Detailed writup on how to drop your 05 stang cutting the stock springs

[gp001]

Aftermarket springs exist mainly because most people are too dumb to do it themselves.

Good jod dude !

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Sorry, I just found that funny

Also, some of us like properly engineered spring rates so we can have a consistent, predictable feel to the car. If you want to cut, more power to you. But I sugest you understand spring rates, spring loads, and their affect on wheel rates before saying people who buy aftermarket springs are "too dumb". Any yahoo can take an angle grinder, cutoff wheel, sawzall, etc to a spring. Not too many people have the ability to determine spring loads, spring rates, etc in their garage. I guess people who cut their springs could use the formula Spring Rate = (Gd^4/8ND^3), but I'm assuming if they are cutting their springs they aren't taking the time for the calculations.

To each his own.

 

[GT-Tronics]

some of us like properly engineered spring rates so we can have a consistent, predictable feel to the car.

Are you saying a shortened springs rate varies from one moment to the next? how?
As in you calculate the rate, wait a few minutes and calculate them again and they are different? I have had that happen before, but I pushed the wrong buttons on the calculator, but the rate didnt change

Yes the rate changed when it was shortened, but it is still absolutely consistant and predictable.

Also, does anyone have the specs on the stock spring so we can calculate the difference?
I would like to compare the numbers to a "store bought" spring.
AND, who said the store bought spring is properly engineered? Its just one groups opinion of what will work.

If you like to buy parts that fine, but I have to hand it to the do it yourselfer for trying to save $$$. I rarely buy anything I can make or fix myself.



.

 

[gp001]

Are you saying a shortened springs rate varies from one moment to the next? how?
As in you calculate the rate, wait a few minutes and calculate them again and they are different? I have had that happen before, but I pushed the wrong buttons on the calculator, but the rate didnt change

Yes the rate changed when it was shortened, but it is still absolutely consistant and predictable.

Also, does anyone have the specs on the stock spring so we can calculate the difference?
I would like to compare the numbers to a "store bought" spring.
AND, who said the store bought spring is properly engineered? Its just one groups opinion of what will work.

If you like to buy parts that fine, but I have to hand it to the do it yourselfer for trying to save $$$. I rarely buy anything I can make or fix myself.



.

I'm all for fabbing it yourself (just take a look at my 66 Mustang), but I'm willing to bet your DIY cutlery excerise will not yield such precision as to be consistent and predictable from side to side, front to rear, etc. Unless side to side consistency is not important to your application (maybe you are circle track racing). And yes, I think Eibach, and other aftermarket manufacturers, have better quality control than home brew hackery.

When you cut active coils from a spring the length changes and rate goes up. While the spring rate remains constant (if the spring was cut properly) the spring load does not. Spring rate and spring load are very different measurements.

Lastly, too high of a spring rate and you negate any of the benefits of lowering the car, except for looking ghetto KeWl dumped in da weeds yo!

 

[PONY XPRESS]

Nice mod, but you need to check your rear end to the center line of the car.

Panhard bar cars when raised or lowered move the rear end side to side. If you have the stock bar in place I am sure your rear is off center & the car is dog legging down the road. It may be a small amount but it is happening. Check the distance of each tire to the rear fender. Not very accurate but may give you an idea of how far the rear moved.

You will need to get an adjustable panhard bar & have a GOOD shop align your car.

My .02

 

[bullitt1609]

There was a detailed write-up in a MM & FF magazine this month on installing Eibach's on an '05. They stated that the Eibach's are rated, I believe, at 190/200 lb/in in the front, where the stock spring is rated at 170 lb/in. I left the magazine at work, but I'm pretty sure the numbers are close to what I listed above.

I spoke to a custom suspension shop here in Tampa, and the tech stated that if you cut the springs, they will get stiffer. He didn't go into calculating it exactly, because at the time, neither of us knew what the stock springs are rated at.

I imagine though, by removing one coil in the front, and say two in the back, it will give you a slightely stiffer ride, but it won't be as stiff as the Eibach's would give you. The Eibach's, in my opinion, are primarily designed to both lower the vehicle, and to increase the cars on-track performance. For someone who loves the way it rides now, primarily drives on the street, and only wants to lower it, then I say cutting the springs is the way to go. I bought some of Ebay and cut those. They are sitting in my garage waiting to be installed tomorrow. I can't wait.

 

[gp001]

According to the Herb Adams book Chassis Engineering, cutting 1 active coil properly from the spring will yield a 10-11% increase in rate.

 

[2MFF-Z28]

so your saying that you'll have a car that rides like crap and bottoms out real easily......................gotcha

been there done that................buy new springs people

 

[bronco78]

Also, does anyone have the specs on the stock spring so we can calculate the difference?

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GT Coupe
Front springs 136.5 lb/in
Rate at the wheel 170.7 lb/in

Rear springs 142.2 lb/in
Rate at the wheel 170.7 lb/in

 

[Rootus]

GT Coupe
Front springs 136.5 lb/in
Rate at the wheel 170.7 lb/in

Rear springs 142.2 lb/in
Rate at the wheel 170.7 lb/in

That better be backwards... the wheel rate will be lower, not higher than the spring rate.

 

[bronco78]

That better be backwards... the wheel rate will be lower, not higher than the spring rate.

