sitting on my desk i have a collection of bumpstops for the front of my car. i have a pair of oem untrimmed stops from a 99 si, some gc "soft" bumpstops, and two pairs of oem trimmed bumpstops. (one pair has 1 1/4" of the "narrow/soft" end trimmed off, the other has 3/4" trimmed off the "firm" end, the latter being what's currently on the car) also sitting on my desk i have recent suspension travel measurements for my current ride height.

currently, i have roughly 3/8" of shock shaft travel left before the first "step" of the bumpstop starts to come into effect. (ride height measured as 4.75" to the jack tabs) this equates to about .6" of wheel travel. less then .4" of wheel travel later, i enter the second "step" on the bumpstop. i figure (thanks to scott r. and the wonders of "wag") that i need about 1.3" of wheel travel just to accomodate body roll with my current spring rate.

i see a myriad of solutions to the "problem" (i use the quotation marks because i'm not 100% sure this is actually a problem). these solutions come about through the use of springs, ride height, and bumpstops, all to varying degrees. the solutions i see are as follows:

#1 increase spring rate (here's another one of those "wag" numbers) 30%, install shorter bumpstop (trimmed oem stop that has had the "soft" end removed), and leave ride height unchanged.

#2 leave spring rate and bumpstops alone, raise ride height 1/2". (not enough to keep me entirely off the bumpstop, but the first "step" is really soft. bathroom scale says about 40lbs of pressure is all that's needed to collapse that portion of the stop)

#3 leave ride height and bumpstops alone, increase spring rate 30%. (again, won't keep me entirely off the bumpstop, but theoretically reduces my needed travel to just over 1", which puts me right at the transition from "step" 1 to 2 on the bumpstop)

#4 leave spring and ride height alone, install longer gc "soft" bumpstops.

#5 leave spring and ride height alone, install shorter bumpstops with the "soft" portion removed. (this has the possibility of serious uca to fender contact if the stop is too short. i have to figure out the final compressed thickness of the two bumpstops to know for sure beforehand... )

now for the questions. which is the better route to go? does someone else see a better combination? (keep in mind i'm limited in camber adjustability and i'd like to keep the cg as low as possible) maybe some pro's and con's of each?? anybody in the "it ain't a problem, just drive it" camp?

nate-2 years in a row riding the bumpstops out in topeka...i figure they seem to be such an integral part of my suspension, maybe i should give them as much thought as i have given the spring rates....

ps. the car is plenty fast enough right now. realistically, the driver is the current weak link. unfortunately, the silly season has begun for me, so until i can work more on the driving, i want to play!

 

can you legally use the new GC upper strut mounts? Won't they give you .75" more shock travel?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by solo-x &raquo;</TD></TR><TR><TD CLASS="quote">anybody in the "it ain't a problem, just drive it" camp?</TD></TR></TABLE>

Me.

Raise it up. Or stiffen it up.

 

man...you have too much time to think about this

i know i'm at least on the first part of my bumpstop. but i'm not too worried about it. stiffer springs along with properly valved shocks will solve the problem.

if i were you, i'd first look at your tire wear to see if you can afford a slightly higher ride height, and if you can't, then increase the spring rates.

or buy the GS upper shock mounts. that's what i'm doin.

 

i left out that i'm already using shortened koni's. my uca's will hit the strut tower if i try to use the gc upper mounts.

yes, i have way too much time to think about this chit.

as for just raising the car, i'll have to see how much camber i can get out of my offset bushings. shooting for -3*. if i don't get enough with the bushings, the ride height will have to stay low.

nate

 

I thought adjustable upper balljoints were legal for STS? Couldn't you use one of those to get your camber back, and add some caster if you raise the ride height?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by WRXRacer111 &raquo;</TD></TR><TR><TD CLASS="quote">I thought adjustable upper balljoints were legal for STS? Couldn't you use one of those to get your camber back, and add some caster if you raise the ride height?</TD></TR></TABLE>

the next phase for my car is SP. i'd like to have the susension worked out before i switch classes. having a part intalled in my suspension that isn't legal in SP doesn't help me in that regard.

nate

 

For reasons of sheer laziness I haven't read your post thoroughly and thought about it seriously.

But, there's interesting thinking to be done.

We don't notice anything dramatic in the drivers seat when we lift off the inside rear. The weight transfer is smooth - no "step".

Depending, as usual, on so many things, we might lift, and continue to roll. That continued roll can be on the outside front spring and/or bumpstop.

I'm not a bump stop expert, so I don't know much more than what the pictures in the TrueChoice catalog look like, but I don't like the sound of "progressively stepped bumpers". I think a bumper should have one smooth exponential curve for our kind of application - starting very soft (even if that means you're into it at ride height).

I also "think" that if you're deep into a bumper you're beyond the dampers range, so I think you'd want to do as much work with the spring as you can.

Of course that exponential rate might let you push your ride height down, and that might pay.

As usual you can only test. And wind up confused at some point. And call that good.

Scott, who thinks that chassis feedback to the driver should be fast, smooth, and consistent...it's all we've got to work with, and russian roulette on each corner is no way to pass the time...

 

I guess I have a few questions first.

1. Are there any understeer issues?

2. Is the front end feel and response consistant with different corner speeds and types?

3. Are there problems with cornering and hitting bumps at the same time?

You can get some idea of how far the suspension is really compressing by using something compressable that will stay there like clay in a baggie up in the spring hat. That would give you an idea how much of the stop you are using. I think you really need to know that before going further.

Has anyone ever tried using an actual spring instead of a foam/rubber stop? Something small diameter with a high rate and a really high fatigue life like a valve spring. It would coilbind when bottomed and bang pretty hard, but it would be linear and could be changed to different rates if needed. You might need to make a plastic collar to fit inside the spring and keep it centered on the shaft, just make it shorter than the coil bind of the spring.