How much effect does the rear suspension set up have on front end alignment?

I'm setting up to overhaul the front end before Christmas. Can I wait to replace the sagging rear springs until I have the cash, or will it mess with my fresh front end alignment? Do I need to just bite the bullet and find some rear springs like, now?

Thanks guys.

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Differences in rear ride height will only affect caster and even then the effect will be small. Put a piece of 2x6 under each rear tire on the alignment rack if you want to be precise. Don't forget to have your weight in the driver's seat too.

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Joshua

Very small effects. Don't worry about a new alignment unless you are raising the rear 4" or something extreme.

Lou

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Home of Slant6-powered fun machines since 1988

Ok thanks guys. I just know the rear suspension is about as shot as the front. And a disk swap was a nice kick in the pants for one end... Rear will just be back to stock, eventually.

Joshie225 - Yes, I love the trick of sitting in the driver's seat. Makes perfect sense!

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Zorg- when the time comes to replace your rear spprings, go to Right Way Spring Co. in Tacoma. They are an old school spring shop who can custom build anything you want. Ride height, spring rate, you name it. They used to have a foundry on site with a metallurgist and everything, but they started outsourcing the foundry work a few years ago. Springs cost a bit less than stuff you buy from JC Whitney, but will be custom tailored to your car.

Sweet Reed. Thanks for the tip! I will look them up sometime when I am up that way.

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No; You DO NOT want someone sittin in the driver seat while aligning the car!

Why not? I always put in a couple of cases of oil or something to simulate driver weight.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Why not, Don? My car never goes anywhere without me in the driver's seat, so why not build that in to the alignment?

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Because believe it or not, it WON'T work; I did alignments for 18 years and you'll wind up with a car that pulls horrible and run out of adjustment to get it there if someone's siting in the car during the alignment; now if Big Bertha that weighs 420 drives it then we would make allowances in the settings; but the alignment specs are designed with a car at curb weight. (which does not include any occupants)
Hell, take a torsion bar vehicle; S 10 4Wd was the most common one Id see like this; specs way off can't get it even close and run out of eccentric cam, measure at the same point on both sides (usually I'd use the center of the wheel well arch) and usually I'd find one side maybe 1/4-3/8 lower tahn the other; not enuf to really "see"; bring the low side up to match the high side and perfect. I finally learned to check this first once I saved the "before" readings for the printout; often other than a toe adjustment all I'd have to do would be to correct the ride height (left side was usually the low side) and it would come in perfect; Most do not realize how much the ride height effects alignment on a vehicle!

I don't get it. Having someone sit in the drivers seat will make it so the car will pull, but getting in the car after it is aligned (w/o an occupant) won't make the car pull horrible?

Also, what if my car is lighter than factory curb weight, and sprung stiffer (both affecting alignment/ride hight)? Seems me sitting in the car might just even things out?

It is also being assumed that I'm not a very heavy fellow...

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