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Old 11-18-2013, 09:18 AM   #1
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Default Diff height, what does it do?

So, all other suspension settings being equal, what does altering diff hieght do?
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Old 11-18-2013, 04:38 PM   #2
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I would say, a change in CG.
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Old 11-18-2013, 04:55 PM   #3
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Lower diffs provide more traction, more body roll, and make car feel more "locked in" versus being free and "on top" off the track.

Higher diffs do the opposite. Less traction, less roll, and make car feel more responsive.

Its going to be a "feel" adjustment so try it to see if u like it.

Lap times will be the ultimate deciding factor...

Hope that helps.

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Old 11-18-2013, 05:22 PM   #4
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Please someone correct me if I'm wrong, but look at the angle the drive shafts have with the outdrives, the more horizontal the more freely they move, especially on power, making it easier for the car to roll and having more grip.

So it's not about putting the diff higher or lower, but making the drive shafts more or less
horizontal.
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Old 11-18-2013, 05:28 PM   #5
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Quote:
Originally Posted by ReneT View Post
Please someone correct me if I'm wrong, but look at the angle the drive shafts have with the outdrives, the more horizontal the more freely they move, especially on power, making it easier for the car to roll and having more grip.

So it's not about putting the diff higher or lower, but making the drive shafts more or less
horizontal.
You are overlooking the distance between the roll center and the spinning differential. The lower the diff the more the car will roll.
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Old 11-18-2013, 10:18 PM   #6
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Higher COG (centre of gravity) will make the car roll more.
Lower COG wil make the car roll less.
Raising the diff = raising COG = more roll
Lowering diff = lowering COG = less roll
Most of the time it's best running the diffs as low as possible.
The angle of the driveshaft does have an impact but im not too sure about the specifics of it.
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Old 11-18-2013, 10:40 PM   #7
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Quote:
Originally Posted by narcotiks View Post
Higher COG (centre of gravity) will make the car roll more.
Lower COG wil make the car roll less.
Raising the diff = raising COG = more roll
Lowering diff = lowering COG = less roll
Most of the time it's best running the diffs as low as possible.
The angle of the driveshaft does have an impact but im not too sure about the specifics of it.

Correct....unless you're dealing with a gyro.
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Old 11-19-2013, 12:33 AM   #8
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You guys are all saying different things. Even one guy saying two different things. That's gonna confuse everyone.
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Old 11-19-2013, 12:57 AM   #9
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Quote:
Originally Posted by Xpress View Post
Correct....unless you're dealing with a gyro.
Quote:
Originally Posted by JimmyMac View Post
You guys are all saying different things. Even one guy saying two different things. That's gonna confuse everyone.
Sorry...there isn't a sarcasm emoticon.

The diffs spinning act as gyros. The further the spinning diff is from the roll center the flatter the car will corner.
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Old 11-19-2013, 01:41 AM   #10
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Quote:
Originally Posted by Xpress View Post
Sorry...there isn't a sarcasm emoticon.

The diffs spinning act as gyros. The further the spinning diff is from the roll center the flatter the car will corner.
Please explain...
So why then, does raising the ride height of the car increase the amount of roll? Since the whole drivetrain (rotating) is raised higher off the ground?
Not arguing, just intrigued
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Old 11-19-2013, 02:32 AM   #11
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The CoG change from altering the diff height is minimal, and not the factor that will determine the change in handling.

The change in driveshaft angle is usually the main thing considered. More angle will give more traction on the power, but probably less corner speed (you never get something for nothing!).

So you'd probably go for low diffs in low traction, and high diffs in high traction.

Overall changing the diff height doesn't have a huge effect on the handling. I've tried it a couple of times and you can feel a change, but it's pretty minor, and never seems to result in more than about 0.05s change in laptimes.
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Old 11-19-2013, 02:33 AM   #12
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Quote:
Originally Posted by narcotiks View Post
Please explain...
So why then, does raising the ride height of the car increase the amount of roll? Since the whole drivetrain (rotating) is raised higher off the ground?
Not arguing, just intrigued
When you raise the whole car, the roll center is also raised. I've never heard the gryo theory before, though.

The biggest factor I've always heard mentioned is that when the driveshafts are spinning (or is it when torque is applied to them?) they apply a straightening force. With the diff low, this causes the driveshafts to push the tires down and the chassis up, hence the increased traction from a low diff.

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Old 11-19-2013, 04:01 AM   #13
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Quote:
Originally Posted by grippgoat View Post
When you raise the whole car, the roll center is also raised. I've never heard the gryo theory before, though.

The biggest factor I've always heard mentioned is that when the driveshafts are spinning (or is it when torque is applied to them?) they apply a straightening force. With the diff low, this causes the driveshafts to push the tires down and the chassis up, hence the increased traction from a low diff.

-Mike
Diff gyro sounds a lot like RC voodoo to me. Any gyro force created by the diff is going to be negated by the 2 bigger more weighty things hanging off it, the wheels. My diff weighs 25 grams, complete with bearings, out-drives and pulley, a single wheel weighs 40 grams has 2 times the diameter of the diff pulley. The entire wheel->cvd->diff->scd->wheel assembly acts as a discrete system, where the greatest forces are at the extremities of the assembly, not in the middle with the diff. Also, within the diff you have silicon oil which , through the counter rotating action of the spider gears, is working against the rotational force of the pulley gear.

Last edited by RogerDaShrubber; 11-19-2013 at 04:22 AM.
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Old 11-19-2013, 04:21 AM   #14
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Quote:
Originally Posted by RogerDaShrubber View Post
Diff gyro sounds a lot like RC voodoo to me.
I am uncertain of the real world effects of it, but it IS a gyro. Just like the wheels and layshaft. Axles.
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Old 11-19-2013, 05:37 AM   #15
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In the corners the "gyros" r minimal cause we r going slow . they might gave a slight effect on the sweeper or faster sections . the drive line bind makes more since
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