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Circle track leaf spring help

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Circle track leaf spring help

Postby 72firechicken » Sun Jun 19, 2011 4:44 pm

Hi anybody out there have any experience with rear leaf spring suspensions? I need some help with a 3450lb limited late model I race on a 1/3 light progressive banked mile ashpalt track 70 chevelle clip. 225lr/200rr Chrysler spring

At what height in relation to the frame should the front eyes be mounted?

What about the rear eye height with spings unloaded? (split between front eye and rear eye)

How much is too much lowering block?

leaf spring toe?

Is the soo much rear steer with leaf springs that you have so offset the rear to compensate for loosness?

Do crysler leafs springs have more rear steer due to the axle locator pin being closer to the front eye?

Thanks!

I though that leaf springs would be relatively simple
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Re: Circle track leaf spring help

Postby RCJ » Mon Jun 20, 2011 8:28 pm

Afcos web site has leaf spring installation tips.I ran camaros and what I did was raise the front eye 3/4 and lower the rear 3/4''.A flatter spring has less rear steer and should have more anti squat.2'' lowering blocks is the most I ran,make some heavy duty ones yourself .I broke several that I bought.Check the toe out in the rear end houseing, heat and quench the tubes to get 1/8 toe in.Then string the car to get the r/r toed in.
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Re: Circle track leaf spring help

Postby 72firechicken » Tue Jun 21, 2011 12:34 pm

Afcos web site has leaf spring installation tips.I ran camaros and what I did was raise the front eye 3/4 and lower the rear 3/4''.A flatter spring has less rear steer and should have more anti squat.2'' lowering blocks is the most I ran,make some heavy duty ones yourself .I broke several that I bought.Check the toe out in the rear end houseing, heat and quench the tubes to get 1/8 toe in.Then string the car to get the r/r toed in.

How do you "quench the tubes" I'm not familir with this process, also when you say string the car this i am familiar with. but "get the r/r toed in" do you mean adjust the rear end so the right side leads? we have had to lead with the r/r 11/16th of an inch to overcome loosness seems that leafs have alot of rear steer. how much leading with the right rear is too much?
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Re: Circle track leaf spring help

Postby RCJ » Wed Jun 22, 2011 8:05 am

What is important is how each tire is toed in or out in relationship to to the center line ofthe car.You can lead or trail the rear axle to get there but,setting the toe in the rearend housing first worked better for me.If the housing has 1/8 toe out heat the front of the tubes till red then throw cold wet rags on them.This will bend the tubes slightly if you go over 1/8 it could cause bearing trouble.
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Re: Circle track leaf spring help

Postby 72firechicken » Wed Jun 22, 2011 2:46 pm

What is important is how each tire is toed in or out in relationship to to the center line ofthe car.You can lead or trail the rear axle to get there but,setting the toe in the rearend housing first worked better for me.If the housing has 1/8 toe out heat the front of the tubes till red then throw cold wet rags on them.This will bend the tubes slightly if you go over 1/8 it could cause bearing trouble.

Yes we keep track of the rear end in relationship to the centerline of the car, but the 1/8 toe in is that an 1/8 total between both sides, so 1/16 per side? also can you explain to me how this helps? I can see 1/8 toe on the r/r helping but not on the l/r? from my experience it seems that when you corner l/r shinks and r/r gets longer giving it rear steer.
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Re: Circle track leaf spring help

Postby RCJ » Wed Jun 22, 2011 7:36 pm

That would be only on the r/r,you could toe the l/r out and the r/r in if the car needed it.If your housing has 1/16 toe out on the r/r you might need to shorten the wheelbase 3/4 to 1'' to get some toe in in the r/r.With r/r toe in the thrust angle of the tire is pointing toward the center of the car.When you pick up the throttle the r/r drives toward the infield and keeps the car tight letting you apply more power. with r/r toe out the r/r wants to go to the wall you have to back steer and this makes it harder to get under a car coming off the corner.You always want to check the rear axle alignment because if you crash and have to put a new axle under it and the new one is toed different you could waste 2 or 3 weeks getting the car back right.I've checked a lot of housing,the winters quickchanges are good out of the box ,but the junkyard and 5 on 5 floaters are all over the place .I have found over years of racing that if my r/r has 1/16 to 1/8 toe in and the car is still loose I need to look at the springs,weight shocks etc..
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Re: Circle track leaf spring help

