Pre-loading coilovers

[AP Autosport]

I just installed my SPL/KTS coilovers last week before an autocross. I adjusted the height without pre-loading the spring any more than the way they came. I set the dampening on level 14 and I was having a problem with the rear drivers side hitting the bump stop. So, I figured I would pre-load the springs about an inch but I was hoping someone would be able to tell me the acual amount this changes the spring rate. The springs are 8f/6r to begin with.

Oh, and by the way my car feels 100% better after the install. I was using kyb's and sportlines before.

Thanks,Andrew

[chmercer]

hrm, i dont have much to add except that i think if you preload them an inch, that is going to feel like a complete rock.

[Nismo_Freak]

Just out of curiosity how are you measuring shock travel?

[AP Autosport]

Well, when I installed them I left them at where they were out of the box and adjusted everything at the strut mount so I could maintain as much travel as possible. When I autox'ed it felt like I hit the bump stop when I was under heavy load turning. How would you recomend that I measure it?

[sr20power]

ok i hear good things about the KTS coilovers...very similar to tein HE's (which i have) only thing i can think of is that there is TOO much play on spring load...

what i learned from signal auto, is that for daily driving 0 spring load is best. so to do this, jack up the corner w/ tire still on and tighten the spring perch so that the spring no play. tighten spring perch only enough so that the spring can't be turned by hand...

hope this helps....

[chmercer]

Just out of curiosity how are you measuring shock travel?

im sure you have a better method alan, but for the benefit of others...

obviously if the bumpstop is all the way up you are bottoming out the shock. to check you can just push the bumpstop all the way down and check where it is after driving. another way to check if your suspension dosent have bumpstops or if for some reason the bumpstop method dosent work for you is to put a ziptie around the shock piston.

edit 0 theres probably some way to do this with tools or somthing, but everything i do is ghetto, so, why not ghettorig this too...

Modified by chmercer at 2:54 AM 3/29/2005
Modified by chmercer at 2:54 AM 3/29/2005

[AP Autosport]

I guess I should check it out, but I am sure it hitting because I can feel it. I don't care about the ride quality, I just want it stiff enough so they won't bottom out.

[chmercer]

are you sure you are bottoming out the shock? with a dual height adjustable coilover that is pretty hard to do unless you have it set up really wierd. i know on my car i will hit the front tires on the frame rails before i bottom the shock.

[sXi]

Im sorry to threadjack.

can some1 please explain "bottoming" and "bumptop" to me please? thank you very much

[Onizuka]

"bottoming out" is when you run out of suspension travel and your car basically slams all the way down

"bump stops" are what the car hits on inside the shock when it bottoms out.

[evildky]

ok, this is a pet peave of mine, people think becasue they have a set of coil overs they have a tuned suspension

first of all the coils should be at least tight enough that with the car jacked up the sping stays in it's seat, if it moves under this situation it is called spring seat hop and needs to be corrected, if this point is further than you would like you can add limiting straps but most unless your a serious racer that won't be an issue

any decent name brand race springs will have their weights printed or stamped on them in a form of lbs per inch, if you have a set of springs without weights then you can add a known weight to the spring and measure distance traveled and get an aproximation of thier weight, a lot of the over the counter kits are sold for bling factor and do not have weights stamped on them

once the springs are seated at full extention the car is to be set on scales and tightened till the corner weights and cross weights are close to equal with the driver in the seat (remember that coil overs are intended for race applications)

now once we have the springs adjusted we have track time and determine how the car handles and change the spring weight to fix whatever promlems are experienced, such as the bottoming out, you'd want to get stiffer springs adding a hundred Lbs is a good start

coil springs come in a couple of diameters and a few different lengths and quality name brand soprings run $50 to $100 per pair in whatever rate you want

[SmithSR]

first of all the coils should be at least tight enough that with the car jacked up the sping stays in it's seat

Would be nice to get the masses to accept this as the starting point. Good input thanks for the writeup!

[BomexS13]

Would be nice to get the masses to accept this as the starting point. Good input thanks for the writeup!

I did my homework, did mine a couple of weeks ago.

[Nismo_Freak]

I just installed my SPL/KTS coilovers last week before an autocross. I adjusted the height without pre-loading the spring any more than the way they came. I set the dampening on level 14 and I was having a problem with the rear drivers side hitting the bump stop. So, I figured I would pre-load the springs about an inch but I was hoping someone would be able to tell me the acual amount this changes the spring rate. The springs are 8f/6r to begin with.

Oh, and by the way my car feels 100% better after the install. I was using kyb's and sportlines before.

Thanks,Andrew

I am pretty sure you are not bottoming out the shock. There is about 3" (at least) of travel in the suspension before it bottoms out. That would require the spring to travel 3" and at a rate of 336 that gives you...

3" x 336 = 1008 lbs. of force + any rear sway bar rate you have.

Thats even if the shock was completely dead.

What is the car doing when you think it's bottoming out? What are your other suspension modifications? When does this happen?

[AP Autosport]

The springs are and have been adjusted like everyone is saying.

The other mods I have besides some misc. braces and such are the pro ruca's(spl) and some whiteline bushings in the rear traction rod. I know the other bushings need to be replaced as well because the are cracked and worn. It seems to make a noise when making hard right turns only during autox. There is another event this weekend so I will pay more attention to see whats happens at what point.

[chmercer]

any more description on this noise? could it be tire rubbing? ball joint popping in the steering rack?