What do I do about rear springs?, My ass is way up in the air! Options

[Zeke]

I have Koni streets on the rear with the non adjustable perch for ride height. I want to lower the car. At this point, if I want to keep Konis, I have to buy yellow "sports" and smaller diameter (2 1/2 ID) springs and threaded collars to accomplish what I need.

After 15 months of construction, I am out of money, but the car is finished save for the rear springs. I just want to track it a couple of times before choosing new suspension stuff. I can't find any short stiff springs to lower the car with the Konis. So, I am thinking of cutting down some 160# stock height springs that came with the street Konis off a six conversion that wrecked.

If I cut the springs and bend the wind at the base to fit in the perch better, I will have about a 185-190 short spring. That fits pretty well with my front 22mm T-bars. I could use some advice before I do this.

[Jeroen]

I may be wrong, but as far as I know, the springrate doesn't change when you shorten or cut them...
So if you cut the 160# springs, they'll still be 160# springs, only shorter
Cutting them shouldn't be a problem, as long as you don't bottom out the shocks

cheers,

Jeroen

[TimT]

I may be wrong, but as far as I know, the springrate doesn't change when you shorten or cut them...

Sorry Jeroen, if you cut a coil off a spring, you have a shorter spring with a heavier spring rate....


Milt is correctamundo.. if he cuts his 160 springs.. he will have shorter spring with a larger spring rate

[ChrisFoley]

Shortening the springs will stiffen them because a coil spring works by twisting, believe it or not. Compressing a spring with less coils by an equal amount means each coil will do more work, or twist more.

I say, go for it Milt! As long as you don't ruin the remaining coils it will be fine. (IMG:style_emoticons/default/smash.gif)

[Jeroen]

Hey Milt,

Well, these guys have proven me wrong (and thinking 'bout it, it makes sence)
So start your cuttin' (IMG:style_emoticons/default/biggrin.gif)

cheers,

Jeroen

[Zeke]

Jeroen, I wouldn't give it a second thought. You have provide a great deal of valuable info in the past. Springs are confusing and become the black art of racing. I just have a temporary problem to overcome and am looking for a cheap way out pending reworking the shock/spring set up on the car ($). The tough part is not how many coils to cut. I can calculate the length to arrive at the rate i want. What is more difficult to predict is the amount of drop I will get. This is why I'm asking around.

Only one person replied over on Pelican and that was Mike Z who posts here too. Guess I know where to go for hard info from now on. Thanks to those who replied. (IMG:style_emoticons/default/smile.gif)

[street legal go-kart]

zeke
having spent a lot of time playing with roundy-round cars [another life ,a long long time ago] i will share the info that cutting the springs can be a successfull project . the key here is to keep the spring as cool as poss. during the cutting process .
allowing the spring to heat up AT ALL will effect both the spring rate and the ride hieght
nothing worse than the car sitting a 1/4" lower on one side when you take it off the jackstands .
the most success i have had is using a plasma cutter
good luck
jt

[Zeke]

Very much appreciated! I'm sure that's good advice for everyone who has thought of modifiying springs. Actually, I was going to cut them with a Sazall and then bend the last coil a little with heat to conform better to the lower spring perch. (I had planned on cutting the bottom of each spring, leaving the tops alone). I may rethink the bending part.

[Mueller]

I think an angle grinder would be much easier to use to cut the spring. The sawsall blade will want to wander around and not bite into the material.

[Bleyseng]

Even if you used a Hackmaster metal cutting blade it still is hard to cut spring steel. Use the mini grinder with a metal cutting wheel. WEAR EYE protection too! Having metal slivers pulled out of your eye is no fun...Happend to me wearing eye protection, no fun at all.
Geoff

[tryan]

if you overload a spring. ( ie compress it beyond yield strength ) you might be able to make it shorter. sounds dangerous, but possible.

heat from cutting or cold working will make the ductile spring steel more brittle. you might pack some ice on the spring while you cut or bend. not liquid nitrogen, but cool.

is there anyway to modify/lower the existing perch? can you canabilize the street koni's off the 6?

you might have the first sport ute porsche. (IMG:style_emoticons/default/rolleyes.gif) naw, somebody already did that.

[Zeke]

The only way to modify (I don't want to canabalize the shock) is to machine the perch completely off. Since welding it back on in a lower position is out of the question, I would have to buy adjustable collars. Back to square one. I promise you, I don't ask simple questions. Sometimes (a lot of the time) it is easier to just buy the right setup to begin with. This assumes you have money. At the end of any project, be it a room addition or a new race car, money is scarce. We won't go into how much Uncle sam nicked me for income taxes this year. Three times as much as ever. So, I'm gonna track the car in it's most basic form, if for nothing else, to break in the motor and seat the brake pads. Then I'll step up and spend a little more money. Keep the suggestions coming, I haven't heard of many cutting their springs. Might turn into a good thing for Koni owners.

[Sammy]

Cut away. But I would get a real old set of stocker 95# springs and practice on them. That way iffn you
screw up you will ruin a pair of springs worth squat, not a $100 pair.
BTW, I love my sawzall and it works very well, but I really doubt it would go through a spring.
If you don't already have one you can get a 4 1/2" right angle grinder at harbor freight for around $20, that would do the job just fine but you should grind for 20 seconds and then cool the metal, then repeat.
I've never tried this, even more reason to perfect the technique on junk, not treasures :-)

[TimMartin]

if you overload a spring. ( ie compress it beyond yield strength ) you might be able to make it shorter. sounds dangerous, but possible.

This process of overloading causes what's called "work hardening". This happens when the metal strains past it's yield point. The metal becomes stronger and more difficult to deform. However, work hardening also reduces ductility, which increases the chances of brittle failure.

I personally would stay away from cutting or changing springs at all. I would get the right size, or have a special shop make springs for me if it was important enough.

.tim

[street legal go-kart]

hey zeke
any modern welding shop will have a plasma cutter
probably less than ten bucks a spring
the nice thing about using a plasma cutter is that the heat is very localized
the process is significantly more rapid than any other , less time to heat up even without cooling or pausing
c-ya

[street legal go-kart]

ps
i totaly agree with the post by tim martin , if its in the budget

[ChrisFoley]

Just have a wet rag handy to cool the hot area after cutting. If you use a cut off wheel cool it partway through as well.
If you heat the end of the spring to make it conform better with the perch, you will lose the springiness from that part of the spring.

[Zeke]

If you heat the end of the spring to make it conform better with the perch, you will lose the springiness from that part of the spring.

Exactly. I had already planned on the "dead coil". This is where it gets tough on the calculation.

[Brad Roberts]

Milt,

send me 60$ and I will sell you a good set of used Bilsteins with lower perch mounts. The 60$ will cover shipping also. I can send them out tomorrow before 3:30 pm. This will solve the cutting springs issue. You wont need too and you can run the threaded collars at a later date.


B