used to adjust f/r weight balance.
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Old 02-02-2009, 06:34 PM   #7
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so what I'm getting is adding shims will increase the roll center and be a more responsive car and will have mor mid bite?
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Old 02-02-2009, 06:56 PM   #8
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Originally Posted by Tulsa TC3 View Post
so what I'm getting is adding shims will increase the roll center and be a more responsive car and will have mor mid bite?
Yes you will raise the rollcenter. You will get more response but less midcorner bite.
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Old 02-02-2009, 07:08 PM   #9
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OIC.I would like my car to be really tight and responsive and want to be able to put it anywhere I want to. I really dont like a loose car, is loose faster?
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Old 02-02-2009, 07:33 PM   #10
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Days of Thunder quote Robert DuValle,

"Loose is fast, and on the edge of out of control."
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Old 02-03-2009, 08:34 AM   #11
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OIC.I would like my car to be really tight and responsive and want to be able to put it anywhere I want to. I really dont like a loose car, is loose faster?
Ultimately yes, but if you are slowing down early to keep the rear end from coming around, then no. You have to find a point where the car is comfortable to drive, but don't worry about making it perfect, learn to use more brakes if you need more turn-in, rolling the throttle if your pushing on power, etc.
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