Postby 72firechicken » Thu Jun 23, 2011 1:12 am

That would be only on the r/r,you could toe the l/r out and the r/r in if the car needed it.If your housing has 1/16 toe out on the r/r you might need to shorten the wheelbase 3/4 to 1'' to get some toe in in the r/r.With r/r toe in the thrust angle of the tire is pointing toward the center of the car.When you pick up the throttle the r/r drives toward the infield and keeps the car tight letting you apply more power. with r/r toe out the r/r wants to go to the wall you have to back steer and this makes it harder to get under a car coming off the corner.You always want to check the rear axle alignment because if you crash and have to put a new axle under it and the new one is toed different you could waste 2 or 3 weeks getting the car back right.I've checked a lot of housing,the winters quickchanges are good out of the box ,but the junkyard and 5 on 5 floaters are all over the place .I have found over years of racing that if my r/r has 1/16 to 1/8 toe in and the car is still loose I need to look at the springs,weight shocks etc..

Great info! checked mine an it has 0 toe, and we have had to shorten our wheel base 3/4" to tighten the car and it does just like you have stated, to far cocked one way or the other and it will try to drive it self into the infield or into the wall! So you have nailed exactly what has been going on with my car. the 1/8 toe in on the rear should really help and keep our rear end straight in the chassis well find out this weekend thanks!!!!!! :mrgreen:
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Re: Circle track leaf spring help

Postby racerx1622 » Thu Aug 25, 2011 4:51 pm

Hello,

VERY informative. I also race asphalt circle track, 1/2 mile. Street Stocks.

When you say 1/16" - 1/8" toe in, at what distance from the drum?
Or at the drum?
Because the brake back plate may be bent, or drum not true.

I'm going to check mine, but I am going to bolt on a piece of straight tubing to the studs, that rests flat against the center hub of the axle, and sticks out about 12" from center. (so overall it's a piece of 24" tubing).
and then check square at the ends.

but, as you know, a 1/16" at the drum could be 1/8" at the end of my tubing.

Please clarify.
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Re: Circle track leaf spring help

Postby racerx1622 » Mon Aug 29, 2011 1:12 am

RCJ?
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Re: Circle track leaf spring help

Postby RCJ » Mon Aug 29, 2011 8:19 pm

Put the tires on it you are going to race then rotate the tire and scribe a line all the way around the tire.Be as accurate as possible.After you have scribed both tires measure 4'' off the ground the distance between the scribed lines on the front side of the rear end then measure the distance between the lines on the back side off the rear end.You might get a number from the front like 72 .5'' , the number from the back might be 72.375 this would be 1/8 total toe out.This does not tell you if one side has 1/8 toe out and the other has 0 toe.Putting the axle in the car measureing from the center line ,string it etc..will tell the toe of each wheel.You might think this crazy but I've looked down the side of enough race cars I can see an 1/8 toe with my eyes.
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Re: Circle track leaf spring help

Postby racerx1622 » Mon Aug 29, 2011 10:27 pm

Thank you!!
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Re: Circle track leaf spring help

Postby racerx1622 » Mon Aug 29, 2011 10:34 pm

We race a '76 Pontiac LeMans with the 4 link rear.
(rules limit us from moving any suspension mounting)
But what is your opinion on using the offset bushings?

I was going to put one in the front of the RR Lower, not offset entirely to the front, but at 10-11 o'clock, to both pull RR in slightly and get slightly better lower arm angle.
(car is good, but when pushed is loose in the middle - off)

(rules limit us to 1" wedge between rear tires when jack under pumpkin also. yeah, fun!)
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Re: Circle track leaf spring help

Postby RCJ » Tue Aug 30, 2011 8:30 pm

Anything you can do to give you more adjustabilty should be a positive.An eccentric bushing that is adjustable is something to look for.1'' wedge with a floorjack,I would be cutting up houseing and moving the pumkin.Swaybar preload and wheel offsets are areas to look at.
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