Posi unit it a dirt track car - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 10 Old 04-22-2009, 12:41 AM Thread Starter
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Posi unit it a dirt track car

I am currently running a Posi Unit in my dirt track car.

Usually we set the rear up with a bigger tire on the RR and a smaller tire on the LR to give it stagger to make the car turn left.

Usually I just weld the spider gears to lock the rear. But this year I decided to run a posi unit. I am running the same size tire on all 4 corners (255/60/15).
I am just currious as to if it will hurt the posi unit to run a 235/60/15 on the LR and a 255/60/15 on the RR?

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post #2 of 10 Old 04-22-2009, 02:17 AM
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Quote:
Originally Posted by GilroyRacing View Post
I am currently running a Posi Unit in my dirt track car.

Usually we set the rear up with a bigger tire on the RR and a smaller tire on the LR to give it stagger to make the car turn left.

Usually I just weld the spider gears to lock the rear. But this year I decided to run a posi unit. I am running the same size tire on all 4 corners (255/60/15).
I am just currious as to if it will hurt the posi unit to run a 235/60/15 on the LR and a 255/60/15 on the RR?
Realistically no

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post #3 of 10 Old 04-22-2009, 07:41 AM Thread Starter
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it wont hurt the clutches?
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post #4 of 10 Old 04-22-2009, 12:48 PM
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Dont understand the "Realistically no"...
How would it not burn up the clutches, with contstantly running different rpms to each end?

IMOHO its a bad idea. I wouldnt even run a spare tire (if I got a flat)that wasnt the same diameter as the other side.

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post #5 of 10 Old 04-22-2009, 03:19 PM
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It will..... When the rotating of the two wheels is different, the clutches are being "used".

That's the way it is. I agree with drudis 100%

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post #6 of 10 Old 04-22-2009, 04:13 PM
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For that matter running a continuous circle in one direction is going to wear the clutches whether you have the same size tires or not. Running the stagger you suggested might equal out or offset some of that wear.

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Last edited by Han Solo; 04-22-2009 at 04:23 PM.
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post #7 of 10 Old 04-23-2009, 10:48 PM
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An inportant fact is he is running on DIRT! The tires will spin long before the clutches slip. The amount of stagger you need to run varies depending on the banking of the track, if any, the radius of the turns, your driving style.

I would try at least two different size tires on the outside wheel or the inside wheel and compare the differences in how the car handles.

When I ran a car on a local oval track, but on pavement, not dirt, we ran huge stagger. But this track you never went straight, it was that small.

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post #8 of 10 Old 04-24-2009, 11:50 AM
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I't ain't like the clutches are that expensive or hard to change. Run it however it handles the best and if they burn up in 1 or 2 races you'll know you need to go back to the welded spiders.

Hell I ran a welded dif in my FWD Mini back in the 70s and used it for autocross. Damn thing would break your arm if you let off the gas in a turn but as long as you had the power down it was like power steering. Worked out fine since you needed to keep the front wheels pulling in the turns anyways.

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post #9 of 10 Old 05-01-2009, 08:22 PM
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My point was it probably wont matter with what he is doing. Id run it, see what happens. Whats the worst thing you do, burn up the clutches?? Id weld it personally.
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post #10 of 10 Old 05-04-2009, 05:24 PM
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have you changed the clutch packs to have 4 clutches and 3 disks or still using the stock setup?


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