Stiffy question

[Dave-R]

My Corvette came with Z06 brakes/suspension. But the front anti roll bar is badly corroded from road salt so the wife treated me to a pair of aftermarket sway bars.

Now these new anti roll bars are a hollow design same as the old ones and only 1mm thicker or so than the old ones.

But they weigh 2lbs more (12lbs vs 10lbs) so obviously they must have 2lbs more steel in them. Maybe thicker walls.

2lbs is 20% more steel.

So my question is, does that mean these bars will be 20% stiffer in operation???

[andyrob]

nope, alot more variables than that I would imagine, depends on what toughness the new ones are made from & extra diameter will give you more than the % increase, wont be a linear relationship, I imagine some body on here will come alongs with x y z & expain it properly

[Dave-R]

Thought as much Andy.

I am just worried I might have gone a tiny bit further than the "slightly" stiffer I was after.

[Ivor]

Andy's absolutely right, it depends all on the hardness of the bars themselves, on my old Lotus Super Seven, I upgraded to a stiffer anti roll bar that was exactly the same thickness as the original bar, but seriously stiffer.

One thing you never had problems with though is it Dave?

[Dave-R]

One thing you never had problems with though is it Dave?

She never leaves me alone as it is mate. I don't want to make matters worse.

[Dave999]

depends on the spring constant K of the spring and that workls for all springs not just wire wound coils

function of cross section and the treatments done on the material in question

i.e you could have two identical bars formed

heat treat slightly differently

and end up with 2 differet spring rates
one will be "stiffer"

you new bar could look identical
in size shape and thickness but with different treatment be stiffer


or they could treat both the same and just make one fatter

or make it out of a different alloy

spring rate shouldn't change unless spring is pushed past its elastic limit
i.e gets fatigued and not elastic anymore. i.e never goes back to where it orginally started i.e elastic hysterisis

over stretching or physical degradation are both candiates for causing this

and in your situation i'd say your orgianl will be showing signs of less springyness

i.e its buggered

new identical spring
or new higher spring rate spring

will certainly change handling

you'll have to tell us if its an improvement

spring stretch is linear in the elastic region of the spring i.e K is a constant for that spring

i.e 1 gram hanging on it causes 1 cm strecth 2 grammes will cause 2cm and 3 will cause 3cm K=1

but your new spring has a different K so the relationship between the two is not going to necessarily be linked just by mass or thickenss K might be 10 for your new spring 1 gramme causes 1mm strecth 2 causes 2mm strecth etc

or 100

Dave

[Dave-R]

The surface of my old one has scabs and flakes dropping off it in parts so I didn't like the look of it.

Have had to re-build the brake calipers too because of corrosion. Rear of the car is fine. It is just from road salt on the front.

[Guy]

The surface of my old one has scabs and flakes dropping off it in parts so I didn't like the look of it.

I am sure you can get cream for that

[Dave-R]

old and new.

[Roger]

The surface of my old one has scabs and flakes dropping off it in parts so I didn't like the look of it.

Have had to re-build the brake calipers too because of corrosion. Rear of the car is fine. It is just from road salt on the front.

Thats not so bad then. Count yourself lucky its not a Z06. Magnesium subframes! We had one in for engine swap, and the subframe was all corroded away around the subframe bolts. Shockingly bad and only 2 years old

[Dave-R]

The the subframes/engine cradle is all aluminium alloy on mine.

Cleans up fine. The brake calipers are cleaning up well too and will be painted a nice bright yellow rather than the stock red.

The problem with many of the people buying Corvettes brand new is that often it is their daily driver and they get used all seasons and weathers for the first few years.

[Dave999]

ahha you can work out what K is now

stick em both in a vice (soft jaw of course)

push 1 with set of bathroom scales

measure deflection for 1kg push a 2 kg push and a 3 kg push may be do 4 as well

do the other

plot on force/defelction graph and work out the slope of the line you plot

force/deflection = k with no units of messurement its just a multiplier

use it to work out spring rate in your chosen units lb/inch N/M etc

Dave

[latil]

The surface of my old one has scabs and flakes dropping off it in parts so I didn't like the look of it

The wonders of powder coating ,well it doesn't look like proper paint on there. I pity all those that powder coat their undercarriage parts.

[Dave-R]

Dave, the problem would be deflecting the bar in the direction it works in (twisting). That would be simple enough to compare the two bars if you could do that.

But somehow I suspect that measuring the deflection would be tricky in a home environment.

The force applied would have to be very high and the deflection (twist) would be very small. In particular on bars like this. Remember that rusty bar I am replacing is designed for weekend track use. The replacement is an upgrade to that. So this is a very solid and highly rated bar indeed.

Plus it is on the car now. That was harder than expected. I couldn't remember how the old one fitted. Thought I had it on the wrong way around at first. Got there in the end.

You don't think a 12lb bar is very heavy until you have been struggling with it under the car for an hour trying to hold it up with a bad arm.

[Ivor]

The wonders of powder coating ,well it doesn't look like proper paint on there. I pity all those that powder coat their undercarriage parts.

I've seen a lot of powder coated suspension parts lifting and flaking off, I can only assume it's bad preparation, but I would always stick with epoxy etch primer and a two pack topcoat.