Springs

[Arrington002]

What would be the difference in running say a 10 inch spring vs. running a 15 inch spring with the same spring rate and ride height?

[Flyin Iowan]

less travel before coil bind on shorter spring

[jsf74]

Nothing other than coil bind. It's my understanding that regardless of length the rate will not change. Unless progressive ofcourse.

[Arrington002]

Right, those were my thoughts as well.Reason for asking was that i had ordered a new RF spring for my car and the one i received was about an inch taller.Was also curious about the different length rear springs as well..

[MasterSbilt_Racer]

Right, those were my thoughts as well.Reason for asking was that i had ordered a new RF spring for my car and the one i received was about an inch taller.Was also curious about the different length rear springs as well..

Different length springs do not matter unless you coil bind or change the attachment point at the chassis to compensate for the spring length. Example: if you have screw jacks that adjust the upper spring seat up and down. Moving that seat up and down to change spring length will have an effect on the roll characteristics of the chassis.

[RACEMAN]

What would be the difference in running say a 10 inch spring vs. running a 15 inch spring with the same spring rate and ride height?

I think what you need to consider is the coil spacing when the spring is loaded. For instance, if the spacing between the coils is the same on both the short and tall springs then theoretically it wouldn't make a difference.

In looking through the spring sections of the various catalogs you'll find some instances of springs where the coils are spaced really far apart. Using this type of spring on all 4 corners the spring could be compressed a LONG ways before you ran into coil bind. Maybe even far enough where the car frame would really scrape the ground.

[racer69]

A longer spring can also help on the LR during hike up. Keeps a little more weight on that corner and speeds up the hike as well.

[HEAVY DUTY]

A longer spring can also help on the LR during hike up. Keeps a little more weight on that corner and speeds up the hike as well.

Only if the longer spring is softer. If it is the same rate, all you do is move the coil over nut up to make up the height difference. You have to preload a spring more to keep more weight on it. If you put 500 pounds on a 200 spring, it will compress it 2 1/2 inches. If it started at 16" it would be 13 1/2. If you started with a 13" spring, it would be 10 1/2. Same 2 1/2 " load. If you put a 100 spring in it, then you would have 5" of load with the same 500 pounds sitting on the spring. If you are on a coil over, and not a weight jack bolt, a taller spring has no effect on the chassis, other than it is heavier, costs a little more, and somebody is trying to sell you something. The only reason to use them is if you are coil binding a shorter spring.

[racer69]

Your right (as always lol)! I forgot that detail half asleep when I replied. Too many late night getting 2 cars done.

[drtrkr244]

Different length springs do not matter unless you coil bind or change the attachment point at the chassis to compensate for the spring length. Example: if you have screw jacks that adjust the upper spring seat up and down. Moving that seat up and down to change spring length will have an effect on the roll characteristics of the chassis.

Agree!The heighth of the top coilover nut determines the roll resistance of the rear suspension due to it being a solid link.The front end, no difference, as it is independent.

Example, any roll center software worth its weight, will have you measure the installed heights of the rear springs.

[Arrington002]

Agree!The heighth of the top coilover nut determines the roll resistance of the rear suspension due to it being a solid link.The front end, no difference, as it is independent.Example, any roll center software worth its weight, will have you measure the installed heights of the rear springs.

So lets say for instance on the right front i have two springs that are the same rate, but one taller by one inch. I put the tallest one on the car and set the ride height, what would be the handling difference in the two?

[joeltjen]

Agree!The heighth of the top coilover nut determines the roll resistance of the rear suspension due to it being a solid link.The front end, no difference, as it is independent.

Example, any roll center software worth its weight, will have you measure the installed heights of the rear springs.

with a weight jack you go by the height of the top spring plate, with a coil over or slider you go by the top heim end. where the adjuster nut is dont matter as the car rotates at the mounting bolt.

[autoshop]

if you got two differant heights , you might ott look at the wire diamater you might suprise yourself later. be sure to check same amount of coils. if they are differant it changes everything.Chances are the wire size is differant on the longer spring.

[drtrkr244]

with a weight jack you go by the height of the top spring plate, with a coil over or slider you go by the top heim end. where the adjuster nut is dont matter as the car rotates at the mounting bolt.

Sorry, Rocket says differently!

[MasterSbilt_Racer]

Agree!The heighth of the top coilover nut determines the roll resistance of the rear suspension due to it being a solid link.The front end, no difference, as it is independent.

Example, any roll center software worth its weight, will have you measure the installed heights of the rear springs.

spring height does not matter on a coilover. attachment point to chassis does not change.

[Egoracing]

spring height does not matter on a coilover. attachment point to chassis does not change.

Correct, the chassis only knows the spring location by its contact point to the chassis. On a coil over that is the bolt thru the heim, on a jack bolt it is the plate location where is contacts the spring.

[drtrkr244]

spring height does not matter on a coilover. attachment point to chassis does not change.

When computing rear roll center/angle, you have to measure from the ground to the top of the coilover nut. If you change those with different spring heights, obviously your final calcs. will be different.

[joeltjen]

When computing rear roll center/angle, you have to measure from the ground to the top of the coilover nut. If you change those with different spring heights, obviously your final calcs. will be different.

take your car out and put the rr coilover on upside down and run it.......see if you notice any difference ( this should change your spring height by quite a bit) now take and lower both mounting holes for your coilover by 2 or 3 inches and try it again..... tell me which one make a BIG change in handleing. sometimes a book will tell you one thing but your butt will tell you otherwise!


i'm not sayimg rocket is wrong because i haven't seen the whole program you are talking about, but i will say about 3/4 of the books i've read on calculating effective rear wheel spring rate on a swing arm car are wrong

[MasterSbilt_Racer]

When computing rear roll center/angle, you have to measure from the ground to the top of the coilover nut. If you change those with different spring heights, obviously your final calcs. will be different.

From real world experience, this is wrong. From a physics standpoint, it makes no sense either. The bolt through the bearing end is the pivot point for that coilover. The coilover unit is one compressible link. It doesn't matter if the compression takes place uniformly or all at one end.

What are you doing with the j bar or panhard bar? I have seen conflicting calculations with it. I don't think roll center calcs are really all that useful for the rear of live axle vehicles.

[dualdj1]

What are you doing with the j bar or panhard bar? I have seen conflicting calculations with it. I don't think roll center calcs are really all that useful for the rear of live axle vehicles.

Yeah, after trying to hash that out before, I tend to agree. they can get you a rough idea, but testing gives you much better information.