Working on turning my parts car into a trailer, I can just cut the springs to lower it right?

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Pistonenvy2@reddit

s13 coilovers will bolt in with a little spacer on the bottom bolt, might need to drill one of the holes out in the upper mount. i have put them on this car, the rear took me like an hour lol

i would not cut or torch the springs, you do not want an unpredictable trailer. even the cheapest garbage coilovers would be better than doing that. you can adjust the preload to make them softer than the cut springs will be.

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Proper_Possible6293@reddit

Pre-load has no effect of spring rate.

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Pistonenvy2@reddit

i didnt claim they do, preload effects travel, if you use a lot of preload it will make your suspension stiffer, if you take all the preload out the suspension will be softer.

on the same spring with a linear spring rate: more travel means softer, less travel means stiffer.

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Proper_Possible6293@reddit

Doesn’t effect travel either, not that longer travel equals softer anyways. A 500 in/lbs spring moves one inch for every 500 lbs no matter how long it is.

It can change ride height, but that’s it unless you get into some weird edge cases like stupid amounts of preload resulting in zero droop. (or highly progressive suspension linkage setups like bicycles often have)

If by “travel” you mean only up travel, that will be reduced by lowering preload while droop increases because your static ride height is lower in the total travel range.

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Pistonenvy2@reddit

genuine question: what do you think preload does?

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Proper_Possible6293@reddit

This is a bit oversimplified but hits the major points. Preload is mostly used to adjust where you sit within the suspension travel range and ensure that the spring is still under tension at full top out. Cranking up pre-load is not a substitute for a spring that is too soft.

“Many people think that by adjusting preload that they are stiffening or softening their suspension. Nothing could be further from the truth. Adjusting preload does nothing to your spring rate.”

http://sonicsprings.com/catalog/preload_tech_article.php

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Pistonenvy2@reddit

again, i didnt claim it changes the spring rate, i said it changes the stiffness of the suspension which it does. if all preload was for was maintaining tension why would it be adjustable?

my comment was specifically about coilovers, where preload is adjustable.

the article you shared explains this. preload doesnt make the vehicle heavier right? so when you preload the spring by 500lbs that means the first 500lbs you add to the car dont move the springs. the initial load to move the springs is higher, therefore the suspension is stiffer.

if you lower the preload the springs react sooner to load, the compress more gradually and feel softer.

preload really has nothing to do with static compression anyway, in a car the main reason you would care about preload is for cornering, dynamic load, or in a drag car you can dial in your squat during launch, etc. there is a whole array of things you can do with preload, but in this particular application my advice was in the interest of keeping this persons trailer from bouncing around like a pogo stick every time they hit a bump, that can be done with preload.

obviously a spring with a lower rate would be ideal but if they could afford that they wouldnt be asking about cutting stock springs lol

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Proper_Possible6293@reddit

Your forgetting that suspension is always sagged.

So adding pre-load doesn’t increase the force needed to move that first inch. The only time that would be true is if you added waaaay too much pre-load and had the suspension topped out at rest which would result in garbage ride quality. Outside of that edge case it will always take 500 lbs to move a 500 lbs spring one inch.

Lowering pre-load on this trailer is just going to lower the trailer and put it closer to the bump stops, which might be a useful bodge (since it’s sitting too high) but the springs won’t get any softer by doing that.

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Pistonenvy2@reddit

youre just not understanding what im saying lol

your own article explained the same thing i just said. its not changing the rate, its changing the initial response weight.

if the sum total weight you will put on the trailer is 1000lbs and each spring is designed to carry 500 and you preload another 250 per spring that means you would need another 500lbs of downward force to compress the springs past where they are at rest.

VS. if you dont preload them at all 500lb is going to move them an inch or whatever the rate is past their static position. does that make sense?

the rate is the same, the reaction to the weight in/of the vehicle is what is being changed. the suspension isnt sagged its under static compression with the weight of the vehicle which is what the spring rate is going to be designed for. when you drastically change the weight or distribution of a car thats when you really should start looking into getting different rate springs which again, would be my suggestion for OP if i thought it was a viable option for them.

like i said, preload has a huge range of implications on how the suspension feels, i never said it changes the spring rate. it also isnt going to change the ride height. you dont adjust preload from the top, you adjust it from the bottom, it wouldnt change ride height unless you had no clue what youre doing.

