Will lowering the rear of car by the leafspring bolts cause the wheels to change camber?
Also does this have any effect on the leafsprings stiffness?

 

The diff center goes down in relation to the wheels so the top of the wheels are pulled inwards

 

Yes..

That's the same effect as suspension compression, and rebound has a similar effect, just opposite angles. The "alignment/camber is set for the common resting or normal ride height. Look at the wheel on any IRS system as a circle that's in a track of up or down over the top of the chassis and down around and under.. As the wheel moves, the center of the chassis is the middle of the circle, so the angles change from 0 degrees @horizontal to 3 degrees + or - (3 degrees positive or neg) that can also be interpreted as camber neg or pos, whichever the case may be. If its NOT set to spec when at normal ride height, then it should be. Its several inches of travel to get only a couple degrees of camber change. I cannot say exactly but you get the idea..
The idea behind IRS is for the chassis to remain stable while the wheels do the traveling to absorb shock and follow the terrain. Another way of looking at it is to see the wheel well and imagine why they do not get destroyed each time the suspension is bottomed out...because the wheel not only travels UP, but the angle changes to INward also. So the wheel well is cleared as the tire swings up and IN.

If you really want to get into brain-tease, add the sway bar and banked sweeping curves to the equasion . The sway bar permits suspension travel while limiting the chassis reaction to the forces encountered in turns, curves and anything other than straight line driving. If not for the sway bars, these angles would be even greater due to the chassis reaction on top of the suspension travel.

This is where Miss Woods shoulda had my attention...
(geometry/algebra teacher fresh out of college) but I was too busy looking at her *** ...I was 16...what can I say?

 

OK that makes sense, I thought my wheels tipped in after I lowered it an inch. I will get it realligned.

What about the spring tension? does it get any softer as it's lowered? In my mind it doesn't look like it should. Looks like it always stays in the same arc. But my but tells me it fells softer in the rear after lowering. Maybe it is the change in weight distribution I am feeling?

Thanks! Randy

 

On mine lowering it made the shocks almost ineffective. Bringing it back to stock height (and we're talking with a rear spring FAR stiffer than yours) the ride quality improved dramatically.

Just something to think about.

 

Yes lowering your vette will affect camber a little and you need a 4 wheel wheel alignment afterwards. (does this via the lower control arms if the angles change ie lowering making the control arms apear more horizontal from it pushes the wheels out at the bottom and in at the top, toe in may also be affected slightly).
The spring rate is still the same however if the front to rear hight has been adjusted diffently with the rear higher or lower it may affect the feel as you will have moved the centre of gravity back or forward

 

OK, so I have it where it has the same clearance from wheel to fender. I probably lowered it 3/4" after I got my 1/4" spacers installed. I couldn't go this low before because the wheel tipped in and rubbed the liner. What sucks is I just had the car 4-wheel aligned this spring when I got knew Conti's.
So the front should still be good? If I knew how much camber/in changed I could just readjust the lower control arm by the same amount on each side and be close enough for me. Other than the minimal increase in wear I actually like the way it handles. It couldn't have changed much with 3/4" drop although I can see from the rear it has a small amount of camber/in.
Is there a Shade Tree garage method I could use to measure and adjust the camber. Like say using a level on the bottom side-wall of tire and measure the distance between level and the top side-wall i.e. 1" then adjust support bar to pull the bottom back in and so I have an acceptable amount of camber/in like say 1/4" space between level? Make cents does in my head.
Thoughts please!

 

Regarding the spring stiffness after lowering....that's a good question. I DO KNOW the ARC of the spring is where the softness or harshness comes from. The MORE arc it has the softer the ride. The flatter the spring the stiffer it is. The famed '84 Z51 springs are as flat as a board...hard as a rock too. So, if you used a little of the ARC in the lowering,. that MIGHT have had an effect on the spring rate...only you can tell.

Doing a DIY camber adjustment on the rear would be possible I'd think, IF you had a reference point before lowering...like a torpedo level across the wheel hub to see where it was before lowering, so you could work toward that setting after lowering. Without a benchmark, its guessing...

Hell, just go back and claim warranty on the alignment...

 

Regarding the spring stiffness after lowering....that's a good question. I DO KNOW the ARC of the spring is where the softness or harshness comes from. The MORE arc it has the softer the ride. The flatter the spring the stiffer it is. The famed '84 Z51 springs are as flat as a board...hard as a rock too. So, if you used a little of the ARC in the lowering,. that MIGHT have had an effect on the spring rate...only you can tell.

Doing a DIY camber adjustment on the rear would be possible I'd think, IF you had a reference point before lowering...like a torpedo level across the wheel hub to see where it was before lowering, so you could work toward that setting after lowering. Without a benchmark, its guessing...

Hell, just go back and claim warranty on the alignment...

 

The Flint Corvette Club used to have a great "how to" on home alignments, but they have since pulled it off their public domain. But there are other sites that explain the "String Method" of alignment.

http://www.negative-camber.org/jam14...alignment.html

 

I've attempted the "string" method and there are definite possibilities there...

BUT, big BUT......

You absolutely have to have a stable and solid way to fix the ends of the string...like a pin or bolt in the garage floor. Jackstands won't do well because the string has to be piano wire tight...so whatever you use has to be pulled very taught.

I found stainless steel wire to be better than string. Its thinner and allows closer adjustments...As thin as kite string is, its a couple degrees thick to a front wheel.

Then you need a means of measuring against the string that will be consistent...a tape can be hard to read trying to hold it steady at but not on the wheel, and at the string... a yard-stick in mm is pretty good for this job. Or make a tool that's an exact length with indicators on it.

The trick is to measure at the exact same point on both wheels same side. Then you need to be able to measure across the tires Left to right, to set TOE...That can be a challenge since the point at mid-tire is hard to get a wire to stretch across with air dams and bumpers in the way...got to do frt and back side of the wheel, both ends. Once you establish TOE, the rest falls into place. TOE on the front is the benchmark for the rest. If that's AFU, the rest will be as well.

Camber is easiest of all. Level and measure.

Caster is impossible so don't mess with the shims unless you are doing camber on the front...just take out or add shims equally on each rod at both ends of the control rod, never just one end.....that screws up caster and its impossible to fix without a laser and Stephen Hawking.

I got 'ok' results using steel pins driven in the ground. I had nothing to secure the string on the concrete floor...so the garage floor didn't work well for me.

Make a set of grease plates and then you can make adjustments and have the wheel follow the adjustment instead of having to jounce and adjust and jounce etc...

Its a lot of stuff for the DIY guy to assemble and store for something that you don't do often, but it CAN be done.

Personally, the $100+ tab for a 4 whl alignment at a neighborhood shop is well worth it as long as they can present a before & after print out showing caster on the front..

if you just like to "see", then the DIY alignment is good for some interesting challenges.

 

No. Spring rate doesn't change.

 

Yeah, that sounds like it's not worth the hassle. for $75 on a laser table.

Oh well it was worth a look. I like doing most things myself but sometimes it just not worth the hassle.

Thanks guys

 

The arc does not set the firmness. The thickness and construction of the spring sets the firmness. The arc is different for different rates merely to allow the vehicle to sit at the same height when you swap out springs. A soft spring will "bend" more than a stiff spring at equal load, so it starts out life with more arc to allow the vehicle to sit at the correct/stock height.

 

Bingo.

 

Well this is about rear geometry