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Old 07-02-2007, 04:08 AM   #1
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Default Roll Centres

low or high settings? Thanks
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Old 07-02-2007, 05:11 AM   #2
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low or high settings? Thanks
How do you want the car to handle. Have you experimented on your own? You can learn alot by going out for a practice and doing some set up changes to feel the difference...
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Old 07-02-2007, 05:17 AM   #3
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How do you want the car to handle. Have you experimented on your own? You can learn alot by going out for a practice and doing some set up changes to feel the difference...
whats the difference between high and low in asphalt indoor? right now i dont have the time to do runs cause im busy.
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Old 07-02-2007, 06:34 AM   #4
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whats the difference between high and low in asphalt indoor? right now i dont have the time to do runs cause im busy.
In general lower roll centres will increase grip, but you have to set them to get a well balanced car.

Have you tried asking in the forum for your particular car.

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Old 07-02-2007, 06:35 AM   #5
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whats the difference between high and low in asphalt indoor? right now i dont have the time to do runs cause im busy.
There are so many variables that it is hard to say. Basically, the smoother and higher the grip levels, the lower you can go with roll center, and the stiffer the spring.

Check out this website:

http://users.pandora.be/elvo/

and look under "Suspension". Roll center is in chapter 2.3
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Old 07-02-2007, 07:12 AM   #6
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whats the difference between high and low in asphalt indoor? right now i dont have the time to do runs cause im busy.
a high roll center will keep the car rolling(leaning)making the car react faster and have more traction, a low roll center allows the car to roll more and react slower reducing responsiveness in and out of the turns. On low bite asphalt tracks with rubber tires run a high roll center
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Old 07-02-2007, 07:21 AM   #7
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@B4bandit

thanks for the link.

@MarcosJ

theoretically the smoother/high bite the track is i can go low on roll center? okay i guess its about time to hit the tracks.

Thanks everyone.

add more tips if you like.
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Old 07-03-2007, 06:49 AM   #8
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@B4bandit

thanks for the link.

@MarcosJ

theoretically the smoother/high bite the track is i can go low on roll center? okay i guess its about time to hit the tracks.

Thanks everyone.

add more tips if you like.
I think he meant to say "a high roll center will keep the car from rolling"

Smoother, high bite tracks (eg. carpet) allow for a higher roll center. The more traction the higher the roll center you can get away with. The less traction the more you need the chassis to roll to achieve the grip you're looking for.

Testing it is the best way to see the effects of roll center settings. I was surprised at the difference a tiny roll center adjustment can make.
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Old 07-05-2007, 06:20 PM   #9
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I think he meant to say "a high roll center will keep the car from rolling"

Smoother, high bite tracks (eg. carpet) allow for a higher roll center. The more traction the higher the roll center you can get away with. The less traction the more you need the chassis to roll to achieve the grip you're looking for.

Testing it is the best way to see the effects of roll center settings. I was surprised at the difference a tiny roll center adjustment can make.
I believe you meant to say that on a high bite track, it allows for a lower roll center, because you can allow the car to roll more to achieve less traction.

Just think about it this way, when the camber link is less parallel relative to the arm, you have a higher roll center.

When the camber link is more parallel relative to the arm, you have a lower roll center.
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Old 07-05-2007, 06:34 PM   #10
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clear as mud now
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Old 07-05-2007, 09:51 PM   #11
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Tek, since when does more roll --> less traction? Forget for a second that the commonly toted words 'more roll --> more traction' doesn't have a solid base in vehicle dynamics study. It's just accepted to be so. You are the first person I have ever seen claim more roll --> less traction.

Guys run high roll centers in foam/carpet because there is already a ton of grip, and having a very responsive and accurate car is more important than generating a little extra grip. My 007 is much easier to drive around a fast carpet/foam sweeper with high roll centers. Also, without high roll centers, you have to run extremely stiff springs to avoid catching the outer edge of the chassis. That isn't ideal for maximizing traction, either.

Low roll centers are used on asphalt because guys want a suspension that is soft and relies on chassis roll to sustain weight transfer rather than using suspension geometry to sustain weight transfer. Using suspension geometry to do that results in high instantaneous loads on the tires and will quickly and easily put the tires beyond ideal slip angle. Frequenting the beyond-ideal slip angle leads to traction loss (understeer, oversteer, or a drift) and heavy tire wear.

I dare guess that pushing foams on carpet over their ideal slip angle isn't as bad as rubbers on asphalt, because the foam/carpet traction coefficient doesn't drop as sharply beyond ideal slip angle. Rubber/asphalt relies heavily on a static grip interaction not present in foam/carpet.

And if you don't feel like reading my vehicle dynamics and tire dynamics mumbo jumbo, just check the 007 setup sheets on teamxray.com. You'll find that carpet/foam roll centers are consistently higher than rubber/asphalt roll centers.

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Old 07-06-2007, 06:24 AM   #12
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Originally Posted by Tek Nickal View Post
I believe you meant to say that on a high bite track, it allows for a lower roll center, because you can allow the car to roll more to achieve less traction.

Just think about it this way, when the camber link is less parallel relative to the arm, you have a higher roll center.

When the camber link is more parallel relative to the arm, you have a lower roll center.
Sorry but I said exactly what I meant.

If you watch a well set up rubber tire car with low roll centers go around the track you can see how much more the chassis will roll back and fourth over a well set up foam tire car with higher roll centers.

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clear as mud now
I know. Sorry.
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Old 07-06-2007, 06:14 PM   #13
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Okay well then I have myself confused then. Now its all clear, somewhat.
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Old 07-07-2007, 09:08 PM   #14
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You can always learn the old-fashioned way,read as much as you can.Once you learn what a roll center is and how it relates to your car's center of gravity it's much easier to figure out what your car needs to handle well.Google these authors if you want to learn more, Don Alexander,Fred Puhn,Herb Adams and Martin Crisp.
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Old 07-12-2007, 12:45 AM   #15
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What would you guys recommend when it comes to running Foams on Asphalt? High or low? Front or rear?
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