Author Topic: Rearend camber  (Read 12691 times)

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Re: Rearend camber
« Reply #15 on: November 17, 2009, 06:14:31 PM »
On the housings that we use at the shop I work at, the camber is machined into the snout that is welded on to the axle tube.  The axle tube itself is still straight.
So what I am doing is having the housing built to fit my car with the 4 1/2" wheels.  The engine is also offset an inch and a half to the right, which complicates things further.  Luckily we have a guy who does nothing but build rearends and he has been willing to work with me on this project.  I'm finding out that there is a whole lot that goes into building your own rearend.
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saltfever

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Re: Rearend camber
« Reply #16 on: November 18, 2009, 12:42:04 AM »
Thanks, Count. How much camber are you going to use? Will the wheel mounting face be in the middle of the rim or offset?

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Re: Rearend camber
« Reply #17 on: November 18, 2009, 07:00:08 PM »
I'm thinking 1/4 deg. camber, and mabybe some toe.  I wish there was a way that I could test this before doing it. But I've really only got one shot at this.  As for the offset of the rims  I had Marsh do the wheels for me and had them get the hubs as close to center as they could.  I'll try to check that out for you tomorrow.  Seems like they were able to do 1 1/2" maybe 2".
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Offline willieworld

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Re: Rearend camber
« Reply #18 on: November 18, 2009, 07:35:43 PM »
i dont know about lsr but ive straightened a lot of drag race rearends that were bent or made crooked and the cars always ran faster in mph and lower in et with a rearend that was straight     willie buchta
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McRat

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Re: Rearend camber
« Reply #19 on: November 18, 2009, 08:52:23 PM »
I was just thinking...

No matter what, the traction (thrust) on the two rear tires is never equal.  The tire with the most traction will want to steer the car to the opposite side.  To keep the car straight, the steering is adjusted, so to at least a minor degree, the car body is travelling a little "sideways".

If you look at the attached caveman wall painting (MSPaint), the red arrow is straight ahead, zero toe.  This will still cause a little steering offset to the right when that is the "dominant" tire.  Green would be the absolute worse case, and require huge steering offset to the right.  The Blue arrow (exaggerated) is toe-in.  At some point between the red and blue arrows, there is a point that will require no steering offset to go straight, hence keep the body perfectly aero. 

I don't think it could actually be calculated exactly, but it seems there is a toe-in number that should actually increase your speed.  The more "perfect" your weighting, tire dia and pressure is at full engine torque, the less toe it will take to make the body straight.  CG location probably comes into it.

« Last Edit: November 18, 2009, 08:58:09 PM by McRat »

saltfever

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Re: Rearend camber
« Reply #20 on: November 18, 2009, 08:53:30 PM »
If you are running a full-floater with that narrow rim width; aren't the hubs going to stick out past the rim or through the hubcab?  Thanks for this thread . . . very interesting.  :-)

Offline jl222

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Re: Rearend camber
« Reply #21 on: November 18, 2009, 10:00:43 PM »
 
  The 9'' ford rear end on the 222 camaro has a drag race style housing. It looks like they used a 2'' wide by 3 or 4'' piece deep of channel steel and welded- fitted and tapered it across the middle of the housing from side to side. Between the brackets for the 4 link there is a 1 1/2 tube welded from side to side and bottom of bar is just even with the bottom of the back of housing. This insures that the housing does not flex up or down or foward or back.

                          JL222

Offline Peter Jack

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Re: Rearend camber
« Reply #22 on: November 19, 2009, 12:05:02 AM »
Saltfever:

The race car floaters aren't like a 3/4 ton floater. They're much more compact and don't stick out very much at all. The only amount that sticks out is the cap and that's probably only a 1/4" or so.

Pete

saltfever

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Re: Rearend camber
« Reply #23 on: November 19, 2009, 01:39:08 AM »
Thanks, Pete. I forgot the NASCAR type were more compact.
Mcrat I wish I was as handy with MsPaint. It’s a great drawing that displays perfectly what we are talking about. I’m not sure green is the worst case. Why wouldn’t the blue line be as bad? Any thrust on either side of the red line would want to move about the CG. If we are discounting toe-out on the left for the green line then toe-in on the left side should be discarded for the blue line no?  :|

McRat

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Re: Rearend camber
« Reply #24 on: November 19, 2009, 01:58:00 AM »
Thanks, Pete. I forgot the NASCAR type were more compact.
Mcrat I wish I was as handy with MsPaint. It’s a great drawing that displays perfectly what we are talking about. I’m not sure green is the worst case. Why wouldn’t the blue line be as bad? Any thrust on either side of the red line would want to move about the CG. If we are discounting toe-out on the left for the green line then toe-in on the left side should be discarded for the blue line no?  :|

The same angle of toe-out and toe-in, the toe-out will have a much more pronounced force applied trying to steer the car from the back end.  It acts on the CG, and has far more "leverage" against it.  And a certain amount of toe in will make it so no steering input is required to go "straight" even when the rear tire traction is very unequal.


McRat

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Re: Rearend camber
« Reply #25 on: November 19, 2009, 02:20:33 AM »
By the way, I'm not sure I'm correct, or whether it's significant.  It just makes sense to me.


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Re: Rearend camber
« Reply #26 on: November 19, 2009, 06:28:43 AM »
McRat, I tend to agree with you, now if I can just figure out that magic number.  It seems to me that if you can make the car more stable, with a minimal amount of drag, and less driver input of countersteer, you should go faster.
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Offline Peter Jack

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Re: Rearend camber
« Reply #27 on: November 19, 2009, 08:26:30 AM »
I know that with the sports-racing and formula cars I've worked on over the years that rear toe out led to immediate, often drastic handling problems and rear toe in was usually totally stable. My tendency would be to run only a touch of toe-in if any. As for camber I wouldn't run any in this application but if a person wanted to I'd again run only a touch. The main thing is to ensure that both sides are identical.

Bye the way a touch is a very precise measurement related very closely to a smidgen!

Pete

McRat

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Re: Rearend camber
« Reply #28 on: November 19, 2009, 10:36:21 AM »
Only slightly related, we had serious handling issues when first started 4x4 dragracing.  Toe-in in the FRONT, will make the truck change directions violently if traction shifts from left to right.  Since we had an open front axle, when one tire broke loose the truck headed with great drama one direction, then as it caught, violently in the other.  We fixed it, so now in the worst case no matter how many tires spin, the most it will do will be having the body point straight down the track, no steering, but it's path curves like when you're bowling.  I figure that's torque reaction, and as long as you don't try to correct it, you're fine.

Offline DallasV

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Re: Rearend camber
« Reply #29 on: November 19, 2009, 02:15:00 PM »
0 rear camber, 0 rear toe, works good for us.
Records or parts, I didn't come all this way not to break something.