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Old 12-09-2009, 11:53 PM   #16
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Originally Posted by smoke81 View Post
Raising and lowering the diff is just changing that bind. Maybe i'm wrong though...
That's about the full extent of the obvious. I can see why for a certain ride height/droop you would want a certain diff height to keep the bind to a minimum. What I fail to understand is why would you want more bind? Even if that is giving you the results you want in terms of controlling the car, I think it is the wrong way to go about it (i.e. introducing more friction by increasing the bind in the driveshaft). This is costing you speed and that can't be good.

My guess is that what they are trying to say int he Losi manual is that they had to change the diff height to those they recommend because of the suspension setup they had (which was probably chosen because it worked best given the grip conditions). That in effect means that you need to change the diff height only to allow your setup to work as intended not because it betters the setup. In other words the diff height doesn't bring anything to the setup, you just need to change it to make sure it doesn't take away something.
Just a guess.
We need to see the actual data of the setup they used (droop/ride height are a must).

Now, with the Losi car having short suspension arms and short driveshafts I imagine the binding effects would be more significant than on some of the other cars on the market.
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Old 12-10-2009, 12:23 AM   #17
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As far as I can tell the lower the diff height, the longer the car stays in roll. You can make the car screw itself into the ground if the diff height is low and you have a low roll center. I think that the hinge pin height to diff height relationship is much more important than the relationship to droop or ride height.

Probably the way to use the adjustment is sort of a mid corner tuning item, and a way to help transition from entry to exit. I know that when the traction comes up, you can help a car that feels like it's "stopping" mid corner by raising the diffs and this does not completely throw the rest of your setup out the window. Sometimes other adjustments like camber link or the shocks would be way too much and have too many other unwanted effects. I guess its a way to bias traction to front or rear, or to "add" or "remove" side bite.
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Old 12-10-2009, 09:00 AM   #18
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Originally Posted by robk View Post
As far as I can tell the lower the diff height, the longer the car stays in roll. You can make the car screw itself into the ground if the diff height is low and you have a low roll center. I think that the hinge pin height to diff height relationship is much more important than the relationship to droop or ride height.

Probably the way to use the adjustment is sort of a mid corner tuning item, and a way to help transition from entry to exit. I know that when the traction comes up, you can help a car that feels like it's "stopping" mid corner by raising the diffs and this does not completely throw the rest of your setup out the window. Sometimes other adjustments like camber link or the shocks would be way too much and have too many other unwanted effects. I guess its a way to bias traction to front or rear, or to "add" or "remove" side bite.
I think you've got a handle on it!


Niznai,

You just need to try it. Changing the diffs in this manner and adding just a hint more or less of "plunge bind" creates no harmful friction as you seem to think. Adding toe in in the rear creates more friction and does more to slow you than a diff change in this manner would.
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Old 12-10-2009, 03:49 PM   #19
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Has anyone actually tested this theory? I have changed heights and did not notice a difference. I know what manuals and word of mouth says but!!!! I am going to mess with it this weekend to get a feel since we are on carpet now.
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Old 12-10-2009, 04:17 PM   #20
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Has anyone actually tested this theory? I have changed heights and did not notice a difference. I know what manuals and word of mouth says but!!!! I am going to mess with it this weekend to get a feel since we are on carpet now.
It's hard to notice a difference in handling when your laying on your lid. How's that traction roll treating you?
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Old 12-10-2009, 04:28 PM   #21
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Hence why I asked the ? Trying to eliminate it, its probably the Team secret on the tires I run, hahaha
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Old 12-10-2009, 04:53 PM   #22
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Hence why I asked the ? Trying to eliminate it, its probably the Team secret on the tires I run, hahaha
The team secret is "don't use those tires".
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Old 12-10-2009, 08:02 PM   #23
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I would venture to guess that a diff height change isn't going to help with traction rolling.

I would suggest putting one or two o-rings on your front shocks to eliminate up travel.
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Old 12-11-2009, 08:54 AM   #24
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Did I get this one mixed up I always thought that lowering the diff height gives you more traction and raising it takes aways traction.

I'm running schuie and I always run my diff low on Front/Rear. When I raised up my Diff my car is so twitchy and traction is horrible. I raised in a medium traction asphalt track. But I guess it's your overall setup.
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Old 12-15-2009, 10:06 AM   #25
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Do the diff heights and bone angles have the same effect on a 2wd vehicle?
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Old 12-15-2009, 11:04 AM   #26
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Quote:
Originally Posted by robk View Post
As far as I can tell the lower the diff height, the longer the car stays in roll. You can make the car screw itself into the ground if the diff height is low and you have a low roll center. I think that the hinge pin height to diff height relationship is much more important than the relationship to droop or ride height.

Probably the way to use the adjustment is sort of a mid corner tuning item, and a way to help transition from entry to exit. I know that when the traction comes up, you can help a car that feels like it's "stopping" mid corner by raising the diffs and this does not completely throw the rest of your setup out the window. Sometimes other adjustments like camber link or the shocks would be way too much and have too many other unwanted effects. I guess its a way to bias traction to front or rear, or to "add" or "remove" side bite.
I have to say, this is the most the most difficult post to understand. I am still trying to figure out what you mean in a few places, I think it's a difference of slang/jargon that separates us. For instance when you say screw the car into the ground, I understand you mean the car is planted not screwed beyond help (as in the setup is ruined). Or is it the other way around?

But the first sentence I just can't figure out. What can diff height have to do with how long the car is rolling for?

As for the relation to hingepin I think that is another way to speak of driveshaft angle. I suppose you are talking about the inner hingepin. The reason I mentione ride height and droop is that they both affect your driveshaft angle. Sure between two otherwise identical cars, changing the diff height will introduce some difference. I am not sure how noticeable that would be.

The second paragraph is a little bit easier and I can see how that theory could work. This makes more sense and seems in agreement with fundamental principles. Your explanation though seems to assume there is some sort of stall point mid corner for some cars/setups. I don't think I have noticed that in any of my cars. By mid corner I take it you mean the point where the car has finished braking/slowing down and starts accelerating i.e. the transition point when weight is transferred around and that changes the grip level/balance between front and rear?

Perhaps you can reformulate some of the first paragraph if that's not too difficult.
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