Help, setting rake...
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With the rear roll center too low the car will just over steer over the place, with it too high it will be mad tail happy... With the rear slightly above the front you get a happy neutral.h
Yep. Its the ridge that you attach your factory jack to.
Last edited by JR4WDTRBO; 06-07-2011 at 06:30 PM.
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Level roll centers means the rear wants to track the front end perfectly. This is a car that pushes, though, since the car has momentum in a straight line. In order to actually make it turn and rotate, you need to have the rear roll center higher than the front.
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In that sentence is "roll center axis" referring to the same thing as "roll axis"? Roll axis as I understand is just straight line drawn between the roll centers, so how could it be out of sync with respect to the roll centers? It's obvious that having the roll axis slope down to the front some is helpful for a miata, but has anyone sat and figured out why, other than testing?
You are correct that the roll center axis is just an imaginary line connecting the front and rear roll centers. To me though, the its not very useful information other than visualization the relationship between the front and rear. Even though front and rear suspension movement effects each other, I prefer the think of them as functioning separate unless I am "doing the math" to keep from going crazy (too much to think about all at once. I also prefer to think of each corner as separate islands of suspension, and I like to forget that the chassis likes to flex..
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Yes, mostly correct (%100 percent correct if the rear suspension was exactly like the front -camber curve, mounting points, arm angles,..) Even on front wheel drives the rear roll center is slightly higher than the front to keep handling balanced, but I suspect you are right [RWD more than FWD.]
Last edited by JR4WDTRBO; 06-07-2011 at 06:31 PM.
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<\pissing contest> You win
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Jerk.
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"The front roll center will always be lower than the rear. If it is too much lower, we will have a car that does not enter corners well and which exits corner on three wheels. The big trick here is to keep the front and rear roll center movements approximately equal to each other--and in the same direction--as the car does its various things while negotiating a corner."
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Thank god this thread came around. I've been wondering why my car seems to want to track straight on turn in - I can work with it, and have altered my technique accordingly, but even watching videos online I could tell other's miatas had much more rotation capability...
All my tools and tent, etc. are still in my trunk from Chuckwalla so I'm going to unload the car tomorrow and then measure... it's probably all wrong.
All my tools and tent, etc. are still in my trunk from Chuckwalla so I'm going to unload the car tomorrow and then measure... it's probably all wrong.
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On page 54.
"The front roll center will always be lower than the rear. If it is too much lower, we will have a car that does not enter corners well and which exits corner on three wheels. The big trick here is to keep the front and rear roll center movements approximately equal to each other--and in the same direction--as the car does its various things while negotiating a corner."
"The front roll center will always be lower than the rear. If it is too much lower, we will have a car that does not enter corners well and which exits corner on three wheels. The big trick here is to keep the front and rear roll center movements approximately equal to each other--and in the same direction--as the car does its various things while negotiating a corner."
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I read something last night on AutoSpeed.com that was interesting:
MX-5/Miata Magnificence - Part Two
Part Two of our look at one of the most successful sportscars in modern motoring...
By Michael Knowling
"[2nd Generation Miata] Suspension - while similar in layout to the original - was heavily revised. Several pick-up points were relocated - caster was increased by two degrees and front roll-centre lowered - and the springs and dampers were revised to suit (including having more travel). Interestingly, concerns of steering kickback caused by increased castor were addressed by re-bushing the steering rack - it was made relatively soft in vertical compliance to reduce transmitted shock."
I didn't realize that the front roll-center had been lowered for the second gen. Very interesting. That means that you could possible get away with less rake on a NB. Wonder how much the front roll center was lowered. Time to start Googling...
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I'm going to measure my ride height today, my car feels shittier than it used to.
I know its been said but its worth mentioning again, DON'T measure from the fender lip like I did.
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