Maybe it is backwards, but it is a direct cut and paste from the FORD " Motor vehicle Manufactures Specifications" . Downloaded from ford.

http://www.fordvehicles.com/cars/mustang/features/specs/ Then click on Manufacture's Spec

So if it is wrong.. Ford sent that data to every manufacture and supplier

 

[blk05gtstang]

so your saying that you'll have a car that rides like crap and bottoms out real easily......................gotcha

been there done that................buy new springs people

I've had 5 people total in the car, gone over some pretty nice bumps and haven't come close to bottoming out yet. Over 1k miles since I did this mod and no problems.

 

[Rootus]

Maybe it is backwards, but it is a direct cut and paste from the FORD " Motor vehicle Manufactures Specifications" . Downloaded from ford.

http://www.fordvehicles.com/cars/mustang/features/specs/ Then click on Manufacture's Spec

So if it is wrong.. Ford sent that data to every manufacture and supplier

The stuff published by Ford is undoubtedly put there by a marketing geek. They make mistakes too . It's not really a big deal, just an observation. The wheel rate is lower because the wheel is farther from the control arm pivot than the spring is, which gives it leverage on the spring. On a pre-05 Mustang it's much more dramatic -- the wheel rate is 1/4 of the spring rate. With aftermarket coilovers it is 9/10ths. From the numbers you gave it looks like the '05 factory setup is 8/10ths.

Dave

 

[El Hamtaro]

Could someone explain how removing a coil will increase the rate of a linear spring? My understanding of springs was that (as an example) a 50 lb/in linear rate spring would compress one inch if 50 lb was placed on it. (It would compress 3 inches if 150lbs was placed on it.) It was my understanding that regard less if it was 2 inches long of 10ft long the spring rate would remain the same and only the length of travel would change.....anyone know the math to explain this to me?

 

[Rootus]

Could someone explain how removing a coil will increase the rate of a linear spring? My understanding of springs was that (as an example) a 50 lb/in linear rate spring would compress one inch if 50 lb was placed on it. (It would compress 3 inches if 150lbs was placed on it.) It was my understanding that regard less if it was 2 inches long of 10ft long the spring rate would remain the same and only the length of travel would change.....anyone know the math to explain this to me?

It's mechanical advantage. With more coils, each coil has to do less work for a given amount of travel. All else being equal, if you remove a coil then each remaining coil will have to do more work when the spring is compressed.

Problem is, cutting a coil reduces the overall length of the spring more than the increased tension compensates for, so you are more likely to bottom out the suspension during hard cornering or over potholes. Not to mention potentially screwing up the spring perches.

Cutting coils is for ricer kids who have no money and are trying to look cool. This shouldn't really even be worth discussing among a group of Mustang enthusiasts -- everyone here has demonstrated they can afford the aftermarket springs that are engineered properly ... if they can't, they are waaaay too close to the edge and have no business financing a $25K+ car.

Dave

 

[GT-Tronics]

at 190/200 lb/in in the front, where the stock spring is rated at 170 lb/in.

By my rough calculation,and assuming the spring went from 6.5 active coils to 5.5 I get a new rate of 201 lbs/inch and about 2 inches shorter.

Which is almost exactly what the aftermarket ones are rated at.

All springs follow a formula, the laws of physics do not change when bubba cuts it or a factory cuts it, they are the same.

.

 

[gp001]

By my rough calculation,and assuming the spring went from 6.5 active coils to 5.5 I get a new rate of 201 lbs/inch and about 2 inches shorter.

Which is almost exactly what the aftermarket ones are rated at.

All springs follow a formula, the laws of physics do not change when bubba cuts it or a factory cuts it, they are the same.

.

Well, if bubba cuts coils, then heats and reshapes the end to match the factory inactive coi,l I would somewhat agree. But since we know people are not taking the time to do such, I would argue it is not the same(and probably not seating correctly or handling load evenly).
Aftermarket springs are progressive so their rate does change when compressed..
And, when cutting you change the spring load. Ever wonder why cars with cut springs tend to sag (and usuallu unevenly)

 

[gp001]

Could someone explain how removing a coil will increase the rate of a linear spring? My understanding of springs was that (as an example) a 50 lb/in linear rate spring would compress one inch if 50 lb was placed on it. (It would compress 3 inches if 150lbs was placed on it.) It was my understanding that regard less if it was 2 inches long of 10ft long the spring rate would remain the same and only the length of travel would change.....anyone know the math to explain this to me?

What you are describing is the affect of spring load on a spring with a spring rate of 50lbs/in
The load at 1" compression = 50lbs
The load at 2" compression = 100lbs
The load at 3" compression = 150lbs

Spring rate remains constant at 50lbs/in.

I posted this formula in a previous response, but here is the explanation

Spring Rate = (Gd^4/8ND^3)

G = torsional modulus (steel = 11.25 x 10^6)
d = wire diameter
N = Number of active coils
D = mean coil diameter
8 = Constant for all coil springs

 

[AvalancheSVT]

you gotta be kiddin me... i can't believe this kind of trash is tolerated in the GT forum of all places.

don't do ghetto mods when there are good parts available.

 

[Jenns01TA]

Makoto..There are those great refined interaction skills again.

~J~

 

[bronco78]

you gotta be kiddin me... i can't believe this kind of trash is tolerated in the GT forum of all places.

don't do ghetto mods when there are good parts available.

Tolerated????? What.. You want some MOD to send a virus Via PM to someone who posts something you do not agree with????

Will I do the cut and hope method of suspension tuning?? No.. But perhaps by this thread, others will come to understand why it is not the better way of dealing with the situation. It is a way,, and many have done it,, on cars built from before most on this forum were born,, to a 2005 Mustang.

I appreciate the Tech replies from those that have posted.. Information is power,, power to choose…to each his own… But let the choice be informed.