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Proper_Possible6293@reddit

If you don’t think suspension is sagged with static vehicle weight I’m not sure what to say. Have you ever changed a tire? Didn’t the wheel drop as you raised the vehicle on the jack? That’s sag.

If you have a 500in/lbs spring at 50% sag and add 1” preload the vehicle will go up 1” and you”ll still Only require 500 lbs of weight to compress the suspension 1”. Nothing got stiffer, the vehicle just got higher in its total travel.

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Pistonenvy2@reddit

look man i didnt come here to debate lol

im a fabricator, i have literally engineered suspensions on racecars from scratch. ive build race cars professionally. properly designed suspension doesnt "sag" sitting still. thats not what sag is.

youre citing a lot of bicycle terms and the article you shared was from a bike shop, maybe just stick to bikes. im sure you know more about bikes than i do.

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Proper_Possible6293@reddit

I find it hard to believe anyone who builds chassis thinks adjusting preload changes suspension travel. No real world application is using coil bind (or full extension) instead of bump stops to control the amount of travel.

The thing is, your right about more preload require more weight to start the suspension movement from the top, but no vehicle is sitting at full extension so that “extra” has already been used up and just results in the vehicle sitting higher in the stroke. It doesn’t change the amount of force required to start moving an already partially compressed spring.

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Pistonenvy2@reddit

it does tho, if you increase the preload on a spring it literally will have less travel. how could it not?

absolutely 0 engineers are using coil bind OR bump stops to control travel lol bump stops are there for extreme circumstances as a safety feature to stop shit smashing together, you should absolutely never have coil bind unless you fucked up big time.

if you designed a suspension properly it absolutely rests at full extension. especially if its an aggressive performance suspension. the reason you see so many cars with cheap coilovers bouncing down the street is they never set their preload right (or even worse, set ride height by increasing preload)

im not going to reiterate what i already said just to explain what the article you shared says lol read the article yourself, it says the same thing i just said in regard to preload. if you increase your preload until your inital load is higher than the weight of the car and you (the driver) you will not lower the car by sitting in it. the vast majority of cars with coilovers dont.

again, stick to bikes where your perspective is more accurate, idk why youre even here. do you even own a project car?

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Proper_Possible6293@reddit

You think cars rest at full extension?

Have you never changed a tire and noticed the wheel drops as you jack the car up?

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Pistonenvy2@reddit

i know they do because ive literally fucking built them.

youre talking about a stock car designed for commuting lol no shit they sit below ride height they dont have any preload on the springs, there are cars that if you jack them up the springs literally fall out.

you have no idea what youre talking about.

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Proper_Possible6293@reddit

What are you building that has no down travel? Some kind of super short travel shifter cart for ultra smooth tracks?

Every street, off road, rally, or track car has down travel from static position.

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Pistonenvy2@reddit

how would you know? lmao

based on what are you telling me? based on the conversation we literally just had about preload you have absolutely no clue how it works or how it would influence the suspension of a car and youre clearly not interested in learning, even from the articles you cite.

if you genuinely want to learn something new, a lot of high performance applications where a shitload of downforce or cornering Gs are achievable, you need more spring than the weight of the car and the driver combined. the suspension is mostly compressing due to those other things adding way more downward force on the suspension than the driver and the weight of the car do.

therefore even when you step into the car it doesnt get any lower. there is zero movement from full extension. even on the street cars ive built, if you want something that can safely get near 200mph you dont want floaty soft suspension, thats how you get unpredictable movements and loss of traction at speed, not to mention body roll and oversteer etc. etc. etc. which are problems you get a lot from modifying stock car suspensions.

off road and rally cars usually arent that stiff, if you hopped in a trophy truck or a rock crawler or a dune buggy it will probably move a whole bunch because its going to be designed to absorb absolutely massive changes in suspension travel. thats what long travel suspensions do, as opposed to a race car on a track that is ideally on a perfectly smooth road that is doing everything it can to keep the tires planted.

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Proper_Possible6293@reddit

So, a bunch of exotic stuff with zero relevance to a trailer based on the back of a Z car that’s going to ride well into the suspension travel where preload won’t do shit to soften or stiffen things up.

What class do you build for?

