20 inch spring

[lapsetter3]

What's everyone's take on running a 20 spring on the LR. Thinking of trying one next season. Just looking for some of the pros and cons. Thanks in advance

[Dirt_Buster]

You don't need 20. That simple.

[MasterSbilt_Racer]

Its just a spring. Con could be if it won't fit. Only reason you would need taller spring is if the shorter one is too short to set ride height.

[badfast47]

Watched a car one nite and the lr of his car was hiked up all the time. I figured he used a taller spring to do this and to help keep the rf pinned. ?? This was a pure stock class and he won some features !

[MasterSbilt_Racer]

Watched a car one nite and the lr of his car was hiked up all the time. I figured he used a taller spring to do this and to help keep the rf pinned. ?? This was a pure stock class and he won some features !

Its all rate. Height means nothing aside from fitting and getting ride height.

[dkibel]

It is all rate, I agree with you MBR but here is some food for thought. When a 20" 125lb spring is compressed will provide the rear suspension with more movement because it takes more movementl to gain the same loading that a 16" 200lb spring would have. So, for 1" that a 200lb spring would travel the 125 would travel 1.6" allowing the rate in the 125lb spring to build slower because it has to compress further to achieve the same rate. One factor that people tend to overlook is the difference in Potential energy in the spring during compression. For arguments sake lets say the wheel weight of the lr at ride height is 1000lbs. So statically your 200lb spring compresses 5" while your 125lb spring compresses 8". Hooks law says the potential energy of the spring=0.5*rate*(compression in inches^2). This means your potential energy on the 200lb spring is 2500 lbs/in^2 and your 125lb spring has a potential energy of 4000 lbs/in^2. Thus, your 125lb spring will react quicker than the 200lb spring making the valving of your shock to control the acceleration of that corner crucial to your success. Im just trying to bring some different theories to the table. Ive tried both avenues and they each have their advantages and disadvantages but I know that shocks were extremely important in either case.

[MasterSbilt_Racer]

It is all rate, I agree with you MBR but here is some food for thought. When a 20" 125lb spring is compressed will provide the rear suspension with more movement because it takes more movementl to gain the same loading that a 16" 200lb spring would have. So, for 1" that a 200lb spring would travel the 125 would travel 1.6" allowing the rate in the 125lb spring to build slower because it has to compress further to achieve the same rate. One factor that people tend to overlook is the difference in Potential energy in the spring during compression. For arguments sake lets say the wheel weight of the lr at ride height is 1000lbs. So statically your 200lb spring compresses 5" while your 125lb spring compresses 8". Hooks law says the potential energy of the spring=0.5*rate*(compression in inches^2). This means your potential energy on the 200lb spring is 2500 lbs/in^2 and your 125lb spring has a potential energy of 4000 lbs/in^2. Thus, your 125lb spring will react quicker than the 200lb spring making the valving of your shock to control the acceleration of that corner crucial to your success. Im just trying to bring some different theories to the table. Ive tried both avenues and they each have their advantages and disadvantages but I know that shocks were extremely important in either case.

You just said what I am saying. Its the rate. And the super tall soft spring is not free to release all its potential energy. That will be determined by the CG height, lateral acceleration, and roll stiffness.

[hogracer3d]

we tried it for a season limited full size impala chassis 3-link super stock on G60 (similar to sport mod rear rule) and it was very good on the driest of dry, but very tight, wheelied up and temperamental if the track had any bite.
Very easily dialed ourselves out of the ball park if not careful.
Finally installed a huge jack bolt , so we can run any spring from 20" to 11" on the LR and settled on 13" for most situations, but on day 2 of a 2 day show, I wouldn't hesitate to go back to it on a bone dry track

[Dirt_Buster]

Rate is Rate and height is height. A 200 20" is the same as a 200 11". Move the weight jack down 9" and have the same (not a nice word)(not a nice word)(not a nice word)(not a nice word) thing. The light tall spring could hurt you. It's all a combo and if you do one thing and not another adjust yourself right out of the park. All I'll say is your trailing arm angle, shock valving and spring go together and why we run what we run. Keep it simple

[brad hibbard]

this is a very good discussion topic----
let me exaggerate the length and rate to illustrate my view on LR spring length
I will use a ride height (chassis height) of 12 inches just as a constant number

using an 8 inch 400 pound spring
and adjusting the chassis to a 12 inch ride height

using a 16 inch 125 pound spring
and adjusting the chassis to a 12 inch ride height

both setups will have the same amount of static wedge

But

as the car rolls onto the right side upon corner entry the 16 inch spring will have much more stored energy within the travel limits to maintain LR traction

with minimal chassis movement the 8 inch 400 pound spring will completely extend having zero affect on LR action and traction---once the spring becomes fully extended it does not matter what length or rate it is ----it is only along for the ride

it has been a 100 years (seems like) since I worked on chassis ---but when we did, this type of car was very popular for us -----things change and stock cars today look like late models to me but I do believe there is still meaning to the length of a spring

Brad
www.race-1.com

[RCJ]

If you are making a big jump in spring length.10''to a 20'' ,especially in a street stock where the spring mounting pads might not be parallel, the taller spring will bow more making it feel a little softer.I don't know if it is enough to make a difference thou.I'm of the keep it simple mind set and have never tried that 20 '' stuff

[brad hibbard]

very good point RCJ and it really applies to RR spring
my illustration focus was on extension of the spring and was assuming all surfaces are parallel but I think the discussion will need to also include deflection to be complete

Brad
www.race-1.com

[stock car driver]

this is a very good discussion topic----
let me exaggerate the length and rate to illustrate my view on LR spring length
I will use a ride height (chassis height) of 12 inches just as a constant number

using an 8 inch 400 pound spring
and adjusting the chassis to a 12 inch ride height

using a 16 inch 125 pound spring
and adjusting the chassis to a 12 inch ride height

both setups will have the same amount of static wedge

But

as the car rolls onto the right side upon corner entry the 16 inch spring will have much more stored energy within the travel limits to maintain LR traction

with minimal chassis movement the 8 inch 400 pound spring will completely extend having zero affect on LR action and traction---once the spring becomes fully extended it does not matter what length or rate it is ----it is only along for the ride

it has been a 100 years (seems like) since I worked on chassis ---but when we did, this type of car was very popular for us -----things change and stock cars today look like late models to me but I do believe there is still meaning to the length of a spring

Brad
www.race-1.com

you only EVER need a longer spring if you are completely unloading the current spring. a street stock isn't going to unload a 11-13-16" unless your running a very stiff spring.