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Author Topic:   Reference point
hoosier transplant
Dirt Maniac

Total posts: 104
posted July 16, 2005 11:52 AM  
I beleive my rearend is angled back on the right rear but I'm not sure where to measure from. I know that measuring from front rim to back will give me wheel base length but I really need to square rearend. I'm loose in the middle and I think the rearend steer is making be loose. I have a full metric frame and was wondering if anybody could tell me how to measure. Thanks

Eljojo
Dirt Forum Champ
Total posts: 968
posted July 16, 2005 02:27 PM  
I'll try to make this easily understandable, but if you have doubts, just ask.
Set the car on jackstands, with the suspension holding the weight of the rear of the car. (stands under the axle housings.
Using a two foot framing square, put one leg of the square flat on the floor and the other leg against the brake rotor or drum. The lower leg of the square will be running in line with the chassis so that you will be able to make a mark on the floor directly under the front of the rotor. Do that on both sides of the car. Using a chaulk line, snap a line thru these two marks, continuing on out from the car 4 or 5 feet.You now have a stationary line that is parallel with the rear axels.
The frame rails of metrics are parallel and offer a great place to pick up the line that parallels the chassis. I like to put the framing square against the framerail at the most forward and rearwrd points of the chassis. (the straight part)
After making two marks on the floor that are plumb with the fraimrail, Repeat the process with the chalk line. Snap this line from behind, all the way to the front of the car. You should now have a + snaped onto the shop floor--one line parallel with the rear axels and one line parallel with the chassis.
Fromthe center of the + measure and mark on the chaulk line on the
shop floor---
8 foot, running with the chassis.
From the center of the + measure ans mark a spot on the floor at 6 foot, running on the line that's parallel with the rear.
From the
mark the 8 foot measure diagonally to the mark at 6 foot. If the rear end is square with the chassis the meaurement will be EXACTLY 10 foot. If it is not, your rear is out of square and you can use those two lines to calculate just how far it is out.
Some of you will say that using a framing square is less accurate than using a plumb bob, but I have found that by using a square, my meaurments are more consistant the trying to get a mark off a swing plumb bob or a small level.
Good luck!

mike9
Dirt Full Roller

Total posts: 72
posted July 16, 2005 03:00 PM  
that is a very good and accurate way to do it , an easy quick way is to string it , make sure you have a straight wheel and the axle isnt bent run a string from the chassis behind the tire and go forwards bring the string in towards the chassis until it just touches the front of the tire sidewall tie it to a jack stand and make sure it is just touchint the sidewall and measure from the string to the rear of the wide straight part of the frame and measure from the string to the front of the siderail if the rear end is square both measurements will be the same

hoosier transplant
Dirt Maniac

Total posts: 104
posted July 16, 2005 10:50 PM  
Thank you both for the reply. I understand both concepts. I was hoping there was a drilled hole or whatever in the frame so it would be simply but I'll just have to time a little more time to check the sqareness. Another thing, I am thinking correctly on the theory that with the right side pulled back would make the car to try and drive to the outside of track, making me loose, especially at middle turn and exit?

mike9
Dirt Full Roller

Total posts: 72
posted July 17, 2005 06:50 AM  
actually there are points on a metric chassis you could measure from to check the rear for square at the rear where the frame kicks up to go over the axle there is a hole on each side about 7/8- 1 inch diameter that the edges are pressed in (not just punched out like the others ) you can measure from this hole to the axle on each side , these holes are reference points in my frame machine measuring system so they are symetrical these will tell you what you need . put the axle on jackstands remove the tires and measure from the hole to the axle on both sides .this will only work if the frame isnt diamond though , because if it is in a diamond condition it will measure square with the frame but in reality be back on one side . a diamond condition is when the frame has taken a hit (usually in its prior life as a street car ) and one side gets pushed back , this is one reason its important to x a metric frame they diamond easy .

hoosier transplant
Dirt Maniac

Total posts: 104
posted July 17, 2005 08:58 AM  
Thanks Mike. That's what I was looking for so I can check real quick to see if I need to square rearend. Just looking at rearend, it looks as though the right side is back but it may just look that way. If it is out of square then I can use a more accurate method for squaring.

hoosier transplant
Dirt Maniac

Total posts: 104
posted July 17, 2005 05:05 PM  
I just got done checking rearend for squareness and found the right rear back 1/2 inch. I've been fighting a loose car since I got it. No matter what I tried to tighten it up didn't help. And it diffently did not like stagger. Am I right in assuming this has been the problem all along? Or at least a big problem. The guy that built the car also had a loose problem and was running traction control to help it. The car enters real good but as soon as I get on the gas it would become loose. I put some weight in rear to get to 52.5 rear and fixed the exit bite, so now it comes out like gangbusters but still had the problem at appex and still wanted to be a little loose(not real bad) on exit but was drivable. So what do you think? Did I help it by squaring rearend? I can hardly wait till Friday to try it out.

Eljojo
Dirt Forum Champ
Total posts: 968
posted July 17, 2005 05:30 PM  
You can bet te farm that you helped it. I lie to run a little (1/4--3/8") lead in the rr to tighten it up. Now get it on a set of scales!

[This message has been edited by Eljojo (edited July 17, 2005).]

hoosier transplant
Dirt Maniac

Total posts: 104
posted July 17, 2005 06:41 PM  
The scales is my next chore. I'm curious as to what that change might have done to my %'s. I had some pretty good numbers after adding the weight. I'm 170 pounds over weight but it sure helped the bite coming out. Before this latest change I had 51% cross, 52.5% rear, and 52.2% left. Had 105# bite. Now, if this does cause a slight push(don't know just speculating) what changes at the track would you most likely make? Take a little bite out? Take some cross out? Just trying to be prepared incase a push developes. I've never had a push in this car before, it's always been loose. Thanks, Donavon

    

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