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Pistonenvy2@reddit

lmfao this is basic information that applies to all cars.

its like saying "oh so you know how caster works, big deal, how does that apply to a go kart?" it does. its actually important, almost fundamental to how they function. one of the few things you need to get right on a trailer is the suspension.

also this question is like when people who have never been in the military try to pull stolen valor accusations on someone by asking "whats your MOS" when they dont know what the right answer should be. i worked in a speed shop where we built whatever the fuck people wanted. mostly it was street cars but we built some drag cars, drift, off road, autocross, show cars, etc. the vast majority of the suspension work i did was modifying mostly stock vehicles to handle at high speed.

theres no specific class for that lol people ran in a huge range of classes, i dont know what class they were in unless i was building them a cage or fuel cell or some other cert requirement which ive also done, but otherwise i dont care lol its not relevant.

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Proper_Possible6293@reddit

While you are trying to remember what car you engineered and built with zero droop, here is a fun video where you can see a (very small) amount of droop in an F1 car even when the downforce isn’t in play.

I can’t wait to hear what you build that has higher cornering forces than one of these.

https://m.youtube.com/watch?v=wsCriICZ-nA

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Pistonenvy2@reddit

ive built many cars with zero "droop"

the fact that youre so incredulous just reveals your total ignorance here, you dont know what youre looking at in the video you shared anymore than you know how to answer any of the other questions ive asked you.

im not engaging with you anymore. this is a complete waste of time.

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Proper_Possible6293@reddit

Built so many but can't name one....sure we believe you

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peepeepoodoodingus@reddit

"we" lol as if everyone here didnt upvote his comment and downvote yours.

this entire exchange makes you look so dumb and insecure, why are you arguing with this person?

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Pistonenvy2@reddit

what kind of name do you want me to give you? lmfao

answer my questions or im blocking you.

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Proper_Possible6293@reddit

What class runs zero droop as a fast setup?

Street cars (even on the track) don’t and neither do off road rigs. So what have you built that sits on topped out suspension at rest?

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Proper_Possible6293@reddit

If you have so much experience this should be easy:

Name one racing class or production car that runs zero droop and then explain how they deal with the regressive suspension system that results.

Thanks.

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Pistonenvy2@reddit

again you dont know what the question means, how can you know the answer?

what do you even think regressive suspension system is? did you ask chatgpt to make this question for you? is that why you are coming to this conversation SO ignorantly but also so confidently?

where is this question coming from when you literally dont understand how preload works and still dont after ive explained it to you 5 times? why should i feel compelled to explain a fucking thing to you at this point? lol

what have you accomplished? have you ever built anything other than a bike? have you even built a bike? why do you feel qualified to test me?

https://www.youtube.com/watch?v=NuBRjCqDsdI

this is an f1 car, its literally designed to go 200mph. look at how bouncy the suspension is, why do you think that is? you tell me.

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Proper_Possible6293@reddit

You build 200 mph race cars and don’t know you need a spring compressor to pull the springs on a family sedan because they are pre-loaded?

Nothing is dropping springs when you jack it up unless you also remove whatever is limiting droop. Otherwise every flat tire would result in someone sitting on the side of the road without springs.

You do realize no one reading this believes you’re a race car designer right?

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Pistonenvy2@reddit

its almost like you didnt read or didnt comprehend anything ive said which tracks because you get all of your perspective from working on fucking bicycles lol

production cars are designed with soft springs, you cant preload a spring to be so stiff at extension the car wont move when you sit in it because the rate is less than the weight of the car, i literally just explained that.

there are older vehicles with wishbone rear suspensions that are designed so the spring is captive by the weight of the vehicle, if those springs sag and you jack up the rear of the vehicle they absolutely can fall out, its happened to me.

i didnt come here to prove anything to anyone i am only still replying to you because this is a public forum where i hope someone who is a little more curious than you might actually learn something from this otherwise pointless conversation.

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Proper_Possible6293@reddit

And a fun little side fact:

If your suspension has a progressive linkage like a mountain or dirtbike you can actually stiffen the suspension by lowering preload since it puts you deeper into the progression curve at rest with the same spring rate.

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JayTeeDeeUnderscore@reddit

I have scars from a failed spring under tension. Tread lightly OP.

