Thread: Any tips on cutting coil springs?

Tweet

I put my 212 lb. Moroso Trick Springs in the front of my car last weekend and hoped they would settle enough to not require cutting, but so far they've only gone down 1/2". I had a feeling they were going to be way too long, but didn't want to cut them until I was sure.

As it sits, the front end is less than an inch from being completely extended. Considering I need approx. 3" of drop to get my ride height/shock extension travel correct, how many coils should I cut?

The spring's free length is 19" and has 11 coils of .625 dia. making it's collapsed length 7". If 212 lbs. compresses the spring 1", then each of the 10 spaces in between coils compresses 1/10". If one coil is removed, then 212 lbs. compresses the spring only 9/10", so the spring rate would increase to 233 lbs. If I need the installed spring length to be 11" for proper ride height, by my calculations I need to cut 3 coils. That would leave a free length of 14" and increase the spring rate to 275 lbs. My front end corner sprung weight is 700 lbs. which would compress the 275 lb spring 2.5" for a installed height of 11 1/2".

Is this approach correct? I read somewhere that when figuring load rate one coil should be added to the formula, but I can't find that article. I wrote to Moroso about this, but they are extremely slow with their replies.

I thought I would pose the questions here to get some feedback. Any comments are appreciated.

Well I don't know my math at all so no clue how you figured all that stuff out but anyways I wouldn't cut any coils. Get the right height coil because especially with that motor you have in there with that power and weight cutting the coils is not good. Not supposed to cut more than 2 coils or so the most but really your not supposed to cut ANY coils. I wouldn't chance it, bring them back and get the correct height.

I already installed them in the car so I can't return them. Drag springs are sold according to front end weight and are all the same length, at least Moroso's are. Although at 1900 pounds my car's front end weight is at the top of what this spring is rated for (1740-1910lbs), this is a light spring at 212 lbs. so I should be able to cut them some and increase the spring rate without causing too much problem. Naturally I don't want to lose the stored energy or make them too stiff, but without cutting them I don't have enough shock/front suspension travel (extension). I figure the front end is going to come off the ground anyway, so the suspension will max out on launch. I'm trying to understand rate/load rate/ride height/wheel ratio relationships so I don't cut too much and so my setup is optimal for my car. The way I understand it, the only adverse affect from cutting a coil spring is that it increases the spring rate. As long as that rate fits my application I don't think it will hurt anything. The next highest spring rate is 230 lbs and is for front end weight of 1910-1980.

I'm trying to follow advice in the Doorslammer's Chassis Book I bought. It's a great book, but doesn't go into detail about cutting springs. It does stress the importance of properly setting up springs/shock/suspension travel/ride height etc. I can't believe how hard it is to get the manufacturer/product information necessary for this aspect of chassis setup.

Ok I see what your getting at now... Someone on here will help you better than I can then, sorry.

dont cut the springs,find yourself monza front springs which are 2 inches shorter than your stock springs

No need to apologize. Like I said, all comments are appreciated. Sometimes just getting thoughts out and seeing what others think really helps, if you know what I mean.

I just heard back from Eaton springs, and even though I didn't buy their product one of the tech guys was kind enough to respond. He said as long as I don't use heat and cut no more than half of what I think I need it shouldn't ruin them or cause too much suspension stiffness. Then wait a week and see if they settle to an acceptable ride height.

Originally posted by larry chastain
dont cut the springs,find yourself monza front springs which are 2 inches shorter than your stock springs

Won't that defeat the purpose of having a longer spring for stored energy on launch?

Well that is good. I guess you might as well and try it. If it works then awsome... If not then you just learned from trial and error which is always the best way to learn something and remember it but not a good way haha.

Yeah, if I screw it up I just wasted $100 It doesn't take long for the money to add up working on these things. So far I've put $3500 in this car getting it up to NHRA specs, getting all the up-to-date safety stuff, reworking the fuel line and wiring and making a few of my own mods.

Right now the car is sitting on jackstands, I've got the carbs and all the wiring and ignition off and axles pulled. I polished all the aluminum. I'm going to port the carbs and mount them sideways for easy bowl access, so it required a new linkage kit. I've still got another $250 to go for c-clip eliminator kits and machine shop labor. I can't wait to get it on the track and start tuning!

WE used to always cut them with a torch, I have even cut and rewelded them back together, the 49 olds rear end in the 31 chrysler had a small coil at the ends with a large washer and bolt to hold them in place. stock was about 6 inches too high. I don't remember which arc rod I used but it was expensive, Today they say use a die grinder with a cut off wheel. probably compress the rest of the spring then cut only half of what you think you need, release the spring clamp and and probably try again.

Torch and a spring don't go well together...

Ok I have a 56 mercury with a 390 FE the car was lowered at the rear 6" off the ground. I bought some springs from the junk yard from a caddilac, and cut them a good 6" or two rows. The suspension is really good, I am so suprised on how they turned out! It's better then the back suspension which is a few leafs and a lowering block. So go ahead and do it, and have fun with it too, just make sure you have good shocks in the front.

Kevin

WE used to always cut them with a torch, I have even cut and rewelded them back together,

If you do that, they aren't springs any more. Heat kills the temper.

When I used to cut springs, I'd figure out what I thought I needed, then take half or less. It's a lot of work taking them in and out, but it beats buying a new set of springs. Also keeps you from having to say "Gee, I cut it off twice, and it's still too short."

I have used a cut off wheel on a die grinder to shorten coil springs , don't cut off more than half a coil at a time . It may not matter to your installation but the springs will get stiffer as you shorten them. Carlg

My stepdad was a blacksmith, we had the shop on the ranch, there was another oldtimer up the road that used to work in the blacksmith shop in the mines. those two guys knew more about metals than any of the engineers at the mine. hands on how to form, weld, heat treat, sharpen mine drill bits. etc work hardened steel then retemper it etc. A lot of their knowledge is lost forever.