Vari-shock problem

[Bow Tie 67]

So I found this problem today, it looks as though the shock bottomed out and the upper eye lock nut cracked the " closer nut " . Just prior to RTTH I found this shock had lost fluid due to the nut coming loose. It was sent out and repaired and does not seem to have lost any fluid.



The Vari-shock has 4" of total travel and I had the car setup with the 9" spring gland nut brought up to take out any slack. The car has an LS1 and is running 550 lb springs. I'm debating on going with a higher rate spring, and will be installing a rear sway-bar.

Has anyone run into this type of situation?



I need to correct this!!!!

[Bow Tie 67]

Ok, I need to address this situation I have with my car. The Chassisworks front subframe has no suspension bump-stops.

I'm debating on how to move forward and would appreciate any ideas from suspension guru's on what they suggest.

1. I'm thinking I need a higher rate spring.

2. I can adjust the front ride height up, prefer not to.
( I had the spring 550 lb set-up snug no compression )

3. I will be adding a 3/4" solid rear anti-roll bar to the Quadra-link.

4. Add bump stops to the bottom of the sub, my concern is in that position can it cause the lower a-arm to be tweaked.

I guess my first concern is preventing the shocks from becoming damaged again. Once that is addressed then I can proceed with other changes. Oh this car will be run hard on a road course and driven on HRPT long haul.

[Rhino]

Where is your static ride height set on your coils? How much available travel do you have for compression? If I recall, CA states that the minimum ride of their coil overs to be 40% of travel for compression.

[Vegas69]

Looks like it's time for a bigger sway bar out front. I'd figure out some bump stops as well.

[David Pozzi]

Thanks for the photo, it speaks a thousand words.

Terminal understeer,
Way too much body roll

I don't know your spring motion ratios, so any spring selection would be a guess, it' wouldn't directly relate to a stock sub spring rate, so what works for a stock sub might be too stiff for yours. I would think an Alston sub would have a higher rate at the wheels than the same spring rate on a stock sub.

You need a rear bar, and 3/4" is a good place to start. The arm length matters a lot and again that's an unknown so hopefully it's close to what you need.

You need bumpstops on the car. I'm surprised Alston doesn't put them on their sub. Running too low a ride height is a common issue, you need at least 3" to 3.5" of travel in bump, and even more with soft spring rates.

David

[Bow Tie 67]

I did some quick measurements on motion ratio and came up with ..43066 giving me an effective rate of 550lb x .43066 = 236 lb at the wheel.

I used this method of checking the ratio at the tire contact patch.

http://eaglewoman.rscsites.org/cobra...tionratio2.htm

When I have more time I will take more accurate measurements but feel this is rather close. I'm not sure how accurate these have to be made, but am fairly confident its in the ball-park.

I also found info on the front roll-bar as being a 3/4" x .120 wall 4130 chrome-moly tube. Some quick measurements put it at 34" width, 8" arm and a 2 1/2" link. Its positioned behind the subframe cross-member and if memory serves me correct I thought I read somewhere that in a rearward position a smaller bar acts as though its larger.

Matt

[silver69camaro]

Bumpstops shouldn't hurt the lower control arms since they are a "last resort" in compression, typically the loads aren't that high due to the spring. You could also add some soft bumpstops in the coilover itself, too.

236lbs/in at the wheel is somewhat soft. I'd step that up to 250-300. Any idea what your roll rate is?

Edit: Reading your post again, 3/4" x 0.120 is very, very soft IMO. At LEAST 7/8" solid for that arm length, but then again I don't know what the motion ratio is for the ARB either.

[slowcamaro]

Bumpstops!

Now how about a question on bumpstops. I know koni offers strut shaft bumpstops. Does anyone else? How does one choose the correct rate bumpstop?

I assume a progressive style stop would be most effective as it would upset the car the least when its already close to the suspensions limits.

I am not using varishocks but I am looking to replace my factory rubber units which have either broken off or hardened to a point where they might as well be solid.

[AJSZR2326]

what were the setting on your shocks set at?

[David Pozzi]

According to my Performance Trends software, a 550 front coil on a stock sub with Guldstrand mod would have a wheel rate of 137. A 720 front coil would be 180. Motion ratio squared is .25

Your springs should be plenty stiff unless your suspension travel super-limited.

[Bow Tie 67]

I spoke with Chassisworks and they are going to rebuild the shocks with a revised closer nut which is stronger an added scraper ring and internal stops. They said its basically a new shock. I also asked it they can get the anti-roll bar rate and their motion ratio from the engineers.

David,

The measurement I came up with was an installation ratio of .65625 which squared is .43066. My original #6 post had the installation ratio in the text which I went back and edited to reflect the motion ratio.

I will go back and double check these tomorrow if I can stand the 20* temp in the garage. Brrrrr

Will the motion ratio at the tire contact patch differ based on track width? or tire height? currently I am taking measurements with tires that will be street only, as I have not received the skulte adapters for my track tires / rims.

As far as springs being stiff enough I believe I will be able to install a custom splined sway-bar, so I'm hoping I can get the current bars roll rate to get an idea of where I'm at now. If not is there a way I can check it myself, with a torque wrench and deflection?

Matt

Here is a pic on a road course exiting a sweeper roughly 60 mph.

[Bow Tie 67]

what were the setting on your shocks set at?

I run 5 clicks on track at the auto-x I was at 2 to give the front outside tire more bite!! and 3 on the street.

[David Pozzi]

We run a bit more shock at autocrosses, the left right corner combinations throw the car more violently than on a road course, this causes more lean than a larger track could generate.
David

[silver69camaro]

According to my Performance Trends software, a 550 front coil on a stock sub with Guldstrand mod would have a wheel rate of 137. A 720 front coil would be 180. Motion ratio squared is .25

Your springs should be plenty stiff unless your suspension travel super-limited.

David,
Those wheel rates seem low to me. What kind of travel do you have with those setups? I assume it's less than what we typically deal with, hence the higher wheel rates.

Matt, that's an awesome shot on that car. Track width will have somewhat of an effect due to the different tread center location. Probably not much though. If you want to get a good idea about what your roll rate is, PM me and we can talk. I can give you a list of all the data I need to accurately calculate it.

[HILROD]

Way back when I rode in your car the rear was definately bottoming on something. I know you upped the shock valving and such since then. What if you removed the springs and run it through its movement and see if it can bottom the shocks?

[David Pozzi]

Matt,
My wheel rates seem low to me too, but my first gen and second gen files are both below 200 on wheel rates and both cars were run successfully with those rates 700 ish for the 67, it's an old guldstrand coil and I can't make it stay in my spring checker, afraid it will pop out, - and the 73 is 670. Mary's car has barely enough ground clearance mainly due to the Hooker super comps that scrape too often. I think there is 4" of header tube to ground clearance and we use every bit of it. I'd have to check to be sure I'm giving you the right height number but it's close.

One of the problems using software is to know if it's telling you the truth. I guess I could verify by stacking weights on the front with the car on turntables, but it would have to be exactly over the wheels.
David

[Marcus SC&C]

The setup you have currently is basically a baseline "nice cruiser" package. Not really intended for serious cornering. Still I`m suprised at the contact issue. What did you have the shocks set at? We generally start at 7 clicks. I`m guessing they were set much too soft based on the problem and pic. The rear bar is a good idea, you may also want to consider the Chassisworks 1" G-Machine front bar. That will really cut down on the body roll. For performance handling applications we usually spec 600lb/in or 675lb/in springs. Mark SC&C