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KamakaziDemiGod@reddit

Especially as springs have closed loops that are flat at the end to help them stay seated, cutting them leaves an angled coil with no support, which could come flying out even just from loading the trailer, and if it goes really badly, OP could lose a foot or worse

Never mess with big ass springs

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Boilermakingdude@reddit

I wouldn't cut them. You want the trailer to be able to support weight. I'd personally order some custom lowering springs with the same amount of spring rate/weight as the stocks.

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Ethan140@reddit

Cutting springs actually makes them stiffer. Which is kinda exactly what op needs if they are going to be loading this thing up.

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What_the_8@reddit

It’s makes them shitter

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Boilermakingdude@reddit

I've ridden on cut springs. Get custom ones.

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2Drogdar2Furious@reddit

Dont even have to be custom. Z1 motorsports will have them. They're very helpful on the phone...

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NorthAmericanRoadz@reddit

air bags then when you park for the night the thing will be slammed to the ground for security purposes.

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qroter@reddit

LOLWTF Did you cut a Z into a parts trailer?! 😂🤣

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MooseLucifer@reddit

If you have the right tools to pull the springs off first, I vote cut 'em. Start small, and if you really want to make it even be prepared to pull/massage one of them a second time. Forums/math will tell you if you need adjustable arms to fix alignment, but hey, this will too! You can always swap in lowering springs later.

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rayhawk81@reddit

You can do it easier than that, just heat a spot on the coil with a torch until it loses its temper and drops down to the next coil.

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Shot_Investigator735@reddit

This is the classic method. Stiffer spring rate, just like cutting. But slightly higher vehicle due to the thickness of the stacked coils.

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Ethan140@reddit

Removing the temper makes them not springs anymore… they will just crack wherever you heat them eventually

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Shot_Investigator735@reddit

Yes. Not springs, but also very little movement. It wouldn't surprise me if they crack right where it transitions from heated to still springy. It's still the old school way, probably been done successfully on thousands of vehicles, if not more

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Lichenbruten@reddit

Interesting idea.

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akep@reddit

Not for cars that drive tho, it will throw your spring rate out the window lol

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filmorebuttz@reddit

1988 300z??

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Fearlessleader85@reddit

Nah, that's a 150zx.

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Fearlessleader85@reddit

300zx/2

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filmorebuttz@reddit

That triangle window trim looked just like my 300z

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JBONE31@reddit

Don’t you ever talk to me or my vg30e ever again.

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t25torx@reddit

gif

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MajorLazy@reddit

W00sh?

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filmorebuttz@reddit

r/whoooosh fr

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Fentron3000@reddit

Made me giggle.

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ShaggysGTI@reddit

On saw blades!

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WTFBEES@reddit

what have you done

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handful_of_gland@reddit

Is this an episode of Red Green?!

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Sufficient-Ad-8441@reddit

I’m trying to think of a worse rear end to make a trailer from. Only a Corvette seems worse.

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mightbeagh0st@reddit

Technically you can do whatever you want

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AnjoMan@reddit

If you really need the spare parts with you at all times, why not just get a full trailer and pull both cars around on it with another vehicle that is more reliable?

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Halictus@reddit

Cutting the springs will make the suspension both stiffer and lower.

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nissanxrma@reddit

Lowering the suspension will increase camber though.. a lot.

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Shot_Investigator735@reddit

Upvote for you. Came to say the same thing. Whoever downvoted you doesn't understand spring rates. Hey, cut a torsion bar shorter and guess what? Stiffer! Now take that torsion bar and bend it into a coil. Then cut it. Guess what? Stiffer!

Depending on how well sprung the trailer currently is for the weight OP plans on hauling, it could be either a good or bad thing.

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Recent_Detail_6519@reddit

Have you tried driving it loaded? If not try loading maxed out then if it's still too high for your liking cut off one coil on each spring one at a time then reassemble it and check it while loaded There is no quick way around it. When a trailer is empty it usually is squirrely so lower it with a load to get the right stance. Sweet trailer have you thought about enclosing it but bigger with a sleeping quarters infront?

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tren_c@reddit

If you're doing welder things, why not add a cup to the top mount and lift the seats an equal distance on both sides?

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bigfatfun@reddit

Is this a real question or did you mean to post to r/askashittymechanic? You can cut them but then it would be an awful trailer. Lower it properly, get shorter springs.

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Fakyutsu@reddit

Who doesn’t like a trailer that’s super bouncy and squirrelly lol

Sounds like fun 👍

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